24-09-2018, 10:36 AM
I have been finding that when (mainly) VK, ZL and FK8 stations are working on the same band, the IC-7400(/746Pro) AGC is depressing the gain as it should and the FT8 signals I am trying to work drop down to the point that WSJT-X does not decode them. Slow, Medium or Fast setting makes no difference, still depressed receive gain. The 'local area' signals are often +3dB SNR or higher, sometimes up in the +10 to +15dB SNR range.
If I notice this effect, I usually try to transmit in the same 15 second block (ie First 00,30 or Second 15,45) as they do but that isn't possible when answering someone who is calling CQ on the 'wrong' timing segment.
What I didn't know is that the AGC functions are adjustable in this radio. You can set each recovery time from the front panel in 0.1 second increments but there is also an AGC OFF selection available. I have changed my settings so that I have 0.5S for Fast, OFF for Medium, 6.0S for Slow. Only takes seconds to alter once you know that the setting is available.
The result : Just saw a VK3 and a YB7 both at +7dB on 14.074 and the weaker signals remained un-depressed.
You still have to remember to manually put it back to Fast or Slow AGC for SSB use but it certainly seems the right setting for FT8.
I have only had this radio 12 years or so, been using it on FT8 since March '18, and only just found the AGC OFF setting.
Makes me wonder what else is hidden in the instruction manual.
P.S. AGC OFF = no S-Meter display/readings !!
If I notice this effect, I usually try to transmit in the same 15 second block (ie First 00,30 or Second 15,45) as they do but that isn't possible when answering someone who is calling CQ on the 'wrong' timing segment.
What I didn't know is that the AGC functions are adjustable in this radio. You can set each recovery time from the front panel in 0.1 second increments but there is also an AGC OFF selection available. I have changed my settings so that I have 0.5S for Fast, OFF for Medium, 6.0S for Slow. Only takes seconds to alter once you know that the setting is available.
The result : Just saw a VK3 and a YB7 both at +7dB on 14.074 and the weaker signals remained un-depressed.
You still have to remember to manually put it back to Fast or Slow AGC for SSB use but it certainly seems the right setting for FT8.
I have only had this radio 12 years or so, been using it on FT8 since March '18, and only just found the AGC OFF setting.
Makes me wonder what else is hidden in the instruction manual.
P.S. AGC OFF = no S-Meter display/readings !!
