TheRadioBoard

I wanted a simple crystal set that would highlight Mike Peebles’ rock stand (‘cause I really like it ) and one that could serve as a nucleus for a project radio. This little “loop stick” radio seems to be just the ticket.



0.5”x4” Amidon ferrite-61 rod,
10t cw #24 magnet wire for the antenna coupling coil,
55t cw 165/46 litz (about 230 uH),
10-410 pf Jackson Bros. capacitor,
Peebles rock stand + crystal, or a diode.

The antenna-ground is connected at the top terminal block and the audio comes out the bottom terminal block.

It works pretty good by itself with a piezo earpiece. But it really perks-up when some bells & whistles are added. Like an antenna coupling capacitor, and/or a Bogen+Benny at the output, and/or a sensitive headset, and/or a loose coupled antenna tuner, etc., etc.. It’s kind of fun to fiddle around with it.

A problem I’ve always had is DUST. I’m banished to the basement for crystal set work and the sets seem to accumulate a thick coating of dust in short order if they’re not covered-up. But I wanted this little setup to be out in the open so the grandkids could see it & maybe increase their interest in radio. (It’s hard to compete with video games!)

I found some $1.50 clear plastic storage boxes - with lids - at Bed Bath & Beyond that make nice dust covers. The radios’ wooden base is screwed to the inside of the lid and the box part then sits on top. No dust on the parts and you can see the inner workings through the plastic. The inside clearance is almost 4” so there’s plenty of room in there - especially if ferrite-assisted coils are used.



Not elegant, but it works.

73, Dan

heh, great idea and a good looking set,
I store my competition rig ( ATU, detector unit, Phones, ultimatch2...) in a similar box, just MUCH larger (22liters), no wooden base screwed to the top, just store.
I also use the box as table for the rig in use (it is Poly Propylene so low loss at RF).

Dan,

Looks great!

Mike

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I like the K-I-S-S Principle: "Keep It Sane & Simple"
http://www.peeblesoriginals.com

Hi Dan,

Nice set and I like the dust cover idea.

Corne

Thanks fellas.

And thanks for all the work you guys have posted -- I sure have learned a lot from you nice folks.

73, Dan

Does anyone know why production loopstick antennas are multi layered?

Good question Homebrew,

My best guess is cost(maunfacturer being cheap). As most of the commercial "loopstick" are probably intended to go into cheap transistor superhet desing radio,s, the loopstick doesnt need the best Q or efficiency.
In these sets the selectivity is controlled by the IF stage, and the sensitivity by amplification either in the RF amp if it has one, or the converter transistor if not, and by the AGC.

Can anyone verify my guess?

To complete the story - I used the little loop-stick radio in the just finished ‘08 Sprint contest. It was single tuned (no antenna tuner) and no diode was used - only “crystal” detectors, primarily galena. Kyocera KBT-44SB-1A piezo elements made-up the headset. I did put a variable capacitor in the antenna line to vary the coupling.

The log is shown below:



Although I didn’t spend a lot of time listening, this simple set will bring-in a lot of stations.

The 2 close-by stations (10 km @ 3.6kW & 11 km @ 5kW ) are VERY loud -- just right for a grandkids’ first taste of crystal radio. Adding a coupling capacitor to the antenna line tamed the “flame-throwers” a bit and then more stations could be heard.

At night, DX stations were strong and in-the-clear. Easy,pleasant listening.

The detector stands’ whisker adjustment was smooth and very stable -- even a grandpa could do it When a VERY light contact to the crystal was achieved, the set’s selectivity improved greatly. A heavier hand produced broader signals. The effect was dramatic to hear.

The addition of a Bogen + Benny makes a worthwhile improvement -- as everyone here knows.

As-is, it’s a kid-friendly, easy to operate, well behaved little set.

When a decent (high Rd) diode like an FO-215 replaces the crystal detector, and an antenna tuner coil - like the one at

http://theradioboard.com/rb/viewtopic.php?t=1132

is loosely coupled to the set - there’s DX all over the dial. Fun stuff.

73, Dan

Nice results.

My only problem was that I was never able to find a link to the 08 contest for rules/entry info etc...

here you are FT, sadly somewhat late.
http://crystalradio.us/crystalsprint/index.htm

i like the incredibly long stick fr0m older portables winding my own
enamald wire round em and tere easy to mount my nostalgia compells
me to usehome brue air cores and vario couplers my next expariment
is a tribute to marconi hes the italian stalion god fater of radio.

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31 years old now playing with crystal sets since 12 years old tweaking and tinkering and sharing ideas ever since...

Elegance is in the eye of the beholder!

I believe it to be elegant.

Gus

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Old age is 'when you still have
something on the ball, but you are just too tired to bounce it.'

Sounds good Goldy, keep us posted.

Thats really nice, Dan. I could use a cover like that over my whole shack I recently built the breadboard rcvr and audio amp that I was showing off here a few months ago. They already look somewhat "vintage" with the tarnished brass.

yah dont have camra yet till after holidays but think out side the ciggar box a varyo copler w tuner selector {tikler coyle} wt optional
det/amp/set three peace ciggar box S.E.T. amp is done with feed back gitar amp neatly hidden in ciggar box witth feed back
controle gain vol for 20 ohm all tgether new sp set.stil working on
other half took 1 ciggar left the rest @ nebors rpm shop for his cellibrations the amps not going to be entrd on contest but a
fools gold piyrite det mated with tuner will be.
feed back by the way on gitar amp. works well with tune n det. sets eavin after trans former and ceramic disc cap. just good gon rite idea i gess might turn old amp box to all together new set or rf osc or somthinng. radio bord is new to me but time cristals
arnt my real name is dan too just braggn idont think
dave wants me to post for a while so i just comment a lot my posts are locked tight !sorry! you like the idea guru? "old school
syle"

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31 years old now playing with crystal sets since 12 years old tweaking and tinkering and sharing ideas ever since...