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 Post subject: 1917 Regenerative Receiver - Build Project
PostPosted: Jul Sun 12, 2020 4:33 am 
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Location: Sioux Falls, SD
I picked up some old magazines and was fascinated by the earliest radio designs, equipment and articles. From this I have started to collect parts and materials for building a period correct radio. I have mocked up a radio to test the design and parts and once complete I will build the cabinet and final radio. I have focused mostly on 30s radios in the past and thought of battery radios from the 20s as old. Now as I am looking for really old parts even stuff from the 20s is too new. My plan is to post along the way and would invite any advice or comments as my key goal is to be period correct.

I have locked on to a circuit design from an Everyday Engineering article from May, 1917. The second circuit was noted to be "used extensively in the Navy",and seems to have survived over the years as I have seen this design from many different references. This was written by Milton Sleeper who had a long career in radio https://worldradiohistory.com/Archive-FM-Magazine/MiltonSleeperBio.htm. I have also studied most of Dave Schmarder's website with his number 30 matching closely http://makearadio.com/tube/1-30.php. Further the World Radio History website has a huge library of old magazines that I have started to search through for old references https://worldradiohistory.com/.



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 Post subject: Re: 1917 Regenerative Receiver - Build Project
PostPosted: Jul Sun 12, 2020 4:53 am 
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For anyone interested here are some of the old magazine articles that I have earmarked so far for having good build instructions. One thing I would love to find would be a copy of the Duck catalog from 1916 or 1917.


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 Post subject: Re: 1917 Regenerative Receiver - Build Project
PostPosted: Jul Sun 12, 2020 5:10 am 
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Location: Sioux Falls, SD
One more post to get caught up to present day. I started working on building the fixed capacitor. To stay true to the era I built the capacitor using layers of real tin foil and mica held together with ebonite plates and brass hardware. The nice thing with tin is it solders easy, not so much with aluminum foil. The above articles often mentioned using either hard rubber (ebonite) or bakelite, my first plan was to resuse some old parts that had a large piece of bakelite but ebonite is still made and I was pleased to learn that it machines real nice, I was able to thread the bottom plate to accept the 4 brass bolts. The dimensions are roughly 2.5" by 5" with 5 layers of tinfoil, it measures approx 0.0026 uf. This cap will be used to across the headphones.

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 Post subject: Re: 1917 Regenerative Receiver - Build Project
PostPosted: Jul Sun 12, 2020 7:16 am 
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Looks very interesting! Have you tried operating the radio, and if so, how does it perform?

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 Post subject: Re: 1917 Regenerative Receiver - Build Project
PostPosted: Jul Sun 12, 2020 6:01 pm 
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Modern Electrics, many construction articles how to build the electrical devices, pre-triode era...

Quote:
ebonite is still made
Sweet, where did you find it and is it still called ebonite, hard rubber?

Chas

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 Post subject: Re: 1917 Regenerative Receiver - Build Project
PostPosted: Jul Sun 12, 2020 6:07 pm 
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The radio works well and with the right antenna probably can be even better, currently I have a long wire strung up the wall and across the length of the attic, also have a solid ground post outside driven 6’ down. I am using a type 30 tube to test with and for now I am sliding the coils for antenna coupling and regen control. With enough adjustment I can separate out a few weaker stations away from the local high power stations. I wound the coils to tune the full AM band and with nothing above 600 meters I probably will skip using higher turn counts and coil taps. My end plan is to build variocouplers for both antenna coupling and regen control. I will be looking for a good set of high impedance phones but for now I wired in a 2k audio transformer to connect a nice pair of modern phones. Volume is good on all stations.

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 Post subject: Re: 1917 Regenerative Receiver - Build Project
PostPosted: Jul Sun 12, 2020 6:16 pm 
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There is a Japanese site that sells larger sheets but the 1/4+” sheets only come in 600x900mm and are expensive https://www.nikkoebonite.com/english_site/order/plates_e.php. If all goes well I may have to place an order for the front panel.

For now I found smaller plate stock and round rod at Vermont Freehand https://vermontfreehand.com/rods/black-ebonite/. The plan is to turn the knobs from ebonite too.

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 Post subject: Re: 1917 Regenerative Receiver - Build Project
PostPosted: Jul Sun 12, 2020 6:17 pm 
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:D


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 Post subject: Re: 1917 Regenerative Receiver - Build Project
PostPosted: Jul Sun 12, 2020 6:27 pm 
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Thanks for the info. I would have never dreamed that a source for ebonite rods would be smoking pipe bit
supply...
Yes, I will treasure what scraps of hard rubber panel I have, even though they are green and warped...

FYI when the former Play Things of Past re-opens there may be a source of used panel material there..

Ingenious mount for the Gates cell, a round capacitor clamp...

How much life do you get from the Cyclon Accumulator? Hmm, at 30ma probably an entire weekend "on the air".

Chas

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 Post subject: Re: 1917 Regenerative Receiver - Build Project
PostPosted: Jul Sun 12, 2020 6:51 pm 
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I've built a '26ish shortwave radio with all original parts including Bakelite panel. It was fun but to a very long time to find all the parts so I'm following this for inspiration.

it interesting how the term "shortwave" changed during that period of time. In 1916 that generally meant 500Kz and higher, IE MW and up. It wasn't until mid to late 20s that folks starting thinking of "shortwave" as frequencies above what eventually became the "broadcast band".

Steve


Last edited by targeteye on Jul Sun 12, 2020 7:41 pm, edited 1 time in total.

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 Post subject: Re: 1917 Regenerative Receiver - Build Project
PostPosted: Jul Sun 12, 2020 7:39 pm 
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Wonder if the schematic was taken from early De Forest prints? Notice the grid leak resistor was left off.

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 Post subject: Re: 1917 Regenerative Receiver - Build Project
PostPosted: Jul Sun 12, 2020 8:21 pm 
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I for one could use an education on how a deforest set may operate without one?


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 Post subject: Re: 1917 Regenerative Receiver - Build Project
PostPosted: Jul Sun 12, 2020 10:19 pm 
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It seems like all of the designs are absent a grid leak resistor. In another article by Milton Sleeper from Jan 1917 Everyday Mechanics (page 28) he states in regards to a grid capacitor “a tiny condenser is attached to the grid to prevent a positive charge from collecting on the grid”, but no reference to any grid resistor https://worldradiohistory.com/Archive-Everyday-Engineering/Everyday-Mechanics-1917-01.pdf.

I will have to go back and search, I thought I found a period article about maybe a grid resistor but most audion tubes wouldn’t need it.

I should note I added a grid leak resistor for my test radio.

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 Post subject: Re: 1917 Regenerative Receiver - Build Project
PostPosted: Jul Sun 12, 2020 10:47 pm 
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The early tubes leaked. For those that didn't, grid condensers had a rough finish to one side of the body to which a soft pencil line provided the leak. A strip of insulating material with holes and machine screws provided the area to pencil-in a line too.

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 Post subject: Re: 1917 Regenerative Receiver - Build Project
PostPosted: Jul Sun 12, 2020 10:50 pm 
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Here's an item you might want to use... :wink:


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 Post subject: Re: 1917 Regenerative Receiver - Build Project
PostPosted: Jul Sun 12, 2020 11:21 pm 
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HA, ha, haaaa. Cute, but too late to the radio party in the early teens.,..

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 Post subject: Re: 1917 Regenerative Receiver - Build Project
PostPosted: Jul Sun 12, 2020 11:35 pm 
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I suppose even a poorly operating regenerative Audion detector would still be more more sensitive than a strait crystal receiver. Did a of reading at the time and the impression i get is they were still not sure exactly how to do it all and it was very much a time of experimentation. When I say "they" i mean Amateurs.

At this time the "receivers" were just that and the "detectors" were separate devices. So I guess a likely true representation would be a loose coupler for your typical DIY station with your external detector of choice. (audion or crystal based). There is a combination unit in the QST artical above but I don't think that would be typical of the time.

Heck one article I read seemed to indicate just getting a decent Audion was hit or miss and Deforest didn't warrant them unless you bought them right along with a Matched Audion Detector unit!

Hope i'm not hijacking the thread.

Steve


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 Post subject: Re: 1917 Regenerative Receiver - Build Project
PostPosted: Jul Sun 12, 2020 11:44 pm 
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 (6) Do not try to use a fixed condenser in series with an Audion Detector. Every one of these instruments has a special mica condenser within it, properly connected and built, and I do not believe it can be improved upon. Unauthorized parties give all kinds of advice, but it seems only reasonable that the manufacturers should know and install what is right

https://en.wikisource.org/wiki/QST/Marc ... the_Audion

Reading between the lines. The condenser is custom made to the particular tube to compensate for its particular leakage and inter-electrode capacitance characteristics.


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 Post subject: Re: 1917 Regenerative Receiver - Build Project
PostPosted: Jul Mon 13, 2020 12:13 am 
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An interesting read, so much said, made obsolete just a short time later...Applying a mystical quality to the Audion... :?

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 Post subject: Re: 1917 Regenerative Receiver - Build Project
PostPosted: Jul Sun 26, 2020 4:28 am 
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Finished up building the air variable capacitor. I used the article from the Nov 1915 Electrical Experimenter (page 39) as my "period correct" blueprint https://worldradiohistory.com/Archive-Electrical-Experimenter/EE-1915-11.pdf.

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The end plates are 8mm thick ebonite with 8-32 threaded brass rod to hold the capacitor together. I "cheated" and used aluminum plates from a scrapped FADA neutrodyne radio. The center shaft is 1/4" brass rod with one end threaded. Note I will cut off the shaft end to length once I determine the final mounting and cabinet. Depending on the circuit I can add or remove plates but right now with 13 plates it measures 27pf to 301pf. Dimension are approximately 4" x 2 1/2 x 3 1/5 inches deep. It took a bit of searching but all of the brass parts and aluminum spacers are available.

I should say as you add more plates it takes a great deal of fine tuning to get the capacitor to work well. I started with the spacers from the FADA capacitor but they were quite thin and I could not get it to turn without shorting out. In fact while the article calls out 7/64" (0.109") spacers I ended up using 1/8" (0.125") spacers to help with this, also 1/8" is what is sold today.

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Last edited by bheggeseth on Jul Sun 26, 2020 4:35 am, edited 1 time in total.

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