[Hammarlund] Re: Sweep Method for Alignment (explain?)

[Julian Bunn]

By the bandwidth, do you mean the width of the IF tuning peak? If so 
then this width is
roughly 1/5 of my sweep frequency range i.e. about 20kHz. It varies 
(narrows) as the
IF tuning is done.

(My goal when tuning the IF is to maximise the height of the peak, which 
is achieved when
the peak is at its narrowest, and so, I suppose, when its bandwidth is 
at a minimum?)

I have a feeling I may be missing understanding something important here 
... if the
width of the peak isn't the bandwidth, then what is it, and how do I 
change it to
observe the ringing effect you and Ken are talking about?

Many thanks!
Julian



James A. (Andy) Moorer wrote:

> You didn't say what IF bandwidth you were using when you tried 
> sweeping it at 100ms, 1s and 10s.
>
> The response of the IF filtering will be related to the bandwidth used 
> - not to the center frequency of the IF train.
> The IF could be 455 kHz, or 5 MHz or anything. If it has a bandwidth 
> of, say, 1000 Hz, then it will take on the order of 1-2 ms to settle, 
> and that time will be independent of the precise IF center frequency.
>
> Your calculation would be correct if it had a 455 kHz bandwidth - but 
> then it wouldn't be a very useful IF strip.
>
> Set the bandwidth to 100 Hz and try your test again. You should see 
> some difference.
>
>
> James A. (Andy) Moorer
> www.jamminpower.com
>
>
>
> ----- Original Message -----
>
>>
>> Regarding the merits of slower sweep speeds, I did a check today, 
>> comparing the
>> IF response curve when sweeping at 1ms, 100ms, 1s and 10s ... there 
>> was no
>> discernible difference at all.
>>
>> Indeed, since the time constant of the IF must be around 1/455kHz 
>> i.e. about
>> 2 microseconds, the system must charge up in much less time than 1ms. 
>> So I don't
>> understand why ringing would be a problem - have I misunderstood?
>>
>
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