Back in the late 1950s early 1960s I found a rather interesting Xtal Set in Sacramento, California that I have wanted to duplicate for years. Now that I am retired/disabled I hope to help fill in these empty hours and realize that dream if I can locate the parts and schematic.

What was unique about this Xtal set, it was powerful enough to require a volume control and drive a 3.5" PM speaker. It was very sensitive and selective for a radio of this type. I noted down the schematic and parts but have lost that information over the years Here is what I can recall and hope that someone might know of this Xtal Set and where I might find the parts, schematic and materials to build it.

It used a 1N34A Germanium diode as the detector. It used (2) two 242a antenna coils coupled with an EL55 coupling coil (Manufacturer?). Standard double gang tuning condenser, assorted caps. and resistors, variable pot., audio output Xformer, and an 8 ohm speaker if my memory serves me correctly after 50+ years.

Any help you might offer would be deeply appreciated

Thank you for your time, have a great day,

Sky
Mühlhausen, Germany

Somehow the answer to your question ended up in the wrong forum. Check here: viewtopic.php?f=19&t=192406
Seems to be an interesting project.

Thank you TexMac. I do hope I can run down the information on that Xtal Set someday. John85 sent some information for another 'like' Xtal Set and will attempt to build it in the near future if I can locate the parts, LOL.

Have a great day,

Sky

I've been wanting to build it for some time now myself, just haven't gotten 'roundtuit'. The original article was in a 1961 issue of Electronic Experimenters.
The coils are actually Miller 6300's.

Edit; this might not be the exact one you are looking for as it doesn't have a volume control.

Hi 'fifties', yes that is the same one that I was directed me towards by 'john85'. Looks like a great little unit and I plan on building it after my eye surgery providing I can find the parts. (I'm not sure if 'Miller' is still in business) I know it would be a great project for some the other research I’m doing to help other disabled/handicapped individuals improve the quality of their lives. Right now it is just a frustrating battle to find some older used and desperately needed test equipment to carry on with that research. I ‘ll manage one way or another, got no choice, LOL.

That Xtal Set still isn't the one that I saw in Sacramento, CA a half century ago. That one only used (1) one 1N34A diode and a vol. control. I remember the numbers on the coils (242a and EL55) but there was no Manufacturer name. I remember those numbers today because I was so impressed with that Xtal Set. I suspect ‘Miller’ also made those coils but I haven't been able to turn up much in my computer searches. I would ‘wind’ the coils myself if I could get all the specs. and material to do so.

If you run across some more of these wonderful ‘Old Jewels’ feel free to share them, I’m always interested.

Have a great day ‘fifties’ and thank you for contacting me and sharing the information. It is deeply appreciated.

Sky
Mühlhausen, Germany

Hi skyflute,

I have a J.W. Miller catalog from the late 70's - early 80's (no date in it), and could not find the numbers you posted, so if accurate, they must have come from some other manufacturer.

A crystal set with a volume control would be quite special indeed, given that it would be relying solely on the RF energy produced by only one Diode, per your description.

I had to downsize the scans quite a bit to fit within the forum's parameters. If you (or anyone) would like larger images, send me a PM with your email addy, and I can attach full size scans with a reply.

Here's a link to a crystal radio circuit that apparently doesn't need an antenna or ground wire;
http://www.arrl.org/files/file/Technolo ... culter.pdf

Where is Mühlhausen, BTW?

I was stationed in Wurzburg (Bavaria).

Hi again 'fifties':

Finding the schematic and parts for that radio has been like trying to find a 'chicken with teeth'. I am pretty sure of the ‘coil numbers stamped on the coils’ and etc. Chances are ‘Miller’ discontinued the coils by the 1970s (Remember, I saw and heard that radio in the late fifties or early sixties) or another manufacturer made them as you suggested. I did a computer search for ‘Miller Coils’ and was directed to another manufacturer …. nothing there..

I tried to locate an old friend in North Sacramento, CA that worked at California Radio and TV Supply on Del Paso Blvd. back then. That is where the young fellow said he got his parts. I was attending American River Jr. College in Sacramento then. Unfortunately he has passed away and I can find little or no trace of Cal. Radio/ TV now; they may have changed their name or closed their doors. Very frustrating!

You asked where is Mühlhausen Germany, LOL. It is nearly dead center of Germany about an hour west of Erfurt or north of Isenau (sp) about 45 km. Just put an X through Germany and go to the center of that X and you will be very close. Good thing you asked, from what I have heard there are at least two-dozen or more of them in Germany, LOL. The Zip is 99974 if that will help.

Thank you for the scans and links, it is deeply appreciated.

Yes, I thought it was a very unique little Xtal Set, but then as an after thought…. Sacramento is a major city with several powerful radio stations (KCRA; KFBK, etc.). What got may attention was he could tune in ‘KGO’ clearly from San Francisco, CA. He had a long-wire antenna strung up high in a pine tree and across his backyard. The idea of finding and making that Xtal Set makes my mouth water just to see how well it would work here in the ‘middle of nowhere’ Germany, LOL.

Have a great day ‘fifties’, great chatting with you.

Sky
Mühlhausen, Germany

Hi 'fifties':

For a while there I thought I was loosing my mind until I found this article from Homebrew Radios!

KyMike Post subject: Antenna Coil Oddity Posted: Jan Tue 30, 2007 7:47 pm

Member
Joined: Jan Thu 01, 1970 1:00 amPosts: 343Location: Louisville, Ky.

Decided to check out a homebrewed crystal set I picked up cheap at a flea market a while ago. Its a very simple circuit, using a Miller 242-A 540-1750 k.c. antenna coil with the secondary tuned by a 365 mmf capacitor, and a 1N34 glass diode for a detector. I noticed a very small ceramic capacitor, one of the ancient tubular types with the leads wrapped around the ends, connected between 1 primary and 1 secondary terminal on the antenna coil. The set didn't work very well at first, then I saw that one lead of the ceramic cap was broken. When I jumpered it to the other terminal, the signals became much louder and the set was picking up stations all over the dial. I'm guessing that the ceramic cap helps to fine-tune the coil to resonance when it is in the circuit, but the question is, why is it connected between primary and secondary instead of across the secondary coil? Or is there some kind of signal feedback going on from secondary back to primary?

Mike

The coils I've been looking for were indeed made by 'Miller!' Now, if I could only find the schematic for that Xtal Set that used two 242-A coils and a source or specs. for/to wind those two coils and the EL55 coupling coil myself; that long time dream just might become a reality, LOL.

Thought I would share this with you.

Happy Days 'fifties'.

Sky
Mühlhausen, Germany

viewtopic.php?t=67036
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Does the above help at all?

Hi Bill:

Thanks for the info but already had it and passed it on. At least it confirms who made the coils. Wish I could find a few of them and the coupling coil. Really wish I could remember what magazine the young lad said he found the schematic in back then. Running down information from 50+ years ago has turned out to be quite a challenge. I'll keep plugging at it. Some 'old tinker', like me, might just have the schematic somewhere. Well, I can dream .... can't I?

Thanks for the input.

Have a great day,

Sky
Mühlhausen, Germany

That 6300 is in Miller No. 61., page 19.

Schematic 5 is simply an adjustable coil; no taps, no other windings.
In the cross reference section they give Meissner 14·7000 as equivalent.

This catalog is also not dated but their "HIGH FIDELITY BROADCAST BAND AM TUNER AND TUNER KIT" (crystal with no tubes or power) touts 'good bet for emergency' CONALRAD use and mentions a 1956 FCC ruling that all tuners and tuner kits are subject to a 10% excise tax, so that places it between 1956 and 1963.

Hi skyflute,

If anyone is losing his mind here, it's prolly me, lol. Regardless, I looked in the catalog again, and can only find these numbers for "Transistor Antenna Rods"; 2000 - 2010, inclusive, and for coils, 6300, 705-A, 70-A, 71-RF, broadcast band coils, A-5495-A & RF, -320-A & RF. This is out of Miller General Catalog 81, which boasts of containing over 4000 items.

Miller did offer a crystal tuner kit, for use as a Hi-Fi tuner, to be connected to an amplifier. I am wondering if the coils you are referring to might not have been a specialized component, made just for that kit.

In the same vein, I have a couple of Heathkit CR-1 crystal receivers, and they use specialized coils I've never seen anywhere else.

Just a thought.

Sorry, I missunderstood which coils. The 242-A is in Miller 61 on page 21

Progressive Wound Coils
These coils are used in quality receivers where precision construction and supreme performance
are indicated. Secondaries are Litz wire wound. High impedance primaries with. capacity coupling,
wound on bakelite tubing and for use with a standard .000365 mfd. variable condenser.
Dimensions: 'Ys" diameter (form) by 23/4" high.
Cal. No. Use Unshielded Range Schematic Llsl Price
241·A Antenna Stage 540·1750 KC 104 $2.00
241.BP Band·Pass Stage 540·1750 KC 1 1.75
241·RF R.F. Stage 540·1750 KC 104 2.00

Schematic 104 is two coils with a capacitor coupling one end each coil's winding to the same end of the other.

The catalog also shows Miller EL-55 as a cross for Stancor RTC·8728 but contains no other information for it and my Stancor catalogs don't list the RTC-8728.

Hi 'Flipperhome':

'BINGO!' Good to know that I am not losing my mind after all and that my 'recall' is still working fine. Was starting to get pretty worried.

Yep, those are the coils (Miller 242-A and EL-55) but I have no way to access that information over here unless you know of some 'links' you could share. I would be very interested in the schematic that you mentioned (Re: Schematic 104 is two coils with a capacitor coupling one end each coil's winding to the same end of the other.). That schematic is getting close to what I am searching for but you mentions no use of the EL-55 coupling coil from what I can glean in your description. I am now wondering how it fit in the circuit and why. I feel that we are getting close to finding the schematic for that little bugger of a Xtal Set. Does anyone still make these coils or a replacement for them or have they also gone the way of the 'Dodo bird'?

Thank you for the information, you just made an 'Old Man' very happy.

Have a wonderful day 'Flipperhome'

Sky
Mühlhausen, Germany

I'm glad to help but not sure how much it really is. The "schematic" is just for the coil, not a 'radio'. I don't remember from where I downloaded the Miller catalog no. 61 but here is the info from it.


By golly, I'm beginning to think I'm a miracle worker. I found an EL-55 reference. It's a "mutual coupling coil" and is used in the Miller 585 "Band Pass TRF Tuner using a germanium diode detector" which, hold on to your hat, also uses the Miller 242-A antenna coil.

I don't know if someone was trying to drive a speaker with it or used the same basic schematic as a front end to something but it uses the coils your memory recalls.

You can get to the schematic from this page http://fmamradios.com/XtalTuner.html

Finding those Miller coils is probably next to impossible but "Dave" rolled his own in his version of the Miller crystal radio.
http://makearadio.com/crystal/16.php

Good afternoon 'Flipperhome':


'Yowza!' I think you found the basic schematic for the one I’m looking for, the Miller 565 tuner but is missing the output Xformer and spkr. that I saw on the one in Sacramento, CA. I looked at ‘Dave’s Homebrewed one’ and the circuitry seems to be a close match also, less the RF Choke.

Is there any way to find the ‘exact coil specifications’ for those Miller coils? Something tells me that lot of the ‘secret’ of the operation (selectivity, sensitivity and etc.) lies in the construction and material used in the original ‘Miller coils’. (I’m no expert and have been out of the ‘Electronic Loop’, so to say, since being permanently injured in 1970.) I just want to duplicate those coils as accurately as possible and build that little ‘beastie.’ Then try to figure out why it worked so well and could drive a small speaker to boot,… without an amplifier. (Something to pass on to my grand kids and others ‘from the old magical years of the first radios.’)

Again, thank you for the information … you truly are a worker of miracles. Ever see an ‘Old Indian’ dance up a storm without drums? Just hope I don’t break something important in the process. LOL.

Have a great day,

Sky
Mühlhausen, Germany

Again it may not help but tubesandmore sells miller 70 and 70A replicas.

The 'secret' is good quality, I.E. high Q, coils and the double tuned 'band pass' circuit. The circuit is there and the rest is good coil winding practice with Litz wire. The Miller catalog says bakelite tubing but just translate that to 'high quality form'. Dave's 'formless' weave coils qualify.
My first reaction to his 'EL-55' clone winding method was to note it appears to be phased wrong, although I'm not sure it matters, but, if it does, that can be corrected by reversing the second '242-A' clone coil polarity.

Actually, I have but am wondering what the Germans think of it