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Radio interference from towers.

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Old 10-28-2013, 07:18 PM
  #1
buzzby
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Default Radio interference from towers.

I have had several hits while flying at my field and have crashed some planes. I am running 72 MHz radios, is the any chance I could be getting some bad interference? I'm not the only one that has had this problem at my field. I can see 4 towers from the field. Is there any way to check this?
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Old 10-29-2013, 03:20 AM
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Use this link: http://www.antennasearch.com/

It'll list all towers and antennas with a 4 mile radius of the address you type in. You then look at each tower and find out if it has a transmitter on 72 MHZ. These FCC LEGAL transmitters are primary users and we as R/C pilots use the secondary channels between the legal ones.

If your radio system is slightly off frequency, it has a chance of listening to the LEGAL transmitter rather than yours.

My advise? Switch to 2.4 GHZ ASAP!!!

Last edited by pettit; 10-29-2013 at 03:23 AM.
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Old 10-29-2013, 04:14 AM
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If the electrical field is high enough it can saturate the AVC (automatic volume control) circuitry on any receiver (2.4GHz as well as 72MHz and others). This is highly unlikely but possible if you get very close to the transmitting antenna(s). All good receivers have an AVC circuit else you could not have the variable range on your low powered rig.
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Old 10-30-2013, 03:46 AM
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I have never had any problems on 2.4-I have had several issues on 72-not only interference but also being shot down by another flyer-
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Old 10-30-2013, 04:10 AM
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There have been some instances on 72 and a few unexplained on 2.4. There is a tower with cellular and microwave about 1-2 miles away and a building close-by that has a wireless alarm system. Some planes on 72 and 2.4 have been hit hard at times ...very few times but they have happened and all in the same location . I still have a few planes on 72 and only two have been hit ;one only gets a wobble for a second and then comes back while the other went crazy but was recoverable after gaining altitude away from the offending signals. So yes antennas,cellular,wireless,WIFI can affect radios.
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Old 10-30-2013, 04:47 AM
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After years and years of radio hits @ Sepulveda basin and theories galore,, it comes to light that a mean little man named John Kim was intentionally shooting people down. Funny thing was I was always nice to the guy and never had radio problems,, But other guys that made fun of him and gave him grief had issues over and over. Never discount a disgruntled ex club member or club outcast.

Good luck
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Old 10-30-2013, 09:15 AM
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Quote:
Originally Posted by buzzby View Post
I have had several hits while flying at my field and have crashed some planes. I am running 72 MHz radios, is the any chance I could be getting some bad interference? I'm not the only one that has had this problem at my field. I can see 4 towers from the field. Is there any way to check this?
There is the possibility of harmonic mixing. Different frequency services mounted on the same tower can mix to form harmonics. That phenomenon can easily explain the problem. There is not a lot you can do about it. The newer Berg and Futaba receivers use DSP to help filter out unwanted signals but even that can only do so much when a high power harmonic lands in the middle of your passband. I seriously doubt the idea that someone is shooting down planes in your area. The obvious fix is to go to 2.4 GHZ but you might not want to do that for whatever reasons you have.
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Old 11-03-2013, 07:09 AM
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A friend and I were going to demonstrate RC flying to an acquaintance and his son. The guy had an open pasture about a mile from a 100 KW Am/FM transmitter tower site. My friend's plane was out of control from the moment it left the ground. It was only pure luck that got it back on the ground without damage. We were sure the transmitter towers over-powered his TX signals. Needles to say the demo was cancelled.
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