Change in sensitivity with Panadapter zoom

BettyLou Huth

I am using a 6700 with SmartSDR 1.2.17 on Windows 7.  I set up for WSJT on 17-M and noticed very little activity near 18.102 MHz.  I clicked the "Zoom Out" icon and the Panadapter changed to "Wide," and suddenly I could see signals where there were none before.  Clicking "Zoom In" returned to the "no signals" situation..."Zoom Out" again showed band activity.  I checked the antenna setting and ANT1 was selected for both RX/TX in both situations. Neither LoopA or LoopB was activated in either case, and the RF Gain was set to 0 db.  AGC-T was 60 in both cases.  Note the S-Meter is reporting approximately -80 dBm with no signals, and approximately -99 dBm with signals present in the Panadapter.

Restarting SmartSDR did not change the behavior, so I turned the 6700 off and on with the front panel push button and everything was restored to "normal" behavior with signals present in both "Zoom" states.  I noted the 6700 shutdown time (with a single push) was in the "long" category.


Here are screen captures of the two "states."

Bernie Huth
W4BGH

Steve N4LQ

When I read this I immediately switched to 17m on my 6300. RX antenna was on ANT1 and i saw plenty of signals. Zooming in and out had no effect. So I went to the slice flag and changed the RX antenna to XVTR. Interestingly I had exactly the same amount of signal but no antenna connected to the XVTR input. Switching back and forth several times changed nothing. I then changed the frequency to just below the 17m ham limit, around 18050 or so. I then switched to XVTR in in the RX ANT popup. Signals immediately went away as they should have.
So I went back up into the ham band, 18102 and now when I switch from ANT1 to XVTR with either the slice flag of the left menu it works properly. Signals disappear with switched to XVTR. 
So something isn't quiet right in the antenna selection department but I couldn't replicate it. I would probably never have noticed it if it weren't for Bernie's post. His 6700 might respond differently than my 6300.
Steve N4LQ