[Hammarlund] Why 2nd RF stage?

[Richard Knoppow]

----- Original Message ----- 
From: "Roy Morgan" <k1lky68 at gmail.com>
To: "Ken Gordon" <kgordon2006 at frontier.com>
Cc: <hammarlund at mailman.qth.net>
Sent: Sunday, November 30, 2014 2:41 PM
Subject: Re: [Hammarlund] Why 2nd RF stage?



On Nov 30, 2014, at 2:37 PM, Kenneth G. Gordon 
<kgordon2006 at frontier.com> wrote:
>
>
> The OT designers weren't stupid, despite not having 
> 'pooters at the
> time…

It’s been my experience that the more fancy and technically 
complicated are the computer systems used to analyze and 
design things, the farther the engineers get from having a 
feel for how the things work.

I’ve just gotten to work one of the mainstay tools used at 
Hammarlund and National to design and test RF stages and IF 
transformers - a Boonton 260A Q-Meter.  I’m just starting to 
learn how to use it, but I expect I’ll gain a seat of the 
pants sense of how coils and transformers work that has 
eluded me so far.

I’ve just realized that the BC-779 I have here may well have 
a product detector that I installed back in the 1960’s. 
When I get it upside down on the bench, I won’t be surprised 
to find a relay and extra tube added under the chassis.  Any 
pointers to what design I might have used would be most 
welcome.

PS: If anyone knows how to use the Q Meter to test crystals, 
do let me know!

     I must say it never occurred to me to use it for 
crystals although it should be able to do that.  There may 
be a clue in looking at the equivalent circuit of a crystal. 
Crystals look like very high Q tuned circuits. Its also 
possible there is something in the literature published by 
Boonton on this application.
     I have made only very elementary tests on crystals 
using a Millen GDO. You can plug a crystal into the GDO in 
place of a coil and adjust the capacitor for maximum 
current. There is enough radiation to pick up the output on 
a sensitive counter. Presumably, if the output frequency is 
adjusted to the marked frequency the capacitor is at the 
correct value for loading.


--
Richard Knoppow
Los Angeles
WB6KBL
dickburk at ix.netcom.com