I tested the $10 oscillator module and it worked as claimed. It had a little over 4 volts PP output using 3 AA cells in series to power it. It had enough stability so it would probably work as-is as a VFO for a homebrew AM transmitter but, once a desired frequency was found with the coarse adjustment pot, I would want to replace it with a fixed resistance for improved stability and just use the fine adjustment for tuning. The coarse adjustment is very "coarse". I was able to tune from 600 to 1600 kHz using only the fine adjustment.

My next test will be to see how it performs as a stand-alone transmitter. Like the XR2206 IC, I was able to send a decent carrier across the room with a 3' antenna attached to the output terminal. It was noted that attaching the antenna didn't affect the frequency.

Dave

Any idea how much power these have? I say 'these' because you are looking at two options here.

FWIW I received the two XR chips but have to go get a 16-pin socket before I can do anything, and also ordered the module yesterday. So I'm following along here belatedly. I'm no engineer or designer but would love to be able to combine one of these oscillators with the MP3 player module, a final to the legal limit, a power supply, maybe an audio compressor, etc.

Keep us posted on your progress and findings please.

-Sam T.

I was able to modulate the module with a very simple test set-up. Using the external speaker jack and on my Sony ICF-5900W and an 1/8" phone plug, I sent the positive battery voltage for the module into the sleeve connection, through the Sony's output transformer secondary, and on to the module's power input taken from the speaker jack's tip connection. Then I tuned in an FM station on the Sony and received the module's AM signal on a Radio Shack Patrolman-9 radio which I found yesterday at a garage sale for $5.00. The results were surprisingly good with decent frequency response and adequate undistorted modulation. I didn't measure it but it seems like I could get about 75% modulation before clipping which would be expected because, after all, I was modulating the module's power supply.

So, it seems this module can be used as a cheap AM transmitter same as those self-contained crystal oscillator modules. The advantage is that it is frequency agile.

Dave

And then there are these...

This can be made continuously variable by using either a ganged pot or two section varicap
http://www.beecavewoods.com/testequipment/sinewave.html

This outputs a crystal controlled square wave, and is useful for substituting for a crystal in a Wenzel type transmitter
http://www.beecavewoods.com//radios/fre ... synth.html

Got the XR2206 chip going, no luck modulating it yet though.
Also tried to run it from a 9V battery and it wouldn't budge, it wants the full 12V.
It will oscillate from 250 khz up to around 1.6 mhz.
Sine wave output looks to be a little less than 3V P-P, square wave is much smaller.
I'm a little concerned about frequency stability - it seems to track up and down within a range of 30 khz.

Waiting on the sq wave module, that one should arrive next week.

Sam T.

Are you saying that it drifts up and down that much all by itself? Mine drifted, too, but only about 1 kHz which I feel is still too much. I was going to try to tame it with parts value changes but I shifted my focus on the square wave module.

Dave

That was an error.. meant to say it drifts about 3 khz, not 30.
I'm anxious to receive the pre-built module and will focus on that instead.
-Sam T.

Any additional findings on these VFOs??

Tom

I was hoping for an update also. I have one of the units on the way from Hong Kong.

I would like information on how to use it on my 2 tube 6888 transmitters.

Ed.

I ordered two a few months back after seeing Dave's post. I asked Norm
about using them with his TX, and his only concern was that they might exhibit
some FMing... but considering the oscillator is buffered by a digital dividers
chain, I suspect that will provide enough buffering to keep that from
happening. If I ever have time to breadboard one I'll post
feedback here; but first I have to find the two tubes I had set aside for the
project!

Pete