Yes, I do have documentation on the enhancements. Unfortunately of the 6 or
7 radios it seems that they all do not exhibit the same exact issues and
therefore I've found each requires different approaches and methods to clear
up the birdies.
On the birdie issue, I start with a 1/2" ID #43 bead which is split in two
halves. I can then put it around each cable, one end then the other, and
observe the difference. Then move on to another one. Once I've found the
optimum for that specific radio I can then go in and in some cases I need to
re-make the ribbon cables as they need to be a bit longer to allow the new
cable to make at least one turn through the bead and include a bead in the
correct place with the new cable configuration. This must be done before
the Mass Termination Connector or ribbon connector is applied. Average
radio may take a couple of days on the bench to seek out the enhancements.
Once all this is done, you will find the receive on the Omni VI Plus to be
superior on the bands with few if any birdies found or heard.
The PA stabilization is basically accomplished by replacing the disk ceramic
caps with chip type components. Specifically, C4, C5, C6, C7, C10, C11,
C12, C13, C15, C16, C17. Also make sure that D2 and D3 are thermally
connected to the heat sink. This effort was done in as much as I run the PA
at 10 to 15 watts, through a resistive attenuator to drive the VHF or UHF
transverters. At that level, there was some "nasty" stuff coming out of the
PA and thus not normally found at rated output. At rated output, the PA is
normally very clean.
It is just so annoying to do weak signal work where one listens and listens
and only discover it is a darn internal birdie about the noise floor level.
Just the nature of crystal mixing radios. They all have them, some worse
than others, no brands/models exempted.
For what it's worth, the Omni VII, the Eagle and the Argonaut VI do not show
any of these issues. Makes for HAPPY HAPPY on the VHF and UHF bands.
73
Bob, K4TAX
----- Original Message -----
From: "Barry N1EU" <barry.n1eu@gmail.com>
To: "Discussion of Ten-Tec Equipment" <tentec@contesting.com>
Sent: Thursday, January 10, 2013 11:39 AM
Subject: Re: [TenTec] Fair Market Price for Omni VI+ will all
filters&matching PS ?
On Thu, Jan 10, 2013 at 4:00 AM, Bob McGraw - K4TAX
<RMcGraw@blomand.net>wrote:
I had done extensive work to get rid of the multiple birdies on 12M and
10M. I replaced the bypass caps on the PA board to improve the stability
of
the stage. Although the changes were strictly component changes,
selected
to be better quality or better suited for the application, and the added
toroids to certain cables inside the box were applied to get rid of
birdies.
Sounds like you certainly added some value to your Omni 6+, Bob. Any
chance you documented those changes? Many of us would be very interested!
Thanks & 73,
Barry N1EU
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