Re: Spectrum analyzer Tektronix 7L13 on mainframe Tektronix 7603


Chuck Harris <cfharris@...>
 

A couple of things:

First, you don't have to get so worried about accidentally putting
DC on the mixer. It is safer, and better to be more conscious of
what you are doing when you make measurements with your SA. Sample
the measurement point with an oscilloscope, to determine the signal
composition, before connecting your SA. Always use the maximum
attenuation that allows you to get your measurement. Make prophylactic
use of probes and loops. Always discharge coaxial lines before you
attach them to the SA.

Second, DC blocks will *NOT* protect your SA against all such DC
abuses. When a discharged capacitor is connected to a high voltage
point, it will instantaneously behave as a dead short circuit. It
will transfer that high voltage point directly to your mixer, as if
it isn't there. Only as the capacitor begins to charge, will that
high voltage/current be removed from the mixer.

If you connect your DC block protected SA input to a 100V point inside
of a transmitter, it will toast your mixer very nicely, and quickly.

Train yourself to use your SA safely. Don't rely on crutches to protect
you from unsafe behavior.

-Chuck Harris

Attilio wrote:

Sorry if I ask some trivial questions, but I am worried by the writing on the RF input of the 7L13 regarding the absolute prohibition of applying a direct current voltage (0 Vdc). I am looking on the internet for a dc-blocking with BNC connectors to be applied on the RF input, but I cannot find the Tektronix part number 015-0221-00, I was thinking of using a small metallic box with BNC connectors and connecting a 1000 pF - 1 KV ceramic capacitor between the BNC connectors, what do you think?
I have seen other DC blockers use a 100nF capacitor but I doubt that when charging it will damage the 7L13's first mixer.
I should equip myself with some accessories, but I have no clear ideas, I should buy a power splitter or a combiner.
I would like to buy a TR502 tracking generator with its power supply in the future.

Greetings and Merry Xmas to all





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