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From: rfc@briar.philips.com (Robert Casey;6282;3.57;$0201)
Newsgroups: rec.ham-radio,sci.electronics
Subject: Re: Pro-2004 going on sale?  (Sorry, but it isn't - read this anyway)
Message-ID: <44256@philabs.Philips.Com>
Date: 9 Feb 89 14:19:36 GMT
References: <7706@netnews.upenn.edu> <1555@anasaz.UUCP>
Sender: news@philabs.Philips.Com
Reply-To: rfc@briar.philips.com.UUCP (Robert Casey)
Distribution: usa
Organization: Philips Laboratories, Briarcliff Manor, NY
Lines: 21

In article <1555@anasaz.UUCP> john@anasaz.UUCP (John Moore) writes:
>I think the Pro-2004 is a heck of a good scanner. However,  one problem
>that it has is front-end desense. On two that I have tested, they
>lost 38dB (!!!) of sensitivity when connected to a good antenna
>that was letting in -15dBm of FM signals (sensitivity loss was on VHF-Hi
>Band). Turning on the attenuator on the back actually improved sensitivity
>by 28 dB. I have found that using the radio shack FM reject filter in
>front of the scanner seems to help, but it is 75 ohm with wierd (F)
>connectors, which is a bit of a kludge.

You could try making a transmission line stub trap.  Get a T coax connector
and put it in the antenna coax line, and connect a length of coax cut to the
equasion:
	       length = 2953 V      where V is velocity factor (0.66)
		       -------
		       f(MHz)           length is in inches
for an open ended stub.
It comes out to 19.5 inches to trap out 100Mhz.  Only problem is that you'll
also trap out 300 Mhz, 500 Mhz, etc.
Use 1/2 the above length if you want a shorted end stub.  
73 de WA2ISE