[HBR] Yet Another HBR Concept

[hbr@mailman.qth.net]

In a message dated 10/10/03 10:15:30 PM Eastern Daylight Time, 
waltah@earthlink.net writes:


> I've continued to doodle on the conversion scheme.  Jim is right -- 
> the one I mentioned last time isn't good, 

I hate when that happens.

but I haven't found a 
> 
> satisfactory one yet.   I'm trying to use common microprocessor 
> crystal frequencies for the 1st IF but most of those frequencies are in 
> use by megabroadcast stations ... not impossible to use, but you'd 
> sure rather not start there.   And I don't want to get the VFO freq. too 
> high either -- it's a lot easier to stabilize a VFO in the 5 Mcs range 
> than at twice that frequency.   Plus the cap I'm looking at for the 
> VFO is fairly large per section so it's a good bet for a lower freq. 
> design.

The Ancient Ones ran into this problem, and there aren't many good solutions. 
That's why the "upconvert everything to 70 MHz" approach took over Ikensu at 
the dawn of the synthVFO era. 

The classic 9 MHz IF/5 MHz VFO scheme works, and lives on in many of the 
TenTec rigs. 

Elecraft uses 4.915 MHz IF, an analog VFO in the 3 MHz region, and a premixer 
design in the K1. Works 80 thru 15, and some have made it work on 10 meters. 
The manual is free for the download. Imitation is the sincerest form of 
flattery.

The Southgate Type 6 uses the Heath heterodyne scheme. Yes, it's double 
conversion like the DAF, but the tunable IF is much higher (8395-8895) so the 
bandpass coupler design is easier. And if you can scrape up a beater HW-100/101 or 
almost any SB, you've got all the het and carrier crystals plus an SSB filter. 
If you're very lucky, a CW filter too. 

"If it was easy, everybody would do it"

Anyone remember the W5OMX receiver?

73 de Jim, N2EY 


> 
> 



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