[Amps] Clean -vs- Unclean

Steve Thompson g8gsq at eltac.co.uk
Mon Jan 9 13:55:19 EST 2006



Tom Cathey wrote:
> Here's a coincidence!
> 
> I just received an email from a buddy who is considering buying an 
> FT-1000MP. They are being closed out and discontinued according to a 
> salesman.
> 
> Here's the salesman's comments about the class A stage. This was written by 
> my buddy based upon his conversation:
> 
> "The MP Mark 5's are being closed out by XXX at $XXXX. [I deleted the X 
> info]  The salesman, a DXer/contester said it is being discontinued. The 
> class A amp capability proved to be a negative. If you can believe this, it 
> allowed others to "nustle" in too close to you if your IMD was that far down 
> and make your RXing difficult if not impossible. You need some artifacts to 
> hold others at bay!"
> 
> 
> I won't even comment on that one... [gag - cough]
I'd often wondered about modifying our contest exciter to provide an 
additional path round the narrow filter after the rf processing - 
putting the cliped signal through a 15kHz filter and injecting some back 
into the tx strip downstream. That way you don't have to wipe out the 
whole band to keep clear air. I never got round to trying it.

Far more fun would be something based around the modern DSP/linearised 
feedback transmitters where (in theory) you can have full control of 
your splatter spectrum, and make it adapt to the situation.

Something I still want to try (one day...) is DSP on rx, where a wider 
band rx looks for signals that correlate with the crud in your wanted 
passband, and use that to cancel it out.

Steve


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