[AMRadio] Receivers


D. Chester k4kyv at charter.net
Fri Sep 21 08:32:18 EDT 2007


My first receiver was a circa 1938 American Bosch  model 585 floor console. 
It covered 150 kc/s to 18 mc/s in four bands.  It had one rf stage followed 
by the usual mixer, oscillator, i.f. stages, diode detector and audio.

I removed the power transformer,  rectifier and filter caps, and used the 
chassis space to build a homebrew BFO, and reconstructed the power supply on 
a small separate chassis.  It worked well on 80m, but the entire 40 and 20 m 
bands took up about 1/8" on the main tuning dial.  It  had a bandspread dial 
of sorts, a short pointer that rotated about a circular 0-100 logging scale 
in the centre of the main dial, kind of like the second hand of a clock.  It 
worked great for 80m cw, where I spent the entirety of my three-month novice 
career.  I could have added a trimmer cap to make a real electrical 
bandspread function, but the idea never occurred to me at the time, and I 
probably didn't have a suitable variable cap for the purpose anyway.

Then I purchased from a local ham, a well-used NC-173. It took me  some 
getting used to that receiver; the broadcast radio actually seemed to work 
better until I got used to the NC-173.

The National was OK, but nothing to write home about.  I used it throughout 
the 60's, but in early 1970 I picked up a 1935 vintage National HRO.  The 
HRO was about 12 years older than the NC-173, but worked so much better that 
I gave away the NC-173 to another ham.  The only exception was 10m.
The NC-173 was far superior on that band.  The old original HRO was 
practically worthless on 10m, with poor sensitivity stability and bad a.c. 
hum modulation in the HFO.  It even displayed hand capacity, shifting 
frequency as you touched the tuning dial with your  hand.  And there was no 
15m bandspread, since that amateur band didn't exist when the receiver was 
built. But by then I wasn't working 10m, so it didn't really matter.  On 160 
through 20, the HRO stood head and shoulders above the '173 in terms of 
stability, image rejection, dial calibration, tuning rate, and it was just 
plain far more "solid".  I still have the HRO but haven't used it for years, 
since I picked up a couple of 75A-4's in the early 80's.

Don k4kyv 



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