Martian Special Radio

[DavePEI]

I received my  three crystal detectors from Alberta this morning, (pictured below). Included is a horizontal cat's whisker, a vertical crystal, and an interesting fixed cat's whisker detector (lower right)... Also included, which I hadn't known were a dozen NOS fahnestock clips.... The crystal detectors are all vintage and used...

I also received 48 4x1/2 inch slotted brass wood screws to mount the fahnestock clips, etc. on the backboard purchased from another seller. I wanted to use these instead of modern screws to maintain the authenticity of the project.

[TelePlay]

Very nice!

On my end, a bit of a disappointing set back.

I got the 3 whiskers from Borden and the whisker is too short to make contact with the crystal.

I did get the phosphorous bronze wire and it can be wound so will have to make a winding jig this weekend and create my own whisker.

Stay tuned . . . 

[DavePEI]

Very nice!

On my end, a bit of a disappointing set back.

I got the 3 whiskers from Borden and the whisker is too short to make contact with the crystal.

I did get the phosphorous bronze wire and it can be wound so will have to make a winding jig this weekend and create my own whisker.

Stay tuned . . .

Can you straighten out one or two of the windings in the coiled portion to make them fit?

Dave

[DavePEI]

I have wound the coils for my radio (actually two different types for two radios). I used my mini lathe as a coil winder. The coil in the left is continually adjustable from 0 to about 240uh, and the one on the right is appx. a fixed 200 uh.

Now, I just have to wait until the snow melts enough to get into either the Museum, or into my barn behind, where I have some gutless subset boxes stored to get a cover to use as a base for the project!

Dave

P.S. How did you make out with your cat's whisker, John?

[19and41]

Nice coils!  That is a good tuning mechanism on the left one.  That ought to give you reproducible results. You'll like that when you find stations you like and want to get back to.

[DavePEI]

Nice coils!  That is a good tuning mechanism on the left one.  That ought to give you reproducible results. You'll like that when you find stations you like and want to get back to.

Works, that is the main thing. Just a long bolt, supported by two eyes, with the wiper made with a nut that fits and a brass wiper soldered to it.... Next best thing to a manufactured roller inductor!

Dave

[DavePEI]

Remember a while back, I said I was building a crystal radio for the telegraph display using (mostly) vintage parts? Well, here it is - the second (back) fixed coil still needs to be mounted as does the capacitor, and Then it will take a very short time to wire. I mounted it on a subset cover from an empty subset. The four fahnestock clips are for antenna and ground connections, as well as a pair for high impedance headphones. The second coil can be connected to increase frequency range.


Update: Updated photo with rubber feet on, Coils mounted - only a good way to mount the 365 pfd. capacitor has yet to be devised. I did find a physically larger 365 pfd. cap in my parts, and I am going to use that, as it looks more vintage. I also found a good dial for it.

[NorthernElectric]

Cool Dave!  I must confess I don't know much about these things, but is that a variable capacitor such as you might find in a superheterodyne receiver at the bottom right?  Is that a feature normally found in a crystal radio?

[DavePEI]

Cool Dave!  I must confess I don't know much about these things, but is that a variable capacitor such as you might find in a superheterodyne receiver at the bottom right?  Is that a feature normally found in a crystal radio?

Yes, in some designs. The capacitor allows more accurate tuning. The one in the really old radios would also be 365 pfd., but would be larger in physical size. This was the only one I could find.

Some had only a coil and a fixed capacitor and the rectifier, be it a diode or a cat's whisker, but this offers a bit more selectivity.

Dave

[DavePEI]

Ok, guys. Everything is now mounted. I would have liked to make the mount for the capacitor out of brass, but I didn't have a piece to use. I may change it over to a brass plate if I ever find a small piece. The radio is completed, and checked using a long wire antenna and a crystal high impedance ear piece. I have a set of high impedance headphones in the barn I will get whenever the snow melts enough to get the door open.

Two views, on from the front, and one from above. I think, other than the capacitor mounting plate, I managed to keep the vintage look I was trying for....

Updated Photos, May 3rd, a.m.

[TelePlay]

Looks very nice, Dave. Did you pick up anything or are you still waiting on the high Z headphones?

[DavePEI]

Looks very nice, Dave. Did you pick up anything or are you still waiting on the high Z headphones?

No, I have several out in the barn. I just need to wait until the snow melts enough to get at them! There is still a drift against the doors, but it is slowly going.

At least I will soon be able to get into the museum, and was able to get into my electronics workshop...

[mdodds]

Wow, this thread is bringing back memories! And that is a really nice build. I built my first crystal radio from a kit and it had a galena cat's whisker crystal, even though it had to be in the mid '60's (I was born in '57). May have been a Philmore kit, I can't remember, but I had to wind the coil and it used Fahnestock clips for connections.
And quite appropriately for this forum, I remember not being able to string an antenna at that time, and I discovered connecting the antenna terminal to the finger stop on a phone dial worked quite nicely :-)

[DavePEI]

Finally, I was able to get into the barn today to begin my search for items I have wanted over the winter. Everything there fared well - there was some dampness on the floor, but everything is on pallets which kept it high and dry.

One amusing thing, isI left a roll of paper towell out there last fall as I was cleaning up. It was unrolled, and stretched today up into the rafters! Some enterprising animal though he would abscond with it!

I have a number if small items there to search for for others, and I will get to that - just be patient.

The main thing I searched for today was a set of high impedance headphones for my crystal radio.. I found several, but the best was a pair of Tower Manuf. Corp. Scientific Navy type made in Boston. Here is a photo with the radio....

[19and41]

It gives one pause to consider that it is coming up on a hundred years since individual experimenters started making up such sets.  When I was a kid, 100 years predated the telephone.