On Thu, 09 Jul 2009 15:35:59 -0700, Jeff Liebermann
wrote:

I just bought a Telonic RHO-TECTOR TRB-50 return loss bridge off eBay.
It's suitable for swept antenna measurements of 0.5Mhz to 1GHz.
Amazingly, it functions. However, I'm curious as to exactly how it
works and what's inside. Duz anyone have a theory of operation,
schematic, or other useful clues?

The best I have so far is:
http://www.qsl.net/n9zia/rlb/texscan.png
which may be the schematic, but I can't tell without tearing it apart
(which with my luck, will probably destroy it). Using my
ohms-guesser, it seems correct.

A bit more....

Photo of Texscan RCB-3 inside:
http://www.qsl.net/n9zia/wireless/rtrn_loss-pics.html

Photo of Telonic TRB-4 (similar to the TRB-50):
http://www.mjs-electronics.se/images/Diverse/trb4.jpg

Telonic is still around, but doesn't have any old info online:
http://www.telonicberkeley.com

I tried to find a patent that covers the return loss bridge, but
failed. Plenty of VSWR measuring devices, but nothing that looks like
the TRB-50 or the possible schematic at:
http://www.qsl.net/n9zia/rlb/texscan.png

Also, lots of similar devices by Wiltron, Aeroflex(IFR), Eagle, etc,
but no schematics found (yet). Eagle used to have some nifty app
notes on using an RLB on their web pile, but it appears to be trashed:
http://www.eagle-1st.com

Drivel: Bing produced fewer results, but far less garbage than
Google. The problem was that most of the hits for both Bing and
Google were various surplus dealers selling MW hardware at exhorbitant
prices.