¿ªÔÆÌåÓý

ctrl + shift + ? for shortcuts
© 2025 Groups.io
  1. HP8924-Family-Spectrum-Analyzers
  2. Topics

Bessel Function on HP8920A...

 

Gang,

I want to do a Bessel Function confirmation of deviation calibration on my HP8920A using the internal RF generator and internal tone. Is there a way to adjust the deviation of the internal tone while watching the spectrum analyzer?

Burt, K6OQK
 
Edited

I cant think of a way to do it via front panel. I'm pretty sure you'd have to flick between screens. Should be able to do it via HPIB/SCPI on the IEEE 488.2 port..
 

you may have to have an external SA to do what you are asking on the 8920

Some service monitors ( like the IFR 1600 and COM-120 ) have a split screen where you can adjust the generator and view the output on the? SA portion of the screen.

The 8920 isn't structured like that.

The best you may be able to do is to setup the generate at one of the nulls and then switch to the SA ,,,,easy way would be to have both functions use the RF I/O port

Typically the 8920's are very close on modulation and output levels.but I usually use an 8902A to verify.

I do use the internal tracking gen function through a jumper to verify the internal alignment/calibration of the RF I/O assembly by making sure the frequency response across the entire 1Ghz is essentially flat.
 



Inline image



After several hours of fumbling around with the HP's menus, I got a SA display of the built in SG output at 146.00 MHz.

At first I used a BNC jumper to get the SG into the SA, but then with more effort, got that coupling to happen internally.

The last hurdle was trying to adjust the deviation without having to switch between SA and SG screens which requires quite a few manipulations.? I? remembered vaguely something about User Keys and thinking maybe that might yield a way, with a few button pushes, to toggle between the two screens which would be fairly efficient.

With a LOT of time spent on menus and getting nowhere,? I couldn't find a way to toggle screens and was sure it couldn't be done.

The great surprise was there was a way to use a Global User Key to adjust the deviation WITHOUT even leaving the SA screen!? That's what you see above with the extra window at the upper left (red rectangle added) showing the adjustment for the deviation that is now visible and adjustable.? It? is set at 2.4k to null the carrier for a modulation frequency of 1.0k.

The orange ELD on the E6380 photographs well.? I reduced the orange intensity by a graphics program.? Use the separate attachment to view the image full size and peak sharpness.? The inline image inserted right in the email suffers from getting reduced to 640 pixels wide by the Groups.io system.

Hank?
 

Forgot the attachment.

bessel5b.jpg

 
Edited

So what were the keys used.

Keith
 

Keith,

The User Keys have to be programmed by you.

You only need one such key for this setup (Global K1, K2, or K3).? Knob spinning or direct numerical entry comprise the other button pushes you'll be using.

I would refer you to page 83 of this book available in our files section for the details.? Also, attached is an image from page 83.

? ? ? ? ? ? ? ? ? ? ? ? Agilent Technologies 8920A?
? ? ? ? ? ? ? ? ? ? ? ? RF Communications Test Set
? ? ? ? ? ? ? ? ? ? ? ? User¡¯s Guide






global keys.jpg

 
Edited

Hank,

I got the attachment. That looks great.? I printed out the appropriate page and will give it a try as soon as I have some time in my shop.? Try it using a tone frequency of 2.0793 kHz.? The first null should give you 5 kHz deviation.

Thanks,

Burt, K6OQK
 
Edited

Hank,

If you could give a step by step on how you accomplished this, it would be really appreciated, particularly how you were able to get the generator function to directly feed the receiver side without the need to use an external jumper.

As I mentioned earlier, if you use a modulating tone frequency of 0.20793 kHz (2079.3 Hz), the first null will occur at +/- 5 kHz of deviation for calibration or calibration confirmation.

Burt, K6OQK
 

Correction:? that should be 2.0793 kHz (2079.3 Hz), not .20793 kHz.? Sorry about that.

Burt, K6OQK


On August 1, 2023 8:20:55 AM PDT, I? wrote:


As I mentioned earlier, if you use a modulating tone frequency of 0.20793 kHz (2079.3 Hz), the first null will occur at +/- 5 kHz of deviation for calibration or calibration confirmation.
 

Awesome! Learnt something today..
 

Chris,

Because you get the summary of messages and?because this Bessel thread?has consisted of several aspects,?it's not obvious what is new for you.? Is there something in particular you learned so far?

Hank


On Tuesday, August 1, 2023 at 06:16:28 PM EDT, zl1cvd wrote:

Awesome! Learnt something today..

 

Global user key..

1 - 13 of 13