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Old 1-Aug-2012, 3:13 PM   #1
thom
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DB4e, the 100 mile club, and periodic loss

(ok, just a couple miles short of 100, but close enough)

Hi All,

Wanted to post some interesting results along with a question. First up, TVFool report here:

http://www.tvfool.com/?option=com_wr...9900d72a6a6117

I'm getting a good picture across the UHF spectrum including KCET (220kW) and KOCE (1000kW). Generally in the 60's and above, and for some channels, pushing into the high 80's (100 scale).

I don't pull any VHF from the 313 bearing, but I do get a surprisingly usable picture (60's) on VHF 8 and 10 from the more than 90 degree off-axis 197 degree heading. Pointing the DB4e directly at 197 yields little to no signal for those.

I have a single DB4e, no splitters, no amplifier (PA-19 is in the mail), and 100 ft of RG6 to a Series 3 Tivo with dual tuners.

The cable is grounded at the lightning block. The mast is not (yet) grounded (doing it this weekend!).

So impressive results, but I do get a periodic droop that seems to affect all the 313 degree stations. I can have a signal in the high 80's that over about 10 seconds will gradually droop to 0, stay there for another 10 seconds, then return to the high 80's in the next 10 seconds. The time between droops is usually around 10 minutes. Will the PA-19 preamp help even this out? My plan is to get a second DB4e for the 148-163 heading, combine them with a Winegard CC-7870, and amplify the 313 degree antenna.

Thanks for any thoughts or insight!
Thom
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Old 1-Aug-2012, 7:09 PM   #2
teleview
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Tv Reception.

Above the roof Install a Winegard HD7084P antenna with a Winegard AP8700 preamp aimed at about 335 degree magnetic compass reading.

Above the roof install a Winegard HD7696P antenna with a Winegard AP8700 preamp aimed at about 150 degree magnetic compass.

If both antennas are on the same mast , put the HD7084P on the bottom and the HD7696P antenna on top , separate by about 3 feet.

Here is how to aim antennas , http://www.kyes.com/antenna/pointing/pointing.html.

If required , here are Strong and Sturdy antenna mounts , http://www.ronard.com/909911.html , http://www.ronard.com/34424560.html , http://www.ronard.com/ychim.html , http://www.ronard.com.

Buy the ronard antenna mounts at solidsignal by typing the word ronard in the soldsignal search box.

Here are some places to buy antennas and etc. , http://www.solidsignal.com , http://www.amazon.com , http://www.winegarddirect.com.

The 2 Tv antenna systems Will Not be connected to gather on to one coax.

The 2 Separate antenna systems Will Be separate all the way to the location of the Tv.

The 2 separate antenna systems coaxes will be connected to a A/B antenna switch , http://www.radioshack.com , #15-1968 , or , http://www.mcmelectronics.com , #32-4425 .

A/B antenna switching is channel surfing friendly , push the button on the hand held remote control , changes antennas and keep on channel surfing.

If more then 1 Tv is connected use , http://www.hollandelectronics.com , also available at , http://www.solidsignal.com , HFS-2D , HFS-3D , splitters

The other way to do it is put the HD7084P antenna on a rotor.

Antenna rotors are not channel surfing friendly , must wait for antenna to rotate.

Last edited by teleview; 1-Aug-2012 at 11:58 PM.
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Old 1-Aug-2012, 7:36 PM   #3
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My first thought is, you're doing extremely well. Reception of distant signals is expected to be a challenge as you're describing. You're dependent on the atmosphere to act as a reflector to guide signals... but because atmospheric conditions change with time of day and as weather systems move through, you have no control over one of the most important parts of the signal path. There are also formidable mountain ridges blocking and scatting signals from the LA area.

I expect the CPA-19 preamplifier will help by eliminating the effects of the cable and splitter losses in your distribution system.

Go ahead, try the CC-7870, it's not too expensive and if it does what I expect, can be removed easily. The problem most people encounter with unfiltered antenna combining (simple reversed splitter and phasing harness methods), stems from the fact that both antennas receive signal from directions other than the few you would prefer. When the output of each antenna is mixed together, the signal from one antenna may add positively but on average, in half the cases, adds negatively and has the effect of being an interfering signal. Then in most cases, the antenna aimed away from a station, also receives a strong version of multipath reflections which increases the chance that the combined signal will be lower in quality if not lower in level.

In the cases where co-channel interference is an issue, the signal from an antenna aimed away from the desired station is far more likely to cause trouble when combined with the preferred antenna output.

If I were going all out, starting from nothing, The DB4e would be an excellent antenna to face southward. An Antennacraft Y5713 would be my choice for making the high-VHF signals reliable. I would combine the two antennas with a UVSJ and try running with no amplifier. If one proved necessary, an Antennas Direct CPA-19 or Channel Master CM-3410 would be on the short list. For the LA signals I would consider using a long boom Yagi such at the Antennas Direct 91XG or a Winegard HD9095P... plus an Antennacraft Y10713 each fitted with separate CPA-19 preamps. I would combined the amplified outputs with a UVSJ. Because this is a 'dream' system, I would mount all of this on a tower that clears all obstructions, and rotate the LA/DX antennas using a HyGain AR-40.

There are several approaches to solving the signal combing problem:
http://forum.tvfool.com/showthread.php?t=820
http://forum.tvfool.com/showthread.php?t=2882
http://forum.tvfool.com/showthread.php?t=8275

Last edited by GroundUrMast; 2-Aug-2012 at 12:31 AM. Reason: punctuation, clarify unfiltered combining
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Old 2-Aug-2012, 3:08 PM   #4
thom
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Thanks for the responses

One more data point, last night I was pulling an inexplicable 98 on KNBC. Is the amplifier going to cause problems here when the stars align, and I'm getting a golden signal?
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Old 2-Aug-2012, 4:06 PM   #5
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Tv Reception.

There are , Tv Dxers , on the internet , it is a hobby and some are stone cold serious about Tv DX , they are after the signals that are impossible to get.

Type , tv dx , in the google search box.
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Old 2-Aug-2012, 4:50 PM   #6
No static at all
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Quote:
Originally Posted by thom View Post
One more data point, last night I was pulling an inexplicable 98 on KNBC. Is the amplifier going to cause problems here when the stars align, and I'm getting a golden signal?
You have nothing to worry about. It takes a LOT more signal to overload than you are dealing with at your location.
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Old 2-Aug-2012, 5:38 PM   #7
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Several points:

Signal meter's on TV sets don't directly measure the strength of the signal, they generally measure the quality of the incoming signal by calculating the error rate of the data packets. A low-strength but high quality signal will get a higher score than a strong signal with impairments that cause decoding errors.

The DB4e is designed for UHF. During field trials that I did early last year, I did observe that any VHF reception it exhibited was well off boresight, usually between 40 and 75 off the straight ahead direction. If your angles happen to line up so that La Jolla is in that off-axis direction, the odds of picking up channels 8 & 10 improve.

Be advised that there's nothing special about the CC-7870. It's just an old-style wire-transformer splitter (and not a very good one, at that) with some packaging. You'd do far better to pick a simple splitter with an internal glass strip design.
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Last edited by ADTech; 2-Aug-2012 at 5:46 PM.
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Old 3-Aug-2012, 3:19 AM   #8
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glass strip?

Thanks for the info. Good to know.

Can't find anyone who describes their combiner as using a glass strip design. Would the CHANNEL PLUS 2512 or the splitters listed on the AD site (i.e. can they be used as a combiner as well?) fit the bill?
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Old 3-Aug-2012, 9:30 PM   #9
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Our splitters are clearly described as "glass PCB micro strip design" on our website.

I'm sure there are others of similar construction but I have no information one way or the other, off hand.
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Old 4-Aug-2012, 2:46 AM   #10
thom
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splitter v combiner

Ha ha, it certainly does, but my question on the AD splitters was whether or not they could also be used as combiners. For some reason most vendors scrupulously avoid indicating their splitters can also be used as combiners (with the exception of VHF/UHF combiners). That's how I wound up with the CC-7870 in the first place.
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