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 Post subject: Anyone seen a two-tube compactron superhet project?
PostPosted: Jan Mon 29, 2007 9:16 pm 
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Joined: Jan Thu 01, 1970 1:00 am
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Location: Redmond, WA USA
I have been looking through my stock of compactrons. I can find twin semiremote-cutoff pentodes. I can also find beam power pentodes paired with a sharp-cutoff pentode.

Here is a twin semiremote-cutoff pentode:
http://www.nj7p.org/Tube4.php?tube=6AR11

Here are tubes for the first and second audio stages:
http://www.nj7p.org/Tube4.php?tube=6bf11
http://www.nj7p.org/Tube4.php?tube=6al11
(and others)

Sounds like the makings of a superhet receiver.

Say we used a crystal diode for the detector, we could then use the sharp-cutoff pentode as the first audio.

The two semiremote-cutoff pentodes could be RF and IF. But the oscillator may be a tad more difficult, I have found no compactrons with a pentagrid converter and a remote-cutoff pentode. I think the oscillator function could share with one of the other stages. Normally an oscillator is a problem because the signal level grows to the saturation level. But Bell System built touch-tone pads with a single transistor oscillator running at two different frequencies (Bell System Technical Journal, Nov. 1960). The trick was to clamp the oscillator levels with diodes.

Perhaps the RF amp could also be the oscillator. I wonder if it would sufficiently mix with the RF to produce enough IF signal. If not, maybe we could use a diode mixer

Use a diode rectifier, and bingo, you could have a decent little superhet with just two fat little compactron tubes.

Perhaps someone has seen such a circuit already, and maybe something close. Please post a link if you have.

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Izzy


Last edited by Izzy Weird on Jan Mon 29, 2007 10:52 pm, edited 1 time in total.

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PostPosted: Jan Mon 29, 2007 9:45 pm 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 2782
Location: Powder Springs,Ga. USA
Not two but three

http://pw2.netcom.com/~wa2ise/radios/compaa3.html

_________________
Terry, K4TLJ
"Never run out of airspeed, altitude and ideas at the same time"


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PostPosted: Jan Mon 29, 2007 9:52 pm 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 1873
Location: Redmond, WA USA
Here is a compactron superhet, but not with two tubes. They used the 6AR11 too.

http://www.geocities.com/CapeCanaveral/ ... mfiles.htm

I really think the first stage can also be the oscillator. In other words, make the old Autodyne (pentode oscillator/mixer) design behave with the help of diode clamps.

http://en.wikipedia.org/wiki/Autodyne

Izzy


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