[Antennas] Return Loss Bridge Questions

[Dennis L. Wade]

Hello everyone,

	I've run across an return loss bridge design I'm interested in and 
have a few questions those of you who are of the engineering mind 
might help answer.  I'm also curious in the design generally.

	The bridge information is at:

	http://www.pollak.sulinet.hu/elektro/hidak/bridge/how_to.htm

		My specific question is regarding minimum drive.  The author states 
that the minimum drive in 100 mw, with typical drive of more like 1 
watt.  I'm more interested in an instrument that can use output 
levels more typical of a good signal generator (I don't want to 
radiate more than I have to) especially on frequencies outside the 
ham bands.  

		What determines minimum drive?  Is it simply a matter of the 
sensitivity of the indicator device, or is there something else at 
work here (probably insertion losses?).  The "how to use" text in the 
above link describes setting the indicator for a full scale range of 
2.5 or 3 volts.  This seems high, and I'm wondering if simply using a 
more sensitive scale would allow lower drive (unless I'm mistaken 
though, I'd have to use the general formula to calculate db of loss 
from voltage changes and not the author's tables which are based on 
2.5 or 3 volts full scale.)

	I'd love to hear any other comments on the design that anyone would 
like to share.  

		Thanks!

					Dennis
-----------------
"If you can remain calm, you just don't have all the facts"

Dennis Wade
KG6ZI
Carmichael, CA