[Hammarlund] Favorite Hammerlund Receiver

[Kenneth G. Gordon]

On 12 Dec 2011 at 18:38, Todd, KA1KAQ wrote:

> That was the one I had in mind too. Those other stages are nice,
> but...

Well, the selectivity between my ears is adequate for every CW 
contact I have ever tried to make....so far...

> > work as well, or better, for AM as it did for CW/RTTY/SSB.
> 
> Interesting. I'm not a big fan of trying to make old radios perform
> like newer ones,

Me either. As far as I am concerned, 99 and 44/100 % (remember Swan 
soap) of ham mods make any piece of equipment work WORSE than it was 
designed. 

The OT designers, for the most part, weren't stupid.

However, we HAVE learned quite a bit about certain aspects of 
receivers since 1939. Detectors, especially. I have never liked the 
diode detector.

I am not against incorporating something better into an older 
receiver, to, for instance, overcome some obvious serious lack, but 
such a mod had better not only make the gear work better, but should 
look like the original designers, and manufacturers, did it.

Trouble is, in most cases, those who make mods to older gear don't 
think things all the way through. The result is much like so much of 
today's medicine: the side-effects are worse than the disease.

> but I do like simple improvements like drop in tube
> swaps. Hard to imagine the AM audio sounding better, though!

Well, it sure did to me at the time. 

At this late date, I suspect that the problems I was having at the 
time were due to some component failure, but, I didn't have either 
the experience, knowledge, or test equipment to find it and fix it 
then.

> > I don't remember ever turning that receiver off after that for a
> > number of years.
> 
> You were using the set correctly, then. With all of the complaints
> about Super Pro drift, I always wonder how many folks ever read the
> original manuals where it says the set was designed to be left on to
> allow it to become temperature stable or such.

Well, I had and read the manual. However, one of the other reasons I 
left it on was because it looked so cool in the dark. :-)

> Strangely, my SP-100
> seems to stabilize pretty quickly when I turn it on. Turn it off after
> hours of listening to AM 740 out of Ontario, turn it back on days or
> weeks later and it's dead-nuts-on. Guess I'm just lucky, though the
> radio has seen some work in its past. I should dig into it and see
> just how much, if anything was done to address drift.

The only mod I know of that properly addresses that drift, was to add 
a 3 pfd N750 cap across the oscillator tuning cap. Supposedly, this 
reduces the warm up drift very considerably. Furthermore, this mod 
was first suggested by a Hammarlund design-engineer, so it has some 
decent provenance behind it.

I read that tidbit of info, by the way, in an old QST magazine. It 
was buried in some article. I can't remember which.

Ken W7EKB