Comments for "30 Metre Autodyne Receiver"

20th March 2012 10:01

Chuck wrote ...


Built a CA3046 version of this circuit with several changes - eliminated Q3 cap to ground, increased Q3 collector R to 5K6 and eliminated its paralleled cap. Could not get the circuit to work with either cap in place. Used an untapped coil on Q2. L1 (untuned T1?) is simply a ferrite bead P:1t S:6t. Pulled in WWV here in Texas with no front end pre-selection (antenna to primary) and stay locked 80+% of the time. Pulled off by strong HF signals peaking from time to time probably. Impressive audio. Added a 2 pole BPF and reached 100% lock w/i 2Hz although my $99 DFC is probably not that accurate. Locks on multiple 31m signals as one tunes the band. Have pics if you like. An effective precision frequency source for a couple evenings' effort. Pretty decent as a simple receiver due to the capture effect - like FM!

Terrific site. It's great to see imaginative applications like yours.



15th September 2011 13:11

Ray wrote...


I built the receiver ugly style very similar to the picture you show. However, I can't get the oscillator running. I've double checked the wiring and it is correct. Any suggestions will be appreciated.

Also, I used a FT37-61 15:3 transformer for L2. I supposed that will be OK. I have a DTC 10 MHz bandpass filter I am going to put ahead of the input once I get the receiver running. I also used 2N3904s instead of the CA3046.

3rd July 2011 21:18

Alan Yates wrote...


It is not extremely sensitive, but for most signals on HF shortwave bands it is fine. It doesn't take too many components really, only a handful of transistors and passives.



20th May 2011 00:27

Bert wrote ...

Hi Alan,

This is quite an interesting and attractive receiver with an output for frequency counter. I am so tempted to build one too, but I can't waste my very-limited components on this, if it turns out to be a bad receiver(eg lack of sensitivity).

I have a question, is this receiver sensitive like all other regenerative receivers? I have never built receivers other than regenerative ones.

30th January 2008 13:25

Alan Yates wrote...

Any old rectifier should be usable as a varactor in this circuit. I used the 1N4007 because I have hundreds of them, but even a LED should work fine.

You could use a real varactor, like the MV209 available from Kits and Parts, but a power rectifier is a whole bunch cheaper and more common. For this particular receiver you only need a bit of fine tuning, the trimmer does the bulk of the tuning.

30th January 2008 12:58

A.P wrote ...

Again, thanks for publishing a review of this.

I am going to get the 1n4004 diodes for the varactor application.


73 de va7aax

29th January 2008 16:29

Alan Yates wrote...

Thanks for that information Nigel!

Do you happen to know if the ABC or other broadcasters use precision clocks for their TV and FM carriers?

29th January 2008 14:37

Nigel wrote ...

Radio Australia at Shepparton uses a rubidium standard to lock each tx's synthesizer. Within the limits imposed by hf propagation it should make a fairly good reference. 5995[14-18UT], 6020, 9580, 9590, 13690 & 15240 kHz are good choices for s-e Australia

The RA broadcasts from Brandon (5995 kHz[08-14UT], 9660 and 12080 kHz) run from TXCO synthesizers - not as good as a rubidium, but ok for checking the bench DFM.

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