The RF gain control is internal. At some point, I might
put a 10K Ohm potentiometer on the back panel to replace the internal
control, which is accessed through a small hole with a screwdriver.
However, I find that with either the Ten-tec
1253 and MFJ-8100 that I rarely have to adjust the RF gain
control unless I have a very strong station.
I found it useful to "tie" the toroid down
to the circuit board after final adjustment with a dab of hot
glue from a glue gun. Very handy stuff.
Both receivers are sufficiently stable for CW and SSB
reception. The Ten-tec 1253 seems to show a small amount of warm
up drift. I have no idea why this should be. It goes away in about
10 minutes. The best bet seems to be to run it from an external
power supply and leave it running all evening.
I have found that external battery operation (12 volt
gel cell for Ten-tec 1253 and 9 volt battery for MFJ-8100) is
the best bet. The usual "wall wart" or converted PC
power supplies generate too much hash at HF for good clean reception.
Both receivers benefit from the use of an antenna tuner
to optimize the matching between the antenna and the receiver
For further reading and study, Google is your friend.
A very good discussion of regenerative receivers can be
found in the paper by Ramon Vargas at
The seminal article by Charles Kitchen is to be found
in the November/December 1998 QST. He has an extensive discussion,
and shows both photos and schematics of an excellent complete
solid-state regenerative receiver.
Also, some very nice material on direct conversion
and Wheatstone bridge regenerative receivers can be found at:
A good source of early books on vacuum tube receivers
and the like can be found at :
I'd like especially thank Rob Grasing for some suggestions
on modifications to the Ten-tec 1253 and the source for some of
the links that I have suggested, as well as on-going discussion
during the development and writing of this paper. It is always
good to have a "second set" of eyes during a writing
I look forward to hearing from other members of the
group for their insights on a always