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-   -   Can't get two strong channels in Denver (http://forum.tvfool.com/showthread.php?t=16681)

Mike4565 25-Sep-2019 5:56 PM

Can't get two strong channels in Denver
 
SIGNAL ANALYSIS - http://www.tvfool.com/?option=com_wr...9038cfbeda1962

ANTENNA - Winegard 7694 (was recommended here). Aimed to about 280deg, turned to provide best picture, on rooftop mast about 25 feet high

PRE-AMP - CM Amplify adjustable (two settings) on the mast, power inserter is about ten feet further downstream.

DIST AMP - CM 8-port, made no difference good or bad, disconnected

OTHER - There are some trees and buildings in the LOS. Long cable run (100') from antenna to 6-way splitter, then to 5 or 6 sets.

As you see on the report, all major channels are located together less than 20 miles away on a mountaintop, and all appear to have good strength. BUT - while we receive most of them well most of the time, we can almost never get TWO stations (Ch 4.1/ real 35 and 20.1/real 19).

At Channel Master's suggestion we added their adjustable pre-amp; two of the sets now get 4.1, but only sometimes; and, curiously, if the signal is initially good, it degrades over time to frozen/pixelated/unwatchable. The other sets continue to show those two channels as "weak," "unavailable," or just a blank screen.

I realize that, theoretically, we shouldn't have to use a pre-amp or anything else, and that doing so risks overpowering these strong signals. But there seems to be no adverse affect on the channels we do receive, with only an inadequate bit of improvement on the two we don't. I've even tried attaching the incoming cable from the antenna to each set by itself, which should provide the strongest unassisted signal - but even that doesn't deliver the two missing channels.

The engineer at 4.1 (CBS affiliate) was unable to suggest why his signal is somehow different, or to otherwise explain why all the other channels broadcast from the same location and with the same strength reach us just fine but his doesn't.

We are willing to try a different antenna if there is a good chance that will help, but it will be a pain to take down the mast to make the switch. We are unlikely to start replacing TV sets to see if a different brand/model/etc works better than another.

What explains why we cannot reliably or consistently receive two channels that seem, at least on paper, to be absolutely no different than those we do receive well? Is there any hope of a solution that we've not tried?

Thanks for your help...
Mike

Tim 25-Sep-2019 7:33 PM

Have you tried just one TV as close to the antenna as you can get with no amplification? With maybe just 25 ft or so of coax cable? That would give you an initial baseline to start from. (I had to take a TV outside when I installed my system, but it gave me a really good picture of what my antenna was capable of.)

Can you get the antenna higher to clear the trees and buildings in LOS?

Looking at rabbitears.info, it shows KTVD 20.1 on real channel 31, not 19. Which is correct?

Can you do a report on rabbitears and post a link to the report? https://www.rabbitears.info/searchmap.php

Sometimes moving an antenna up or down or side to side just a couple of feet makes all the difference in the world.

Tower Guy 25-Sep-2019 8:02 PM

I would start with diagnosing for a basic system failure.
Things to consider are:
Water in coax
Bad balun
Proper assembly of the antenna
Crushed coax
Faulty F connector

If these are OK, interference might be the cause. Possible causes could be:
Cellular interference
Electrical interference
Noisy computer or charger
Faulty battery charger for household tools
RF emission from solar panel inverters
Oscillations from a faulty amplified FM antenna

All of these possible causes require trial and error detection along with patience and some logic.

Once you find the problem you should not need the preamp.

Good Luck

rickbb 25-Sep-2019 8:27 PM

The report shows that channel 20, RF 19, KTVD has a co-channel warning with channel 19, KSBS, (no RF listed). That may be why you can't get that one.

I can't see any reason why you can't get 4, unless there is a strong FM station nearby overpowering it's signal.

A cheap FM filter/trap would be an easy thing to try.

Also try looking up your channel map on rabbitears, the database here is old and not well maintained. They may have more up-to-date info.

Mike4565 25-Sep-2019 11:17 PM

Thanks for your questions and suggestions...

Here's a link to my rabbitears report:
https://www.rabbitears.info/searchma...study_id=14610

The FCC shows the RF channel for KTVD 20.1 as 19 in one place, and 31 in another:
https://publicfiles.fcc.gov/tv-profile/ktvd
https://publicfiles.fcc.gov/find/ktv...-match/filter-[]/
https://publicfiles.fcc.gov/api/mana...e39e28172c.pdf

I'm unable to raise the antenna to clear the stuff in the LOS. WRT other possible causes - do they affect channels differently? None of those things appears to be affecting the other stations we receive, which broadcast from the same place, and with signals of similar strength, to the two stations that are being pesky.

Mike


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