The AM Forum

I really like my Multi-Elmac PMR8, but even after alignment the dial readings are laughably  approximate. I have several small Chinese-made frequency counter modules and thought about using one to get a digital readout. At least that way I could watch the numbers change as the receiver drifts up and down around the target frequency. These little modules even have the ability to set the i.f. offset, either negative or positive.

So, where would be the best place to pull off the signal without loading things down and affecting receiver performance? Second i.f. is 262kHz.

I know, I know, why work with boat anchors and insist on digital accuracy? But these little modules are so darn cute and only about $10, and I couldn't resist. Now I have to find something to do with them.

Doug

I don't think there is anyplace you can pick off the actual HF frequency.  Nothing internal runs at the frequency.

If you want to be on precise frequencies you need to use an external standard, like a crystal in the Tx  unit, or a precision oscillator, or a modern transceiver.   

The most flexible way is to use a mil surplus frequency standard like the LM series (navy) /SCR522? (army).  They were designed for exactly this use with both receivers and transmitters.  If you buy one, ensure it has the matching serial number calibration book.  With out one you have a bit of a chore to create your own cal book.

http://maritime.org/tech/radiocat/lm.htm

(How about some army types giving him pointers to the equivalent)

Well I missed the most obvious application.  Which is to use a loop of wire to pick off the freq from your transmitter, then use your tx to 'spot' the receiver.

Essentially the same thing the LM crystal calibrators do.

Of course, don't know what I was thinking. Actually, I wasn't. Thinking, that is.

Doug

 With a "frequency counter".. the transmitter spotting WILL work, no doubt..  For a dedicated accurate readout for the receiver independently , you need a conversion scheme utilizing the LO:

http://www.electronicspecialtyproducts.com/dd103.html

I believe you can input your conversion (offset) into that unit manually, even if not listed on the site.

That's just one example.. there are others out there, including home built stuff.  Having accurate independent receiver readout is a GOOD thing!  

You pick up the LO frequency and offset the freq counter, and it will read the EXACT receive frequency.
I do not know about the $10.00 ones but the ones from almost all digital electronics have an adjustable offset (say 455 KHz) and a preamp that allows you to only need to get a wire close to the LO, no direct connection needed.

Here is one built into my homebrew receiver:

http://n2dts.smugmug.com/Ham-radio/i-MNgG3tR/XL

Since it reads the LO frequency, it self corrects for drift, that is the display always reads the actual frequency.

You could use it on almost any old receiver, they make models to offset for ssb rigs, multi conversion, up and down conversion, etc.
You can get one in a small cabinet to sit on top of the receiver.

http://www.aade.com/#dfd

Here is the AADE link!