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Old 26th Aug 2012, 3:48 pm   #1
PJC58-Hythe
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Default 80m AM / SSB Receiver from a scrap VEF10

I was given a couple of VEF 10 Russian sets which cover MW, LW and several shortwave bands. I was able to make one good set from the two, but this left me with a more or less complete PCB minus the audio section (as this was shot).

As these sets are very well designed with a seperate oscillator and mixer and a well desgned IF strip with good characteristics, I thought it would be fun the see if a I could make a set to cover the 80m amateur band. I used the 41m coils and added the correct amount of capacitance to bring the oscillator and mixer down to the correct frequencies for 80m. I then added some series capacitance to a dual gang tuning capacitor I had lying around so it would tune 3.5MHz - 3.9MHz. As there was no audio section I simply used a pair of amplified PC speakers I had lying around rather than headphones (although heaphones do work extremely well with it).

I was able to listen to the AM net on 3.615MHz easily with a decent antenna, and was actually quite impressed at the sensitivity of this set. I then decided to knock up a BFO and product detector for SSB reception. I used the MW coil from the set and the correct capacitance to construct a colpitts oscillator BFO at about 470KHz, this then feeds into a two transistor product detector along with the IF signal to give audio. It works extremely well and will resolve both USB/LSB and CW. I have included the circuit of the BFO and product detector for interest and a photo of the 'lash up' which I will probably put in a box at some point.

Its amazing what you can make from 'left overs' - nothing goes to waste here!
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Old 26th Aug 2012, 3:57 pm   #2
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Default Re: 80m AM / SSB Receiver from a scrap VEF10

Well done. It's good to know the art of homebrewing amateur radio gear is not dead.

Better than being a plug snd play operator any day.
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Old 26th Aug 2012, 10:04 pm   #3
G6Tanuki
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Default Re: 80m AM / SSB Receiver from a scrap VEF10

Congratulations on your cunning!!

Kinda reminds me of my first foray onto 80M using a 'modified' medium-wave Philips transistor portable [AF117s and OC81D/OC81 push-pull output] - taking turns off the ferrite rod at random until it worked.

And I love the 'top-hat' transistors the Soviets used - distinctly reminiscent of the Ediswan XA/XC-series.

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Old 27th Aug 2012, 9:39 am   #4
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Default Re: 80m AM / SSB Receiver from a scrap VEF10

Great! It's so good to see a bit of art and thought go into even a simple project like this. It's the kind of thing I do when I'm feeling idle.
Those top hat transistors are like the ones in my 60's RRR Selga.It was a teriffic performer and dragged in the offshore pirates like Billy-O.
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Old 27th Aug 2012, 1:29 pm   #5
PJC58-Hythe
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Default Re: 80m AM / SSB Receiver from a scrap VEF10

Thanks for the encouraging comments.

I love doing this sort of thing and it's something I have done all my life (started in the 60's with military surplus kit). I think there is a great deal of satisfaction in creating something that works and serves a purpose - even if it's just for fun! While I have no problem with people buying commercially built stuff, if they don't design and construct as well I think they are missing out on two things. The learning experience, and the tremenous sense of satisfaction gained when building something. I know technically this was not from scratch, but I would happily design and build a comms Rx or Tx/Rx from the gound up, if only I had the time....

Peter
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Old 19th Sep 2012, 3:55 pm   #6
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Default Re: 80m AM / SSB Receiver from a scrap VEF10

Finally it ended up finished... Made a few mods - added an RF amp and RF gain, stablized the BFO and OSC with 5V regulators, screened the product detector and BFO, changed the way the mixer works slightly added a meter for signal strength and a simple RC bandpass filter for 300Hz - 4KHz just before the auidio amp.

The receiver is incredibly sensitive, and although there is the option to connect an external antenna the telescopic one does just fine on it's own.

Really had a lot of fun with this!

Peter
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