[Hammarlund] HQ-129-X Question

[Bob Macklin]

In the case of my NC-109 on band C with 5MHz right on 14MHz is about 200KHz 
LOW with the minimum setting of the padder. With same setting 10MHz is about 
100KHz low.

In any case with the 1MHz calibrator it is accurate enough for me to use.

Do you have a crystal calibrator for your HQ-129?

Bob Macklin
K5MYJ
Seattle, Wa.
"Real Radios Glow In The Dark"
----- Original Message ----- 
From: "Kenneth G. Gordon" <kgordon2006 at frontier.com>
To: "Bob Macklin" <macklinbob at msn.com>
Cc: <Hammarlund at mailman.qth.net>
Sent: Monday, November 29, 2010 3:44 PM
Subject: Re: [Hammarlund] HQ-129-X Question


> On 29 Nov 2010 at 15:12, Bob Macklin wrote:
>
>> On any single band there are only 3 frequency determining components.
>> The tuning capacitors which should not change with age. Especially the
>> Hammarlund variables. The inductor which may change a little with time
>> and the trimmer.
>
> In many receivers (and transmitters) there are also parallel padding
> capacitors, usually fixed micas.
>
>> The only one that has an effect on the linearity between the end
>> points is the main variable.
>
> Well, James Millen, among others, might argue with you about that. :-)
>
> I think linearity, with regard to the main-tuning cap, has more to do with 
> the
> SHAPE of the variable capacitor plates, although the relationship between
> the main-tuning cap, the inductor, and the padding caps comes into play 
> too.
>
> According to a couple of articles I have read on the subject, one by 
> Millen,
> another by Langford-Smith in "The Radiotron Designers Handbook", linearity
> in a capacitor-tuned circuit is VERY difficult to achieve as there are, 
> quite
> simply, too many variables involved. It often isn't economically 
> reasonable to
> go to the max.
>
>> And I doubt it has changed a measurable
>> amount.
>
> You're absolutely right, of course.
>
>> I am having similar problems with my NC-109. I have bands B and D very
>> close. Close enough for a receiver with a string drive.
>>
>> But I cannot get band C close to the manual. I can make it correct at 
>> 5MHz
>> ( the bottom) and 7MHz but not at 14MHz (the top).
>
> To my mind, since it is right on on bands B and D, and not on band C, then
> the tuning cap cannot be the problem. Therefore, it has to be something in
> the circuit unique to band C.
>
> Possibly a shorted turn in the inductor?
>
> A fixed mica padding cap gone bad on ya?
>
> Powdered iron in the inductor (if there is any) gone weird on ya?
>
> All of which, although very rare, I have run into at least once in my 
> almost 56
> years in electronics.
>
>> I am going to try and get it close between 5MHz and 10MHz and ignore
>> the portion above 10MHz.
>
> Well, if you are anything like me, it will still keep bugging you, 
> yeasting
> around in the back of your mind, sometimes for years, until you figure it 
> out
> and get it fixed. ;-)
>
> Ken W7EKB
>