The following is submitted without recommendations or comments:
The other day we were investigating the RF voltage output of various
analyzers under the normal 50 Ohm load, as reference to testing receiver
input impedances, and the safety of hooking them up direct. The units I
tested ( MFJ and AUTEK) were characterized by their dBm levels, that is,
milliWatts into 50 Ohms.
Some were interested in what the voltage would be if there were no load, or
a high impedance load, so today I made that measurement and here are the
results, in RMS Volts:
MFJ 259 (not B): .670 V @ Hi-Z, slightly less @ 2K Ohm (which is less power
by a magnitude if I did my math right. It was 2 mW @ 50 Ohms, and only .2
mW@ 2k Ohms)
Autek RF-1: .8V @ Hi-Z, slightly less @ 2K Ohm.
If these voltages are higher than you care to use under your particular
circumstances, consider using a simple home-brew Return Loss Bridge to
characterize the circuits impedance. Refer to ARRL Handbook or the Solid
State Design Handbook by Demaw/Hayward for circuits and procedures. Speaking
of which, hey Wes, when is Volume II coming out? We eagerly await.
Happy Homebrewing, Geo>KØFF
http://homepages.dstream.net/K0FF
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