[VHFcontesting] Multi-op interferance on IF freqs

[Rogers, Ron]

Terry,
We fought the same problem with common IF frequencies in the transverters at the W8VP Multi-op group back in the 1980s.  So over the years (and culminating with the W9ICE Multi-op station) we had migrated away from transverters (except for 903) and went to Icom single band radios for 5 of the bands. 
 
IC-575H, IC-275H, IC-375a, IC-475H, and IC-1271a. No IF interference.
 
I then only had to use a single cavity filter in front of the 432 preamp to keep the 2 meter 3rd harmonic knocked down on 432.
 
Ron
WW8RR
 
________________________________

From: vhfcontesting-bounces at contesting.com on behalf of w8zn at comcast.net
Sent: Mon 1/26/2009 8:58 AM
To: vhfcontesting at contesting.com
Subject: Re: [VHFcontesting] Multi-op interferance on IF freqs





----- Original Message -----
From: "John D'Ausilio" <jdausilio at gmail.com>
To: "paul rollinson" <ke1li at sbcglobal.net>
Cc: vhfcontesting at contesting.com
Sent: Monday, January 26, 2009 8:38:18 AM GMT -05:00 US/Canada Eastern
Subject: Re: [VHFcontesting] Multi-op interferance on IF freqs
Now here is a very interesting subject. This past contest when out for the first time in a long while as a rover, I experienced this issue somewhat with my partner, but only on 903. After building up K8GP for the last 10 years, I found that you can not maintian the same IF frequency for transverters, even at 10m for 6 - 432. For my rover, 1296 and up all use a 146 MHz IF and I had no interference at all except for some harmonic trash just due to close proximetry of the antennas. On 903, I hadn't moved my transverter to 146 yet and interference was very bad.



At K8GP, I had to move even the 10m IF's to keep folks from hearing our own IF signals. Since we used TS850's on all bands and they were all set for all band tx. I ordered special crystals for the DEM transverters and moved them around to avoid this issue. 6m stayed at 28 = 50, 2m went to 26 = 144, 222 = 27 and 432 = 25 (using DEM's standard 28 = 437 crystal). For 903 and 1296, I moved the IF's to 147. Using a 2m intermediate IF transverter with 26 = 144, this moved my tuning range to around 29 MHz. For 2304 and above we used a 146 IF and the 2m intermediate transverter was 26 = 144 which meant the tuning range was around 28 MHz. There was some issues with the 6m IF being heard on the microwave station but since we now use K3's for 6m natively, that issue has gone away.



In most cases with a rover, I would suspect it's just close proximetry of all the antennas. My 2m station running 350w was only 6 feet away from the 903 and up stack of antennas, it hard to fight that!



Terry




I'm considering moving all my microwave IFs to 145Mhz to solve this
problem in the Jitney (which is a 2-op rover) ..

de w1rt/john

On Mon, Jan 26, 2009 at 8:29 AM, paul rollinson <ke1li at sbcglobal.net> wrote:
> Good morning all,
>
> During the last contest we expanded the bands we worked up to 10G from the bottom 4. This created a huge problem.
>
> We had to shut down the 2, 220, and 432 stations to use the upper bands due to interference from the lower, high power stations on the IF rigs for the transverters. 6M had little effect but we only had 100W running. Murphy reduced our power level.
>
> I speculate that a common patch panel and close proximity of the antennas may be the culprit but I'm looking for other opinions and potential solutions. Especially from the big multi-ops that run legal limit on 2 and 432 which we use for IF's.
>
> June is coming and I'd like to start clearing this problem asap. We always run out of time.
>
> 73 and thanks for the input,
>
> Paul, KE1LI
> _______________________________________________
> VHFcontesting mailing list
> VHFcontesting at contesting.com
> http://lists.contesting.com/mailman/listinfo/vhfcontesting
>
_______________________________________________
VHFcontesting mailing list
VHFcontesting at contesting.com
http://lists.contesting.com/mailman/listinfo/vhfcontesting
_______________________________________________
VHFcontesting mailing list
VHFcontesting at contesting.com
http://lists.contesting.com/mailman/listinfo/vhfcontesting