Insignia + Question

[cd637299]

Hi all....

Finally I have a DTV that is not the Win card. I purchased 2 Insignia boxes (with pass thru) 2 weeks ago & hooked up one to my bedroom TV yesterday. Very nice, and I thank all of you who recommended it.

Including repeating network affiliates & 2 ION stations + subchannels, I think I get 38 channels now OTA.

Now, a question.

Somehow, when I revert back to analog, now it seems that many of the analog UHF channels don't come in as well as they used to, since the installation....and that also goes for the TV in the living room (using the same antenna), which has not been hooked up yet with my other box!

Does anyone know why this is, or has trouble with this? I am trying to pull in the UHFs that broadcast from the Miami-Dade/Broward county line antenna farm...this includes a few LPTVs. *Is it possible* that these analog stations have now lowered their power, gradually to phase out? Does anybody know of any action/non-action in that area? My antenna is pointed right at them, and the DTVs from that area come in fine, generally.

Any ideas?

cd

[CasualOTAer]

Hi all....
Somehow, when I revert back to analog, now it seems that many of the analog UHF channels don't come in as well as they used to, since the installation....and that also goes for the TV in the living room (using the same antenna), which has not been hooked up yet with my other box!


I haven't heard of stations reducing analog power now. (There may soon be some that turn it off completely before Feb.) They'd have to be careful, or their advertisers might get wind of the fact that they took an action which might reduce the number of viewers they reached.

In the DC area, some stations have digital signals on channels adjacent to UHF channels with analog signals. For the heck of it, you might check (using tvfool.com or your Insignia's manual tuning) to see if the reduced quality UHF stations have one or two digital stations on their neighboring RF channels.

I don't know for certain that digital signals on adjacent channels can interfere with reception of their analog neighbors, but it just might.

Here's another thought. When there is enhanced tropospheric propagation, you may receive digital signal from a remote market on the same RF channel as your local analog UHF stations. If/when this is the case, the effect might be to raise the noise floor level on one or more channels of your analog UHF locals.

Using the manual tuning menu on your Insignia, scroll to the RF channels for the now poorly received UHF stations. Does the Insignia show any DTV signal strength on those frequencies??

The tools on www.tvfool.com would help you check the rf channels of DTV signals in other TV markets within 200mi or so. Look for ones listed on the same rf channel as the Miami analogs. Let us know what you find out.

[cd637299]

Thanx for the info.....apparently I tend to think that there was some brief maintenance on the towers, for the signals were restored late last night. I had no problem then.

Thank goodness....I was starting to think I had to repair my antenna or get a new one!

cd

[Robert Grant]

All of those are -possible- reasons that your analog stations may appear weaker, but, there is one other thing to consider.

There is no perfectly lossless RF device, every inch of coax, every connector, every switch, will incur some RF pass or insertion loss.

Having the weaker analog signals pass through the DTV box is likely producing enough insertion loss to make those stations a little more snowy.

In the case of a box that actually -splits- the RF source into two paths (such as a CECB that lets you watch an analog signal and a digital at the same time, or the traditional analog VCR for recording one program while watching another, unless it has some form of electronic or mechanical switch), the laws of energy state either or both of the paths will have an insertion loss of at least 3dB, and if one path has less than 3dB, the other path must have more.

Case in point is reception of WKBD-DT 14 in Temperance (literally right on the cusp of WKBD-DT's service contour). When I ran the antenna system through a VCR, WKBD-DT was reliable only when trop was in. When the system was plugged directly into the TV, WKBD was 95+% reliable (failure usually caused by co-channel interference from superpowered WCMH-DT Columbus, OH, when trop is in). Eventually I ran the antenna through switches and patch cables (far less lossy) to solve the problem.

One would notice the loss more on UHF, where most of the noise is in the amplifier circuits of your set. There will be loss on VHF, but most of the noise on VHF, especially lowband (often atmospheric, or generated by consumer products) will be lost along with the desired signal, and the picture may look the same.

If a CECB were to have an internal RF amplifier stage, it could overcome this problem (I do not know which, if any, or all, CECBs have such a stage)

Rob Grant, N8NU.

[w9wi]

I haven't heard of stations reducing analog power now. (There may soon be some that turn it off completely before Feb.) They'd have to be careful, or their advertisers might get wind of the fact that they took an action which might reduce the number of viewers they reached.


This (analog power reductions) is happening in some cases, for a number of reasons.

- Station doesn't have enough room (or enough amps of AC service) to hold a full-power analog transmitter and a full-power digital transmitter at the same time. They're reducing analog power to allow removal of some amplifier stages to make room for a more powerful DTV transmitter. (example: WMPN-29 Jackson, Miss.)

- Analog transmitter is failing and the station doesn't want to spend large amounts of money on repairs to a transmitter that will be turned off in six months. (example: WBGU-27 Bowling Green, Ohio)

- Station is installing top-mounted digital antenna for maximum permanent digital coverage - and must move analog antenna lower on the tower to make room at the top. (power usually isn't reduced but antenna height is)

- Temporary reductions necessary for the safety of tower crews installing upgraded digital antennas.

[cd637299]

I tend to think Doug has the idea here, that it may have been a safety issue.

And, for Robert----it had nothing to do with the CECB. I ran the cable right into the other tuner(s) I had.

I had a feeling it was a maintenance thing.

cd

[NN2E]

FWIW I ran a test with the Zenith box (same box as Insignia with a different name on it) and could see little, if any, loss through the box in the pass through mode. I checked several local signals with the Icom R-7000 through the box and then direct to the antenna.
73, Ed NN2E
Owner / Operator - Murphy's Law Test Site & Thunderstorm Proving Grounds