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Old 29-Oct-2019, 6:15 PM   #1
digitaljunkie
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Fringe reception help

Hi Everyone,

I'd appreciate anyone who could review my scenario as follows and provide me with your thoughts and guidance. Thanks very much!

I recently installed a 72 DMX tower. I use an 91XG UHF yagi and Stellar Labs 30-2476 VHF antenna. I run them through the RCA pre-amp. It was my intent to use a CM7777 pre-amp, but I've had poor luck with both out of box issues as well as reliability/durability issues so went with the RCA as it has a nice dual VHF/UHF connector. I have a straight run of 100' of RG6 from the antenna into the television.

TV fool report is here -

http://www.tvfool.com/?option=com_wr...903892f8fac321

I receive all of my local channels with no issues.

It was my hope to receive the Detroit and mid Michigan channels with more regularity during non tropo events. All of these transmitters are between 100 and 110 miles of my location and are TROPO only according to tv fool.

With my current set up and tower height, I always have an active signal on these channels, however, it often has drop outs and signal fluctuations ranging from 0 60 % strength - (there are some variances where I can get a good lock generally late at night in favorable weather and this is during non TROPO events when there is tropo I receive all Detroit transmitters easily). I know Im on the extreme edge of reception at these distances, however, with a constant signal there, Im wondering if there is anything else I can do to solidify these stations? Or, am I simply too far away and terrain prohibited from expecting any further enhancements?


Thank you,
Jamie
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Old 29-Oct-2019, 8:51 PM   #2
GroundUrMast
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You're doing remarkably well as is. I doubt that quadrupling the height of your antennas or replacing them with custom built designs that added 10 dB of gain compared to what you already have would give you much improvement. It simply boils down to the variability of the path those distant signals have to travel.

Having given my two cents, please don't let me discourage you from experimenting... I find that to be more entertaining than much of what I see on TV.
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Old 29-Oct-2019, 11:33 PM   #3
rabbit73
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Quote:
Originally Posted by digitaljunkie View Post
TV fool report is here -

http://www.tvfool.com/?option=com_wr...903892f8fac321

I’m wondering if there is anything else I can do to solidify these stations? Or, am I simply too far away and terrain prohibited from expecting any further enhancements?

Thank you,
Jamie
Hello, Jamie. Thank you for the report.

For comparison, here is a report from rabbitears.info that is based on my guess of your location:
https://www.rabbitears.info/searchma...study_id=23734

This is an extract from that report:


That's an impressive tower. I agree with GroundUrMast, you are doing very well but have reached the point of diminishing returns. It would require a lot more effort even for a small improvement.

I assume your 7777 is the second version with only one antenna input. My favorite was the original 7777 with two antenna inputs.

The RCA TVPRAMP1R is attractive because of its low price and two antenna inputs. I ordered two new ones in sealed boxes and they both failed. There are many reports of poor quality control. I'm not willing to recommend it without a note of caution. You got a good one.

The 7777 with one antenna input was rated at 30 dB gain. The one CM sent to me measured about 24 dB. I think they made a silent design change because they had so many returns which were not only from failure but from overload in strong signal areas.

I have two of the 7777HD Amplify preamps with adjustable gain (30/17dB). The are quite stable and I use them indoors as test amps. The enclosure for the 7777HD doesn't look suitable for outdoor use, but it could be put in a housing with the coax leads coming out the bottom. My impression of the 7777HD is that it is a better quality amp than the 7777 with one antenna input. It looks like it was made in the same factory as the CM distribution amp, which are very reliable.

I had some concern about the 7777HD because it operates on 5VDC, but the measurements I made indicated that if you keep the voltage at the amp above 4 VDC, you can go out much more than 100 ft.

Having a preamp with two inputs for UHF and VHF isn't that big a deal, because a UVSJ has a very low insertion loss when used to combine a UHF and a VHF antenna before a preamp with a single input.

It is possible to switch to a preamp with a lower Noise Figure like the Kitztech 200, but I'm not convinced it will make your distant signals much more reliable. Ultra low noise preamps are more sensitive to static damage, but protective diodes are now being inserted to protect the input.
Attached Images
File Type: jpg digitaljunkieTVFreportRE2.jpg (467.5 KB, 245 views)
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Last edited by rabbit73; 30-Oct-2019 at 3:23 AM.
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Old 29-Oct-2019, 11:53 PM   #4
JoeAZ
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With repack, you will probably lose those few U.S. stations
you intermittently receive. I also understand CRTC is working
with the F.C.C. to reduce U.S. television signals into Canada.
Apparently CRTC cites canadian broadcasters being unable to
compete with the U.S. programming. You already probably
know that CBC and others are barely viable, financially.
Stations in border cities will be expected to significantly reduce
their coverage into canada. Buffalo, N.Y. is expected to be
one of the first markets to test sometime in 2021, possibly
earlier.
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Old 30-Oct-2019, 12:19 AM   #5
rabbit73
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These are the Repack changes for Detroit:
https://www.rabbitears.info/repackch...=&lss=&status=

Phase 8 is 1/18/2020 to 3/13/2020.

This is the map for 73 feet:



I had to set the antenna height to 500 feet before the green signal line to Bay City would come on. The Detroit lines didn't come on:





The red marker is your location.
Attached Images
File Type: jpg digitaljunkieTVFmap72ft.JPG (115.9 KB, 236 views)
File Type: jpg digitaljunkieTVFmap500ft.JPG (117.7 KB, 238 views)
File Type: jpg digitaljunkieTVFcovWXYZ.JPG (199.9 KB, 232 views)
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Last edited by rabbit73; 30-Oct-2019 at 12:48 AM.
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Old 30-Oct-2019, 11:45 AM   #6
RMinNJ
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I can only add that the RCA preamp I brought (because it can act as a VHF/UHF combiner) did not work at all...the quality control is consistent with the amazon reviews.
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Old 30-Oct-2019, 12:46 PM   #7
digitaljunkie
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Thank you everyone for your thoughts. I too was thinking I had pretty much maxed out my results currently.

The 7777 pre amp I had was the single input. My main consideration was whether this unit with the extended gain may enable a little more stability on some channels but it sounds like the gain would be minimal.

I don't see any issues here with the re-pack as there is only the one channel moving to RF20 that may cause some disruption with OMNI. All others from Michigan moving will be slotted into open RF's.
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Old 30-Oct-2019, 3:19 PM   #8
Tower Guy
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If you want more reliability you need more antenna gain. One way to go would be to construct a gang of four 91 XG antennas. That will help the UHF stations. It would not help WJBK.

More info here:

http://www.hdtvprimer.com/antennas/ganging.html
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Old 30-Oct-2019, 3:36 PM   #9
digitaljunkie
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Thanks tower guy. I did actually think of that. Would be a bit of a job to install. Is there a simple formula to determine the gain provided by ganging 2 vs 4 91XG's?
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Old 30-Oct-2019, 5:56 PM   #10
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Quote:
Originally Posted by digitaljunkie View Post
Thanks tower guy. I did actually think of that. Would be a bit of a job to install. Is there a simple formula to determine the gain provided by ganging 2 vs 4 91XG's?
Doubling the antennas will in theory double the total received power... Expressed logarithmicly, that's 3dB. In practice you also have to consider loss in the cabling and combiner network as well as the fact that each antenna may not actually receive an equal amount of energy. 2 to 2.5 dB of gain would be a realistic estimate for properly ganging two identical antennas.
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If the well is dry and you don't see rain on the horizon, you'll need to dig the hole deeper. (If the antenna can't get the job done, an amp won't fix it.)

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