N4AHJ 2004 CONTEST CRYSTAL RADIO and OTHER INFO

ANTENNAS: (1) End-fed inverted V long wire, 135 feet with apex at
40 feet, two 135 feet counterpoises under the antenna.

(2) Vertical, 48’ tall Tee; top-loading consisted of two
parallel wire spaced 38’ and run 90’ to Southwest and 40’
to Northeast; 10 radials with lengths from 40’ to 100’;
series fed at base with single wire feed. Vertical core
consisted of a cage of four parallel wires spaced 12"
and two wires from each of the top-loading legs dropped
down, spaced 4" from core center, and connected to base
to provide broader bandwidth.

(3) Sloper, 118’ with far end at 50’ and station end at 8’,
oriented toward East-Northeast.

(4) Sloper, 130’ with far end at 50’ and station end at 8’,
oriented toward West-Northwest

Ground system: Ham station ground - six ground rods
interconnected and connected to shack with two quarter-inch
copper straps; supplemented by one 8’ ground rod directly
under Vertical antenna and 2-4’ ground rods under the wires
dropped from the top-loading legs, all inter-connected with
copper wire; both ground systems connected with two runs of
copper braid salvaged from old RG-8 coax. Radials were 17-ga
aluminum wire (used for electric fences).

TRAPS:
(1) Tunable(1) - 2-section variable, sections in parallel,
   240pF total; Rook coil with
18 gauge wire, 5.25 inches effective diameter, 47 turns;
   air-coupled to the Detector coil.

(2) Tunable (2) (located in Antenna Matching Unit) - both
   use 14 gauge enamel wire on
   FT-114A-61 cores and dual-section variables with both
   sections in parallel.

(3) Fixed (9) (located in Antenna Matching Unit)
   - 14 gauge to 22 gauge enamel wire on FT-114A-61 cores,
   silver mica fixed capacitors, and plated ceramic trimmers
   (one trap for each of the local "powerhouses").
   Each link-coupled to the antenna feed to the set.

ANTENNA MATCHING UNIT (AMU):
One 4-section variable capacitor, four fixed capacitors
(500pF, 1000pF, 2200pF, and 5000pF), and two coils (42 turns
14 gauge enamel on a FT-240-61 and 26 turns 16 gauge enamel on a
FT-114A-61). All components switched to provide four matching
arrangements: series LC, parallel LC, inductance only, and
capacitance only. Both inductors tapped to provide 23 settings.
An antenna switch is provided for switching between up to five antennas.

TUGGLE TUNER:
Capacitor - 520pF variable, 4 sections, 2 used in Tuggle arrangement,
vernier is a surplus right-angle unit with a 25:1 ratio.

Coil - Two Rook coils with 16 gauge enamel wire, 5.25 inches effective
diameter, 15 turns each, 30 turns total; bandswitched to provide either
series or parallel coupling to provide Low band and High band tuning,
a la Ben Tongue’s arrangement; air-coupled to the Detector coil.

DETECTOR TUNER:
Capacitor - 420pF variable with home-made vernier with a 32:1 ratio
(vernier constructed from gears salvaged from a VCR and a TV tuner).

Coil - Two Rook coils with 16 gauge enamel wire, 5.25 inches effective
diameter, 20 turns and 21 turns, 41 turns total; bandswitched to provide
either series or parallel coupling to provide Low band and High band
tuning, a la Ben Tongue’s arrangement; switchable taps (High Band:
100%, 75%, 50%, 25% and Low Band: 100%, 87.5%, 67.5%, 50%, 25% )
on coils to provide matching to diodes.

Diodes - Three 1N34A Radio Shack equivalents, paralleled and matched
for Forward and Reverse resistances.

AUDIO:
Matching - Reproduction of Steve Bringhurst’s Ulti-Match circuit.

Headphones - Two Automatic Electric GH-66919 elements
(manufactured 1942) out of a military handset.

NOTES:
The basic set is the same as my 2003 contest set. I moved the fixed
traps from the Tuggle Tuner to the AMU and complemented them with two
tunable traps. There were a number of times when I used all three
tunable traps and one, or more, fixed traps!

I determined optimum AMU settings across the AM BCB for each antenna
prior to the contest.

These pictures and discussion are from Dave's site at:
Dave's #35 DX Radio

This is the Crystal Radio to End all Crystal Radios. Hello there.
Can't you just feel the tension rising? With this new radio I shift
gears again. Large litz wire, high quality variable capacitors,
schottky diodes. It won't get much better than this. Last night I
am proud to announce that I heard KMOX in St. Louis on this radio.
That is my furthest DX ever. I am sure that the ionosphere was hot
and the wind was blowing my way, but a heard station is a heard station.
Enough bragging and on with the show.

This radio is built in modular form. Mike Peebles gave me the idea
when he had his modular crystal set published in the Crystal Set
Society newsletter. The first part built is the detector. This consists
of the main tuned circuit with my 660/46 Überlitz Coil. This is of my
own design. I am a big fan of litz spider coils, and this is a big
litz spider coil. I believe I hit crystal set heaven with this coil.
The detector unit also has a selectivity / sensitivity control using
a differential capacitor. Besides all of this there is, of course, the
detector diode itself. I made a board with a three position link switch
and places for three diodes to be connected. This allows me to easily
compare 3 diodes in the same set. After the diodes is an audio output
transformer and RC network. The 27 mh choke provides a DC return path
for the diode circuit.

The variable capacitor is an old one made by National Radio. I made
a wheel and fashioned a vernier tuning system with a grommet and a
dowel rod. I get nice, slow and smooth tuning with this system. You
can use a vernier dial instead if you don't have one of these
capacitors in your junkbox.

The selectivity and sensitivity are handled by a differential

capacitor and a piston trimmer. This system was first used in the
Hobbydyne II circuit by Jim Frederick. The piston trimmer is for
tracking adjustment. You adjust the piston trimmer until the main
tuning needs no touch up after turning the differential capacitor.
This is a breakthrough in weak signal reception on a crystal set.

The audio transformer matches the very high (100 k ohm +) detector
circuit with the much lower impedance headphones. I am using a 100k
to 1.5k ohm transformer. If you can find a high quality transformer,
go for it.

This covers the detector section of my high performance radio. Next
comes the antenna input circuit and maybe a wavetrap.

My tuning unit is now complete. The coil is made from 660/46 litz.
The hub diameter of the coil is 3 inches. The coil form made from
1/16 inch styrene sheet is 6-1/2 inches wide and 7-1/2 inches tall.
There are 33 turns on it for an inductance of 150 µH. The variable
capacitor has 600 pf per section. Smaller ones can be used, however the
low end of the band might not tune. You could probably get away with a
500 pf per section capacitor. This antenna tuner is wired as a
"Tuggle Tuner".

Earlier I had used a 150 micro henry coil made from 40/44 litz wire.
This worked quite well. One night very late, I scanned the dial and
with this set up I heard 40 stations. Not bad for a September night.

The two units are placed next to each other. The coil distance for
good overall operation are about 15 inches apart. Careful adjustment
of the antenna tuner and detector tuning are required. The Q of these
types of coils have been measured at over 1000! This ain't your
grand pappy's crystal set.

If you build one of these, let me know how it plays for you.
Happy crystal set dx. Dave, N2DS