I'm new here but so far have found the info here really helpful and informative. Bob Achison is the vintage radio tech that has got the electronics restored on all my vintages radios I have acquired. He suggested I post my latest crystal radio replica here.

It uses a chunk of galena for the diode and I will be making the "pot" interchangeable so I can quickly swap out other types of rough semiconductor rocks. It's suspended in a pool of silver solder and the whisker is some very fine ga piano wire. I machined all the parts except the plates on the varicap.

The whisker arm moves on three planes. Left/right, up/down and extension and retraction. Each plane can be locked in with a tension bolt. The vintage varicap is a single 0-65 pf and I turned the knob from bronze then turned a cocobolo wood insert to go into it. The coil is 110 turns and is variable tapped with a locking brass slider.

To keep it homebrew as much as possible I made a waxpaper-aluminum foil fixed capacitor and encased it in a maple burl tube I turned. I also made that to easily swap out so I can play with different homebrew fixed cap designs.

It's fed with a 1/4 wave quad antenna that I made for my vintage radios. I live in a very remote area and have a 103' deep water well that makes an excellent earth ground. I use a pair of 80 y/o German high Z headphones for it.

I live 65 miles from the nearest AM broadcast towers and it pulls in two of them very well day and night. At night when the skip is running it grabs almost too many stations. KNBR 680 out of San Francisco (750 mi) rockets in perfectly. The tuning has good rejection, better then any of the dozens of crystal sets I've made over the years.



The galena rock.



Fixed cap, no idea what value but it makes a difference when connected.

Excellent work!

Silver solder has a really high melt temperature. Your material looks more like Woods Metal, which melts below 200F. That's what I use to pot crystals. Normal solder causes them to fracture.

Rich

The spool said "silver solder" and I heated with a propane torch and fed it in until it was close to the rim. Then I dropped the piece of galena in. I didn't buy it pre-made, the only pre-made componet used was the vari cap. The brass cup has a lot of mass and so the solder cooled very slowly thus the crystalline surface appearance. More oxidation occurred then if it had quick cooled.

I use Woods Metal and a heat gun. Works really well.



Rich

A beautiful piece of work!

I'm curious about the wood coil form. It looks like it may be hollow. How did you make it?

Thanks! I turned it on my lathe and made sure I got it as thin as possible. I didn't want it to affect the coil at all. But the thinner it got the more risk of it launching out of the chuck. Same with the burl tube capacitor.

A lathe is about the only sawdust maker I don't have. Didn't think I needed one until seeing your work.

You haven't fully lived life until you make a maple burl capacitor and an Oregon Myrtle coil.

OK, as soon as I build an addition to the garage for Old Henry's benefit, I'll buy a lathe and turn some Alaska birch.

Beautiful work! The brass parts and wood really go well together!

Thanks. A vintage radio collection is not really complete w/o a crystal set with an actual crystal. Just a couple weeks ago I had an opportunity to buy a very old original set but the seller changed his mind. So I had to console myself by building a replica. My next project will be a little one tube receiver. So far this site has provided some great info on one tubers.

Hey Brent,

INCREDIBLE WORKMANSHIP !

Being so far out in the country has it's advantages, almost everything you hear will be long distance without those pesky locals cluttering up your radio.Your particular antenna and ground really help too.

FWIW, I just went camping and used a Johnson Smith "Spy Pen " crystal set (like the ones in the old comic books) to do my listening. I ran 300 ft of low wire and used the car's battery negative as a ground.

Great LOUD signals from 300 to 400 mi.No where CLOSE to my crystal set record , but lots of fun.

You gotta love crystal sets.

K

Using the car's negative as a ground is a new one on me!

Since the car battery negative is connected to the metal body, you are effectively using the body as one plate of a large capacitor. The other plate is the earth under the car.

Your car radio antenna uses the same principle.

You can connect your radio ground to any place on the car body (if you scrape away the paint!).

Rich

I'm jealous! I wanted one of these when I was a kid (saw them advertised in "Boys Life" magazine), but I didn't have the money and my mom used that most hated of parental sayings (or at least one of the top ten): "You don't need one".

I used the finger stop on the old rotary dial phones for an antenna and it worked great. My second crystal set was a Yogi Bear one my aunt bought me when I was 7 y/o. That just had a tunable ferrite coil, diode and ear phones.

Hey All,

Yup. I sort of "stumbled" on to the negative battery some years ago by clipping to the car's ignition key. I then figured it might be a bit better directly to the batt.

I had used the dial stop (at times) as a kid. But mostly I used a steam radiator gnd and outside long wire antennas in my bedroom.

A kid in my neighborhood used to GIVE me tons of junk ( and working ) radios (his dad was a TV repairman). He had a Yogi Crystal set and I tried and tried to get it (cash, trade , etc). But he wouldn't budge.

Spy Pen's , Yogi's (and other "novelty" sets of that era) can now command some fairly BIG dollars on epay. Some are quite rare .Their "inexpensive" construction ensured that many did not survive the last 40 + years.

Out of all the many crystal sets I have, the Pen is the only one I have in the "novelty" class. I bought it because I had one as a kid. It once got WBT Charlotte (from my home near Boston) TWO whole nights in a row. But strangely, only when clipped to the medicine cabinet. On the big antenna ,I only got locals. On the third night and beyond- NO WBT- NOTHING.It would be many , many years before I heard any other long distance crystal set stations again.So the Pen has a special meaning to me.

K

Do you have a pic of the spy pen crystal radio? I haven't seen one in probably 40+ years since I have read comic books.

Hey Brent,

Sorry, No pix ( some day I GOTTA learn how to post pix, but don't have lots of time and my kid is in Europe,so no one to show me).

My Pen is not truly "original" ( I didn't care too much about maintaining the original condition of the rig as a "collector's piece". I wanted it to easily work well to use and enjoy it- not just sit in a box).

Since the earphone leads needed to be cut anyways, I gently tied the radio to a small strip of poly'ed wine crate and took the three terminals out to small ceramic stand off terminals. A fixed bleed resistor goes between the phone terminals.

The tuning rod has a large original alligator clip clipped on to it. This clip slides along the wood strip to provide just a tiny bit of friction that will hold a station (unless the rig is really tipped or moved). Having a tuning "tiller" or "handle" is also VERY nice. One downside to these radios is when new, the rod slides WAY to easily. You almost just have to LOOK at the radio and it will move off frequency.

The only minor boo boo I did was placing the terminals too close together. I would have liked to be able to wind a temporary ant coil on the outside of the radio and base board,but I really can't do it now. Oh well, no big deal, the radio worked well enough as is.

I have plenty of junk box parts to make home brew small permeable sets of this type, so no big deal to make a dual coil set if I really want to some time .

FWIW there are pix on line ( google Spy Pen radio). I even found an ad for one on collectorsweekly.com.

K