David,
I also do some 2 meter weak signal, been doing it for many years. I also
have the KX3, PX3 but I use the KX3 internal 2 meter module. I have other 2
meter SSB rigs but find the KX3 to be very good on 2 meters. Your email
made me curious and I did find the signal near 144.4 but I could not find
any other signals being picked up from the PX3. I use the cables that come
with the PX3 and my PX3 is mounted above the KX3. I also have an external
DEMI 222/28 transverter connected to my KX3, again with great results and no
signals picked up from the PX3. Using the PX3 on these bands is great, I
can cover a large area of the bands and monitor everything I want.
Hope it works out for you, good luck, let us know how it works out. 73
Emory WM3M
-----Original Message-----
From: David Anderson
Sent: Wednesday, May 27, 2015 1:26 PM
To: Elecraft Mailer
Subject: [Elecraft] KX3 and PX3 with 2m Transverter comments
I bought a KX3 and PX3 with a view towards using them with an external high
performance transverter for 144MHz (with an IF of 14MHz). My main interest
being weak signal operation on VHF. The ability to use the I/Q outputs with
a sound card or PX3 and the excellent receiver performance in reviews seemed
to indicate this would meet my needs.
Unfortunately it looks like this is not going to work out for me, as the
level of radiated noise at VHF from both the PX3 severely masks weak
signals, there is also a huge radiated birdie from the KX3 near 144.4MHz.
Turning on the PX3 and listening on 144MHz gives bands of noise every few
kHz which mask weak signals in the noise and I can liken it to listening to
the 6m band with a Band 1 TV transmitter putting out video sidebands over
the band.
Without the PX3 switched on I can hear distant beacons in the noise, but
they are buried by the PX3 when it is switched on and plugged in to the KX3.
The antenna is 60 feet away from the rigs and is fed by Heliax. Have tried
separate supplies for transverter and PX3, running from batteries on KX3,
nothing seems to reduce the QRM from the PX3 to an acceptable level.
There also is a huge S9 spurious near 144.4 from the KX3 that is independent
of band/freq/mode. Confirmed by listening on another receiver in the shack.
It is so hugely disappointing, I had looked forward to this day, having
finally got my rotator and antenna back up on the tower I am faced with
looking for another rig to drive the 2m transverter. Unfortunately I don't
think it will be Elecraft. Perhaps Elad might be an alternative, but I need
to consult the weak signal VHF community first. I will keep the KX3 and PX3
for QRP HF work most likely as selling it at a loss would be a bitter
alternative.
On HF where the band noise and signal strengths are much higher I don't find
the same problems, though there are still spurious signals shown on the PX3
there. I could live with them I think, but on what is a nice quiet 144MHz
band here, the racket from the PX3 is impossible to put up with.
Incidentally I wonder what causes that big birdie near 144.4 from the KX3,
and if is it related to the similar one reported on the K3? There doesn't
seem to be a lot of commonality between the designs.
Sorry if this sounds like I am trolling, I am not, I love the Elecraft ethos
and products, it is just they don't appear to work for my specific needs.
Unfortunately it wasn't possible to try before you buy here and I ended up
being the guinea pig.
73
David Anderson GM4JJJ
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