Tek 7904 scope

Tony Duell ard at p850ug1.demon.co.uk
Sat Feb 17 17:32:50 CST 2007

> >The 7A29 is a single channel 1GHz plugin, 7B92A or 7B10/7B15 timebases.

It's been a while since I used any 7000-series stuff [1] but IIRC the 
timebase to look for is the 7B92A. It's a dual timebase, you can use one 
timebase to delay the other (which is very useful) and it only takes up 
one slot in the  'scope. 

[1] There was a 7904 and an assortment of plugins in the lab where I did 
my Ph.D. I was the only person ever to use it, really, everybody else 
thought it was very old-fashioned. It was, but it's a darn good 'scope. 
I'd like one for home in some ways _but_ they are full of custom silicon 
and Tektronix no longer supply spares. If a chip fails you've got problems...

> Never having owned a decent scope before, please help me out a little.=20
> Well, I do have a 60mhz Hickok that's really beat up.
> If I want to get up to 500 MHz (70 cm is 400+ right?) I could try to loca=
> te=20

Well, if you want to look ot the output of a 70 cms transmitter (which is 
about 430MHz, at least in the UK), you really want to be able to see at 
least the 3rd harmonic. Which means going up to 1.2GHz+. 

However, the most useful instrument IMHO for setting up a transmitter is 
an RF spectrum analyser (then you can see just what you're shoving out 
out-of-band). Yes, you can get spectrum analyser plug-ins for the 7904 
(they have 7Lxx modul numbers, where xx varies with the band they cover), 
but you want to be sitting down when you hear the price!.

> >The S4/7S11/7T11 combo is cool if you want a10+GHz sampling capability.
> Yikes, I'm not sure I would know what to do with 10 GHz capability.

I have the 1S1 sampler (and cathode follower probe [2]) in my old 
500-seires 'scopes. That give a 1GHz capability, and I have used it (when 
setting up the local oscillator of a 2m receiver, for example). These 
sampling modules essentially work by aliasing the signal down into the 
passband of the 'scope and thus only work for repetitive signals. Fine 
for looking at a carrier (or local oscillator) signal, not so useful for 
other things.

[2] An active probe with a tiny triode valve inside. 


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