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7659Problems using an Icom IC-251a on the WSJT modes

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  • em12pt
    Sep 2, 2010
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      Hi All,

      Is there anyone in the group that is using or has used an Icom IC-251a for the WSJT modes? If so I'd like to hear from you.

      In the process of putting the 2m station back on the air and running some FSK and JT65b tests, I have encountered a couple of short comings that may make trying to revive the radio for EME and MS a waste of time. However, it is still just fine for CW/SSB and FM.

      Here are the problems I've encountered thus far...

      1. The radio definitely drifts during the transmit cycle and to a lesser extent during the receive cycle. I haven't played with it long enough to see if it will stabilize after warming up for a period of time.

      How much drift is tolerable on JT65b/EME before the software no longer decodes the signal?
      Are there any known mods or fixes to stabilize the frequency drift?

      2. The RX audio pass band appears to start rolling off about 1200-1500 Hz. This is indicated by the spectrum window in the upper right hand corner of the WSJT software when running FSK441. I would assume transmitted audio also rolls off at the same freq/rate but don't have any way of measuring it at this time. I found a post on the WSJT usergroup from 6 years ago regarding this problem but no solution or outcome was given. Again any known solutions for this?

      3. While running some JT65b tests, the receiving station said copied what appeared to be three separate sync signals and could not decode the signal. He had indicated that the signal was fine then the additional traces appeared like I had changed something. No changes were made on my end. This same is the same setup I use on the IC-756P2 on HF/6m without problems. May be over driving the radio? Any ideas?

      Thanks in advance,

      Scott AA5AM