Depending on how much chirp one is prepared to accept (there is quite a bit) the power output is around 50-70mW, which is enough to cross the Atlantic on a good day. With less output the chirp should be reduced. The receiver audio output into the high impedance crystal earpiece is low, but I can hear down to around 2uV (-100dBm) in a quiet room. The circuit is a colpitts oscillator used as a TX oscillator with the key down and as a direct conversion receiver with a single stage oscillator-mixer and separate audio gain stage with the key up.The rig is full break-in going from RX to TX when the key is pressed. It works as I have already heard Ws on the band today. Broadcast breakthrough does not seem to be an issue. I hope to have a few local QSOs soon, but really believe it will get much further. It could do with tidying up and boxing and it really needs a small low pass filter for serious use.
Hi Roger
ReplyDeleteThat design is so simple and easy to build. Thanks again for another future project. BTW with an overtone crystal oscillator could this idea work for six and four meters.
A simple CW transmitter with your NE602 converter would be a quick way of getting on Four meters.
Tony
Never tried a simple one transistor transceiver on four meters.
ReplyDeleteTony
The amount of chirp on TX is really too excessive on 10m so going any higher would be pushing it Tony. I am still trying to think of other ways of making this rig simpler still!
ReplyDeleteEven simpler?
ReplyDeleteA car ignition coil and a very narrow bandpass filter ? :-)
73
David - G7UVW
Roger
ReplyDeleteDid you see this Months PW Carrying On The Practical Way The Rev. George Dobbs G3RJV presents two very simple receivers one a FET regen and the other using the mixing technique for your 28 MHz CW transceiver.
Tony
I am looking at this schematic, the variable capacitor and the two unlabeled 47 capacitors, are these pF, nF, or uF?
ReplyDeletepF
ReplyDeleteSee my website www.g3xbm.co.uk for a later design.
ReplyDeleteHow many turns on the toroid to get 0.4uH?
ReplyDeleteHi Fashguru - I am not sure how many turns as it was so long ago! There is a better version on my website.
ReplyDeleteHi Roger,
ReplyDeleteI built the lesser-chirpy circuit (not this one) and I have a question.
When I use the transmit button (shorting R3 120 to GND) and pressing the KEY, the signal gets weaker and weaker almost immediately until it dies out.
Although if I use the Key only (without connecting R3 to GND), I get a stable RF signal out.
Do you have any idea what could cause this error, and how could I fix / improve on it?
Thanks!
I have a digital vfo, SDR QRP HF Transceiver HAM Variable Frequency Oscillator VFO RF Generator.
ReplyDeleteI was wondering if I removed the crystal and installed this vfo in its place and added a 1000 of capcitor between vfo and transistor, would it work.
I also have an antenna tuner as well.
Your thoughts on possibly making a multi band transceiver with your schematic.
Hi NF5L
ReplyDeleteMy advice is EXPERIMENT. The more complexity that is added the further the design moves away from real simplicity. I have no idea whether the changes you suggest will work. At least it is a simple circuit, so if it fails to work, it should be easy to de-bug! Please note the later circuit (Lesser Chirpy) is better as the chirp was excessive at 10m. Once again, please take it as a starting point. My designs can usually be improved,HI. 73s Roger G3XBM