Re: RF Filters
- From: Vladimir Vassilevsky <antispam_bogus@xxxxxxxxxxx>
- Date: Mon, 08 Sep 2008 09:09:15 -0500
David Lesher wrote:
So a fellow EE asked me:
There is a 107.9 MHz FM transmitter about 3 miles from my house. There is a 107.3 MHz FM transmitter about 45 miles from my house. See any problem?
Very well could be.
Do you have any suggestions for a notch or lowpass filter to kill the 107.9 MHz signal (Hip-Hop format)? I believe it is causing intermod distortion on 107.3 and other FM stations.
I already tried a 5-element directional antenna at various orientations (vert/horiz, tilt up/down, etc.)
Did you try a simple attenuator at the input?
Are you sure the interferror gets through the antenna? May be it is picked up directly by the receiver PCB.
I was looking at the following: 1) Coax stub notch filter.
Coax stub made from a reasonable cable will not have sufficient Q at 100MHz.
2) Filters from Tin Lee Electronics. 3) Filters from Par Electronics.
I do not have particular experience with those, however the required notch filter is definitely doable with the lumped components.
4) Complaining to 107.9 and getting a free filter.
5) Moving to the different location?
I wonder if anyone here has experience with 2 or 3? I suspect 1) will not
have enough Q, and the 4) people won't have enough clue. [Anyone here
remember back when radio stations had Chief Engineers with a First Class
License?]
Vladimir Vassilevsky
DSP and Mixed Signal Design Consultant
http://www.abvolt.com
.
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- From: David Lesher
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