F6300 unstable LF carrier?

Steve G1XOW

Hi, looking for other peoples check/feedback please.

I know I should not expect too much from the F6 series below 1MHz, but I have found two odd unstable carriers (looks like SMPS warble to me). They are both around 800-815kHz (see example pic). They wobble around a bit and sound like an unstable SMPS.

However, the really odd thing is that the signals is still there, and just as loud with no antenna or coax connected to the flex RF socekts....puzzled, what does yours look like please?

I guess I may have a QRM source, but other than the PC (can't turn off for obvious reasons) nothing else is close enough to generate that high level of signal with no antenna connected.

There is no other carrier/qrm showing from 150kHz to 1MHz with no antenna connected, so these two really stand out. 

Thanks, Steve G1XOW

Steve-N5AC

Steve, there are switchmode power supplies in the radio and they are likely the source.  Part of the design process is to minimize the number of internal sources in the radio and ensure that they are not in the ham bands.  SMPSs generally do not use a high-accuracy source because they are not necessary for operation, they add unnecessary cost and contribute to spur production by raising the overall signal level on a single frequency and its harmonics.

G8ZPX

Steve, thanks for confirming my assumptions. Would 800khz be about the right area?  It is not a problem for me, I was simply doing a shack-wide QRM sweep to iron out some minor noise sources from USB and RS232 cables (now all gone).

Thanks, Steve G1XOW

Steve-N5AC

Yes that's about where it is now.  It is under software control so we can move it around some if we need to in order to avoid new bands, etc.

Stu Phillips - K6TU

LOL!  With an antenna on, these signals would be lost in the phase noise alone from KGO - one of our "clear channel" AM stations here in the SF Bay Area.  Its main carrier is -10 dBm on my 160m TX antenna!

Good place to stick these!
Stu K6TU