1-AD 2006 Contest Report

It soon became obvious my new 957 acorn tube BFO was not working
right. The BFO has double (or multiple) resonances a hundred or
so Hz apart. When one resonance was zero-beat, the other(s) was
squealing away -- and vice versa. Not good for hearing anything.
Reception was much better on the plain crystal set with the BFO
turned off -- but that's not the point of the contest.

After a half-day of frustration, I cast my lot with -- Ta-Daa! . . .

The Brianodyne
a BFO'ed Diode Doubly-Balanced Mixer (DBM) suggested by
Brian Hawes. The Local Oscillator is last year's 1-FET Hartley BFO.
The RF source is simply Antenna and Ground. IF Output
(which is actually at audio frequency) goes directly to the
Big Can Phones, with no matching transformer. In fact,
no tuning or matching is done at any of the DBM ports.
All tuning is done with the FET BFO.

I figured it would at least it will be an interesting
1-AD entry. Though it doesn't match last year's
1-FET BFO/MRL #39, performance has been very gratifying.

The spread sheet doesn't reflect the performance of the
radio. The radio catches all the locals with excellent volume.
I didn't try to track down spanish speaking stations, and
I have several contacts in the log for stations that just
didn't seem to want to ID themselves.

For the contest I did not use any impedance matching, only
the Western Electric Type II Signal Corps headphones I
refurbished with a home made cord, re-magnified the magnets,
and cleaned up the head band. The quality of the audio from
these phones is outstanding and the sensitivity the
best of my 2k phones.

The circuit is the MPF 102 JFET circuit from Mr. Owens site,
except I made it a double tuned set with a 360 VCAP in series
with the ground. With this configuration I couldn't seem to
resonate the antenna below ~ 800 khz. The solution would be
to add another vcap in parallel with the antenna coil,
but I really wanted to keep this radio simple.

The Det. Coil is 300 uH close wound (left over from previous
experiments) and the space wound antenna coil at 270 uH is
the second coil I wound for this radio in an attempt to get
it to resonate the antenna below 800 khz with a single Vcap.
Both coils are 26 guage on a 2.5 ups cardboard coil form.
The tickler coil is 8 turns of scramble wound 16 guage
plastic coated wire.

The set was constructed completely out of stuff I had on hand,
went together in about three hours, minus the trip to radio
shack for another JFET (I toasted the first one). I plan to
make a shortwave version of this set, and I plan to redo
this radio with a much higher Q factor for next year.
This contest was a whooole lotta fun. Thanks yall.

Good job on the contest. This was the first time I had used
this type of receiver and it was very enjoyable experience.

I am using a single tube regenerative kit from Mike Peebles.
It uses a 1T4 tube with regeneration controlled by a variometer.
The kit is stock except for using a larger knob on the VC for
easier tuning. The sensitivity was good, and selectivity was
more than adequate to separate stations 10 KHz apart.
Headphones are WE-509's, antenna is 40'of wire laid on the
roof with an 8' down lead. This is my crystal set / SWL
antenna. This year we tried covering it with a foot of
snow on the second evening of the contest. It did not help.
(Actually it did not hurt either.) The set was run bare, without
antenna tuners or traps. Spotting was done with a Grundig YB-400.

Thank you for sponsoring the contest, I look forward to next
year with a scratch-built radio.