[Hammarlund] Old Hammarlunds

[djed1 at aol.com]

Good point, Todd.  Henry's web site has an outstanding writeup on the history of the Super Pro (he has a photo of my SP-400 at the end).  Given the state of receiver design in the mid-1930s, the Super Pro was as much a revolution in technology as the R-390 was a generation later.  Despite it's shortcomings, I have restored my BC-779 to original condition and greatly enjoy listening to it.

As an aside- I've spent a couple of years trying to complete restoring the BC-779 to all original, and one of the last steps was to source a nice power cord.  About the only thing I'm missing now is a set of the knurled nuts which secure the dust cover.  I've made up some reproductions, but they don't have knurling.  If anyone has some they wish to part with, please let me know. I can supply a photo if that will help.
Ed  W2EMN

 

 


 

 

-----Original Message-----
From: Todd, KA1KAQ <ka1kaq at gmail.com>
To: djed1 <djed1 at aol.com>
Cc: Hammarlund <Hammarlund at mailman.qth.net>
Sent: Tue, Apr 12, 2011 1:45 pm
Subject: Re: [Hammarlund] Old Hammarlunds


On Tue, Apr 12, 2011 at 11:23 AM,  <djed1 at aol.com> wrote:



> 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.



And that really is a big point that many seem to miss. The original

Super Pro 200s were a 1939 design that evolved from the earlier SP-10

and -100 models. It's important to keep in mind things like the higher

bands weren't the big draw then that they are now. In fact, the

standard Super Pro covered the BC band to 20 mc only. Only the SX

model, made in much lower numbers, added coverage through 10 meters at

the expense of much of the BC band. Compared to other radios of the

day, the Super Pros were at the top of the pile with the HRO, They

were used through WWII virtually unchanged other than some power

supply upgrades.



A lot changed over the roughly decade and a half since the the SP-200

series was introduced. The SP-600 is an entirely different beast, a

Super Pro in name only. And the R-390 series with the famous Collins

PTO was and in many ways, still is the benchmark for old tube

receivers. Which is why it's important to keep things in perspective

with respect to things like drift, features, and so on.



As Ken mentions and as the manual states, the receiver was designed to

be left on for extended periods to stabilize. It takes a while to

bring all of the mechanical bits into harmony, so to speak. Once it

stabilizes though, it's as solid as a rock. Having the receiver in a

location where it can experience temperature changes (near an outside

door, for example) or fluctuating line voltage wouldn't be desirable.



For anyone who hasn't seen Henry Rogers' great site yet and would like

to read more on the Super Pros, I highly recommend it:



http://www.radioblvd.com/hammarlund_super_pro.htm



Henry outlines many of the issues (operator-generated, in many cases)

that have given them a bad rap over the years. I can verify his

findings, especially using the correct feedline impedance for low

noise operation.



The only trick is bringing them up to spec and using them as designed

and detailed by the manuals. Known primarily as a workhorse, they are

really more the thoroughbred of their day. I love my early Super Pros,

they are some of my favorite receivers. In fact, I use a 1937 SP-100

as a bedside receiver driving a large Jensen speaker in an EV

enclosure. Apparently I'm extremely lucky, as it shows no appreciable

drift from turn on to 3-4 hours or more later.





~ Todd,  KA1KAQ/4