[Hammarlund] Old Hammalunds

[Kenneth G. Gordon]

On 13 Apr 2011 at 9:37, Eugene Balinski wrote:

> Can someone please repost the sweep alignmment method info?

Sure:

First of all, it requires an oscilloscope with an external sync (horizontal) input, 
and a swept signal generator (sometimes called FM) also sometimes called 
a "Sweep-Function generator" with a sync output. The sync output should be 
a sawtooth shaped wave, although a sine wave will work, but not as well.

The sweep-function generator is set with the center frequency at the IF of the 
receiver, and the sweep width is set somewhat wider than the expected IF 
passband.

The sweep-function generator SIGNAL output is connected to the grid of the 
mixer tube, or to the input of the first IF. I prefer the grid of the mixer tube in 
order to keep the signal levels input to the IF low enough to NOT cause 
inaccuracies by overloading any IF stage.

The sweep-function generator SYNC OUTPUT is connected to the 'scope's 
external sync, or horizontal, input. The purpose of doing this is so that the 
'scope's horizontal position is controlled by the sweep-function generator, 
and NOT by the 'scope.

The 'scopes VERTICAL input is connected to the output of the detector, 
usually the "hot" end of the diode load resistor is a good spot.

Then you fire everything up and adjust all controls so that you see the IF 
passband shape on the 'scope screen.

Depending on the scope "persistence" you may have to use a very low 
sweep rate and dim the lights in the room. With a better scope, you can use 
a faster sweep rate, and will see a brighter image.

You then adjust the receiver's IF adjustments to achieve the proper shape. It 
should be symetrical and as narrow as possible.

OK?

Ken W7EKB