Surplus QRP Gear (GRC-109)

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From: Jim Kearman (jkearman@arrl.org)
Date: Sat Apr 24 1993 - 18:13:04 EDT


Well, I got my GRC-109 rig on the air today. It's a pretty
neat collection of boxes. Considering it works on 80-15
meters, including all points in between, it's not a bad
deal at $120, which includes a copy of the manual (they
don't give anything away at Fair Radio Sales). You need
FT-243 crystals for the transmitter.

In case you're interested, here's some information I
obtained today:

FREQ POWER OUT (WATTS, MAX)

3560 10
7040 15
14060 15 (no 30-meter crystals)
21060 12 (no 17-meter crystals)

The open-circuit keying voltage is +60. The rig is cathode
keyed; off-resonance keying current is 125 mA, 100 mA at
resonance.

The weak link is the receiver. While sensitive, the tuning
rate is quite fast and it has 9-kHz selectivity. An audio
filter will help some, I'm sure, but that's still a lot of
signals in the passband. I may splice a ceramic filter in
there, 4-kHz bandwidth or so. The good news is, it has
provision for crystal control also, so you could arrange
an external VFO for the receiver (F + or - 455 kHz).

On the other hand, I was able to work W2FO in New Jersey
on the coax running up to the W1INF beam, on 40 meters, and
hold the frequency for as long as I could send on the built-in
straight key: about 20 minutes.

Antenna and headphone connections are via spring-loaded binding
posts (jacks would be hard to waterproof I guess). I am using
old electromagnet headphones (hi-Z); I rigged up an SO-239 on a
piece of zip cord for the transmitter output. You can run full
QSK, but, even though the key shorts the rcv antenna when
transmitting (!), it's noisy. Hard to find your frequency, as
the rcvr overloads. I had to back off the drive. They should
have included a spotting switch.

There's NO AGC in the receiver. The BFO runs continuously. It's
output is sampled and rectified to provide a gain-control voltage
for the receiver! When you want to listen to R Habana (to see if
your clandestine operation has been detected), you just turn the
BFO control to the OFF area marked on the panel. That raises the
BFO frequency above the range of hearing.

Okay, so it isn't an HW-9. You could probably throw these things
out of a plane at 500 feet without a parachute and they'd survive.
You tune up the transmitter (Remember those days? You're probably
eligible for QCWA) by peaking two neon bulbs and a #47 lamp
arranged as an antenna ammeter! SWR? What's that. The book says
it will match 72 to 1200 ohms. I noticed the loading cap is fully
open when looking into 50 ohms. Especially on 80 meters, I got
the feeling I could squeeze more power out if I could match the
lower impedance.

Yes, it will drive random-length wires--it was designed to use a
75-100 inverted L. There may be a problem with harmonic suppression
when you use a random wire. There may be a problem with harmonic
suppression when you use a 50-ohm load. Am I going to put this
thing on the spectrum analyzer? Hmmm. On 80 and 40, my operation
will result in harmonics falling on the ham bands. On 30 and
up.... I think I'll run it through a Johnson Matchbox--they take
harmonics down pretty well.

There's a hand-cranked generator out there for this thing, but
I'm not sure I want to use it on FD. It could be useful for
aerobic exercise, though.

If you have any questions, feel free to send email to me. If
you put one of these sets on the air, I'd like to work you. Just
give me time to rig up my keyer!

72,

Jim, KR1S

--
jkearman@arrl.org


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