GM Jerry...
Changing to one of the Ten Tec radios might help your FD problem. We had
that also, but have built some stubs out of 8x coax (rg 8 or 213 would
probably better) and have knocked about all our interference out between
stations. Also, I owned a 940 a few years ago, and finally got rid of it due
to it's self destructive nature. But the one I had would run 125 watts plus,
so that may have been some of the problem too. Of course, they aren't as
good as bandpass filters, but being the pack rat that I am, I had plenty of
the 8x already.
73, Mike K9MI (club FD station W9VCF central IN)
----- Original Message -----
From: "Jerry Volpe" <kg6tt@arrl.net>
To: <tentec@contesting.com>
Sent: Friday, June 02, 2006 04 32
Subject: [TenTec] Omni-VI+ Phase Nosie and INRAD roofing filter mod?
>I am selecting which of my transceivers to take to Field Day with the
> choices either my Corsair II or my Omni-VI+. You would think this to be
> a slam dunk decision in favor of the newer radio. However, I still have
> a very bad memory from last Field Day when I took a Kenwood TS-940SAT
> which had so much Phase Noise that when transmitting I wiped out the
> other two club stations. I have subsequently deep six'd that
> transceiver. Now not wanting a repeat of that experience I decided to
> make a very simple test.... and got rather disturbing results.
>
> Test One: Omni-VI+ to a dummy load. 14.005 MHz. Power output varying
> between low and hight power. Keyed with electronic keyer. Corsair II
> with unterminated receiver (basically on a shorted connector of the same
> switch connecting the Omni-VI+ to the dummy load). As I tuned across
> 20-meters I could not hear the Omni-VI+ transmitting until I was pretty
> much on the transmit frequency +- say 3 kHz. This was satisfactory.
> Changing the Corsair II's XTAL filter to 1.8, 500, or 250 Hz made the
> reception tighter as expected.
>
> Test Two: Reverse the roles. With the Corsair II transmitting at even
> the least output possible the Omni-VI+ presented 'keying' noise across
> the entire 20-meter band with a few false signals to boot! Inserting
> different first or second IF filters did little to reduce this.
> Eeeaaoooouuucchhhhh! Granted the noise floor alternately raising and
> lowering with the keyed Corsair was maybe an S-3 to S-4 level but having
> that noise constantly present for 24 plus hours..... Hmmmmm.
>
> To be sure that this was NOT the Corsair II's problem I turned on
> another transceiver..... an Argosy with an 8-pole first IF filter. The
> Argosy's response to the keyed nearby transmitter was even better than
> that of the Corsair II's!! Hmmmmmm, something to be said for
> single-conversion designs.
>
> I got on the phone and talked to a tech at Ten-Tec about this. He did
> NOT indicate that this was abnormal for the Omni-VI+. He did state that
> the Corsair II was arguably the finest 'analog' transceiver ever
> made..... still he recommended my using the Omni-VI+ as he believes it
> to have a better receiver. Now this is something I have never been able
> to confirm. I said what about the Omni-VI+'s susceptibility to the
> nearby transmitter? Long pause..... No comment.
>
> Next I asked him if he thought adding the INRAD roofing filter might
> help. I had my doubts as the interference was felt across the entire
> 20-meter band! Knowing that the Omni-VI+ has a 16 KHz monolithic crystal
> roofing filter already I wasn't sure how putting a tighter filter would
> help. Still I am grasping at straws here.
>
> He did say that a number of INRAD roofing filter equipped Omni-VI+
> transceivers have found their way to Ten-Tec and that there was a
> 'noticable improvement'..... and that INRAD filters have been found to
> be of very high quality.... Yada yada. Would it help with what I am
> experiencing? No way to know.
>
> So what do you think? Have you installed an INRAD roofing filter in your
> Omni-VI+? Which... 2.4 or 500 Hz? And did you use your
> unmodified/modified transceiver in a multi-contest environment?
>
> Thanks for the input.
>
> Jerry, KG6TT
>
> --
> KG6TT
> Ralph Jerald "Jerry" Volpe
> ARRL Member, VE
> FISTS Member 12304
> Solano County
> CM88xg
>
> kg6tt@arrl.net
>
> _______________________________________________
> TenTec mailing list
> TenTec@contesting.com
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>
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