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Crystal Radios Of The 2005 Contest Entrants

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Lem Morrison

Crystal Radio Group contest Entry 2005

N4AHJ 2005 CONTEST CRYSTAL RADIO and OTHER INFO

The picture shown is the set in the 2004 Contest configuration.

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; loose-coupled to the Detector coil.

(2) Tunable (2) (located in AMU) - 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 AMU) - 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 “blow torches”). 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 are tapped to provide 23 L settings. An antenna switch is provided for switching between up to five antennas.

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

Coil - Two Rook coils with 14 gauge enamel wire, 6.25 inches effective diameter, 15 turns each, 30 turns total; bandswitch provides either series or parallel coupling for Low band and High band tuning based on Ben Tongue’s approach; loose-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 14 gauge enamel wire, 6.25 inches effective diameter, 18 turns each, 36 turns total; bandswitch provides either series or parallel coupling to provide Low band and High band tuning based on Tongue’s approach; impedance taps (High Band: 100%, 75%, 64%, 50%, and 28%; Low Band: 100%, 72%, 50%, 28% ) on coils to provide matching to diodes.

Diodes - Two (one marked FO215 and one marked 3502) in parallel.

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

Headphones - Two Automatic Electric GH-66919 elements (manufactured 1942) out of a military handset and a set of Steve Bringhurst’s enhanced SP cans.

NOTES:
The basic set is similar to my 2004 contest set. The primary > differences: larger Rook coils with larger gauge wire, hotter diodes (thanks to Steve Bringhurst), 20 uA meter, and new front panels.

I determined optimum AMU settings across the AM BCB for each antenna prior to the contest. These settings were reasonably reproducible during the contest, even when it rained!

The capability to switch among three antennas was great, especially between vertical and horizontal polarization. A station that was uncopiable on one antenna usually would be loader on one of the others. Generally, I used the vertical the most, but I noticed on several occasions that I could hear a station on one of the slopers when I could not on the Tee.

By the way, I live on a city lot that is 85’ wide and 165’ deep. However, I am blessed with having very good relationships with my neighbors on both sides and with a wooded area directly behind my lot. After Hurricane Ivan destroyed all my antennas (three oak trees ranging from 50’ to 80’ tall fell!), both neighbors allowed me to re-erect the Slopers across their backyards. Also, the 90’ leg of the Tee ran well into the woods behind my lot.

Crystal Radio Group contest Entry 2005

Crystal Radio Group contest Entry 2005

ANTENNAS:
(1) Tee, 46’ tall; top-loading legs consist of two parallel wires
spaced 38” and run 90’ to Southwest and 40’ to Northeast. The
vertical core consists of a cage of four parallel wires spaced
12” apart. To provide broader bandwidth I added two vertical
wires from each of the top-loading legs (spaced 4’ from core center),
and one additional vertical wire on Southeast and Northwest sides
(spaced 4’ from core center). All of the vertical wires are connected
at the base and series fed with a single wire.

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

(3) 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 the Tee and 4-4’ ground rods
under the wires dropped from the top-loading legs, all inter-connected
with copper wire; both ground systems connected with a run of copper
braid (salvaged from old RG-8) over a #10 copper wire. Radials are 17-gauge
aluminum electric fence wire; used 12 radials with lengths from 30’ to 135’
(one radial attached to the city water system!).


Mike Tuggle

Crystal Radio Group contest Entry 2005

As it turns out, all loggings were made in the 'BROAD' configuration.

The DX gods never really smiled this time, maybe an occasional
smirk. Still, I guess I can't complain.

Crystal Radio Group contest Entry 2005

Philip Miller Tate (Ge_Whiz)

Crystal Radio Group contest Entry 2005

The radio is a loose-coupled set. The antenna coil is heavy solid copper wire, 16 turns on a two-and-a-half inch diameter ABS drain pipe, tapped every other turn. The aerial is coupled in via one stage of a dual 120 + 120pF variable capacitor; the other is in parallel with the coil. There is no earth connection – the set works better without it – but the earth level is hard-wired through to the detector coil. The aerial itself is a total of 120 feet of wire running from the end of the house, 50 feet to the shed roof and back at an angle of about 35 degrees to the opposite end of the house, average height 20 feet above ground. Note that there is no vertical section, as the radio is located on the top floor of the house.

The detector coil is eight turns of 660/46 Litz wire with an inductance of 5uH, wound on a five-point rook former of the same ABS pipe, in parallel with a 350pF variable capacitor with three-turn gearing. The combination tuning system covers approximately 4-15MHz. The detector is an AAZ18 germanium gold-bonded diode. Output is to a Select-to-Match transformer system and thence to a pair of DLR-5 military balanced-armature headphones.

Alongside the detector coil, as shown above, is the plug-in coil of a homebrew gate-dip oscillator connected to a Racal Nixie-tube digital frequency meter. By carefully adjusting the tuning of the GDO, the dip of the detector coil resonance can be found to about +/-20kHz accuracy, and used to find the station on the spotter radio, a Sony IC100.


Rich Shivers

Crystal Radio Group contest Entry 2005

I have followed the comments on the Rap 'n Tap board, and agree that conditions were not very good this year. Compared with last year my total station count was down and DX stations were just not there. Disappointed, yes; did I have fun, yes.

I am using a large tapped single coil set. It's an air core basket weave coil 5" in diameter, about 8" long. 66 turns of 14awg THNN household wire. It is tapped every 11 turns with separate rotary switches for the antenna, detector, and capacitor. Normal arrangement has the antenna and detector tapped near the bottom of the coil. By tapping down the tank circuit I can band-spread the top of the band for improved selectivity. The tuning cap is a three section 400uh unit. One section across the coil, the other two section in parallel from the bottom of the coil to ground. A 8 to 1 vernier dial drives the tuning capacitor. Between the antenna and tank coil is a wave trap constructed of a tank circuit and a coupling coil. Both trap coils are wound on a single ferrite core. Headphone are WE 509's. Detector is a 1N34. Antenna is a T arrangement; 40' across the roof, with an 8' lead-in, the other leg drops straight down for 12'.

Crystal Radio Group contest Entry 2005

Crystal Radio Group contest Entry 2005

Lou Dayich

Crystal Radio Group contest Entry 2005

I built a new set for this year's contest. Some components were transplants from the 2004 contest. This set uses three coils and 5 variable capacitors, you will also notice three knife switches that were used in various parts of the receiver.

The antenna coil is aproximately 30 turns of close wound magnet wire, apx. 3 inch diameter. The caps (top and bottom) on the left side of the receiver provide parallel and series tuning to the antenna coil. The alligator clips on both caps allow the caps to be easily taken out of the circuit. The detector and trap coils are apx 4.5 inches, 9 point basket weave coils. During most of the contest, I actually set this up with the trap in the middle and the set became triple tuned.

The detector coil is a dual gang Russian variable cap (built in vernier) and the knife switch allowed me to use one or two gangs for detector tuning. The bottom right cap uses the same type of cap and knife switch arrangement for ground leg tuning. The top right cap was fitted with a 10 to 1 vernier reduction for wave trap tuning. The phones are sound powered cobbled from some USI elements and a bogen matching transformer can be seen mounted under the "shelf". I used two diodes at different times during the contest, an FO215 (solo and configured in a Hobbydyne set up) and a schotty diode.

As you can see the radio case "was" a wooden breadbox and the door came off making a nice shelf. On the left side you will see a stand alone inductive antenna tuner, this helped during the contest and is really great for casual listening; with the caps configured in a certain fashion, I can tune 5 or 6 of my regular stations just by clicking the rotary switch on the tuner. I had more points and station count with this year's receiver, but due to high winds just prior to the contest lost my best antenna. I ended up with a sloper apx 80 feet long and about 25 feet at its highest. Lots of fun! It is great to see all the radios that been built.


Dick Kleijer

Crystal Radio Group contest Entry 2005

My receiver is build with separate unit's.
- the antenna unit
- detector unit
- audio transformer unit

The coils are made with litz wire 660/46 and are wound on very low loss polypropylene formers. The diode is a double shottky diode, type: HSMS282K. The transformer unit has a input impedance of 1600 k.Ohm, this is about the impedance of the detector LC circuit, so there is maximum power transfer.

As loudspeaker, I use a driver unit of a horn loudspeaker. The antenna is a 22 meter (72feet) wire, with the highest point on 18 meters (59 feet). On the picture, you see the antenna wire coming down from the top of the mast. More info about my receivers, you will find on my website: crystal-radio.eu

Crystal Radio Group contest Entry 2005

Antenna

Crystal Radio Group contest Entry 2005

Antenna matching unit.

Crystal Radio Group contest Entry 2005

Detector Schematic

Crystal Radio Group contest Entry 2005

Audio matching unit.


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