For your next project, eme reception using a half eaten kebeb found outside a pub. 😊

@SimonsSolarShed

5 ай бұрын

@spakkajack There is all sorts of stuff that make a kebab so it would not surprise me that he could actually make something out of it 😀😃

@peter-vk3acz

5 ай бұрын

Ah, so you you found out about Peter’s next project, eh? Cool…

You're right about listening to signals from half a world away. Used to be able to pick up Radio South Africa on the 11 meter broadcast band on the superregen I built from F.G Rayer's book "How to build Walkie-talkies" back in 1980 from here in the UK. It really was magical and this was during the apartheid era

When first licenced as a G8 in 1974 on 2m I made a valve super regen rx and valve xtal a.m. tx from one of the A.R.R.L. Handbooks. It worked okay. G4GHB.

Good video. The quench frequency is actually determined by the r/c network below the emitter choke. The value of the choke is somewhat irrelevant. As c charges thru choke it becomes positive and cuts trx off. Discharges thru parrallel r and so on.

The bias of the transistor should be adjustable to control the level of oscillation. Too much oscillation reduces sensitivity. Also, there should be quench filtering prior to the audio stages to prevent overload by the supersonic quench signal. Quench frequency is determined by the RC time constant in the emitter circuit, and for an AM receiver should be as low as possible before it starts to become audible or produce annoying intermodulation artefacts, for best sensitivity and highest audio output. About 20kHz is satisfactory.

@SimonsSolarShed

5 ай бұрын

Great tip actually variable bias

@vk3ye

5 ай бұрын

Thanks. I've increased the 33k resistor to 100k, reduced the 330k resistor to 100k and connected the hot end of the latter to the wiper of a 50k potentiometer connected across the power rail to vary the bias. In this it behaves a bit like a regen control but there's no reception before the point of oscillation. Adjusting from low to high voltage oscillation starts at a low audio frequency. At around 8 - 10 kHz (according to a measurement across the emitter 1k resistor) the receiver is hearing signals and is far more selective than it was. I am guessing that provided signals are not strong it could separate stations maybe 30 kHz apart. At higher quench frequencies the sound of the hiss changes and selectivity deterioriates. I like the idea of a series tuned circuit at the quench frequency across the audio amplifier input so might try that next (eg 10 mH RF choke & suitable capacitor).

@vk3ye

5 ай бұрын

And I've subsequently cut the 100k in the audio down to 2 x 22k in series but at the junction put a 1nF capacitor to try to act as a LPF. Audio output is higher that way. The 10mH idea didn't help.

@cool386vintagetechnology6

5 ай бұрын

@@vk3ye I have played around with 10mH chokes for quench filters but the reactance is still too low to be of any use at what are really frequencies just above the audio band. Best performance is with an active filter, eg. Sallen-Key, but of course this adds more circuitry. Ordinary RC filtering is a good enough compromise.

I’ve always been a fan of superregens. The first kit I ever soldered together was a Radio Shack P Box superregenerative receiver for the FM broadcast band. I soldered it with a 100 watt soldering gun and amazingly it still worked. I turned it on for the first time and got that rushing regen noise only there were no FM stations in range to receive.

Impressive build and listening!

Absolutely brilliant might have a play with this myself cheers.

Hi Peter, big fan of your videos - Idea for future presentation. Using a cheap AM Broadcast kit from usual sources (aliexpress) but modify lower end of broadcast band to TX on 630M band with CW or digi modes. Max EIRP in most jurisdictions is 1W anyway; perhaps an interesting way to play with 630M.

👍Thanks for posting.

"they don't say very much" 😆🤣 Indeed!