Adam (VA7OJ/AB4OJ) wrote:
"It is highly significant that professional receivers manufactured by the
likes of R&S, Rockwell-Collins, Racal and Harris have a single roofing
filter. This filter is typically 12 to 16 kHz wide, to pass multi-channel
ISB, VFT (multiplexed teletype) and high-speed crypto, all of which have
extremely stringent in-band IMD requirements. To quote a British engineer
who used to design shipboard HF receivers for the Royal Navy:"
Adam
I wouldn't get too hung up on commercial/military designs, while not
wishing to start a thread running off at a tangent... a friend has a
well maintained Racal RA1792 military receiver which is hopeless
compared to even moderately good amateur gear such as his Kenwood
TS-850, I appreciate the 1792 wasn't one of the better Racal receivers
but they weren't cheap. A listening comparison - even under "non
contest" conditions quickly leads to the Racal on/off switch. Add the
generally poor sensitivity of those designs, weight and cost and there's
no way they will ever compete with a K2 or K3. I don't come across many
hams using ex military/commercial gear in preference to amateur gear...
At least not those I work on QRP CW.
73 Dave
K1, K2 and soon K3/100 (on order)
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