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

[Carl]

----- Original Message ----- 
From: "Glen Zook" <gzook at yahoo.com>
To: <Hammarlund at mailman.qth.net>; "Darrell Bellerive" 
<drbellerive.va7to at gmail.com>
Sent: Sunday, May 08, 2011 11:20 AM
Subject: Re: [Hammarlund] Drift of Newer Hammarlunds? was Re: Old 
Hammarlunds


> 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.

Those were and are still good CW and AM receivers and a 30 minute warm up 
was the minimum that was generally used acoss the board with a tuneable 
front end oscillator. I used a HQ-129X for years on SSB also up to the early 
60's. Those were the days before transceivers and a QSO that started on one 
frequency often became split operation(-;


.
>
> 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.

The later versions were called the 170A and 180A and kits to update earlier 
ones were available. My 180 has that upgrade and is quite stable after 5-10 
minutes.


> 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.

The Super Pros from the 30's until the end of WW2 were notorious drifters, 
especially the ones built by Howard. The postwar SP-400X introduced some 
basic temperature compensating and is a nice CW/AM radio.


>
> 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.

Hallicrafters only had one SSB stable radio in the pre transceiver days, the 
SX-115 which is ham band only. Later ones were fairly good also.

National had the ham band only NC-300 in 1955 and it was a fine SSB radio 
and the NC-109 was pretty good also for a much lower price. The NC-270 had 
its good and bad ones and was the end of the tuneable front ends as the 
Drakes put an end to the drift problem in an affordable radio.

The general coverage Nationals in the upper price ranges were all stable for 
AM/CW going back to the 1935 HRO..after a 30 minute or so warm up. The 
NC-101X, NC-200, NC-240D, NC-173, NC-183, NC-183D, HRO-50, and HRO-60 here 
are all capable of acceptable SSB reception once completely refurbished. So 
is the NC-400 if you got a second run model.
The 50 and 60 requires a selected 6C4 and replacing a defective TC cap in 
various coils as needed. Collins has the same problem with that era TC caps 
in their 75A line sets.

Carl
KM1H