Rear tv not getting same channels as front tv?

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bigP0ppaJ

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We have a 1995 Rexhall Aerbus, but a previous owner retrofitted it with HD flat panels in the front and rear.  On previous trips, it had always worked well with the crank-up antenna, but on this trip, my wife tells me (I don't really watch the tvs while camping) that the front tv was scanning and finding tons of channels at each campground, but the rear tv would only get a few or none.  At one stop, she said the front tv had 34 stations, and the rear tv only had 4.

The equipment I know about is:
- crank-up antenna
- signal booster box up in the front.  It's switched on and the red light is on.
- a switch in the front to switch from antenna to cable.
- a switch in the back to switch from antenna to cable.

My wife says she's tried all combinations of moving switches around and re-scanning for channels.

Is it possible I need a second signal booster in the back?  It's weird that it always worked before and has just stopped working now.
 
We have experienced the same issue. Believe it or not after a lot of telephone time it was learned that the cable was bad!!!

Never would have thought that, but it was.

Try a new cable, loosely, before fishing it through the coach just to be sure.
 
Yeap. Bad cable to rear tv. That includes a broken wire,corroded connector, or an inline splitter somewhere that has died. You might try running a new piece of coax direct to the rear tv, just to verify that the problem can be fixed that way. if the tv then gets more channels, you can start chasing down where the existing cable and connections is bad.

If you have a video switch,  a box that allows you to send different signal sources (antenna, DVD, etc) to front or rear tvs, check that as well. Sometimes they go bad. Bypassing it by connecting the tv direct to the antenna coax is a quick way to tell.
 
Good advice!  I have some long cables at home and will try one out when we get back.  Thanks!
 
Is it possible that when doing the channel scan the antenna/cable setting on each TV is different?
 
Generally RVs are cabled with lowest bidder RG-59.. This is a high loss cable so if the signals are "Marginal" what you see can easily happen.

And as someone noted cables can go bad, connecitons can come lose the crimp on connectors they use if you sneeze hard they pop right off the end of the cable (Ok, not quite that bad)  If you have a matrix switch (Box of many buttons) the switch for TV-2 may be going bad (exercise it with the power off like 50 times,, just press every button in the box save for the two on the left like 20 to 50 times each then turn power back on (left button)

And back to marginal signals... Some TV's are marginal too.. that is, for example. in my RV I have 3 TVs and two digital converters.. the converter in the rear is (per a Broadcast engineer) superior to most of the converters out there when it comes to weak signals. (The one in front he did not know, but from what I see it's no slouch either).

Fact: Many broadcast statsions (AM/FM) need thousands of watts to make it across town.

We Ham Radio types go cross country on a mear 100 watts OR LESS and in fact when I go digital I go around the world with less than half that (Since I have to reduce power due to the 100% duty cycle)  Why can we do with 30 watts what a nearby broadcast station needs thousands to do... Better receivers, better antennas.
(But your basic Winegard Sensar with wingman is one dang fine antenna).
 
Come on! The difference lies primarily in the propagation charactrristics of the different frequencies, not the quality of equipment.

Ernie
 
There are also settings in the tv itself for the channel scan, i.e. scanning for cable channels is different than scanning for air antenna channels. Cable and "air" channels are different and the tv tuner will miss a bunch of channels the proper one is not selected.
 
John From Detroit said:
Why can we do with 30 watts what a nearby broadcast station needs thousands to do... Better receivers, better antennas.
Click to expand...
Think bandwidth and power required - the old ATSC was minimum 4.5 Mhz bandwidth, the NTSC is more bandwidth efficient but still wider...typical HF AM voice BW is 3.5 Khz...dit-dot-dit (CW) is less. Just a simple comparison divide 4.5 Mhz by 3.5Khz is approximately 1300 - multiply that by 30 watts for a line-of-sight (LOS) comparison power required (39,000 watts) for equivalent signal+noise/noise ratio at a receiver.
Also, consider frequencies and propagation characteristics...no sky wave, skip, troposcatter, etc. for TV broadcast. And reliability for TV is almost mandatory whereas amateur radio can be inconsistent.

To point on the subject, if coax is defective it can cause the problem you have...RG-59 and even the higher quality RG-6 can fail and usually at the cable ends or connectors. Check for loose or corroded connecters at each end. Gary's suggestion of running a temporary cable is probably the best method...continuity testing may reveal a problem also - either an open or a short in the cable to the rear TV.
Good Luck!
Bob
 
Also, consider frequencies and propagation characteristics...no sky wave, skip, troposcatter, etc. for TV broadcast.
Click to expand...

Not quite true.  In the '50s I would regularly get a double or even a triple skip on 6 meters (50-54MHz), right in the middle of the VHF TV bands.  I could often talk to CA and FL on 6M with just 50W of power, both required skips to reach.
 
Ned said:
In the '50s I would regularly get a double or even a triple skip on 6 meters (50-54MHz), right in the middle of the VHF TV bands.
Click to expand...
Yea and I could sometimes get skip over 600 miles with VHF 108 Mhz narrowband voice using an 8 Watt transmitter but not reliable as a way to do business :).

 
Had the same problem with our 95 Aerbus on our trip out west. Didn't have new cable but had aluminum foil. I wrapped the coax cable that passed through the closet with aluminum foil and the problem was solved. We now get the same channels on both tvs.
 
I also want to say that I did this because I found that the electrical equipment that is located in the closet was causing interference in the lightly shielded coax cable. I will be changing that cable out before the next big trip.
 
As mentioned previously, bad coax or loose or corroded connections can cause major problems. Here is a link to an article that may be of help for people having reception problems:
https://web.archive.org/web/20130814121735/http://blog.rv.net/2008/06/tech-tune-up-your-tv-antenna

One thing to keep in mind with the Winegard Sensar (aka Batwing) antenna is that the arrow on the knob does not point toward the front of the antenna. The front is actually 90? to the left or right of the arrow.
 

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