[Hammarlund] Drift of Newer Hammarlunds? was Re: Old Hammarlunds

[Darrell Bellerive]

Interesting thread. I would never have expected any receiver to have 75
KHz of drift during warm-up. Perhaps I have led a sheltered life. :-)

How about the newer Hammarlunds? I can't imagine an HQ-215 drifting much
at all.

I've never owned a Hammarlund, but I am here because some day I would
very much like to.

I am curious though as I have seen posts about the more modern receivers
such as the HQ-170 and HQ-180 having drift problems. Compared to what? A
current radio on a rubidium frequency standard? Perhaps some are just
picking at nits? Or did they really have drift problems?

What were the Hammarlunds really like when they were new? I can
understand that a classic today could have some problems today due to
component aging, and might need some capacitors replaced. But once it is
properly restored?

What were the most stable Hammarlunds and how much did they really drift?

My first receiver was an Hallicrafters SX-140, and I don't remember
drift being that much of a problem. Selectivity yes, drift not so much.
My Drake 2B seems quite stable to me. By todays standards and
measurements I suspect both would be lacking, but in a practical way,
just making contacts on the air, I guess I just don't notice.

So please chime in with your stories of Hammarlunds and drift. I, for
one, would love to hear the real experiences.

73,
Darrell
VA7TO

On 04/12/11 09:04, Kenneth G. Gordon wrote:
> On 12 Apr 2011 at 11:23, djed1 at aol.com wrote:
> 
>> I have both a BC-779 and a SP-400, so I'll offer my experiences. It's
>> been a couple of years, so some issues are a bit hazy. I restored the
>> BC-779 and was surprised at how bad it drifted- 75 KHz from a cold
>> start at 20 MHz.
> 
> That sounds about right. An early QST says "...50 Kc...", but I think that was 
> wishful thinking. 
> 
> However, from my experiences with an essentially new BC-779 back in 
> about 1959 or so, after mine had been left turned on for about a week (rack-
> mounted), in a temperature-stable environment (basement shack), drift was 
> no longer a problem. On 20 meters, mine drifted back and forth a few 10s of 
> Hz.
> 
> As I said, I found it quite pleasant to listen to...
> 
>> I finally found some TC caps, and put in two 10 pf in
>> series. This reduced the drift to about 50 KHz.
> 
> According to a short article in QST magazine, adding 3.3 pfd of negative TC 
> caps to the oscillator section of the tuning cap in the BC-779 reduced the 
> drift to 200 cycles....but I find that difficult to believe...maybe in a 
> temperature-controlled oven. ;-)
> 
>> This is with the dust
>> cover on- it may be significantly better in open air, but nowhere
>> close to anecdotal numbers. As for the SP-400, I got one that had TC
>> caps installed, but I have no idea if they are original. The radio had
>> been worked on, so they may have been added. I did get the original
>> manual, and the schematic doesn't show any compensation.
> 
> The manuals I have downloaded don't show any either.
> 
>> I do remember
>> that the SP-400 drift was much better than the BC-779 when on the
>> bench- maybe 15 KHz. But after I put it in the cabinet it wasn't much
>> better than the BC-779.
> 
> We were always told to prop the lid of the cabinet open, which reduced the 
> drift noticeably.
> 
>> Just to show how the technology changed, my
>> SP-600 drifted about 12 KHz from a cold start, and the R-390A drifted
>> 0.4 KHz. Ed W2EMN
> 
> Yes. 
> 
> But in my experience, once most of these old receivers have been "heat 
> soaked" in a temperature-stable environment, they're all right. Not perfect, 
> mind you, but quite acceptable.
> 
> I suppose that one could, with considerable effort, and a handful of TC caps, 
> reduce the drift on every band to much more reasonable proportions.
> 
> I have another article that proved that the Swan 350 drift could be reduced to 
> VERY acceptable proportions with that sort of work.
> 
> Ken Gordon W7EKB
>