Hi gang,
I have been playing around with VHF "rushboxes" for a while now. Very interesting circuit. I have built some for 6M as well as 2M. Some have been copies of existing designs (i.e. Heath, CB walkie talkies) while others I have struck off on my own.
My best so far will produce a useable audio output down to around 2uV RF in. I plan to add an RF amp ahead of the detector to see if I can improve that, although convention wisdom says that is a dead end. We'll see.
Virtually every part in the circuit can be tweaked to have some kind of effect on performance, which is both a blessing and a curse!
One interesting phenomena I discovered by accident almost had me shove the circuit off the table into the wastebasket and go have a drink(s). One circuit was working fine, and I was playing around with some values. Suddenly the darn thing would not demodulate at all. 1V of RF at the input gave nada. Suddenly the circuit would come back to life. Finally I discovered that when I had my Metcal soldering iron turned on it killed the circuit! I know Matcals use RF to heat the tip, and apparently it kills the operation of the circuit.
All of my various iterations of the circuit exhibit this effect to varying degrees.
I would be remiss to not include the caveat of not connecting any sort of antenna to a superregen without some kind of unity gain amp/buffer between the detector and antenna. Superregens are a part time oscillator and you don't want to get a pink ticket! This would be especially true when playing around with one on the aircraft band.
My end goal is to make a couple of 6 or 2m walkie talkies to show off at the ham club meeting (if we ever have anymore....)

73
Bob WB0POQ

In article ,
says...

Hi gang,
I have been playing around with VHF "rushboxes" for a while now. Very interesting circuit. I have built some for 6M as well as 2M. Some have been copies of existing designs (i.e. Heath, CB walkie talkies) while others I have struck off on my own.
My best so far will produce a useable audio output down to around 2uV RF in. I plan to add an RF amp ahead of the detector to see if I can improve that, although convention wisdom says that is a dead end. We'll see.
Virtually every part in the circuit can be tweaked to have some kind of effect on performance, which is both a blessing and a curse!
One interesting phenomena I discovered by accident almost had me shove the circuit off the table into the wastebasket and go have a drink(s). One circuit was working fine, and I was playing around with some values. Suddenly the darn thing would not demodulate at all. 1V of RF at the input gave nada. Suddenly the circuit
would come back to life. Finally I discovered that when I had my Metcal soldering iron turned on it killed the circuit! I know Matcals use RF to heat the tip, and apparently it kills the operation of the circuit.
All of my various iterations of the circuit exhibit this effect to varying degrees.
I would be remiss to not include the caveat of not connecting any sort of antenna to a superregen without some kind of unity gain amp/buffer between the detector and antenna. Superregens are a part time oscillator and you don't want to get a pink ticket! This would be especially true when playing around with one on the
aircraft band.
My end goal is to make a couple of 6 or 2m walkie talkies to show off at the ham club meeting (if we ever have anymore....)

73
Bob WB0POQ



Unless you have seen it, in the 1966 ARRL handbook is a 420 MHZ
transceiver that will do what you want. It uses a nuvister tube and 2
transistors. The nuvistor is a super reg receiver or a modulated
oscillator. As that was at a time before transistors worked very well
at 400 MHz, a transistor or FET may be able to be subistuted now with a
minor circuit change. A few coil/capacitor changes would put it on
either 6 or 2 meters.