[R-390] OT - CX-1363/U test lead

[Charles Steinmetz]

Stan asked:

> I'm looking for a schematic of the CX-1363/U test lead.  I was hoping
> someone on the list could confirm if this test lead is simply a .1 uf
> capacitor @ 400 vdc between the input and output with a 510 pf
> capacitor @ 500 vdc across the output to ground?

Roy Morgan posted the following on 1/17/15:

> In the URM-25B manual, I found this:
>
> 12. TEST LEAD CX-1363/U.
> (See figure 2-17)
 >
> a. The Test Lead CX-1363/U should be used for
> making interstage receiver measurements. It consists of a 0.1
> microfarad capacitor (C-601) in parallel with a 510
> micromicrofarad capacitor (C-602) enclosed in an aluminum
> case similar to the antenna simulator and fixed attenuator
> units. One end of this case is terminated in a type UG-185/U
> connector. Two 18" long clip leads extend from the other end.
> The capacitor network is in series with the red lead, whereas
> the black lead is grounded to the case.
 >
> b. The capacitor network is inserted to protect the
> attenuator (E-112) of the signal generator from accidental test
> probing at points of B + potential and should always be used
> when making interstage receiver tests.
 >
> c. The reactance of the test lead capacitors should not
> normally affect the accuracy of the meter (M-101) voltage
> indication since, in most cases, the impedance at receiver
> interstage measurement points will be high. It must be
> realized, however, that when the CX-1363/U is used at test
> points of low impedance (below 400 ohms) the meter
> indication can no longer be depended upon to reflect the
> actual signal voltage applied.

See <http://mailman.qth.net/pipermail/r-390/2015-January/055118.html>

NB:  The 510pF capacitor is in *parallel* with the 0.1uF capacitor, from 
input to output, for better performance at higher frequencies (above the 
self-resonance frequency of C-101).

I am not bothering to post Figure 2-17.  It is just a poor photo that 
adds nothing to the understanding.  But see the attached image of the 
similar CX-2919/U test lead, as shown in Figure 2-18 of the URM-25F 
manual.  The CX-2919/U uses just one capacitor, 0.047uF.

A single 1kV ceramic capacitor anywhere from 0.01uF to 0.1uF should work FB.

Best regards,

Charles