XV144 Question

[Glenn McNeil]

Hi Group,

I've just finished an XV144 Transverter for another Ham who lives just
down the street for me while I'm waiting for my K2 to clear VK Customs (
Bummer ).

We fired it up today and all went well...very well in fact, but one
thing I did notice with the counter plugged into the 144 Mhz Output
through a 30db pad, I could see a reading on the counter up above 6Ghz
with the XV144 in Rx Mode. Removing the IF Driver made no difference,
and removing the RF lead from the Transverter output did...i.e the
signal is coming from the XV144. My counter is good to 18Ghz and needs
around -30dbm to get a lock. I cannot have a look at the output as my
Spectrum analyser gives up the fight at 1.8 Ghz.

Any ideas on what I'm seeing here...and does it need attention. All
other tests appear fine and the Transverter works FB on 144 MHz.

73
Glenn
VK4TZL



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[Robert Friess]

Hi Glenn,

I designed the XV144 for Elecraft and I am very interested in your
observation.  I just had a look at a XV144 here and can not duplicate your
finding here.  I also looked with a spectrum analyzer and I don't see
anything unusual.  What you are describing sounds like the preamp could be
oscillating.  It would be interesting to touch your finger in the region of
the preamp and see if the frequency moves.  If it does, it would confirm an
oscillation in the preamp.  If that is the case, check the soldering of the
smd capacitor C72 at the drain of Q1.  It is a small 4.7 pF capacitor
intended to roll off the gain of the preamp to prevent the possibility of
oscillation in the microwave region. While you are looking around, look for
cracks in C72 and the other SMD caps around the preamp.  These are sometimes
hard to see without a microscope and are usually found at the junction of
the metalized terminals of the capacitors and the ceramic body.   Please let
me know what you find.

73,
Bob, N6CM


----- Original Message -----
From: "Glenn McNeil" <[hidden email]>
To: <[hidden email]>
Sent: Wednesday, December 29, 2004 10:06 PM
Subject: [Elecraft] XV144 Question

> Hi Group,
>
> I've just finished an XV144 Transverter for another Ham who lives just
> down the street for me while I'm waiting for my K2 to clear VK Customs (
> Bummer ).
>
> We fired it up today and all went well...very well in fact, but one thing
> I did notice with the counter plugged into the 144 Mhz Output through a
> 30db pad, I could see a reading on the counter up above 6Ghz with the
> XV144 in Rx Mode. Removing the IF Driver made no difference, and removing
> the RF lead from the Transverter output did...i.e the signal is coming
> from the XV144. My counter is good to 18Ghz and needs around -30dbm to get
> a lock. I cannot have a look at the output as my Spectrum analyser gives
> up the fight at 1.8 Ghz.
>
> Any ideas on what I'm seeing here...and does it need attention. All other
> tests appear fine and the Transverter works FB on 144 MHz.
>
> 73
> Glenn
> VK4TZL
>
>
>
> --
> No virus found in this outgoing message.
> Checked by AVG Anti-Virus.
> Version: 7.0.298 / Virus Database: 265.6.6 - Release Date: 28/12/2004
>
> _______________________________________________
> Elecraft mailing list
> Post to: [hidden email]
> You must be a subscriber to post to the list.
> Subscriber Info (Addr. Change, sub, unsub etc.):
> http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/subscribers.htm
> Elecraft web page: http://www.elecraft.com
>
>

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