The rig for the 2006 contest is a Jim Frederick design, the Hobby Dyne 2.
I added crystal switching and use a reduction on the tune side capacitor.

The headphones are sound powered made from SP mike elements. A bogen
transformer handles the output transformation.

The antenna is a 100 foot wire bent to fit the lot!
A cold water pipe handles the ground.

The unit at the left rear is the antenna tuner. The coil is 33 turns of
#22 magnet wire. The cap. is a dual 365pf variable purchased from the XSS.

The unit at the center rear is the detector tank. Its coil is 40 turns of
#24 magnet wire. The front cap. is a dual section variable salvaged from a
junked radio. The smaller front section is not used.
The rear cap. is used for band spread.

The unit at the right rear is the inductive trap. The coil is 40 turns of
# 24 magnet wire. The cap. is a single gang 365pf purchased from the XSS.

At the right front is the detector stand mounted on a salvaged trophy plinth.
The mass of the wood and marble lowers the detector stand's sensitivity to
vibration. All logged stations were heard with the cat whisker and galena
crystal. At the start of each listening session, I would tune in a weak local
station using a germanium diode and then disconnect it and match the signal's
strength and clarity to a hot spot on the galena crystal. The whole process
took less than a minute. The crystal was purchased from the XSS.

The unit at the right front is my version of Steve Bringhurst's
UltiMatch 2. I used a pair of RCA "Big Cans" connected to the Red tap
of the Bogen transformer.

Mark Roliff

..Note that the audio impedance matching unit is a copy of
Steve Bringhurst's UltiMatch 2...only the Bogen T725 transformer was
used, and the Benny was bypassed...

My interest in crystal radios was less than a month old when I
found out about the DX contest. The result is my entry which, for
reasons that will become obvious, I have dubbed the Comedyne.
If you find any of this humorous rest assured that you are
laughing with me and not at me.

I entered the formula for calculating coils into a spreadsheet.
Later on I modified the formula so that I could enter the diameter
instead of the radius and promptly forgot that I had done so. The
coil form I used was 4 inch PVC that I turned down and threaded
at 22 TPI. When I went to calculate the length I entered a 2 instead
of 4 and came up with a length of 5 inches. This resulted in a coil
of 800 uH instead of the 280 to 300 uH that I wanted. I was too green
to recognize that this was not right and of course the coil was all
soldered up before I found my mistake.

The one thing that went right on the coil was the winding and
tapping. I had tried various methods of making taps on a coil with
little success. Seems I don’t have the patience, eyesight and
requisite number of arms to do a decent job of it so I came up with
a new (at least to me) idea. I drilled line of small holes at
every 5th thread. I placed the coil form in the freezer for a while
to shrink it and then quickly wound the coil. Then I scraped the
enamel off each wire that passed over a hole with a sharp pointed
hobby knife. I bent a small hook in the end of each tap wire passed
it through the hole, turned it 90 deg and "hooked" the winding.
I placed a tiny dab of flux on the wire and then folded the tag end
of the hook down tight on the coil. A dab of solder finished the
job. The result was a nice tight, neat (if slightly over-wound) coil.
I bridged all the taps together with a loom to help take the stress
off of the solder joints.

The only caps I had were some I ordered from Antique Electronics to
play with because they were cheap. They are 4 section totaling 240pf
and 540 deg. rotation. I found out why they are so cheap. Nobody in
his right mind would want a VC designed for PC board mounting. I
finally figured out a way to mount them and only destroyed one in
the process. I didn’t have time to order a shaft extension so I
machined one out of some plastic rod.

When selecting a diode from two dozen 34As two of them accidentally
touched together and the sound level really jumped up. I called them a
pair and mated them forever. My antenna is an almost 300 foot wire
running due north/south. It ranges from 15 to 20 feet off the ground.
The ground is a piece of ½ inch black pipe driven 6 feet into the ground.

I used 12 pos. rotary switches from Antique Electronics for the antenna
and tuner taps. For the other switches I used the slide type strictly
for looks. (Certainly not for the "ease" of mounting!) The tuning
knob and slide switches are from Radio Shack.

Four of the slide switches are for the capacity. 200pf, 30pf, and
85pf on the variable and a 150pf fixed cap. The other switches the
ground to switch out half the coil. My grand plan was to be able to
do some short wave tuning. (I did manage to do some.)

I’m an admirer of Art Deco and Arts and Crafts design so I set out to
make a case for the radio that would look at home in a room designed by
Frank Loyd Wright. I also wanted it to look like it had been around for
50 or 60 years. The sides are the very last scraps of some birch plywood
from a project I did over 6 years ago. The remainder is solid oak and some
oak trim that I modified. An artfully sloppy stain job (left dark in cracks
and crevi and lighter on the corners and edges) with Minwax English
Chestnut stain gives the look of age. It is finished with three coats of Deft
semi-gloss. I am more or less pleased with the result. The trim above the
faceplate is a little too wide and I’m not crazy about the
flat top. I may do something about the top.

The faceplate is 1/8 in plastic that I found laying around the engineering
shop at work. I made a milling template on Autocad and adhered it to
the plate. After milling I soaked it off with some WD-40. I then modified
the Cad drawing for the graphics and printed it out on some parchment
looking card stock that I found at Hobby Lobby. Adhering the graphic
onto the faceplate in proper alignment was another comedy of errors.
Needless to say there are come creases and wrinkles that worked out
perfectly in my plan for the "aged" look. Two coats of spray poly were
applied to protect the paper.

The back plate is a 97-cent clipboard from Wal-Mart. I cut it to fit
and shot it with some cheap black spray paint. It has the perfect
cheap-black-fiberboard-radio-back appearance. Maybe because
that’s what it is.

The set tuned very broadly. That may have to do with the huge coil. A
local was smeared all over the dial in the daytime and half of it at night.
A hastily constructed trap was used to block the local until they signed
off at 11PM. Then I would reconnect the antenna directly to my set.
Even switching out half of the coil had little effect on the selectivity.
Strong stations like WHO and WWL covered a lot of my tuning range.
Using the trap as an antenna tuner may have helped but I wanted to
stay within the hobby class regulations.

Still I think I did pretty well. I managed to get about 35 stations
for a score of just over 55,000 points. The furthest was CBC in
Vancouver BC. I will wind a proper coil for the set when time allows.

...Turned out to be quite a contest. Conditions were very flat until
the second Friday (20 Jan.); then propagation really picked up. Area
T-storms produced a moderate static level Sat. & yesterday,
but good prop. seemed to persist.

Same set as last year's event, except I did put a lead telluride
rockstand on the stronger local stations. (This was the same detector
I heard KRVN 880 Nebraska on several contests back.
But that was on the Lyonodyne 17 set.)

Two of the stations heard were new: KXTK 1280 never heard before on
any set; CFAC 960 first heard in last year's 1-AD contest.

Mercifully a clandestine neighborhood super noise source held
off during prime listening hours...