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holl_ands
Advanced Member
Username: Holl_ands
Post Number: 297
Registered: 06-2004
Rating: N/A
Votes: 0 (Vote!) | | Posted on Sunday, February 20, 2005 - 08:10 pm: | 
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DTV PROPAGATION PREDICTION PROGRAM (PPP No. 1)
Fol. link is a DTV Propagation Predition Chart for (unoccupied) CH37 from Mt Harvard (ie Mt Wilson) in Los Angeles:
http://www.transmitter.com/images/ch37dtv.png
Save and double click to use your default image file viewer for zooming in.
Color sequence is at bottom of chart.
The chart covers portions of N. SD County. It was generated by SPLAT!, a free Linux based program. Explanation and downloading links are in Dave Lung's latest TV TECHNOLOGY column:
http://www.tvtechnology.com/features/On-RF/F_Lung-02.02.05.shtml
(Message edited by holl_ands on March 15, 2005) |
holl_ands
Advanced Member
Username: Holl_ands
Post Number: 338
Registered: 06-2004
Rating: N/A
Votes: 0 (Vote!) | | Posted on Monday, March 14, 2005 - 02:00 am: |
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DTV PROPAGATION PREDICTION PROGRAM (PPP No. 2)
Here is an edited SPLAT! chart for LA Stations being received in N. SD County.
Using a 4-Bay Bowtie and a Preamp, I calculated that a reasonable Fade Margin would still be maintained with Path Loss as much as 165-170 dB.
My son resides on the very thin light-green spike (160 dB Path Loss) located a few miles north-east of Temecula.
I'll be posting an Excel spread sheet in the near future that will assist in using this and similiar charts forthcoming re SD Stations.
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holl_ands
Advanced Member
Username: Holl_ands
Post Number: 339
Registered: 06-2004
Rating: N/A
Votes: 0 (Vote!) | | Posted on Monday, March 14, 2005 - 03:17 am: |
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KGTV-DT & KSWB-DT: DTV PROPAGATION PREDICTION PROGRAM (PPP No. 3)
ANTENNAWEB.ORG says I need yellow antenna for KNSB-DT and KPBS-DT, a red antenna for KSWB-DT and violet for KUSI-DT.
And no other DTV stations....but most people believe that it is overly conservative.
I also found that the prediction was the same for me at the bottom of the 60 foot hill and my neighbors at the top...so go figure...
I'm still hoping that some enterprising Linux expert is interested enough to download SPLAT! (free) and do some charts for SD stations....
In the mean time, I ran across RADIO MOBILE, a FREE VHF_UHF PPP that (also) embeds the Irregular Terrain Model:
http://www.cplus.org/rmw/english1.html
It has lots of capability, nearly as much as the expensive commercial products.
Which means, of course, that it requires some CommSysEng knowledge and lots and lots of patience...
A few examples follow, but first some landmarks:
Mt Soledad is "big" hill on the coast with Mission Bay below (and Pt Loma in #3).
I8 runs along the river channel at south end of Mission Bay.
I'm located West of I15, just south of Camino Del Norte and a few miles north of Rt56 (that's the big canyon.
That big lump of RED is caused by the shadow of Black Mtn.
First image shows how Black Mtn blocks signals coming from Mt Soledad, even though I'm only 14 miles away.
I don't even get multi-megawatt CH 8 and 10. Also note how lots of other nearby areas have blockage.
Mt Soledad is a terrible location for a TV transmitter.
Second image shows the calculations for KGTV-DT reception from Mt Soledad....looks marginal.
Third image is twice the scale of the first and shows how well KSWB-DT covers San Diego, and blockages in mostly distant valleys.
So I guess, theoretically, all of the SD DTV stations can be received at my location with at least a 10 dB Fade Margin.
It also says I can receive most LA stations with same or better Fade Margin.
Right now I'm rather skeptical about Radio Mobile results....it may be too optimistic.
Perhaps others can correlate their on-air performance to the predictions....
KGTV-DT Signal Levels:
KGTV-DT to holl_ands Path Calculation:
KSWB-DT Signal Levels:
(Message edited by holl_ands on March 15, 2005) |
holl_ands
Advanced Member
Username: Holl_ands
Post Number: 340
Registered: 06-2004
Rating: N/A
Votes: 0 (Vote!) | | Posted on Tuesday, March 15, 2005 - 01:13 am: |
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XETV-DT: DTV PROPAGATION PREDICTION PROGRAM (PPP No. 4)
Wouldn't want to overlook Gary's favorite station.
I was pleasantly surprised by the coverage from Mt San Antonio.
Unless you are blocked by a mountain, most of North County had a usable signal, although a preamp may be required.
On the other hand, the program predicts over 10 dB Fade Margin for north of Temecula, but we didn't see a signal when we tested with a preamp and a 4-Bay antenna 8 feet in the air.
I tweaked the contrast and color levels so the strong signal areas are easier to see.
Unfortunately, one of the SRTM-1 Terrain Database segments is missing data below Tijuana and doesn't recover until much further south.
and the extended area:
(Message edited by holl_ands on March 15, 2005) |
Don Falkner
Member
Username: Donf
Post Number: 21
Registered: 01-2004
Rating: N/A
Votes: 0 (Vote!) | | Posted on Tuesday, March 15, 2005 - 06:17 pm: |
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The problem with XETV-DT 23 in the North County, at least along the coast, is interference from KTBN-DT 23 from Los Angeles. The only time that I can get a lock on XETV is when weather conditions are not conducive for KTBN, like during Santa Ana conditions. |
holl_ands
Advanced Member
Username: Holl_ands
Post Number: 344
Registered: 06-2004
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, March 16, 2005 - 01:48 am: |
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Don: I reread your Sep04 post re. XETV-DT OTA PROBLEMS.
Could you provide your location to the nearest cross streets so I can calculate expected receive signal strengths on CH23?
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Don Falkner
Member
Username: Donf
Post Number: 23
Registered: 01-2004
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, March 16, 2005 - 05:37 am: |
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I'm near Saxony, just south of La Costa Blvd. in Encinitas. |
holl_ands
Advanced Member
Username: Holl_ands
Post Number: 363
Registered: 06-2004
Rating: N/A
Votes: 0 (Vote!) | | Posted on Tuesday, March 22, 2005 - 01:22 am: |
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DTV PROPAGATION PREDICTION (PPP No. 5):
RADIO MOBILE SETUP INSTRUCTIONS.
I've checked antennaweb.org antenna recommendations for about half-a-dozen FnznFam.
Invariably, the outlook wasn't very good.
Except for Winchester, CA, only two to four DTV stations for Scripps Ranch, PQ, N. County Fair and Escondido.
So, after hearing forum comments about it being "too conservative", I looked for better methods.
Especially methods that give more insight into the underlying models, assumptions and effect of user parameters.
The FCC uses a version of the Longley-Rice Irregular Terrain Model (ITM) to calculate required power for a given
coverage area and to help prevent interference between stations.
Although I started to configure the (free) NTIA version of ITM, I ran across a program that used the ITM model,
but had a much better user interface....and LOTS OF PRETTY MAPS!!!
I've been building up the database with SD/LA specific files (available via private message).
Radio Mobile can be downloaded for free from fol. site:
http://www.cplus.org/rmw/english1.html
Unzip the "helper" files into the same directory as Radio Mobile.
Follow "How To" directions to download SRTM-1 files into a mapdata directory (N32W116 to N34W120).
(Virgina Emerg Network works, NASA site is painful).
I replaced two of the SRTM-1 files with the fol. 90m resolution SRTM-3 files due to missing data: N32W116 and N32W117.
Also print the user documentation found in the "How To" links.
Radio Mobile is very easy for a novice to setup and use....the hard part may be interpretation...
Use "Map Properties" to display map database by linking SRTM data source to mapdata directory.
The map scale is controlled by the "Height" field, since the "Width" field is not working.
For LA to TJ: Height = 200 km, LAT = 33.35, LONG = -117.3
"Picture Properties" allows the user to select several different B/W, Color and Rainbow displays.
I use Rainbow with Absolute Scale settings tailored to provide realistic colors.
If Radio Mobile can't find a map or satellite image overlay file on disk, it will automatically try to locate it on the Internet.
Once you're set up, you can tell it to quit nagging you about missing files you don't need.
(Message edited by holl_ands on March 22, 2005) |
holl_ands
Advanced Member
Username: Holl_ands
Post Number: 364
Registered: 06-2004
Rating: N/A
Votes: 0 (Vote!) | | Posted on Tuesday, March 22, 2005 - 01:54 am: |
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DTV PROPAGATION PREDICTION (PPP No. 6):
RADIO MOBILE vs ANTENNAWEB.ORG COMPARISON
The fol. Excel file compares the Radio Mobile predictions with antennaweb.org results for three locations.
It seems to be better than antennaweb.org, but there are still anomalies, esp UPN KCOP-DT (who cares) and KABC-DT.
I am still working on another Excel spread sheet that will calculate individual channel performance,
including stipulate parameters for individual channels, such as antenna gain, cable loss, cascaded Noise Figure, etc.
1. BRI, attic CM4221 4-Bay, N of French Valley Airport, Winchester:
Antennaweb was missing 4 out of 17 received OK.
KVMD-DT on Ch23 blocks reception of XETV-DT and KTBN-DT.
KABC-DT and KCOP-DT were inexplicably NOGO, despite Fade Margin of about 28 dB.
2. DON_FALKNER, Yagi, Encinitas:
Antennaweb was missing 10 out of 13 received OK.
KVMD-DT on Ch23 is 19 dB higher than XETV-DT,
difficult to overcome with antenna F/B Ratio
KCOP-DT is inexplicably NOGO, despite Fade Margin of about 28+ dB, same as 3 others.
3. HB_SD, antenna shopping, Hidden Meadows, Escondido:
ALL SD & TJ stations very strong, Line-Of-Sight.
KVCR-DT, PBS from San Bernardino also strong.
XETV-DT is 5 dB stronger than KVMD-DT (29 Palms).
Antenna Front/Back Ratio should be enough to suppress KVMD-DT most of the time (but not always)
SOURCE OF INTERFERENCE TO XETV-DT IS KVMD-DT (SHOPPING X 3) !!!
Time permitting, I'll add a couple more sites in the near future...
(Message edited by holl_ands on March 22, 2005) |
Don Falkner
Member
Username: Donf
Post Number: 24
Registered: 01-2004
Rating: N/A
Votes: 0 (Vote!) | | Posted on Tuesday, March 22, 2005 - 09:47 am: |
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Holl_ands, thanks for all your research. You must really enjoy this :-).
A couple of comments on your spreadsheet. I can no longer receive KABC-DT. It used to come in pretty strong, but a couple of months ago it stopped. Gary S. (from XETV) mentioned in another thread that they were having serious antenna problems, so I assume that's the cause of the dropout.
Also, I don't doubt that KVMD-DT is the primary source of interference to XETV-DT, but KTBN-DT is in the mix there as well. I was actually able to lock in on that signal when weather conditions were right. I've never locked in on KVMD-DT.
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holl_ands
Advanced Member
Username: Holl_ands
Post Number: 368
Registered: 06-2004
Rating: N/A
Votes: 0 (Vote!) | | Posted on Tuesday, March 22, 2005 - 10:46 am: |
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At your location, RM predicts KVMD-DT to be strongest, with KTBN-DT 10 dB lower and XETV-DT another 3 dB down.
So, in order to receive KVMD-DT, the antenna pattern would have to suppress the other sources by at least 5 dB if there was no multipath,
but in the real world, another 10-15 dB of suppression would be necessary...which is difficult to achieve without some assistance from fortutious propagation conditions.
==============================================
Thanks for the update re recent KABC-DT reception problems.
Have you tried rescanning as well as punching in 53.1/53.2/53.3 direct?
The LA section on avsforum has reported that they continue to have PSIP problems.
(Message edited by holl_ands on March 22, 2005) |
Milo Flaska
Intermediate Member
Username: Milod
Post Number: 73
Registered: 01-2004
Rating: N/A
Votes: 0 (Vote!) | | Posted on Tuesday, March 22, 2005 - 09:20 pm: |
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Don-Regarding KABC-DT---Has Gary reported a recent
change in antenna problems? He had mentioned difficulty of KABC-DT reception prior to last summer. Last summer, I received it when reception conditions were good, and lost it when they were not. I haven't kept good tabs on it, but I haven't been able to receive it at all for at least the last month or two-maybe longer. |
Larry G
Member
Username: Larryg
Post Number: 11
Registered: 02-2005
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, March 23, 2005 - 03:10 am: |
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You know what's weird about KVMD? Is that on Adelphia Cable here in Hemet, it carries local sports programming, which I kinda like. I only wish it did so when my stepbrother was playing high school football.
Is it a digital-only station? Apparently, according to the FCC, the transmitter is located on the foothills between Big Bear and Desert Hot Springs/Yucca Valley, giving it peripheral coverage (theoretically) to the eastern portions of L.A./Orange County.
They also run a local program called "Southern California News", not sure where this originates.
Again this brings me to the DMA madness, that a station licensed to Twentynine Palms is carried on cable locally, but they can't manage Palm Springs or San Diego in this area (Hemet) due to DMA issues, though I do believe the problem with PS is more due to geographic limitations.
BTW, another station now carried is KBEH, which is now a Spanish station based in Oxnard, but was a UPN affiliate, KADY, presumably serving the Santa Barbara market.
Which reminds me, KEYT, the ABC out of Santa Barbara, has a surprisingly strong signal. People with overhead antennas regularly pick this up in fits and starts (nothing permanent) here which amazes me. Dunno if the ocean is carrying the signal or some kind of mountain coverage.
At any rate, most of what I'm talking about is analog, so apologies for the off topic.
One other thing I'd like to do is thank whoever is simulcasting the various news reports/weather from KNSD (nbcsandiego.feedroom.com) over the internet. It is nice to see some stories from San Diego up this way, even if delivered over the world wide web. I wish the other stations would follow suit for those of us north of North County. 
Larry
(Message edited by larryg on March 23, 2005) |
holl_ands
Advanced Member
Username: Holl_ands
Post Number: 369
Registered: 06-2004
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, March 23, 2005 - 03:16 am: |
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DTV PROPAGATION PREDICTION (PPP No. 7):
MORE ON KVMD-DT INTERFERENCE TO XETV-DT
The following chart depicts where each signal is stronger. The grey areas in between are approx equal signal strength.
As can be seen, portions of North County are especially challenging for XETV-DT.
An antenna not only needs a good Front/Back Ratio but preferably deep side-lobe nulls towards 29 Palms.
FCC must think Ch23 is a "party line" that anyone can join.
(Message edited by holl_ands on March 23, 2005) |
Merle F McClelland
Junior Member
Username: Axolotl
Post Number: 10
Registered: 12-2004
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, March 23, 2005 - 02:21 pm: |
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I'm in western Valley Center, 33.2491 N 117.0879 W. I haven't seen any signal from KVMD at our location, although I've tried. Line of sight to their transmitter appears to be blocked by the west end of Palomar Mtn.
I receive all of the LA stations even though our LOS to Mt. Wilson goes directly through Saddleback Peak in Orange County. Ch. 7, 9, and 11 are weak and not reliable, although I'd say they come in 75% of the time. KTBN-DT is very weak, and cochannel interference from KVMD may be at fault. However, I do occasionally see KTBN.
Presently I'm using a Channel Master Stealthenna with the internal preamp mounted a few feet above the roof lin, with an antenna rotator. The rotator was a big help - Ch. 7 is very directional and the difference of just a few degrees makes a huge difference.
I have a CM 4221 and 7777 preamp awaiting installation, which will hopefully give me more signal strength on those weaker channels. I do not receive any San Diego/Tijuana DTV stations - my house is too close to a mountain just to the south.
If you have a clear view to the northwest from Hidden Meadows I suspect you'll be able to receive most of the LA stations, since you're pretty close to my location.
- Merle |
holl_ands
Advanced Member
Username: Holl_ands
Post Number: 372
Registered: 06-2004
Rating: N/A
Votes: 0 (Vote!) | | Posted on Thursday, March 24, 2005 - 12:27 am: |
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Larry_G: I was curious whether you picked up the low power KUSI repeater on VHF Ch12?
That is a handy source for SD news in my son's Temecula/Winchester location. |
holl_ands
Advanced Member
Username: Holl_ands
Post Number: 374
Registered: 06-2004
Rating: N/A
Votes: 0 (Vote!) | | Posted on Thursday, March 24, 2005 - 03:33 am: |
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DTV PROPAGATION PREDICTION (PPP No. 8):
DTV FADE MARGIN CALCULATION EXAMPLE
Now that I've shown you SPLAT! and RADIO MOBILE predictions for Path Loss,
it's time to reveal what I do to calculate the FADE MARGIN, along with a lot of other useful information.
This helps to gain insight into the underlying assumptions.
It also is needed to pre-calculate receiver sensitivity for use by RADIO MOBILE.
The attached Excel spread sheet shows an A/B comparison (with and without a Preamp)
for KFMB-DT to Don_S location in (La Costa) Carlsbad. Or enter your own data.
It shows just over a 10 dB improvement in sensitivity, hence a 10 dB Fade Margin increase.
Note that the spread sheet calculates a Cascaded Noise Figure, including a
Preamp, Distribution Amp, HGTV and intervening loss elements.
Carefully follow instructions if you aren't using all three.
Try some "what-if" exercises to reveal the effect of various changes to a system.
Ever wonder how much summer heat affects the Thermal Noise level? Not much.
Of course, the accuracy of the results are only as good as the assumptions for your local situation.
I'm still looking into "Land Use and Land Clutter" Loss and Attic Loss Guestimates.
I've included references to help explain some of the parameters, including a link to find the
ATSC Performance Assessment Report (12Apr01) which deals in depth with many of these subjects.
I use a similiar spread sheet that has been expanded to cover most of the LA area DTV stations.
But I still haven't put one together for SD. Sounds like an exercise for the student...
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Larry G
Member
Username: Larryg
Post Number: 12
Registered: 02-2005
Rating: N/A
Votes: 0 (Vote!) | | Posted on Thursday, March 24, 2005 - 09:32 am: |
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No, unfortuantely. But I only tested it on my multiband shortwave radio with the TV bands.
I was really surprised, but I haven't yet given it a real test from my TV yet. Ironically, the only strong signal I got was KNBC, which surprised me because that station is traditionally the weakest.
But, I'm gonna give it another try on my regular set.
As for San Diego TV news, I recently got broadband and was pleasantly surprised to find that KNSD streams, so I can at least watch their weather update now online, which is great. Though the story on the giant squid in Oceanside was something. Sometimes ignorance *is* bliss. <grin>
I do wish they'd add KUSI to the Hemet system though, as it is not affiliated with any network. That'd be great. WGN is in that slot up here.
If you want to watch a local broadcast in Riverside, KHEM Ch. 27 has a nightly newscast at 9. They're airing it on cable on the Adelphia Channel. It's *very* local, quite funny, but a nice source for local stuff and covers Temecula/Murrieta as well. Not sure if they reach S.D. County like Fallbrook or not.
Larry |
holl_ands
Advanced Member
Username: Holl_ands
Post Number: 381
Registered: 06-2004
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, March 26, 2005 - 03:54 pm: |
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In the above "DTV Fade Margin Calc Example.xls" spread sheet, I found an error in the section that tried to compare the predicted Diffraction Path Loss to theoretical Free Space Loss.
This has been fixed in the RevA version, plus I clarified the nomenclature in a few places and added two lines to assist in determining if Preamp Overload is a problem.
Since antennaweb.org will not provide distance and magnetic compass heading for all possible stations,
using your LAT/LONG position, the fol. site will provide more complete info:
http://www.2150.com/broadcast/
Careful, it lists the True North Heading, whereas antennaweb.org lists the Magnetic Compass Heading.
(Message edited by holl_ands on March 27, 2005) |
holl_ands
Advanced Member
Username: Holl_ands
Post Number: 389
Registered: 06-2004
Rating: N/A
Votes: 0 (Vote!) | | Posted on Tuesday, March 29, 2005 - 03:19 am: |
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I found one more (final?) error in the "DTV Fade Margin Calc Example Rev A.xls" spread sheet.
Left off the Noise Figure degradation due to loss between Preamp and Distribution Amp.
See fol. corrected version: |
holl_ands
Advanced Member
Username: Holl_ands
Post Number: 551
Registered: 06-2004
Rating: N/A
Votes: 0 (Vote!) | | Posted on Thursday, July 21, 2005 - 04:11 pm: |
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DTV PROPAGATION PREDICTION (PPP No. 9):
SIGNAL OVERLOAD CALCULATION: Minimum Distance to Transmitter
Being 22 miles from Mt Miguel (and only 14 miles to Mt Soledad, but with a big hill in the way),
I knew that I would have to be careful about using a Preamp, such as choosing a low gain (15 dB) device.
So I finally sat down and put together an Excel spread sheet (thereby replacing the back of an envelope).
So now we can relate the various Preamp overload specs (such as they are) to at least a guestimate
for how far away we need to be from the transmitter site to use a particular Preamp.
Also note how easy it is to overload the input to your HDTV/STB.
And think twice before cascading a Preamp with a Distribution Amplifier.
Please let me know if you find any problems in the spread sheet.
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holl_ands
Advanced Member
Username: Holl_ands
Post Number: 556
Registered: 06-2004
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, July 23, 2005 - 01:39 am: |
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DTV PROPAGATION PREDICTION (PPP No. 10):
Typical HDTV/STB Noise Figure and Sensitivity
As calculated in the above DTV FADE MARGIN CALC spread sheet,
the thermal noise power is about -106 dBm for typical temperatures inside an HDTV/STB.
Noise Figure is a measure of how much more noise is generated in an amplifier on top of the input thermal noise.
As discussed in the above spread sheet, a Preamp reduces the effect of any loss after the Preamp by the amount of Preamp Gain.
Hence a Cascade Noise Figure can be calculated for the amount of additional Noise power generated by the combination of the Preamp,
downlead, RF Splitters and finally the HDTV/STB.
Various laboratory tests using non-fading Gaussian Noise have shown that the ATSC signal needs at least 15.2 dB SNR
in order to provide a minimum acceptable signal (give or take a few tenths of a dB).
The Minimum Sensitivity can be calculated as follows:
Sens (dbm) = -106.0 dBm + 15.2 dB + Cascade NF (dB)
[Example: typical NF = 7 yields Sensitity of - 83.8 dBm]
Note that this is for best case, non-fading conditions (very rare in the real world).
In order to operate in the presence of various multipath conditons,
additional signal strength will be needed to protect against random signal dropouts.
The amount of Fade Margin required to minimize these dropouts may range from
under 10 dB to over 30 dB, depending on geometry and terrain.
As is usual with the "real world", it is very difficult to predict how much Fade Margin is needed.
================================================
FYI: It is very difficult to discover the NF spec for any specific HDTV/STB.
The following spread sheet provides some specs for those few ATSC Tuner Modules that I was able to find
on manufacturers websites (and who had the courage to actually publish).
However, it is next to impossible to match a Tuner Module part number to a particular HDTV or STB without looking inside.
Observe the unusual insensitivity for the LG Innotech ATSC Tuner Modules employing the
much anticipated LGDT3303 5th Generation ATSC Decoder chip.
But this may be just what is needed for the high signal strengths found in the inner city
where the LGDT3303's extended equalizer capabilities are targeted.
PS: The Noise Figure for several common Preamps were provided in the DTV OVERLOAD CALC spread sheet.
Unfortunately, most other Preamp suppliers do not provide NF specifications.
PPS: Believe it or not, there is a LAW that says the HDTV/STB Noise Figure can not exceed 14 dB.
Plus another 4 dB "loophole" if an RF Splitter is used to feed an embedded VTR or Dual PIP tuner (and embedded DVR?):
http://www.part-15.org/fcc/part15/15-117.htm
(Message edited by holl_ands on July 23, 2005) |
holl_ands
Advanced Member
Username: Holl_ands
Post Number: 595
Registered: 06-2004
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, September 03, 2005 - 12:45 pm: |
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DTV PROPAGATION PREDICTION (PPP No. 11):
Typical Preamp Gain, Noise Figure and Overload Specs.
I was very surprised at how many Preamps were must worse than their specified Noise Figure.
I only saw three UHF models that I would consider buying (no surprises here):
The first was the UHF only Channel Master CM7775 Titan2 series (and presumably also the VHF/UHF CM7777).
The second were the Winegard AP-2880, AP-8700 and AP-4800 and related series.
The third was "Amplifier #1" which was specified to have a VHF/UHF Gain of 19 dB and
VHF/UHF Noise Figure of 3.8 dB (typical measurements at 3.3 and 2.9 dB).
Unfortunately, I haven't matched these specs to a known model number....maybe someone else knows....
=================================================
Fol. is an Excel spread sheet listing manufacturer specs for various TV Preamps,
including Gain, Noise Figure and Overload (such as it is).
I have also included specs for various General Purpose (i.e. 50 ohm) Preamps
and a few individual LNA (Low Noise Amplifier) chip specs.
Actual measured Noise Figure values for a few select Preamps at a few selected channel
frequencies have been posted at www.hdtvprimer.com/ANTENNAS/basics.html
and in the article "The Performance of Antenna Amplifiers Used for Terrestrial DTV Reception",
IEEE Transactions on Broadcasting, Vol 50, No 2, June 2004.
Although the latter article did not list the manufacturer model numbers,
they did list the manufacturer's specified Gain and Noise Figure specs,
making it easy to match them to the model numbers with a fairly high confidence.
(Message edited by holl_ands on September 03, 2005) |
holl_ands
Advanced Member
Username: Holl_ands
Post Number: 598
Registered: 06-2004
Rating: N/A
Votes: 0 (Vote!) | | Posted on Monday, September 05, 2005 - 01:53 pm: |
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REV C CORRECTION TO
DTV PROPAGATION PREDICTION (PPP No. 8):
DTV FADE MARGIN CALCULATION EXAMPLE
Fol. is Rev C correction to DTV FADE MARGIN CALC spread sheet.
The Broadcast TX Antenna Pattern Loss cell was corrected for 20*log(Field Strength) vice 10*log() since
Relative Field Polar Plots on FCC website are presumably expressed as volts/meter vice power gain.
These corrections are usually small, unless you are in the direction the station is trying to reduce coverage.
Thanks to Nitewatchman on avsforum for taking the time to double check these calculations.
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holl_ands
Advanced Member
Username: Holl_ands
Post Number: 600
Registered: 06-2004
Rating: N/A
Votes: 0 (Vote!) | | Posted on Tuesday, September 06, 2005 - 04:41 pm: |
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DTV PROPAGATION PREDICTION (PPP No. 12):
DTV Antennas: Specs vs Measurements vs NEC Simulations
Fol. spread sheet summarizes manufacturer spec sheet info for various DTV antennas.
It also includes some comparisons to NEC Simulations and actual antenna measurements
for the Channel Master CM4228 and Winegard PR8800 8-Bay antennas found in the fol. short thread:
http://hdtv.forsandiego.com/messages/1/3476.html#POST18833
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holl_ands
Advanced Member
Username: Holl_ands
Post Number: 612
Registered: 06-2004
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, September 17, 2005 - 10:05 am: |
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DTV PROPAGATION PREDICTION (PPP No. 13):
Another Overload and DTV Fade Margin Example
These files compare the Preamp Overload calculations for the W-G AP-4700,
new W-G high overload HDP-169 and CM-7777.
The example is for a difficult location in Santa Rosa, CA trying to receive from San Francisco:
http://www.avsforum.com/avs-vb/showthread.php?p=6206737#post6206737
It was determined that the CM-7777 was operating right at the overload point
and was also heavily overloading the HDTV Tuner.
First recommendation was to insert a Variable RF Attenuator on the HDTV input.
Second was to insert a W-G UT2700 notch filter on the two strong overload sources:
8 dB notch on CH22 and 8 dB notch on CH23.
Antenna solutions are also possible.
In this case, the W-G AP-4700 Preamp was the best choice,
since it provided higher gain than the HDP-269, while the signal levels
still had adequate "head room" below the Preamp spec overload point.
|
holl_ands
Advanced Member
Username: Holl_ands
Post Number: 613
Registered: 06-2004
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, September 17, 2005 - 01:14 pm: |
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DTV PROPAGATION PREDICTION (PPP No. 14):
Component Specification Updates
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holl_ands
Advanced Member
Username: Holl_ands
Post Number: 614
Registered: 06-2004
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, September 17, 2005 - 04:16 pm: |
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And the updated DTV ANTENNAS spread sheet,
which compares manufacturer specs to NEC Simulation results and (for a few) actual measurements.
It now includes many non-U.S. antennas.
Note that outside North America, many different channel spacing and number schemes are used.
Fortunately, most specs use frequency rather than channel number:
(Message edited by holl_ands on September 17, 2005) |
holl_ands
Advanced Member
Username: Holl_ands
Post Number: 692
Registered: 06-2004
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, October 19, 2005 - 02:42 pm: |
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The fol. on-air measurements of sensitivity for various ATSC Receivers was
found in Echostar's 7/5/05 Reply Comments to the FCC re SHVERA rule making.
Follow link in Doug Lund's recent DTV column:
http://www.tvtechnology.com/features/On-RF/f_doug_lung-10.05.05.shtml
Measured Sensitivity by Channel (dBm)
D12 D23 D29 D41 D43 D47 D49 [DTV Channel Number]
-81.9 -82.6 -84.1 -82.8 -80.4 -81.1 -81.8 LG LST-4200A
-80.9 -80.6 -83.1 -80.8 -81.4 -81.1 -82.8 Samsung SIR-T451
-78.9 -83.6 -83.1 -83.8 -83.4 -82.1 -82.8 Motorola HDT-101
-81.7 -82.9 -84.1 -82.9 -82.8 -81.5 -81.9 Dish DP-942
-75.9 -78.6 -82.1 -77.8 -77.4 -78.1 -78.8 RCA DTC-100
-75.9 -78.6 -79.1 -77.8 -79.4 -79.1 -79.8 Zenith DTV Demod-S
Variation in Sensitivity:
5.8 5.0 5.0 6.0 6.0 4.0 4.0 dB
Average Sensitivity:
-79.9 -81.7 -83.3 -81.6 -81.1 -80.8 -81.6 dBm
FCC Performance Factor:
-81.2 -84.2 -84.2 -84.2 -84.2 -84.2 -84.2 dBm
========================================
To convert from Sensitivity to Noise Figure:
N.F. = Sensitivity (dBm) - (-106 dBm) (thermal noise floor) - 15.5 (dB) (minimum SNR for ATSC)
The thermal noise floor will vary somewhat with temperature (as measured at the first RF chip).
The minimum SNR for ATSC will vary somewhat between units and typically is slightly worse for both weak signals and very strong signals.
(Message edited by holl_ands on October 19, 2005) |
Bubby
New member
Username: Bubby
Post Number: 1
Registered: 11-2005
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, November 04, 2005 - 09:39 am: |
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Hey all
I want to share my "story", as well as thank everyone in this forum for all the valuable information. I have been lurking here for about 3 months planning my attack on OTA HD, and everyone here has been a huge help. Every step I have taken in this process has been taken from this forum. Point is, keep posting because you are helping people like me.
First, the vitals. D* HD Tivo, living in North County SD (San Elijo Hills). I am at about 850 ft elev., with a completely obstructed view to the south, but unobstructed north and west. Antennaweb has me at 313 to Mt Wilson.
So I set out to tackle LA stations. Got my CM4221 from warren electronics (good price, but a bit slow on delivery, especially when you are chomping at the bit to get this think going). It arrived the day of the USC/Notre Dame game. I quickly connected it up at leaned it against a north facing fence in the backyard. Presto, all LA stations in HD! Watched the game before doing anything else.
So now I have mounted it on the chimney, and the results have been great. However, I lost ABC and FOX is spotty. I gather from reading here that those channels have been problematic for others, but does anyone think that leaning against the fence had anything to do with the change in reception? Anyway, I'm getting a readable signal, just not strong enough. Next step is to try pre amp.
Now I just received my CM7777, and will be hooking up this weekend. I have a question for anyone who can help. I was think about placing the power supply to the pre amp in a media closet in the master bedroom (and prehaps a distribution amp if needed) and feed the rest of the house from there. However, I read that the power supply should be place as close a possible to the TV. What is the correct answer?
BTW, getting KEYT Santa Barbara pretty regularly, except during the recent Santa Ana conditions. Since I grew up there, it is nice to watch the local news once and while.
Thanks again to all. The only downside to all of this is that now watching SD local channels over D* in standard signal is like finger nails on a chalkboard. Thinking about cancelling local channel subscription (the extra $4.99/month) if I can reel in ABC and FOX from LA.
Sorry if I posted in the wrong topic, but I figured this was an LA story. |
holl_ands
Advanced Member
Username: Holl_ands
Post Number: 733
Registered: 06-2004
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, November 04, 2005 - 05:20 pm: |
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It doesn't matter where you mount the CM7777's power module, as long as there aren't any RF Splitters
or other DC blocking components between it and the Preamp.
Most RF Splitters will block +18 VDC power. If for some reason your setup requires RF Splitters
in between the Power Module and the Preamp, then you'll need to make sure you use
"Satellite RF Splitters" that have DC PASS capability.
-------------------------------
Where did you read that the power module should be placed as close as possible to the TV?
C-M's "Off-Air Antenna Installation Guide" only says "the power module is mounted indoors, usually near the TV set".
That is only because in most older homes, that is where a conventient power outlet was located.
Today, the power module might be in the garage, along with the Multiswitch for the SAT dish.
Or located in the attic, along with the antenna.
(Message edited by holl_ands on November 04, 2005) |
Micawber
New member
Username: Micawber
Post Number: 2
Registered: 11-2005
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, November 04, 2005 - 07:02 pm: |
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In my installation, with power fed through the coax and the in/out coax on the power supply, putting the power supply remotely would increase the coax run. |
Micawber
New member
Username: Micawber
Post Number: 3
Registered: 11-2005
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, November 04, 2005 - 07:15 pm: |
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Unless it was along the normal shortest coax path, of course. |
Bubby
New member
Username: Bubby
Post Number: 2
Registered: 11-2005
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, November 05, 2005 - 12:08 am: |
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Quote from Titan 2 instruction sheet:
(Under Indoor Power Supply Installation)
1. Choose a location for mounting the indoor power supply as close to the television set and a 120 volt 60Hz AC electrical outlet as possible. Using the two screws... etc
Don't know what to make of this, maybe it is just dated material. |
Micawber
New member
Username: Micawber
Post Number: 4
Registered: 11-2005
Rating: N/A
Votes: 0 (Vote!) | | Posted on Sunday, December 11, 2005 - 06:29 pm: |
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Here are results looking North from my new antenna and preamp from my location in the far west side of San Marcos. Antenna is up 30 feet with rotator:
TV GUIDE TO STATIONS AVAILABLE, NORTH
Channel Call Network Direction RF Signal/notes
2.1 KCBS CBS 340 60 Strong, usually 100% +.
4.1,2 KNBC NBC 350 36 80%; 2 is wx
5.1,2 KTLA 350 31 65%; weak
7.1,2,3 KABC ABC 340 53 80%; 3 is radar
9.1 KCAL 340 43 75%
11.1 KTTV FOX 350 65 70%
13.1 KCOP 335 66 50%, weak
18.1 KSCI Indl 340 61 70%
22.1 KWHY Spanish 338 42 70%, Long Beach
24.1 KVCR PBS 340 26 95%
28.1,2 KCET PBS 340 59 95%
30.1,2,3,4 i Ind 350 38 75%; 2 is PAX, 3 is Worship, 4 is Faith
34.1 KMEX Spanish 350 35 80%
46.1 KFTR Spanish 350 29 75%
50.1,2,3 KOCE PBS 340 48 90%; 2 & 3 are more
56.1 KDOC Ind 340 32 50%, weak; Anaheim
58.1,2,3,4 KLCS PBS 340 41 75%
62 KRCA Spanish 340 68 50%
(Message edited by Micawber on December 11, 2005)
___________
Winegard HD9095P
Winegard AP-8275
DVICO HDTV PCI card
|
Micawber
New member
Username: Micawber
Post Number: 5
Registered: 11-2005
Rating: N/A
Votes: 0 (Vote!) | | Posted on Monday, December 12, 2005 - 05:49 pm: |
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Conditions today were very good. All stations up about 20+%.
I found my location on Google Earth to be 585 feet. With my antenna on the peak of the house it should be at 615 feet above sea level.
___________
Winegard HD9095P
Winegard AP-8275
DVICO HDTV PCI card
|
Bubby
New member
Username: Bubby
Post Number: 4
Registered: 11-2005
Rating: N/A
Votes: 0 (Vote!) | | Posted on Monday, December 19, 2005 - 01:53 pm: |
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Micawber
You are getting some great reception from LA. I am higher than you in San Elijo with no obstructions. Using a CM4228 with CM7777, not getting the results you have. Any tips or is it just the Winegard antenna+amp? antennaweb has me at 314 to LA stations (which is pretty accurate based on my antenna orientation now), so I believe that puts you west of me. Maybe that's it. Might be worth the money to try that antenna... |
Micawber
Junior Member
Username: Micawber
Post Number: 9
Registered: 11-2005
Rating: N/A
Votes: 0 (Vote!) | | Posted on Monday, December 19, 2005 - 02:27 pm: |
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Thanks.
I bought Winegard because that is what I had before in a VHF/UHF setup with preamp. I could see Santa Barbara Ch 3 most days with that.
I find this antenna is very sharp; a few degrees makes a significant difference. That tells me that the gain on the antenna is very good. And it is supported from the rear of the antenna, eliminating overhang at the south of my house (when the antenna is pointed north) where birds used to roost and "decorate" our patio.
The amplifier is the lowest noise, highest UHF gain I could find. If I remove the amplifier, the KCBS signal goes from 100%+ to 0, even though the amplifier is supposed to be 27 db gain.
That was true for my last setup, too.
What about SD stations?
(Message edited by Micawber on December 20, 2005)
(Message edited by Micawber on December 20, 2005)
___________
Winegard HD9095P
Winegard AP-8275
DVICO HDTV PCI card
|
Micawber
Junior Member
Username: Micawber
Post Number: 10
Registered: 11-2005
Rating: N/A
Votes: 0 (Vote!) | | Posted on Monday, December 19, 2005 - 02:50 pm: |
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Also, the CM7777 is a combination UHF/VHF amplifier? The web says there is a switch to set the connectors to separate UHF/VHF?
___________
Winegard HD9095P
Winegard AP-8275
DVICO HDTV PCI card
|
Bubby
New member
Username: Bubby
Post Number: 5
Registered: 11-2005
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, December 21, 2005 - 10:53 am: |
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The only switch I know of is an FM trap, which is set on from factory. I left it that way. But I see also from the web a "configurable" separate set up. Is that (what is) optimal? Will look into that. For San Diego, my view is blocked by a two story house next door. I have a CM4221 that I might put on top of the 4228 for an outside chance of picking up ABC and CBS(although CBS I get from LA fine). Laying the 4221 against the mast on the chimney, I can get PBS from San Diego solid, but I haven't investigated further. If I can get ABC, FOX will be the only network I cannot get HD, as D* has turned on NBCW for me (though I get KNBC from LA 98% of the time) |
Bubby
Junior Member
Username: Bubby
Post Number: 6
Registered: 11-2005
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, December 21, 2005 - 11:06 am: |
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Sorry, NBC from orientation 137 degrees. Not ABC and CBS. Should also have a chance at KUSI and WB. Since I get NBC from D*, I haven't been in a hurry. It's the 174 (ABC and CBS)orientation that is obstructed. Fox at 153 may or may not be partially obstructed. That is my outside chance. |
Micawber
Member
Username: Micawber
Post Number: 11
Registered: 11-2005
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, December 21, 2005 - 12:33 pm: |
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From your results, I doubt there is a switch problem.
Sounds like you are much closer to SD than I am. Or have a better angle. I have KPBS, KSWB and KNSD at 150 degrees. I have difficulty getting KPBS.
CBS from LA is the strongest station here by far. Today, the signal levels are down on all other channels although CBS, KCET and KOCE continue strong. I find the hot weather to adversely affect reception.
My antenna is very selective; 10 degrees off 340 drops CBS by 20%!
(Message edited by Micawber on December 21, 2005)
(Message edited by Micawber on December 21, 2005)
___________
Winegard HD9095P
Winegard AP-8275
DVICO HDTV PCI card
|
Sean C
Member
Username: Sc88
Post Number: 25
Registered: 07-2005
Rating: N/A
Votes: 0 (Vote!) | | Posted on Thursday, December 22, 2005 - 09:34 am: |
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this is great work, holl_ands! I live in Escondido 92029 and have problem receiving 8.1 and 10.1 (25 and 55 physical). would you mind analyze my location for KGTV or KFMB? my closest cross streets are Ridgegrove Ln and Bernardo Ave (or 11th Ave).
I don't have line of sight to Mt Soledad because of the DelDios mountains near Lake Hodges as mentioned in another thread. I also have a small hill between those and my house: my house is midway on that shadowed slope in the NE direction... that hill is one of the blips above Lake Hodges's mountains in the NE direction, near where 78 and 15 meet.
the XETV map above shows I should get a good signal (gray). but I don't. your KGTV map is just a little small to cover my house... I have no problem receiving anything from the Mt Miguel direction. I just don't get XETV, KGTV and KFMB. my antenna is attic mount yagi due south with a signal amp. yeah I know I should use a pre-amp instead. but it's better than not having it because I have 100ft+ cable run... |
Micawber
Member
Username: Micawber
Post Number: 12
Registered: 11-2005
Rating: N/A
Votes: 0 (Vote!) | | Posted on Thursday, December 22, 2005 - 10:29 am: |
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Just a note on preamps: The big benefit is getting the RF signal high at the antenna without amplifying any noise on the cable, especially on very long runs (like 100 ft).
___________
Winegard HD9095P
Winegard AP-8275
DVICO HDTV PCI card
|
Sean C
Intermediate Member
Username: Sc88
Post Number: 28
Registered: 07-2005
Rating: N/A
Votes: 0 (Vote!) | | Posted on Thursday, December 22, 2005 - 10:55 am: |
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that's a good point. so the signal amp is put in the attic, right at the antenna feed. I used it just to counter the 100ft cable loss. without it I noticed some stations dropping out. I also tried with a pre-amp. with that I could pull in a couple more analog stations than the signal amp. but we don't watch those channels much and it wasn't a big enough improvement to justify the extra $50 (according to the wife). |
Micawber
Member
Username: Micawber
Post Number: 13
Registered: 11-2005
Rating: N/A
Votes: 0 (Vote!) | | Posted on Thursday, December 22, 2005 - 10:58 am: |
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But doesn't the signal amp require a separate power line up to the attic? The preamp would be powered through the coax.
___________
Winegard HD9095P
Winegard AP-8275
DVICO HDTV PCI card
|
Don-RB
Advanced Member
Username: Donrb
Post Number: 2144
Registered: 08-2003
Rating: N/A
Votes: 0 (Vote!) | | Posted on Thursday, December 22, 2005 - 01:30 pm: |
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FYI, an antenna in an attic can lose 1/2 or more of the signal strength compared to locating it outside. |
Bubby
Junior Member
Username: Bubby
Post Number: 7
Registered: 11-2005
Rating: N/A
Votes: 0 (Vote!) | | Posted on Thursday, December 22, 2005 - 02:23 pm: |
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Micawber
Very similar to me. CBS, KCET, and KOCE remain solid all the time. Hot or dry weather leaves me with CBS and maybe KCET and KOCE. So CBS is certainly the strongest. The 4228 is very selective as well. I was able to throw the 4221 up and just point it. With the 4228, I need to make fine adjustments. Although the added gain with the 4228 is worth it. As mentioned before, I will put 4221 on top of 4228 and try to get ABC from SD. If no luck, I will turn it around to LA for what I believe will be added gain. |
Sean C
Intermediate Member
Username: Sc88
Post Number: 30
Registered: 07-2005
Rating: N/A
Votes: 0 (Vote!) | | Posted on Thursday, December 22, 2005 - 03:46 pm: |
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yeah, I get power up in the attic. there's a light and an outlet.
Don,
what makes that attic mount so bad is primarily the stucco - more accurately the metal screen it is applied on. the small elevation of the antenna above that stucco siding is about 3ft. and the roof is concrete slates: bad when its wet. there's also a large metal chimney a few feet to the left of the due south direction. I really need to get this thing out of the attic... but wait, I am on the board of directors for my HOA. hmm. interesting proposition.
I take that 1/2 is -3dB? |
Don-RB
Advanced Member
Username: Donrb
Post Number: 2148
Registered: 08-2003
Rating: N/A
Votes: 0 (Vote!) | | Posted on Thursday, December 22, 2005 - 04:16 pm: |
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Yeah, the loss due to attic is between -3 and -6 dB. You can get a low profile CM4221 UHF antenna and hide it very easily by mounting to a small mast downwards under an eave on the back or side wall - nearly invisible since the CM4221 is only a few inches deep. Doesn't even look like the standard long VHF antennas, so that helps camoflauge it as well! At least try a quick outdoor test, you might be surprised on the difference in signals. I moved mine around and even a few feet difference in location or elevation made big differences especially if you don't have perfect line of sight - you have to find the "sweet spot" |
holl_ands
Advanced Member
Username: Holl_ands
Post Number: 803
Registered: 06-2004
Rating: N/A
Votes: 0 (Vote!) | | Posted on Thursday, December 22, 2005 - 06:15 pm: |
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Various instrumented tests have measured a very wide range for attic loss.....usually more than 10 dB.
Bob Chase (Station Engineer in Houston) measured 15-20 dB in his attic vs roof mount.
A lot depends on how it is constructed:
whether there are any openings in the stucco that could leak some signals into the attic,
whether there is an aluminum mylar "thermal barrier wrap" or foil backed insulation above the antenna (yikes!!!),
how far up the antenna is mounted away from the "floor" of the attic and various electrical wires and metal structures (e.g. rain gutters). |
Don-RB
Advanced Member
Username: Donrb
Post Number: 2150
Registered: 08-2003
Rating: N/A
Votes: 0 (Vote!) | | Posted on Thursday, December 22, 2005 - 11:37 pm: |
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Wow that much, amazing! I know you can get other issues due to reflected and bouncing signals indoors too that makes proper aiming difficult. Better to mount it hidden outside or at least pointing thru a glass window. |
Sean C
Intermediate Member
Username: Sc88
Post Number: 32
Registered: 07-2005
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, December 23, 2005 - 09:07 am: |
|
thanks for the pointers. I will definitely try mounting it outside. there's a spot in the north corner of the backyard, high up next to the fence at about shingle height. I will need to run some longer wire to get there. or I can hang it under the eave on the southeast side wall. that doesn't need nearly as much wires: I may be able to even trim 50ft off that 100ft run. yet a third spot is 3ft off the ground in the south corner of the backyard, hung from a swingset. this spot was tried last time with a CM4228 with a pre-amp, with relatively good results. but I don't recall that it pulled in 8.1 and 10.1 by the USDTV tuner used then. it had trouble tuning in 6.1, fluctuating between 100% to 0% signal.
that southeast side wall is visible from the street. being on the HOA board makes it an interesting proposition for the eave mount. I hate to be the one to "start it" even though FCC ok's it... the backyard mount should be ok. I take that the CM4221 is half the height of CM4228.
that southeast side wall is full stucco up to the eave. there's no aluminum wrap or any kind of thermal wrap on the inside of the roof. all of the insulation is under the antenna. the antenna is about 3ft from the "floor" of the attic (and the top of the stucco walls). there's no rain gutters. I was thinking about installing those in the future... 
now with that souteast sidewall, the antenna will see part of the wall when pointed south, and probably won't pick up much signal from the southwest direction. last time I put the CM4228 next to that wall midway under the eave and it was worse than option 3. I didn't try it higher up though. option 4 is under the eave at the front southeast corner of the garage. but that's very objectionable from the street... |
Sean C
Intermediate Member
Username: Sc88
Post Number: 33
Registered: 07-2005
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, December 23, 2005 - 09:23 am: |
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isn't there anything else that can do as well as the CM4221, and yet look like a satellite dish? that square shooter is close. but I hear that it's not as good as the CM4221, and cost 4x as much. heck, I am thinking taking an old dish large enough but not too large, and put the CM4221 on top of it, and put a gray nylon mesh over the thing if needed. leave or take down the LNB rod. would that setup hurt the performance? if not that's a good business op.
how much is it to encapsulate a CM4221 in circular plastic enclosure that looks like a dish? heck the dish can become the reflector so you would just need the bow ties. I think there are also ways to make the physical sizes of the bow ties smaller.
you guys interested? |
holl_ands
Advanced Member
Username: Holl_ands
Post Number: 804
Registered: 06-2004
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, December 23, 2005 - 12:20 pm: |
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Fibreglass panels are transparent to RF signal.
You could construct a frame (Vinyl or PVC) very inexpensively and connect it either to the rear
of the antenna or as a separate aesthetic screen.
Of course, increased wind resistance means you want a sturdy mount.
===========================================
Kathrein, Scala Division makes the CL-1469B UHF Log Periodic Array inside a radome case:
http://www.kathrein-scala.com/catalog/CL-1469B.pdf
Note the very high Front/Back ratio, which will help to minimize multipath interference.
Scala also makes the K72314 series 4-Bay Panel Antenna which is intended for transmit applications:
http://www.kathrein-scala.com/catalog/K72314%20series.pdf
Unfortuantely, Scala antennas are not inexpensive...
http://www.kathrein-scala.com/contact.htm
Bob Chase used the Scala LPA as his "standard" antenna in various on-air antenna comparison tests:
http://www.avsforum.com/avs-vb/showthread.php?p=5399471#post5399471
As you can see, like most LPA's, it isn't the highest gain antenna, but it's a lot better than a SquareShooter.
FYI: He also used Scala in an attic location vs roof-mounted test:
http://www.avsforum.com/avs-vb/showthread.php?p=5410432#post5410432
which helps to answer the question of how much loss to expect in at least one person's attic. |
holl_ands
Advanced Member
Username: Holl_ands
Post Number: 805
Registered: 06-2004
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, December 23, 2005 - 12:52 pm: |
|
Recotron TV3000 gain specs apparently INCLUDE the preamp, so it's hard to say what the real gain is:
http://www.amazon.com/gp/product/B00000J4BL/103-6312931-7390261?n=172282
Without additional info, I would guess that it is no better than a SquareShooter.....if that....
===========================================
Fol is new flat panel VHF/UHF antenna from First Principles, the TennaCorp Signal Star...but no specs:
http://www.firstprincipals.com/Antenna.pdf
Maybe it's the Recotron.....and maybe it's not....
==========================================
I currently use a DX DTA-5000 Smart Antenna, which requires the Sylvania 6900DTE OTA STB to control it:
http://www.avsforum.com/avs-vb/showthread.php?p=5979741&highlight=6900DTE#post5979741
In the posted on-air comparison test, the DTA-5000 was about as good as a 4-Bay "Hoverman" antenna I've had in my garage for eons.
More recently, I did some comparisons to a CM4228 8-Bay antenna, which showed significant improvment relative to the DTA-5000.
If you want to try an inexpensive "similiar" stand-alone adaptive antenna, you might want to consider the manually controlled DX DTA-3500:
http://www.sadoun.com/Sat/Products/Winegard/DTA3500DX-Antenna-Active-Amplified-Multi-Directional.htm
http://www.amazon.com/gp/product/B00022O9VW/ref=nosim/103-6312931-7390261?n=172282
I doubt that it will be as good as the full adaptive DTA-5000, but it should at least be better than the gain deficient SquareShooter.
=========================================
I found that placing the CM4221 up against a brick wall significantly reduced the signal level.
Rather than simply attaching it to the grounded metal dish, you would probably be better off building (or adapting) something non-metallic.
Of course, your mileage may vary....
(Message edited by holl_ands on December 23, 2005) |
holl_ands
Advanced Member
Username: Holl_ands
Post Number: 806
Registered: 06-2004
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, December 23, 2005 - 02:52 pm: |
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Sean C: Here are RADIO MOBILE runs for your location.
If you had a moderate gain outdoor antenna with a preamp, RM calculates a 50% median fade margin of
about 28 dB for DTV from Mt Soledad. This "should" be adequate to receive them.
However, I would recommend using my Fade Margin Calculator spread sheet to make a more accurate
and complete calculation.
For instance, RM apparently does not support input of antenna gain vs frequency.
Only the PATH LOSS values are used from RM, the rest is tailored for your location.
====================================
The path fortuitiously follows the Lake Hodges river valley....you got luckier than me on that one....
However, that hill just SW of you is 100 foot higher and causes 40 dB of additional path loss....YIKES!!!
If you can get the antenna higher, the signal levels should increase quite a bit.
And of course, getting out of the attic will also help.
 
(Message edited by holl_ands on December 23, 2005) |
holl_ands
Advanced Member
Username: Holl_ands
Post Number: 807
Registered: 06-2004
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, December 23, 2005 - 03:05 pm: |
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Here are KFMB-DT results for standard 10 meter antenna height and if increase to 20 meters:
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Jon Rodriguez
New member
Username: Vc_rod
Post Number: 1
Registered: 12-2005
Rating: N/A
Votes: 0 (Vote!) | | Posted on Monday, December 26, 2005 - 02:00 pm: |
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Hi, all.
I am new to OTA HD reception and am trying to determine what kind of set up I need giving my location.
I live about 1 mile south east of the High School in Valley Center.
I did a little experiment with an indoor amplified antenna - a TERK TV5 and found that with that I could pick up KCVR in San Bernadino with a 65% signal strength (using a DirecTV HR10-250 HD receiver), as well as KTLA (VHF?), but only at 45% or so.....could not get any signal from the San Diego stations...not that I was expecting much from a little indoor antenna. What I really want to do is get the SD stations.
AnntennaWeb says I should be able to pick up the following UHF stations:
DTV Antenna
Type Call Sign Channel Network City State Live
Date Compass
Orientation Miles
From Frequency
Assignment
KVCR 24 PBS SAN BERNARDINO CA 328° 51.1 24
KSWB 69 WB SAN DIEGO CA 161° 39.5 69
KWHY 22 IND LOS ANGELES CA 304° 90.5 22
KPXN 30 i SAN BERNARDINO CA 314° 75.4 30
KXLA 44 IND RANCHO PALOS VERDES CA 304° 90.5 44
KSCI 18 IND LONG BEACH CA 304° 89.6 18
KUSI 51 IND SAN DIEGO CA 161° 39.4 51
KNSD 39 NBC SAN DIEGO CA 161° 39.5 39
KPBS 15 PBS SAN DIEGO CA 161° 39.4 15
KMEX 34 UNI LOS ANGELES CA 304° 90.4 34
XUPN 49 UPN TIJUANA BC 150° 68.5 49
KLCS 58 PBS LOS ANGELES CA 304° 90.2 58
KCET 28 PBS LOS ANGELES CA 304° 90.2 28
I live near the top of the hill at an elevation of 1800 feet. Hill drops away toward the north, but there is rolling terrain toward the south, with one or two larger hills between me and Escondido.
My car's GPS says my Lon / Lat coordinates are
116 degrees 59'4"W and 33 degrees 15'5"N.
GlobeExplorer shows that my address maps to:
Lat 33.2658216689029
Lon -116.994540873239
Holl_ands, was hoping that if was not too much trouble that you could run a signal propagation prediction of what I could be able to get in from San Diego (or if not good that way, from the LA stations on Mt. Wilson).
I have been looking into the following antennas:
Televes DAT-75
a CM4221
or a DB4 or DB8
Would welcome suggestions about which choice would be best and type of signal amplifiers to use.
Thanks for your help |
General over-the-air (OTA) 
DTV Propagation Predictions
DTV Antennas RevC
KBHK-DT Reception Map