[Lowfer] CW on 21.15 kHz

[Graham]

It might very well be a mixing problem.

I have been using Spectrum Lab fed with a Emu-Pre USB sound card as a 
simple VLF SDR. One day I noticed what looked like CW on the waterfall 
right around 18.1KHz which I knew was were the Russians have a VLF 
transmitter on which you will sometimes hear CW, usually FSK CW however. 
Afer a while I started to notice occasional CW and carriers elsewhere 
uptoward 28 KHz so I had a listen using the SAQ VLF SDR program. Turns 
out it was amateur radio transmissions on most likely 80 or 40 meters (I 
think  - I never did find the correlating signals on HF) - turned out to 
be some sort of intermod or mixing that day. I haven't noticed it since 
but I do keep and eye open for it. At the time I thought I witness to 
something interesting going on on VLF apart from the day to day 
NAA/NLM/NLK transmissions I see with boring regularity.

cheers, Graham ve3gtc FN25ig



On 14-01-21 01:41 AM, Dexter McIntyre W4DEX wrote:
> I just heard CW while monitoring VLF with SpecLab.  Is this possible?  
> I suspect a mixing problem.
>
> https://dl.dropboxusercontent.com/u/15095569/vlf/cw_21.150-khz.jpg
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