Monday, March 15, 2010

PFR3A Group 2 calibrations

At the end of the Group 2 build, there are several calibrations that can be done, providing of course, that you have the proper test equipment. These include the reference frequency calibration, the IF offset adjust and the BFO adjustment.

To perform the reference frequency calibration and the IF offset adjust you need a good frequency counter and a good oscilloscope. I have both; but neither are very good. My oscilloscope is an antique that someone gave me. This boat anchor has to date back to the 50s or the 60s. I suppose I might try the IF offset adjustment this weekend; but I'm probably better off passing this by.

The reference frequency calibration requires a good frequency counter. I have a small Radio Shack job that I picked up used - I can't even remember where. It's not really that good; or that accurate, I suspect. Again, I will probably pass by this adjustment also. Both of these are there to make if you have the equipment. If I don't, I suspect that I will be "close enough".

The BFO adjustment was easy. All I needed was my ears; and even these old ears were good enough to match the pitch of the side tone and the BFO beat note.

On to the Group 3 assembly (the transmitter section) next!

Note to self: Start buying lottery tickets so as to be able to afford fancy test equipment.

72 de Larry W2LJ


  1. You know, your K2 has a good frequency counter in it....

  2. I've never had a frequency counter nor, until a few days ago, any kind of an oscilloscope. The way I have always done frequency calibration is to tune in a station of known accuracy. Tune it in so the dial is 1kHz off the known frequency, then adjust until the heterodyne beat note is 1kHz. You can use a digital mode program like Fldigi to measure the beat note, though your frequency counter may be accurate enough at audio frequencies.

  3. Your K2 has a pretty good frequency counter in it, and if you have a MFJ 259 antenna analyzer, don't forget that it also has a frequency counter. I have a calibrated Stinger Singer FC in an Altoids tin I can loan to you if you want to try it out.

  4. Paul N0NBD10:19 AM

    Larry, I have been following your progress on your PFR3. I was tickled to read you got the receiver going. My PFR3 was in the first bunch of 100...[yea I broke my rule and bought early] I also do not have any good equipment so I passed the techincal measurements. It has turned out to be a fine rig as is and I use it as my main rig. I will follow along de Paul N0NBD