Subject: [Elecraft] RE: Using K2 as IF for VHF/microwaves
Date:     Sat, 31 Jul 1999 04:59:35 -0400
From:    "Roger Rehr" <>
To:        <>

I finished K2 #334 yesterday.

Today I used it as receiver IF for 144 MHz EME contact, in place of my ICOM 735 which usually is the IF here for 144 MHz through 2304 MHz.  The K2 was a definite improvement over the 735, due mainly to the variable width crystal filters.  The ability to tune down to 100 Hz without ringing was very helpful.

Also very helpful was the 1 KHz /revolution (approximately) tuning rate.

Having the ability to turn off the AGC is also critical for this weak signal work, and something the 735 does not have.

I did not use the K2 for transmit because I have split RCV/XMT paths to the transverters, and this would have entailed some work on the K2 that I didn't have time for.

I hope to split the RCV/XMT paths in the future using a combination of the Second Receive Antenna option and the Transverter Port option, when they are available.  Also, I really could have used the noise blanker option; pulse noise came up as I was preparing to call EA3DXU random (and HB0/PI4TUE) and pretty much wiped me out, even with the filters in and software DSP running.

I found that running the K2 at 400 Hz filter width (and 400Hz center) and following it with software DSP for LMS noise reduction and then coherent bandpass filtering at 400Hz center freq and 150-300 Hz bandwidth worked best for me tonight, but when the S5 pulse noise arrived the system was overwhelmed.

I also tried using the K2 as IF for the 2304 MHz transverter.  There is a 2304 MHz beacon in Philadelphia, about 60 miles away, that I can usually detect visually with FFTDSP, and often hear faintly; tonight conditions were quite good and the beacon was easily heard using both the K2 and the 735 as IF, with the tower at 72 feet.

AMAZINGLY, after I cranked the tower down, I could still intermittently hear the beacon with the K2 as IF, with the boom sitting at about 26 feet, and the DSP program confirmed the presence of the signal (although I heard it first with the DSP bypassed!!).  I have NEVER heard the beacon with the tower at less than about 50 feet elevation before.  Out of curiosity, I swapped the 735 in as IF, and could NOT hear the beacon at all.  The difference, I think, was again the variable CW filter on the K2, as I couldn't hear the beacon with the K2 at 1.5 or 1.0 kHz filter widths, but could at 400 and 100 Hz.

IN summary, I bought the K2 because I thought it would make a great IF for VHF and microwave work, and am very pleased with how it is performing.  I suspect that it will find lots of use in this way as word gets out about how well it performs in this service.

Plus, with the battery option installed, I can now roam around the neighborhood and find that pesky pulse noise source!!

Finally; no problems with the K2 in spite of 1500 watts of RF at 144 MHz floating around and the K2 wired to the transverter, as well as the computer for DSP.

For those (if any) that are interested in the EME set up here, etc, you can explore at: and

73 from
Roger Rehr  W3SZ ex-AA3QK ex-WA3JYM        FN20ah
2 Merrymount Road, Reading, PA  19609