Wednesday, February 29, 2012

Regen receiver audio and UHF oscillator

Here's a small video of the ARRL simple regen receiver working, for posterity...

Note the "Swiss army" tuning shaft on the trimmer cap... as we say: "those without a dog hunt with a cat.."...

I think it's not this time the regen will get a new box, I already started cannibalizing one of the boards to make some tests on UHF, maybe an UHF receive converter will come out of this...

The result:
The circuit:

..another nice photo...

The circuit came from LY3LP 70 cm rx, I just used the T3 oscillator part.

Here's what I had of drift after 1m warmup with the circuit just bellow a reading lamp:

Considering the runing frequency I think it's not bad... the idea is to feed this LO (290Mhz) to an ADE-1 mixer down-converting 440Mhz to an 156Mhz VHF FM module I have (it's in the photo bellow the frequency counter) and didn't managed to program it in another frequency. An PLL stabilizer is then also needed.

I noticed that for a frequency bigger than 490Mhz I had to short-circuit C32 for the circuit to oscillate. I used an BB105 varicap and BFR91 transistor instead of the components in the original schematic, for L6 in the "final" prototype I used an ferrite bead (around 3mm long with 1mm hole and the wire passing inside one time only) recovered from a computer motherboard (good source for beads), R17 used 56 Ohm instead of the 33 one. Not critical I guess!

Have fun, generate some signals!

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