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Over the air tv interference
- Thread starter 455monte
- Start date
I had a similar problem with a large TV antenna mounted on the same mast as my 5/8th wave. Radio was even messing up TV channels that had no harmonic relationship to the frequency in use. I added two back to back signal diodes with a 27 MHz. trap on the input of the 20db pre-amp.
All needed parts were donated by an old blown up mobile CB. The two 1N4148 diodes were easy to find on the board. The final stage tuned output circuit was repurposed as the trap. Just a coil and cap in series, with the two diodes also across the pre-amp input. The coil or cap are adjusted for resonance at 27 MHz. to provide minimum interference.
Another trick is to use a more directional TV antenna that is mounted in a location so that when in points at the TV stations, one of the back corners of the TV antenna, faces the CB antenna. This places the CB antenna in the least sensitive area of the TV antenna, since reception on their back corners is much weaker than any other angle.
There is also a big difference in TV pre-amps. While you don't need an expensive one, some of the cheapest ones (under $10) are fairly poor performers that suffer from lots of interference and overload. On the other hand, there are some very good ones between $12 and $20 available from online places that specialize in TV reception.
I've had very good luck with the rectangular metal boxes that offer 20db gain with a variable. Some models like this have a switchable FM trap but, that option was not very useful and some were tuned wrong so that they attenuated the TV signal too. It is best to locate the pre-amp as close to the TV antenna as possible so the cable does not pick up more interference for the amplifier to boost.
All needed parts were donated by an old blown up mobile CB. The two 1N4148 diodes were easy to find on the board. The final stage tuned output circuit was repurposed as the trap. Just a coil and cap in series, with the two diodes also across the pre-amp input. The coil or cap are adjusted for resonance at 27 MHz. to provide minimum interference.
Another trick is to use a more directional TV antenna that is mounted in a location so that when in points at the TV stations, one of the back corners of the TV antenna, faces the CB antenna. This places the CB antenna in the least sensitive area of the TV antenna, since reception on their back corners is much weaker than any other angle.
There is also a big difference in TV pre-amps. While you don't need an expensive one, some of the cheapest ones (under $10) are fairly poor performers that suffer from lots of interference and overload. On the other hand, there are some very good ones between $12 and $20 available from online places that specialize in TV reception.
I've had very good luck with the rectangular metal boxes that offer 20db gain with a variable. Some models like this have a switchable FM trap but, that option was not very useful and some were tuned wrong so that they attenuated the TV signal too. It is best to locate the pre-amp as close to the TV antenna as possible so the cable does not pick up more interference for the amplifier to boost.
Ok guys now that i have the interference issue solved let me ask another question.
When i have rf all the way up on the anytone i get a s4 noise floor.
When i unscrew the coax from radio and pull out slightly but leaving the center conducter stuck partially in the radio, the noise floor drops.
So how do i drop my noise floor permanently so i can hear more stations?
When i have rf all the way up on the anytone i get a s4 noise floor.
When i unscrew the coax from radio and pull out slightly but leaving the center conducter stuck partially in the radio, the noise floor drops.
So how do i drop my noise floor permanently so i can hear more stations?
The easiest thing to do is turn the rf gain down so it's not as noisy. Modern radios are made this way for some reason. The old President Madison and Cobra 148 have the best receivers in this regard.
Shadetree Thats what ive been doing.
The rf gain is around probably 85 percent and sqeulch at 2 to 3. To silence the noise.
When i use auto sqeulch i get sporadic signals.
I was wondering if 1 of those myantenna common mode chokes would help drop a s point or 2. 90 bucks is a lotta money for me to not know for sure if it will help
The rf gain is around probably 85 percent and sqeulch at 2 to 3. To silence the noise.
When i use auto sqeulch i get sporadic signals.
I was wondering if 1 of those myantenna common mode chokes would help drop a s point or 2. 90 bucks is a lotta money for me to not know for sure if it will help
My experience is that chasing noise abatement solutions works (mobile, for me), but it starts to get expensive.
PALOMAR ENGINEERS has plenty to look through on their website. Doesn’t always reveal itself on first go-through. See articles, first. Then go through from different start points.
I’ve spent quite a lot there and am happy at the effect received. But, to tally up the many purchases is $$$$. (My excuse is that I have four vehicles — big truck, pickup and two cars plus an RV).
.
PALOMAR ENGINEERS has plenty to look through on their website. Doesn’t always reveal itself on first go-through. See articles, first. Then go through from different start points.
I’ve spent quite a lot there and am happy at the effect received. But, to tally up the many purchases is $$$$. (My excuse is that I have four vehicles — big truck, pickup and two cars plus an RV).
.
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