TX Bandwidth - Something I Didn't Know

  • 1
  • Problem
  • Updated 2 years ago
  • Acknowledged
Hey... something isn't right. I am not sure how to explain it.

In RTTY mode my TX Low Cut is set to 1910, High Cut 2510. When I tune, the signal is generated at the high tone within the TX passband and tuning works correctly.

In DIGU mode my TX Low Cut is set to 1500 Hz, High 2000 Hz. When I tune, the signal is generated at the VFO frequency outside the TX passband. Bad. What's worse, SWR shows 1:1 and reads Success Byp Mem.

Why is DIGU working differently than RTTY when generating a TUNE signal?

Why is the ATU showing Success Byp Mem when in fact it is not tuned and the SWR is >3:1?

You may be asking why I set 1500 - 2000 Hz for DIGU. I mostly use WSJT-X and I keep my signal between 1500 Hz and 2000 Hz so I set my TX filters that way. Seems logical to me. But it kind of puts me in a position where I think I'm tuned up but I'm definitely not.

For me, the ATU doesn't not seem to work correctly unless the TX Low Cut is set to 600 Hz or below. Should this be considered a bug? Maybe, in TUNE mode the low cut filter should be ignored or the TUNE signal should be within the TX passband?

It's been a hectic day. I'm hoping I made sense.

73,
Kev K4VD
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Kevin K4VD, Elroy

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Posted 2 years ago

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Tim - W4TME, Customer Experience Manager

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Official Response
For sideband modes (DIGx included) the TUNE signal is at the dial frequency to prevent QRM in the RX passband of those receiving on the same sideband mode.

I agree that the ATU is not behaving as designed in this circumstance and I have added this report to our bug tracker as issue #4486