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REVIEWS
1) New kit from K1SWL & MidnightDesignSolutions
by Mike Maiorana, KU4QO
(posted 18-Nov on qrptech.io)
I got my "Old Friend"
transceiver kit from MidnightDesignSolutions a few days ago,
shipped in a padded envelope. I took a relaxing evening
yesterday and built it, so I thought I'd give some feedback. The
kit was very easy to build! Most of the through-hole parts were
separated on individual cards, labeled with their value and
reference designator. That made the inventory very easy to
accomplish, with no searching for parts. All the surface mount
parts were already assembled on the PCB (I was a little
disappointed that I didn't get to build the SMD parts). The
assembly is done in sections, with some sanity-check testing at
the end of each section, which gives you confidence to continue.
In total, the build time was about 3 hours, give-or-take. It
worked perfectly on power-up. The calibration of the PLL was
simple and easy to complete with a frequency counter. Even
without calibration, it was within a few hundred Hz. Power out
was right around 5 watts (maybe a shade less) with a 12VDC
supply. Power draw was less than 1A on transmit, 130mA on
receive. I haven't looked at the output spectrum yet, but I'll
try that later. I don't expect to see anything unusual.
My kit was built for 40
meters. I connected it to my dipole last night just to have a
listen. There were a TON of signals, and on a crowded band, the
DC receiver shows some of its weakness with signals on both
sides of zero. The audio peaks at around 800Hz (the sidetone
frequency), but isn't razor sharp, so it doesn't have that nasty
ringing like you are listening inside a tin-can. The front-end
and mixer were solid, with no broadcast interference. I do hear
the "tick tick tick" from the Wifi router in my office, but if I
cover the board with my hand (or an aluminum tin) it vanishes. I
think when this is mounted in a metal enclosure that will
disappear.
The tuning encoder they
included seems like a high quality part. There are no detents,
but you can feel the bumps from the internal switches ever so
slightly while tuning. The software has "ballistic" tuning,
where if you tune slowly it jumps 20Hz, but when you turn more
quickly it jumps by 100Hz. Encoder tuning always feels a bit
clunky to me, but this setup isn't bad at all, and is very
simple.
The audio out is at a fixed
volume, which set me back a little bit. It is designed to drive
a pair of low-impedance headphones. I used a decent pair of
headphones for testing (Sennheiser HD598). The band noise level
was a bit loud for me, but not offensive. Weaker signals sounded
good. Dave designed in a limiter that prevents very strong
signals from blowing your ears off. It works very well and is
seamless, unlike some AGC systems that cause annoying pumping of
the audio level. However, the really strong signals lose that
smooth sinewave sound and sound clipped (which they are). Again,
it isn't hard to hear, it's just different. One thing to keep in
mind is that different headphones have different sensitivities.
If you use a pair of very sensitive headphones, the volume may
be a bit too high. Likewise, if you use a very inefficient pair,
it may sound a bit too weak. All that being said, and keeping in
mind the simplicity of this radio, it works fantastically. I
love it.
Hats off to Dave and the guys
at MidnightDesignSolutions for a great kit!
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