What's going on at 3.915 & 3.905 mhz?

Ken Davis

When tuning on 80m when I pass through 3.915 and 3.905mhz I hear a relay clicking in the radio. It doesn't matter if I am going up or down the band. Sometimes it will move the noise floor line up or down by -5 to -8. Sometimes also the background of the Panadapter will slightly change intensity. As best I can tell, the signals I receive either above or below 3.915 are unaffected. 
The question is: What is the relay all about?  Why does the noise floor line move?
Thanks for any input.
73
Ken
W0KRD

EA4GLI

It doesn't happen to me. Is your ATU enabled?

k3Tim

Can you turn off the ATU and retest?  

k3Tim

pse disregard as Salvador beat me to the suggestion.
Tim

EA4GLI

Ken Davis

OK, just turned off ATU and it quit!! Well snap.  Tim you got it.  Inquisitive minds want to know, why is it so???
Thanks a bunch.
Ken

Ken Davis

Sorry I did not see your response Salvador, thanks to you too...

EA4GLI

It's the ATU memory selecting a different Tune setting based on the frequency. Totally normal.

EA4GLI

No worries.  I am lurking on the forum waiting for the 1.6 announcement to pop up and just going through every single post! 

EA4GLI

At least you replied right away. The other day I took the time to post a complete tutorial with pictures on how to setup something on N1MM and the person that asked hasn't even acknowledge the answer. That was almost a month ago. 

k3Tim

Somewhere in the SDR software manual it talks about how the ATU works.  Something like every 100Kc it sets up a new tuning data set  for the particular band.  I've noticed with my end-fed ATU code can sometimes do it more frequently and when you roll past one of the "node points" the ATU relays click for the next setting.  It also seems a wide band, 80 to 75 meters, one can tune the lower CW portion and if you meander up-dial to the top end of 75, the ATU won't have the tuning settings (at first run) and drop out / off.  Once the entire band is tuned it's saved.

Once setup the ATU is pretty much transparent except for an occasional click.

Before ATU memories, just changing modes (CW to RTTY) would require a retune.  It's nice to bee past that minor inconvenience.


Tim

Ken Davis

Oh that is great information. Thanks for the education.
Ken
W0KRD

DrTeeth

I get a similar clicking when tuning around, not that often though and I do not have the ATU installed. IIRC, it happens whilst tuning through top band

G8ZPX

check ATU, preamp, antenna selection settings etc. as these are all "per-band" and may (will) change as you slide out of a designated ham band in to general/broadcast bands. Also, watch for any button/slider changes on-screen as the relay clicks in/out that should tell you what is changing.