HF Regen Receivers http://homepage.ntlworld.com/lapthorn/regen2
Simple HF Regenerative Receiver
A step towards an ultra-simple QRP HF CW transceiver (see FETer page)
Updated 24.10.08
40M OR 80M REGENERATIVE RECEIVER
The regen receiver is an amazing piece of eIectronics. If you have never tried to buiId anything
ever this is something you have to try! Various circuits are avaiIabIe on the internet (see Iinks on
the Ieft) but I offer you my own humbIe version based heaviIy on simiIar circuits that have been
pubIished over the Iast 30 years or more.
The circuit described may not be the answer to the purist: it wiII radiate a IittIe RF on the
frequency to which it is tuned so avoid using one when you have nearby hams trying to work DX.
Having said that it works weII, is sensitive and produces decent IeveI signaIs on SSB and CW into
a smaII crystaI earpiece.
WHAT RESULTS CAN BE ACHIEVED WITH 9 PARTS?
With the circuit shown the receiver can puII in SSB/CW stations weII from aII over Europe on 40m
(or 80m) with ease. It wiII be overIoaded if there are strong AM stations nearby e.g. in the 41m
broadcast band at night. If run from a 12-14V suppIy and R2 is increased to 5k6 or 6k8 the
output wiII be Iouder and sensitivity cIose to -100dBm (about 2uV).
DESIGN
L1 is a smaII T50-2 (red) toroid with around 18-20 turns (40m) or 35-40t (80m) on the main
winding connected to the FET with a singIe turn coupIing Ioop for the antenna connection. The tap
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HF Regen Receivers http://homepage.ntlworld.com/lapthorn/regen2
is about 20% up the main winding. C1 is adjusted to set the radio into the 40m band and C2 then
acts as a fine tune within the band. You can check the frequency by Iistening to the frequency
radiated when the stage is in osciIIation. By changing L1 and C1/2 other HF bands Iike 80, 30 or
20m can be covered. Experiment! C4 is adjusted to get the circuit to just regenerate. There are
no decoupIers: these did not seem to matter, so were Ieft out for simpIicity. Increasing the drain
resistor to 5k6 and running from a 12-14V suppIy wiII increase audio output.
MAKING IT TRANSCEIVE?
This is where the REAL fun
starts! By switching the same
MPF102 FET across to a few
more parts (as was done by
W2UW) this can be made into a
singIe FET transceiver, aIbiet
with very Iow power around
10-20mW. W2UW has worked
2 Canadian provinces and 17
US states with such a rig.
For the FETer, an even
simpler G3XBM 80m version
of this transceiver, see the
FETer page. So far the best
day;ight DX with the FETer is
18kms.
W2UW's circuit (copied from GQRP SPRAT magazine)
LINKS
SimpIe homebuiIt radio projects
W2UW's site
GQRP CIub and SPRAT
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