Morning Bill, It never ceases to amaze me how receivers (and antennas) attract so much comment. Is it because the majority of us are using receivers designed for the amateur market as benchmarks, or is it something that results from habit? I suspect that the "Money Men" get involved closely in the design
My $0.02 worth for ham band only coverage: 1) Dual vs Single conversion. Both can be a disaster if the IFs are not chosen properly With the IFs chosen properly, and the receivers built properly, up-conversion to the first IF with the LO on the high side, there are far far fewer spurious responses to be found in a dual conversion than found with a single conversion receiver, and "weaker". The RF preselector in a "Dual" has something more to add to attenuation. 'Built properly' is very important. Narrow first IF filters are essential in double conversion for "strength" reasons, selectable by reed relays not diodes. Here I use VHF 12 poles, 6,3 and 1.5kHz. 2) Effect on Noise Floor. Assuming the use of strong mixers (+50dbm) and strong low noise figure IF(s), the difference can be zero. 3) LO purity. Both require a low phase noise LO(s), free of spurs. Until a cheap low phase noise PLL appears, I'll stick with premix systems running at VHF. Much more work, but worthwhile. 4) DSP. I fully agree. I see little point in having a ho-hum filter at the front end of the IF, letting a cocktail of signals romp down the IF to be dealt with by a DSP module. Great will be the day when a DSP unit running at VHF, with a high IP3in etc, and low noise figure becomes practical. 73, Geoff. GM4ESD _______________________________________________ Elecraft mailing list Post to: [email protected] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
