[AMPS] DAF amplifier

[Peter Chadwick]

Peter says:

	>Finally a question, when talking IMD, enlighten a mere mortal as to
>where this distorsion is to be heard. Is it within the passband, outside of
>the passband or maybe both. 


Peter,

Generally, if the distortion is bad enough to be noticed on the signal, it's
tearing up the band for a long way either side. I've been consistently
surprised in tests just how bad IMD has to be before it's really noticeable
on the signal itself. I suppose it shouldn't be that surprising because how
good a signal to noise ratio does one  get on the HF bands? I guess on 10m
you can get 30 to 40dB on a real strong signal. But most receivers do not
have very good Signal to Noise Improvement Ratio figures, which will mask
things.

The real test is 5kHz away! ITU requirements ( Recommendation. SM.329) don't
actually call for emissions to be 43 + 10logP dB down (not exceeding 50dB
for amateurs) (P is the PEP in Watts) until you are about 6.25KHz away from
the assigned frequency - which is 1400Hz away from the carrier for SSB.

For being reasonably popular, you need to be rather better than that.

> Can we hear a difference of 15 db IMD with our ears on the bands or is it
>academic ?

It depends on how strong you are.

You may well have a DAF that is linear with speech, but if so, it does
appear to be a rare bird.


73

Peter G3RZP


--
FAQ on WWW:               http://www.contesting.com/ampfaq.html
Submissions:              amps@contesting.com
Administrative requests:  amps-REQUEST@contesting.com
Problems:                 owner-amps@contesting.com
Search:                   http://www.contesting.com/km9p/search.htm