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 Post subject: Popular Electronics 1955 "One Tube Wallop"
PostPosted: Sep Wed 11, 2019 5:47 am 
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Hi Folks, I've built this radio twice and I'm still not happy with it, I'm sure of the construction. I make mistakes but even I'm not that dumb. I have poor volume at best and the 1955 project article says it should power easily a 3-ohn speaker, also with a 10-foot antenna which again should be ok for a few stations I receive WBZ Boston which so powerful that a piece of wire can hear, I struggle to hear 3 stations.

Any help would be appreciated I've include two copies of the original article.
Tony

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 Post subject: Re: Popular Electronics 1955 "One Tube Wallop"
PostPosted: Sep Wed 11, 2019 6:16 am 
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Location: Omak,wa,usa
Hello Tony,
anyway looks like it should be a nice build how is your ground or did you ground it to earth ground .

Sincerely Rich


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 Post subject: Re: Popular Electronics 1955 "One Tube Wallop"
PostPosted: Sep Wed 11, 2019 7:32 am 
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Popular Electronic construction articles weren't always the best. I built a tube set in 1959 from one of their projects and never could get the damn thing to work. I even had my electric shop teacher review it, and he couldn't figure it out either.

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 Post subject: Re: Popular Electronics 1955 "One Tube Wallop"
PostPosted: Sep Wed 11, 2019 11:38 am 
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Location: Revere,Massachusetts U.S.A.
Hi Rich, I use a cold water pipe for a ground that's the only way I get any signal at all however, I didn't mention that per the instructions to align ask for an RF Generator to be placed at the antenna & Ground connection. Set the radio to 1600
khz and drive a signal through, I couldn't do that.

I double-checked the generator and it's working fine, I also went over the schematic just to see if a wire was placed wrong and I couldn't find it? Well I hope this helps and again Thanks So Much

Tony

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 Post subject: Re: Popular Electronics 1955 "One Tube Wallop"
PostPosted: Sep Wed 11, 2019 12:46 pm 
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Location: 13 Critchley Avenue, PO Box 36, Monteith Ont, P0K 1P0
To my eye it looks like a pretty poor radio. There's a tuned RF tank, but no RF amp because the tank feeds directly to a diode section of the tube. That's followed by two stages of audio. In my opinion you'd be better off to use a dual function tube (triode pentode or even double triode) for audio and do your detecting with a crystal. The way this set is built, unless your tank circuit is well built(hi Q), it's not going to "select" well.

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 Post subject: Re: Popular Electronics 1955 "One Tube Wallop"
PostPosted: Sep Thu 12, 2019 12:45 am 
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One suggestion that might help a little. The antenna input VC is just 3~30pF. That's OK for SW but too small for MW BC. Especially with a short antenna. Try putting a larger cap across that (100pF~470pF). That should increase the signal level. It might even work to simply connect your antenna directly to the tank; after all, it's basically just a crystal diode with audio amplification.

Rob


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 Post subject: Re: Popular Electronics 1955 "One Tube Wallop"
PostPosted: Sep Thu 12, 2019 1:53 am 
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It's basically a tube version of a crystal set, with a two-stage audio amplifier. It will have all of the reception problems of any crystal set; you'll need a good antenna and ground. Are you using a standard antenna coil?

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 Post subject: Re: Popular Electronics 1955 "One Tube Wallop"
PostPosted: Sep Thu 12, 2019 3:47 am 
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If you are interested in a one tube radio with the same tube perhaps consider one of these?

The first is a regen with a single audio stage and the other is a TRF with a single RF stage, detector and audio amplifier.

http://makearadio.com/tube/1d8-sw.php

http://onetuberadio.com/2015/02/25/one- ... iver-1945/

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 Post subject: Re: Popular Electronics 1955 "One Tube Wallop"
PostPosted: Sep Tue 17, 2019 3:03 pm 
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Location: West Point, PA 19486
Tim Tress wrote:
It's basically a tube version of a crystal set, with a two-stage audio amplifier. It will have all of the reception problems of any crystal set; you'll need a good antenna and ground. Are you using a standard antenna coil?


I agree. When I saw the Miller 6300 coil it reminded me of the Alfred P. Morgan crystal set I built. Reception was lousy, even with an amplified speaker. This One Tube Wallop is basically the same setup as the crystal set and amp.


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 Post subject: Re: Popular Electronics 1955 "One Tube Wallop"
PostPosted: Sep Wed 18, 2019 12:21 am 
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Joined: Nov Mon 06, 2017 2:35 pm
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Location: Texas, U.S.A.
.......
Tony, the 1D8GT pentode needs about 6.4 V RMS at its control grid (pin 5) for full 200 mW output with the 90 V dc supply shown and with 12 k ohms plate load presented by the audio output transformer. (ref. RCA data sheet)

The 1D8GT triode section voltage gain with the 100k load is around 17.

6.4 / 17 = around 375 mV RMS audio required at the triode grid for full audio output.

To test the audio gain of the tube, turn the volume control to the full volume position and use an audio frequency source to inject around 375 mV RMS audio between the triode grid (tube top cap) and ground. If the speaker impedance is close to 3.2 ohms, the voltage across the voice coil should be around 600 to 800 mV RMS.

Assuming an amplitude modulated RF signal of 100% modulation, ideal operation of the diode and R1 set for zero attenuation, 1.06 peak to peak RF volts would be needed across the tuned circuit to produce 375 mV RMS audio at the triode grid.

I endorse Shinkuukan's suggestion of increasing the capacitance of C1, and the other suggestions to convert the receiver to a regenerative circuit.

--------------
Eric LaGess
WB5HDF


Last edited by infzqi on Sep Tue 24, 2019 8:45 pm, edited 1 time in total.

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 Post subject: Re: Popular Electronics 1955 "One Tube Wallop"
PostPosted: Sep Thu 19, 2019 3:42 pm 
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Just thinking. If your objective is to use all three elements of the 1D8, the most effective radio you might make with the one tube might be a superhet. Utilize the triode as an autodyne converter, and the pentode as reflexed IF and audio amplifier stages. The diode would remain as the detector.

A little RF and IF regeneration might bump up the gain.

This would still be marginal for driving a speaker, but could make a pretty hot headphones set.

I agree that a regenerative detector followed by an audio stage would give the most performance for something simple, but then that diode is wasted.

Ted


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 Post subject: Re: Popular Electronics 1955 "One Tube Wallop"
PostPosted: Sep Mon 23, 2019 1:22 am 
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How about a regen with the triode and the pentode for audio? That ought to drive a speaker and be more selective. You could check later issues. I don't know how bad they were but the ham mags were always publishing a circuit and then next month or later, adding the corrections in small print hidden in some corner of the magazine. At least if you built from the Handbook, you could assume by that time the circuits were debugged?

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 Post subject: Re: Popular Electronics 1955 "One Tube Wallop"
PostPosted: Sep Mon 23, 2019 4:16 am 
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Hello guys,
anyway this looks like fun project


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 Post subject: Re: Popular Electronics 1955 "One Tube Wallop"
PostPosted: Sep Mon 23, 2019 6:03 am 
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Rich, there have been too many one tube circuits published over the years to fiddle with one like this, that apparently does not perform well.

I built a one tube set using a 1T4 back in the fifties, and just using a modest antenna wire picked up a variety of stations, including KFBK in Sacramento, about 400 miles away. Granted however I had to use a headphone, as the B supply was just a 22-1/2 volt battery.

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 Post subject: Re: Popular Electronics 1955 "One Tube Wallop"
PostPosted: Sep Mon 23, 2019 6:51 am 
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Location: Tucson, Arizona U.S.A.
How about the one the September 1956 issue https://americanradiohistory.com/Archive-Poptronics/50s/56/Pop-1956-09.pdf on page 75. It is a one-tube superhet with a reflex circuit so it should out-perform the one you built. Since it uses a 6U8 triode-pentode, you can probably whip up a version using the tube you have. The diode in the tube could be used as the detector, CR2. Only one semiconductor would be needed, the mixer diode CR1.

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 Post subject: Re: Popular Electronics 1955 "One Tube Wallop"
PostPosted: Sep Tue 24, 2019 12:14 am 
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If you like one-tubers you might want to look at the German Kleinempfaenger for inspiration. It used a triode-tetrode. I made a version of this set using a 16A8 triode-pentode. It has an 8-inch speaker and has plenty of volume on local stations while using about 15 feet of wire strung around the room as an antenna. Using an outside antenna of 50 feet or so will bring in stations from hundreds of miles away at night.

Don't believe stories on the net about the originals only being able to receive local stations. This is nonsense propagated by those who have no understanding of propagation.

RRM


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 Post subject: Re: Popular Electronics 1955 "One Tube Wallop"
PostPosted: Sep Tue 24, 2019 12:40 am 
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Retired Radio Man wrote:
If you like one-tubers you might want to look at the German Kleinempfaenger for inspiration. It used a triode-tetrode. I made a version of this set using a 16A8 triode-pentode. It has an 8-inch speaker and has plenty of volume on local stations while using about 15 feet of wire strung around the room as an antenna. Using an outside antenna of 50 feet or so will bring in stations from hundreds of miles away at night.

Don't believe stories on the net about the originals only being able to receive local stations. This is nonsense propagated by those who have no understanding of propagation.

RRM

Here's a link: https://antiqueradio.org/KleinempfaengerDKE38.htm. It is regenerative detector followed by a one stage power amplifier. When I was in high school, I built a similar set using a 6C4 and a 6K6. It worked fine on local stations; I wasn't interested in DX.

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 Post subject: Re: Popular Electronics 1955 "One Tube Wallop"
PostPosted: Sep Tue 24, 2019 4:47 am 
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Posts: 3982
Location: Florida
A web search will bring up lots of sites about the Kleinempfaenger (the name means small receiver). Years ago while on a trip to Europe I had a chance to buy one but at the time I didn't know anything about then so I passed it up. Bummer, since the prices are a lot higher now.

In Germany during the war it was a crime to listen to foreign stations. There was a little reminder tag provided that fit around one of the knobs. How many people ignored the warning I have no idea but the Nazi government wasn't known for leniency.

RRM


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