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

[Glen Zook]

For AM use the Hammarlund receivers were fine.  It was when SSB became popular that the drift in a number of the receivers started becoming problematic.  The series starting with the HQ-120X, then the HQ-129X, HQ-140X, and the HQ-150 were all generally very stable after between a 30 minute and 1 hour warm up period.  However, the majority of the HQ-100 series, HQ-110 series, HQ-160 series, HQ-170 series, and HQ-180 series were not that stable especially on 14 MHz and higher frequency bands.  Those receivers that had 6-meters (HQ-110 series and HQ-170 series), the vast majority of them never got stable enough to really be of use on that band.  Since the "VHF" versions, which added a 2-meter converter, used the 6-meter segment the stability on that band was just as bad as the 6-meter segment.

When Hammarlund started including the clock / timer on the receivers, one of the advertised "features" of having this was so that the receiver could be turned on to stabilize before actual use.  The later versions of the HQ-170 and HQ-180 added a separate filament transformer which bypassed the off/on switch which kept the tunable oscillator tube heater activated so long as the receiver was connected to the AC line.  This did help somewhat in the stabilization of the receiver.

Even the SP-600 receivers are generally pretty drifty above 10 MHz.  Yes, the military did use hundreds of the SP-600 in fixed links (i.e. RTTY).  However, those units were the "JX" series which used crystals for frequency control.  Since a crystal was used to control the actual received frequency the tunable local oscillator was not used and the single frequency was very stable.

In terms of practical stability, during the 1950s and into the early 1960s, the Hammarlund receivers were about average in frequency stability.  The stability did not even come close to the stability of the Collins receivers, and Hallicrafters, National, and RME had a few receivers that were more stable as well.  But, the "run of the mill" Hallicrafters, National, etc., receivers generally drifted as much as the Hammarlund receivers if not more so.

Now the drift, once the receiver had warmed up, was not measured in the 10s of kHz (except maybe on 6-meters with certain receivers), but the short term drift was bad enough to requiring "touching up" during a single SSB transmission if the transmission took longer than a couple of minutes.  Also, after transmitting the receiver often had to be "touched up" when the other station started transmitting.

Glen, K9STH

Website:  http://k9sth.com


--- On Sat, 5/7/11, Darrell Bellerive <drbellerive.va7to at gmail.com> wrote:

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.