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Re: Return loss bridge (2.4 gHz ) report

Hi All

I have had several queries about the Return Loss Bridge.    I do not have
any affiliation with the making or selling of this equipment.    Just a
happy customer.


Phone  925-513-1597
Fax     925-513-1797

Jim  VE5FP
Eric  KN6KC@arrl.net

Equipment needed to make the Return Loss Bridge work"

Common 9 volt Battery.
50 microamp (ua) meter movement.
External reference.
Something to test .

The bridge is a two port device that requires a reference on one port
that has a DC resistance equal to the desired impedance of the antenna
under test.
If the antenna is to match 50 ohm coax then an N connector with a 50 ohm
non inductive resistor installed can be used .      Eric had some 50 ohm
reference loads available .    I obtained one and found it was a heavy (
thick ) N connector made to keep thermal stability.

As a reference the following are current levels measured for the various
conditions and devices .

Reference on port 1 .    51 ohm DC  ( Fluke 73 )    

Shorted  port 2       26 ua
Open      port 2       35 ua
Small UHF connector  Dummy load,  50.8 Ohms    5 ua
Home brew UHF connector Dummy load,   56.2 ohms              32 ua 
TSI dipole        2 ua 
BBQ dish dipole w/ 16-5/8 square aluminum tube w/ splash plate  0 ua   no
BBQ dish dipole w/ 6-1.4 square aluminum tube w/o splash plate 3 ua    no
Home brew vertical for the DEM WSS 2400B test oscillator       2 ua
I know Eric , the person I dealt with, has gone on vacation for three
weeks.    He was my only contact .


On Wed, 13 Jun 2001 05:38:34 -0000 "Dave Lamont"
<lamontd@paradise.net.nz> writes:
>Hallo Joseph,
>I would be grateful if you could provide an e-mail or
>url address for these guys.
>Kind regards
>Dave Lamont   ZL2AMD
>           Uni_Trac Satellite Tracking System
>              www.qsl.net\zl2amd\
>----- Original Message ----- 
>From: "Joseph Murray" <k0vty@juno.com>
>To: <amsat-bb@AMSAT.Org>
>Cc: <ericlawson@2xtreme.net>; <hurst_cj@msn.com.au>
>Sent: Wednesday, June 13, 2001 2:42 AM
>Subject: [amsat-bb] Re: Return loss bridge (2.4 gHz ) report
>> Hi All
>> In the Sep/Oct 2000 AMSAT Journal pages 13 - 19 two Amateurs ( KN6KC 
>> VE5FP ) teamed together and produced a Bridge unit to test 
>return-loss on
>> 1.2 and 2.4 gHz antenna systems.    I wish to report that I have
>> purchased a 2.4 gHz bridge and it is an excellent device.    There 
>> nothing like being able to measure your 2.4 gHz antenna impedance 
>> loss rather than modeling  or just plain guessing about it.     It 
>> small, simple and easy to use.
>> I purchased the kit and examined it carefully .    I came to the
>> conclusion after making a devise to hold each component as I 
>soldered it
>> to the PCB that at 72 I could not put this SMT Bridge together 
>> significant 
>> risk .      I return the kit for a completed unit.   The additional 
>> that I spent was well worth the cost to me.      The completed 
>Bridge is
>> pricy ( $200 ) but how pricy the knowledge that the antenna is ok 
>can be.
>> I made a home brew, 20 turn Kraus helix using the  W0OQC matching 
>> and had very good return loss.    That W0OQC matching system is easy 
>>  Much easier to build and to adjust for return loss than the Kraus (
>> Miller ) tapered shim ( non adjustable ) and it allows grounding of 
>> antenna proper to protect the sensitive Preamp devise from static
>> electrical build up on the antenna.     Thanks William.
>> Checking the dipole for return loss that comes with the TSI 
>converter,  I
>> found it very good .   This surprised me some what since return loss 
>> effected by the dish reflectance coefficient and I expected the 
>> (not mounted on a dish) return loss would be worse.   That will 
>cause me
>> to want to try it on a dish if I get the chance.
>> Note:   If you purchase the kit, do not handle the active elements 
>if you
>> expect to return it for a completed unit.
>> ________________________________________________________________
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