[Elecraft] I need a Sherlock Holmes (weird spurs on 40m)

[David Woolley]

OFDM is also what is used for [A]DSL, and, but at UHF, or SHF, digital 
TV (terrestrial and satellite).  It's also, at least in Europe, for 
digital radio, at VHF.  I think it is also used for 4/5G mobile. phones.

It is not intrinsically secure.  It's main advantage is that it gets 
close to the theoretical (Shannon) limits on error free bit rates in the 
presence of purely Gaussian noise, and has good multipath tolerance (not 
useful for ADSL, though).

Encryption isn't required.  Scrambling may be done to avoid spectral 
peaks, but actually encryption, if used, is done at a higher level.

-- 
David Woolley


On 08/06/2022 09:22, Dynolab wrote:
> Your 24kHz spaced spurs from 6.6 MHz to 7.4MHz sounds very much like Orthogonal Frequency Division Multiplexing (OFDM).
> A secure type of modulation encryption that is often used on the HF bands for High Frequency securities trading.
> If it is a foreign source, they may not respect our 40 meter ham band frequencies.