[ARC5] Updated: 80/40 Meters to Longwave Converter

[David Stinson]

Several people have been asking me about the simple little
converter I build so receivers like "ARC-5" Q-5ers,
RAK etc. can be used to receive HF.
I've improved the circuit to make it simpler, cheaper and,
if you wish, band-switching for 80 and 40 meters.
And you don't have to wind any coils.

I started with a simple little Vectronics VEC-101K
"Shortwave Converter" and extensively modified it.
No case yet.  Here's a photo of it atop my sweet
Mackey Marine longwave receiver, listening to
 K5KZQ and K5DOA in QSO on 7055 KC.
KZQ has a nice "musical" note:
http://home.netcom.com/~arc5/75toLFconverter/newconverter.jpg

Here's the circuit:
http://home.netcom.com/~arc5/75toLFconverter/newconverter0415jpg.jpg
All parts are cheap from Digikey.
The programmable oscillators are like $4 for any freq you want.
You can skip the switches etc. if you just want one band.
Once you power it up, generate a known freq and adjust
the trimmers for max sig level.  Don't just use noise because
it's easy to tune it up on image freqs.

As with any "simple" circuit, there are trade-offs.
Images can be a problem, but I haven't been bothered
by them much except one on 40 meters.
I used a 6800 KC oscillator for 40 because that puts
7000 KC output at 200 KC for a "Q5er."  But that
puts a SWBC image at 7030 KC.  You can either put
 a wave trap in front of the converter to reject the
image or use a different Osc freq. to move it.
I used a 3500 KC Osc I had on hand for 80,
but that puts the Osc tone right at 3500 of course so
you can't listen to signals below about 3503 KC,
which I haven't found to be a bother anyway.

I'm probably going to put a "wave trap"
(one trimmer cap, one coil) in front of the 40 Meter input
to reject the images.

If I can answer any questions, drop me a line.

73 OM DE Dave AB5S