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Frequency Conflict Concerns

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Old 08-11-2006, 06:50 PM
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rightflyer
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Default Frequency Conflict Concerns

We have become concerned that we have a possible frequency conflict with local WCMH TV Channel 4. We were told by another club in the area that channel 4 conflicts with RC channels 20 and 21. This conflict generates a harmonic that interferes with other nearby channels. One of the other are club members say they ban 20 and 21 due to this problem and say it is a problem known by the AMA. So far, this is basically just a rumor so I am trying to confirm this with someone with more radio knowledge than I. I appreciate any help you can offer. Our club wants to make sure that we fly safe, but we also do not want to force pilots to vacate these channels without cause.
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Old 08-11-2006, 08:05 PM
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Default RE: Frequency Conflict Concerns

Its channel 20, do a search and there's some good explanations about whats going on. You can also contact Steve Kaluf at the AMA he's the technical director and or Tony at http://www.radiosouthrc.com he's the district V vp and owner of Radio South, either one can give you the straight poop.

FWIW we fly channel 20 in at all 3 fields in Jacksonville and have a Channel 4 tv station w/o any issues.
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Old 08-11-2006, 08:28 PM
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Default RE: Frequency Conflict Concerns

First, thanks for the reply. I will follow-up with Steve or Tony. By the way, both our club and the channel 4 transmitter have been in place for over 15 years and we have never banned channel 20 and have not experienced known problems before. But I will investigate more as you suggested. If we do close 20 or 21, I want to give any members on that channel to migrate if necessary.
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Old 08-11-2006, 08:45 PM
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Default RE: Frequency Conflict Concerns

I don't remember the math but I think it mixes with one of the carrier waves and creates a difference thats the same as the IF that single conversion receivers use, so with DC recievers I don't think its an issue.

If I was bored at work I'd work it out for you, this is just off the top of my head.
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Old 08-11-2006, 08:53 PM
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Default RE: Frequency Conflict Concerns

http://www.rcuniverse.com/forum/m_36...tm.htm#3688020

See Alberts post about half way down. I knew I'd seen this come up not too long ago.
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Old 08-11-2006, 10:37 PM
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Default RE: Frequency Conflict Concerns

truth be told, the 2nd IF in most dual conversion receivers is also 455 KHz.. but the signal would have to be awful darn strong to get around the 1st IF filter - not impossible, but highly unlikely. Most of the DC receivers I'm familiar with only use a two pole crystal filter at 10.7, you get some selectivity, but a large portion of the receiver's selectivity still comes from the 455 KHz filters.

But - the signals would have to be quite strong for a DC receiver to suffer..
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Old 08-12-2006, 07:44 AM
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Default RE: Frequency Conflict Concerns

good info thanks.
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Old 08-12-2006, 01:41 PM
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Default RE: Frequency Conflict Concerns

We have banned 20 and 21 down here in Chillicothe too, severe hits but no one has really found out why.
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