The Modern Radio Laboratories One Tube All Wave Receiver

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This is a Modern Radio Labs 1 tube regen radio, purchased as a kit from Elmer Osterhoudt in 1985.
Headphone jacks, antenna, ground and battery connections are all are in the back.

Back view. Phone jacks on the left, antenna and ground on the right.
This model is in pristine condition.

MRL made antenna tune capacitor. MRL made switch on main tune capacitor.

The instruction manual, and the underside. The battery is a 22.5 volt Eveready  #505. Notice the handmade coil socket!

Elmer Osterhoudt started Modern Radio Labs in 1932.
The copyright date on the instruction manual is 1953 but
we might guess he was selling them before that.
This radio was purchased in
1985 from the MRL catalog. Click for full sized view.
It's almost an accident that the radio remained in such fine condition. It was because of the hand made coil socket, which came already mounted on the base by Elmer.

When mounted beneath the base there is a 1/8" gap between the coil and the socket. The coils kept popping out! To listen to the set you had to hold the coil down with
your finger. I put the set in a cabinet, intending to modify it the next week.
That was 28 years ago.
The reasoning behind the handmade coil socket.
- from "RADIO FLYER No. 1, June, 1982."
Elmer also made the antenna trim variable
capacitor by hand.

In February of 2013 it was time to finish the project.
The coil socket and dead battery came out.
In went a Chinese made coil socket from ebay. Elmer rolled over in his grave!

You can still purchase the battery, for around 100 million dollars! I dropped this into the shopping cart and the price
remained at $99999999.00. In reality they can be had for about 12 bucks, but I tortured Elmer enough with the Chinese
coil socket. He recommended 9 volt batteries in series.

Elmer drew his schematics freehand. (with a straight edge) No computers back then.

C1 = Two plate variable capacitor 
C2 = 25 - 280 mmfd trimmer
C3 = 365 mmfd variable capacitor  (C2 & C3 are the same two section capacitor)
C4 = .0001 mfd mica capacitor
C5 = .00048 mfd mica capacitor
R1 = 2.2 megohms
R2 = 10K to 50K

The rewired base. The battery is gone, the coil socket has been
replaced and the aluminum binding posts were replaced with brass.
This is a set of MRL coils. Except for the pins and the
wire, they were completely hand made by Mr. Osterhoudt.

Crooked pins and sloppy coil cement. Today these coils are treasures.
The ultimate coil would have Elmer's fingerprint on it, which did happen occasionally.

Time to test it out. The complete setup, minus the high impedance headphones.

So how well does it work? SAH-WEET!
A 1.5 volt D cell powers the filament of the vacuum tube. The set comes on instantly, there is no warm up time.
In pitch dark the tube gives off a faint orange glow.

With a long wire antenna and no ground it had no trouble picking up stations on the broadcast band. My usual "test" of a radio is to tune it to AM 1210, broadcasting from Philadelphia. It is hard to pick up here in Upper Gwynedd, PA because their transmitter is in Moorestown, New Jersey! I was able to find it after some searching on the dial. Various short wave stations came in with no trouble at all.

However, without being grounded the set suffers from hand capacitance on weak stations. There is also a problem with capacitance in the headphone cord. If I took the headphones off and put them back on a few minutes later I had to retune the set.

With an earth ground connected the set is more sensitive and the hand capacitance isn't such an issue. With some weak stations the regeneration is so critical you can never quite pick them up. Others come booming in. This is normal for a simple regen.

Tuning a regen receiver is an art in itself, but I was very pleasantly surprised at how well this little set works. I tried various numbers of 9 volt batteries. The set worked with 9 volts to 45 volts. (It BARELY works at 9 volts and I could have gone higher than 45 volts but Elmer showed 22.5 volts in the schematic.) I settled on 18 volts.

The headphones used were a pair of Superex Deluxe SD, made in USA, with an impedance of 2000 ohms.
I kept Elmer's coil socket, it's a piece of radio history.

This circuit is over 100 years old, invented by Edwin Armstrong on September 22, 1912. It revolutionized the radio field, being the first circuit that could amplify a radio signal. (The patent was later stolen from him by Lee de Forest, inventor of the triode vacuum tube which was used in the circuit.) At this time in history most radio signals were of Morse code. The first commercial broadcast of voice was made on November 2, 1920 by Westinghouse station KDKA. Seven years later the airwaves were so packed with stations that the Federal Communications Commission was established to assign frequencies to broadcasters.

After looking through my records I found that the set I got in the mail was intended for Robert W. Lyons of 24th Street in Allentown, PA. We both ordered the same thing.

Here is the strange part: I have the envelope addressed to Robert Lyons with a return address of Modern Radio Labs. In the envelope is the order (from Robert Lyons) for the one tube set, dated December 3, 1984. Also included is the letter Elmer wrote back to Robert explaining that he mounted the vernier dial to the front panel. The stamps are CANCELLED. The cancel date is March 1985. If the stamps are cancelled, it must have made it to the Lyons residence! So how did the envelope with an order from Robert Lyons for the one tube set end up being sent to me?

Robert ordered the set as a Christmas present. My theory is that three months after Christmas he received the set in the mail, then sent it back to MRL along with the envelope. Elmer got my order in March and sent me the set Lyons sent back to him, with the envelope and order form from Lyons still in the box. My set came with the vernier dial already mounted on the front panel, as stated in the letter to Robert.

Anyone who has ever ordered from the old MRL knows how long it took Elmer to send out the order. The fact that he had to include a personal note with each order didn't speed things up any. For Robert Lyons to send in an order in December of '84 and not receive it till March of '85 was perfectly normal for MRL.

In January of 2016 I found a phone number for Robert and called it. His wife answered and verified I had the correct name, address and phone number. When I mentioned "radio" she said, "I got rid of all those radios last year. My husband has been passed away for 30 years." I apologized and hung up. He died in September of 1985 at the age of 51.

Though Elmer Osterhoudt is no longer with us, MRL lives on thanks to Paul Nelson. The MRL website is found here.