[HBR] HBR 16 Owner Pondering Building My Own

[N2EY at aol.com]

In a message dated 4/7/05 11:10:11 AM Eastern Daylight Time, 
Scott.Freeberg at guidant.com writes:


> What I'm looking to do is figure out the 'best one for me'.  I'm looking to 
> build a nice CW receiver, then build up a matching homebrew transmitter.
> 

With all due respect to W6TC's excellent designs, the HBRs do leave something 
to be desired in CW operation - IMHO:

As I see them, the HBRs were meant as general-purpose ham receivers, mostly 
for 'phone or noncritical CW use. And they do the job very well for the 
complexity and cost involved, and the parts available at the time. 

The problem was that getting really good CW selectivity from the 100 kc. IF 
would require a lot of IFTs, and then some sort of complex switching 
arrangement to widen things up for 'phone use.

In addition, AGC and an S meter are of limited use in CW operation. A really 
slow tuning rate and high stability are  much more desirable.

My low-cost solution, back in the 1970s, was to build a basic 80 meter 
CW-only receiver, then precede it by a crystal-controlled converter for the other 
bands. For selectivity I used a crystal filter using FT-241 xtals in the 470 kc. 
range. The filter uses triode phase splitters and APC trimmers, and 
resistance coupling. Adjustment is simple - the trimmers are adjusted for maximum 
rejection of the unwanted side of zero beat. The circuit appeared in QST around 
1960 - it was first done at 1690 kc, then adapted for ~455. Two stages gives a 
really nice CW filter characteristic. 

Since the VFO only covers one range, it can be made very stable and unit 
construction can be used. A "squashed" ARC-5 VFO can do the job very nicely, 
without a lot of metalwork.

Of course this is a completely different approach from the HBR, based on 
different tradeoffs. But for CW work, it's a real advantage to have that sharp 
filter!

One rx I built around some of these ideas is shown on the HBR website.

73 de Jim, N2EY