[R-390] the saga cont. pt 9

Mon Sep 20 16:39:36 EDT 2010

Well, I bit the bullet and ordered a UG-971 twinax-to-C adapter [I already
have a PL-259-to-C jumper for feeding the unbal input.  We'll see how it
goes.

73, Brian KA9EGW

-----Original Message-----
From: r-390-bounces at mailman.qth.net
[mailto:r-390-bounces at mailman.qth.net]On Behalf Of ka9egw at britewerkz.com
Sent: Monday, September 20, 2010 2:58 PM
To: William A Kulze; R-390 at mailman.qth.net
Subject: Re: [R-390] the saga cont. pt 9

My understanding is the two 68ohm resistors thing, is to put a signal in as
common-mode for adjustment of one trimmer per band, the balancing caps
nearest the front panel, only.

I'm using a couple pins to feed my balanced inout, but it only works when
reversed from the pin-out Chuck Rippel recommends, and it's that way on all
bands.  And no, P206 and P207 are not reversed.  Odd.  Very odd indeed.  And
it's that way with 2 different rf decks.

73, Brian KA9EGW

-----Original Message-----
From: r-390-bounces at mailman.qth.net
[mailto:r-390-bounces at mailman.qth.net]On Behalf Of William A Kulze
Sent: Monday, September 20, 2010 1:59 PM
To: R-390 at mailman.qth.net
Subject: Re: [R-390] the saga cont. pt 9

I've got some 90° adapters, SO-239 to the twinaxe. They don't seem to have
anything inside, just grounds one side of twinaxe, like recommended for
feeding twinaxe input in the R390a info out there. Now, I've always heard
that if you don't use the balanced input you're skipping a stage of
preselection that will null any unbalanced noise that may be on the balanced
line.  How's all this work if you're connecting 50ohm coax to the balanced
input? If you feed your Sig Gen to the junction of two 68ohm resistors at
the balanced input to make the adjustment, are you still going to see any
improvement if you ground one side and feed with coax?

Bill W2NVD

-----Original Message-----
From: r-390-bounces at mailman.qth.net [mailto:r-390-bounces at mailman.qth.net]
On Behalf Of rbethman
Sent: Monday, September 20, 2010 2:19 PM
To: r-390 at mailman.qth.net
Subject: Re: [R-390] the saga cont. pt 9

  The "Twinax" connection was meant for something around 120 to 150 ohms
for Z.

It really doesn't matter unless you have a way to alter the impedance of
the signal generator!

These were originally aligned with the AN/URM-25(X) series of signal
generators.  They came with a "dummy" antenna of 50Ohms Z.

If you perform the alignment with a 50 Ohm Z signal output, then you are
going to be in a "better" position, since today's antenna systems are
"normally" a feed impedance of 50 ohms.

Tweak and peak accordingly!

Forget the "twinax", and use the "C" connector next to it.  It was meant
for 50 ohms Z.

Bob - N0DGN

On 9/20/2010 2:01 PM, ka9egw at britewerkz.com wrote:
> What fun...got my Amphenol 82-5628 BNC-to-Twinax adapter in the mail
> today...it doesn't seem to work very well; I get better results off the
> unbalanced input and the adapter whows some fraction of an ohm between
pins
> and between either pin and ground.  Does anyone know if it has some sort
of
> balun or the like in it, and if so, what's the Zo and freq range?
> 73, Brian KA9EGW

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