Partial OTA reception problem

[mkatts]

A couple of weeks ago I had posted that I was having spotty reception on some of my OTA's and i corrected it by tightening up some connections to the ant.

Well earlier this week, I lost NBC completely with no change to the reset of the wiring or ant. signal power hangs out around 10-15. All other channels are ok.

So I start eliminating possible causes again only to not have any luck fixing my problem.

I should mention that I have the Winegard Sensar 2000 ant with no diplexors. The signal comes into the house, into an 18v power injector, then to a splitter, sending one line upstairs and one to the living room. I have no nbc on either box.

I don't have a mutilmeter to verify what voltage is coming out of the injector. But when I unplug the inject, nbc comes in strong with a 65 signal strength. I plug it in and the signal drops to 15. To complicate the matter, without the power injector, i can't get abc, cbs or fax. But with the inject I can't get nbc but I get abc, cbs and fox.

Any ideas before I venture into a possible service call with Voom?

 

[mikekohl]

You have not indicated which frequencies you are using for local reception.
Are your locals UHF or VHF, and are some analog rather than digital?
If the NBC station is higher powered and closer to you than the others, connecting an amplifier may boost its level to the point of causing an overload. Other issues may involve widely spaced transmitters that
must have separate antennas for proper reception in your location.
Unless you are in a market where all stations are on the same tower,
there will be some compromises when attempting to use one antenna
to get all stations.

You may need a "real" technician out there with some street smarts about off-air reception and local knowledge about where each station's transmitter is located; hopefully not someone armed with the biggest antenna possible and extra amplifiers to sell. Sometimes it is about filtering BEFORE doing any amplification, possibly use of multiple directional antennas, THEN attempting to get all off-air signals balanced so they are all fairly equal in signal strength before processing.

Good luck!

Mike

 

[mkatts]

attatched is from antennaweb.org

All stations are digital. I don't know the exact power but I know that cbs is the highest power with nbc a close second, abc and fox are a low power. This info came from my installer though, so take it with a grain of salt.

The reason I didn't mention any of that, was I don't believe the problem to be with the channels themselve, frequencies or uhf/vhf. Direction of ant. You can see from the picture that nbc, cbs, abc and fox are all only a couple of degrees off from each other. A week ago, all 4 stations had a 50-70 signal strength. Now it's only nbc that gives me a problem. The ant has not moved. When i got it right, I marked it to keep track. So a week ago i loose nbc. It's in the guide just a low signal. I take the amp out and boom perfect signal. If it was any of the info that you asked about, wouldn't have been happening all along?

 

[mikekohl]

How many miles are you from the transmitters?
Here in Wisconsin, at 45 miles away from Madison, and
partially blocked by terrain, I see some fluctuation due to
propagation changes. And sometimes (late at night)
I have seen a station purposely drop their power.
Unless they are doing maintenance at a common transmitter
site, the problem is likely in your wiring / preamplifier.
IF you are within 15 to 20 miles of transmitters, there is little
reason to have a preamplifier, provided you have a good outdoor
UHF antenna. You might consider taking a short jumper coax with
appropriate transformer and connect directly to your digital tuner
(brought outside with a TV set to see if the signals are getting
to your antenna at all). If it works out there, go down the line
until you get indoors. What happens if you bypass the preamp and the
power supply with a pair of barrel (F-81) type splice connectors?
My money is on the preamp or one of the antenna connectors into it.
But see how things work without a preamp.

Mike

 

[mkatts]

well as I said in my original post, if i remove the injector, nbc comes in great. but i loose the other. If I put the injector back in, i loose nbc and gain all the other back.
To take it a step further, i don't even have to remove the injector from the path, to get nbc in. all i have to do is remove power. but then i still loose abc, cbs, and fox. the minute i put power back to the injector, i get abc, cbs, and fox back but loose nbc.

So there is something going on, either with the injector, or the ant amp that the two of them are not playing nice. the injector is a channel master, S037 ant. amplifier. 18v output.

we haven't had any lightening strikes or anything like that. The injector's power supply is not on any type of surge protector, so it's possible that it took some sort of power surge. I am going to bring my multimeter home from work and see what kind of voltage it's putting out.

I took a picture of the amp too. And befre anyone asks, yes it is connected correctly. I have triple, triple checked.

 

[snappingfish]

[VOOM] Re: Partial OTA reception problem

Two suggestions:

1. Go to this web page:
http://www.avsforum.com/avs-vb/forumdisplay.php?s=&forumid=45
On the right hand side of that page, there is a "search this forum"
box. Type in the name of your city and click the "go" button. See
if there is a thread discussing local OTA reception for your town.
Many times local TV station engineers participate in those forums.

2. Call the engineering department of your local NCB station. Ask
them if they recently increased the power on their digital
transmissions. It's quite possible that it was increased and it is
now overloading your current setup.


--- In VOOM@yahoogroups.com, mkatts <mkatts.18ssin@n...> wrote:
>
> well as I said in my original post, if i remove the injector, nbc
comes
> in great. but i loose the other. If I put the injector back in, i
loose
> nbc and gain all the other back.
> To take it a step further, i don't even have to remove the injector
> from the path, to get nbc in. all i have to do is remove power. but
> then i still loose abc, cbs, and fox. the minute i put power back to
> the injector, i get abc, cbs, and fox back but loose nbc.
>




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[Ilya]

Looking at you antennaweb attachment, the NBC is only 14 miles from you and if it is indeed one of the strongest stations, as your installer said, Mike's "overload" theory makes sense. I am not familiar with your OTA amplifier, but I wonder if there is a way to decrease the amplification in it?

 

[jawilljr]

If it is an overload problem on NBC, then I would try to use a Radio Shack Attenuator. Attach it inline with your OTA and slowly adjust from Min to MAX attenuation to see if NBC comes in. Hopefully you can find a setting to receive all of your stations.

Jerry

 

[mkatts]

I'll give it a shot. Thanks all for the suggestions!!!