UK Vintage Radio Repair and Restoration Discussion Forum - View Single Post - Looking for a cheap and simple shortwave regenerative kit

MrBungle · 24th Jan 2018, 10:33 am

Did some research for this just now as I'm going to have to do the same thing. I have all the bits lying around though, and a couple of VFOs I've already built...

There was someone selling a VFO kit specifically for this, but as you can see, it's no longer for sale: http://www.tuckley.org/vfo/

Jabdog sell a complete kit for a VFO only. This might be a good option for you! See: http://www.jabdog.com/kits-txrx.htm

However a note: such is life and it's pretty difficult to throw together a VFO these days because of parts availability. The original varicaps/varactors specified tend to simply not exist these days or be tiny SMD parts. Air variable capacitors are dead and gone. Polyvaricons are terribly unstable, fragile and unreliable. Everything is heading towards cheap digital synthesizers such as AD9850 variants or Si570's. I rather like the latter as you can get it to generate the VFO and BFO frequencies.

RSGB does however have some advice here as they seem to be way behind the times and backtracking: https://thersgb.org/publications/boo...ediate-vfo.pdf

Just a point with the hfsignals kits; they are actually already complete and you are only required to attach the various control tentacles to the board and throw it in a box. That wouldn't cover the requirements to build and align the VFO as it's prebuilt and pre-tested.

Here's a VFO I did yesterday to evaluate using LEDs as varactors, because they're cheap. Add a 10 turn pot (£9) with some pad trimmers and you have a nice tuning system. This tunes low half of 40m (7000-7100khz):

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I think this is about £2's worth of parts and this has a power amp on it too.

A point with clubs though, at least in my experience, is that the few people I've talked to would never have actually built a VFO in their life so some of the advice isn't necessarily good. Always double check it elsewhere. Also there's a lot of religion in this stuff which makes no sense whatsoever.

24th Jan 2018, 10:33 am	#11
MrBungle Dekatron Join Date: Jun 2016 Location: London, UK. Posts: 3,687	Re: Looking for a cheap and simple shortwave regenerative kit Did some research for this just now as I'm going to have to do the same thing. I have all the bits lying around though, and a couple of VFOs I've already built... There was someone selling a VFO kit specifically for this, but as you can see, it's no longer for sale: http://www.tuckley.org/vfo/ Jabdog sell a complete kit for a VFO only. This might be a good option for you! See: http://www.jabdog.com/kits-txrx.htm However a note: such is life and it's pretty difficult to throw together a VFO these days because of parts availability. The original varicaps/varactors specified tend to simply not exist these days or be tiny SMD parts. Air variable capacitors are dead and gone. Polyvaricons are terribly unstable, fragile and unreliable. Everything is heading towards cheap digital synthesizers such as AD9850 variants or Si570's. I rather like the latter as you can get it to generate the VFO and BFO frequencies. RSGB does however have some advice here as they seem to be way behind the times and backtracking: https://thersgb.org/publications/boo...ediate-vfo.pdf Just a point with the hfsignals kits; they are actually already complete and you are only required to attach the various control tentacles to the board and throw it in a box. That wouldn't cover the requirements to build and align the VFO as it's prebuilt and pre-tested. Here's a VFO I did yesterday to evaluate using LEDs as varactors, because they're cheap. Add a 10 turn pot (£9) with some pad trimmers and you have a nice tuning system. This tunes low half of 40m (7000-7100khz): I think this is about £2's worth of parts and this has a power amp on it too. A point with clubs though, at least in my experience, is that the few people I've talked to would never have actually built a VFO in their life so some of the advice isn't necessarily good. Always double check it elsewhere. Also there's a lot of religion in this stuff which makes no sense whatsoever.