[R-390] IF sweep alignment

[Curt Nixon]

When I became a Tektronix field engineer, one of the first things I did 
was to borrow what I needed and did a swept alignment of my R-4A.  I did 
it pretty much like you are, using a nice triggered scope and 
programmable generator.  The results were predictably good.

Now, here is my impression of an alternate and very simple way to do 
same with no real equipment...

Use a noise generator..lots of info around..basically a conducting diode 
junction.  Feed into the rig.  THis produces a broadband"flat" input.  
Now, look at the output of the rig in the frequency domain using one of 
the free PC software tools like Spectran.

What you see is a perfect, textbook display of the response of the DUT. 

I have not performed a full alignment this way YET, but have looked at 
the setup and output using only off-the-air atmoshpheric noise.  It 
works quite well.

Anyone else use this method?  To do just an IF strip, you would need a 
flat detector but that too is pretty simple.

FWIW

Curt
KU8L
.


KA9EGW wrote:
> Trying to do IF sweep alignment so I can look at the bandpass visually.  I
> haven't done this since '79, and then the receiver under test was an
> HQ-1w29X, with a then-30-year-old 500kc heathkit scope and a 1950's Eico
> sweep generator.  Now I'm trying to do it with a HP8640B sig/gen and a 20MHz
> dual-trace Hitachi.
>
> So I feed the FM-modulated RF into the antenna input of the 390A, feed the
> scope's vertical plates from the IF output on the rear of the 390, and feed
> the scope's horizontal plates from the 400Hz sinewave output of the 8640B.
> Can't get her to sync up with the scope in x-y mode.
>
> Before I consume too much more bandwidth, is the fact I'm feeding the
> horizontal plates with the 400cps modulating freq the problem?  Seems to me
> last time I did this that old Heath scope had a sawtooth output on the back
> with which I fed the external sweep input on the sweep gen, which sawtooth
> output the Hitachi scope doesn't have. :-(
>
> I'm thinking I ought to see if I can borrow a function generator from work
> that does sawtooth and feed both the external modulation input of the
> generator and the scope's horizontal plates with that.
>
> [Of course I'm also thinking this would be a good excuse to buy a better
> scope, but alas, having just acquired that 8640B I dunno if I could get a
> new scope past the "Appropriations Committee" HI HI].
>
> Am I on the right track here?  I mean as far as my test setup goes.
>
> 73, Brian KA9EGW
>
> -----Original Message-----
> From: r-390-bounces at mailman.qth.net [mailto:r-390-bounces at mailman.qth.net]
> On Behalf Of Curt Nixon
> Sent: Saturday, February 26, 2011 10:26 AM
> To: r-390 at mailman.qth.net
> Subject: [R-390] My New R-390A Rework Project Blog
>
> GM:
>
> For any interested, here is a link to my blog on re-working my first R-390A
> Please feel free to comment there or here--I'm a newbie w/the R-390A so
> having a ball scoping out all the istory and information available on-line.
>
> http://curtsworkshop.blogspot.com/
>
> Curt
> KU8l
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