View Single Post
Old 17-Aug-2016, 12:44 PM   #6
Retired A/V Tech
Join Date: Aug 2012
Location: S.E. VA
Posts: 2,738
Good detective work, Nick! You have found the source of the problem.

LED lights and CFL lights can cause interference.

They raise the noise level on VHF which reduces the SNR of the signals to less than the minimum of 15 dB required.

You will need to experiment and move the antenna away from the interference source to find out how far away is needed.

That type of interference affects VHF signals more than UHF signals because it is usually weaker as the frequency increases for the higher channels.

It can be radiated through the air, conducted through the power lines, or both. I suspect it is mostly radiated through the air in your case. When it is conducted through the power lines, a power line filter can help when placed on the AC line to the lights or on the TV reception equipment.

Sometimes you can use a battery operated portable radio tuned to a vacant frequency on the AM broadcast band to listen for interference. Try the low 550 end first, and then the 1600 end. The antenna in the portable radio can act as a direction finder. You can also listen on a portable radio that can tune the VHF Aircraft band, which is also AM. An FM radio doesn't work as well.

Forum member MikeBear had a similar VHF interference problem that was caused by a battery charger; he listened on his car AM radio.

One channel issue, high VHF

Originally Posted by MikeBear View Post
Ok, I did find heavy interference (buzzing) on AM band at 530. It starts as I drive into my 220' long driveway, and stays as I get into my garage. This parallels the power line wires going to my house.

Anyway, I read on Denny's antenna site (he's only about 35 miles from me) about another person that unplugged a "power tender" charger, and got rid of the interference. I also have a $20 Harbor Freight power tender charging a battery in my garage. I unplugged it, and the AM interference stopped IMMEDIATELY!

My wife is watching tv right now, so I can't check VHF 12 to see if this did anything for that issue. However, since my car radio could pick this up from over 200ft away, I'm betting (I hope!) it might now be cured.

Does/can interference like this actually BROADCAST itself along the incoming utility power cables?
If you can not measure it, you can not improve it.
Lord Kelvin, 1883

Last edited by rabbit73; 17-Aug-2016 at 1:15 PM.
rabbit73 is offline   Reply With Quote