[Hammarlund] Re: Sweep method for alignment.

[Kenneth G. Gordon]

Here are two messages that this list may find helpful. I have forwarded 
these from the Glowbugs list.

Ken Gordon

------- Forwarded message follows -------
On Apr 12, 2006, at 3:23 PM, mikea wrote:
>>
>>    I sweep the 10.7MHz IF strips in my domestic tube receivers by
>> snatching the sweep out signal from my scope and feeding it as
>             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
>> a modulation waveform to my signal generator, set to FM mode. Works
>> remarably well, even though I will probably try to find a 'proper'
>> sweep generator' some day.
>
> _Way_ cool! I hadn't thought about that, but I'd be using the scope
> anyway, and it's guaranteed to be in sync! So all I need is my old
> HP 8640B, some BNC-to-BNC cables, a probe or two, the scope, and the
> RX.
>
> Much obliged!
>
> Thanks, & 73, de

   You are welcome, Mike. <G>

   I happen to use my HP 8656A together with my stone age 10MHz 
Philips scope, and I like the results. Only problem is that the 
maximum deviation is limited by the signal generator, +/-100KHz in my 
case. That just happens to be barely enough for aligning 10.7MHz FM 
IF strips, where the normally stated maximum deviation is +/-75KHz.

   Here are a few snapshots of the final results of aligning a 1956 
Grundig 3033 receiver (six tubes), which has seven 10.7MHz tuned 
tanks, plus ratio detector. The asymmetry in the IF response is due 
to a peculiar reflex coupling of the first IF stage in the VHF tuner. 
Notice that both IF and discriminator curves are inverted in Y, since 
the ratio detector provided negative voltages wrt. ground.

   Arbitrary Y axis, X is 10.7MHz center +/- 100KHz (20KHz/div.)

<http://www.warpspace.com/glowbugs/oz1ioc/grundig_3033/testing/ 
10.7_IF_passband.jpg>

<http://www.warpspace.com/glowbugs/oz1ioc/grundig_3033/testing/ 
discriminator.jpg>

   The whole set:

<http://www.warpspace.com/glowbugs/oz1ioc/grundig_3033/g3033.jpg>

   More photos from before and after restoration:

<http://www.warpspace.com/glowbugs/oz1ioc/grundig_3033/>

   Vy 73 de Frank, OZ1IOC.

------- End of forwarded message -------