VHF band now free from intermod interference

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JayMojave

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Hello All:

Thought this was worth reporting on. I bought a Par Electronics Intermod Filter thay connects between the outside antenna and the scanner, Part Number VHFSYM152HT. This Filter rejects the 152 MHz pager data transmissions that many times fills the scanner with all kinds of intermod interference.

I no longer hear the constant roar of the data transmissions interfering with MY BCT-15 and Pro 2006 scanners. VHF is very much active with Fire and police traffic. The outside discone antenna coax feeds the filter, then feeds a radio shack divder/combiner to feed the two scanners.

This filter was well worth the 70 dollars. I got it from Grove at:
http://www.grove-ent.com/filters.html

Jay in the Mojave
 

mtindor

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Jay,

Glad you had a good experience with the PAR. Dale hooked me up with one of the same kind but tuned to filter out TV Ch 9. Works great. I agree, definitely worth the 70 bucks. Makes all the difference on vhf.

Mike
 

af5rn

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N. Tex / S. Fla
This is good to hear. I may get one of their air band filters. The one from Scanner Master is absolutely worthless. It doesn't filter out anything. You get what you pay for!
 

mancow

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I picked up a PAR filter for 158.100 a few months ago. I have a 500 watt P.O.S. paging transmitter about a mile away that just incinerates the front end of any scanner on any antenna of any gain at all.

The filter completely eliminated that horrid thing. It was so bad the entire Vhf Fed band was useless on the 996 but now it's as if I'm out in the country side.
 

JayMojave

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Hello Mancow:

Yes its great to be able to have the scanner work on the VHF bands without hearing that darn buzz zaw on every other channel. I now even have the aero band (118 to 136) interference free.

So now the scanner antennas can be raised up another 20 feet above the roof!

Jay in the Mojave
 

JayMojave

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Mojave Ca
One other thing that I need to mention here about the notch filters. For the VHF band they also sell a notch filter for the 158 to 159 area which also has the pager and data, high power VHF transmitters. That also cause the intermod interference.

I used a tunable receive to search over the VHF band and found a incredibly strong data signal on 152.395 which was causing all kinds of interference on my scanner and even my poorly filtered 2 meter ham radio.

So tune around and figure what VHF frequency is causing the buzz saw intermod interference, before ordering the filter. I know guys have both filters connected to each other who live close to a repeater site. Hope this is help to those who have the intermod interference.


Jay in the Mojave
 

trooperdude

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I daisy-chain a bunch of PAR intermod filters.

The two PAR vhf paging filters, his FM broadcast filter, National Weather Service xmitter filter on 160mhz, and UHF TV CH 14. (the latter was a custom tuned filter).

If you can't tell, yes, I am in RF hell, but the PAR filters make it so I can actually hear again.
 

krazybob

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Oct 26, 2003
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Lake Arrowhead, Southern California
I'm with Trooperdude and others on this one. We at SBN have been using the PAR Eletronic filters for years with great success. Our Whittier, CA feed, just outside of Los Angeles, gets pounded. The catch-22 of using an outside antenna is INTERMOD!!!

My new mountain home location is at 6300 feet overlooking all of southern California and intermod is a huge problem. I have already ordered PAR fioters. Remember that when daisy chaining filters you need to place an electrical 1/4 wavelngth jumper between them.

Another thing that is helpful is to actually introduce nloss into your antenna system. You may do this by placiung a CATV attenuator inline. A Variable attenuator works great and you simple park on a VHF channel that normally gets intermod and note that it 2-3 bars of signal strength even when no signal exists. Rotate the varriable attenuator until the signal strength hits zero. Scanner overload will generate its own intermod.

Antenna -> PAR filter -> CATV attenuator -> Radio

Also, using a tuned antenna for each band helps.
 
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