[Boatanchors] GR 1606A RF Bridge question

[Richard Knoppow]

----- Original Message ----- 
From: "Ispoulin--- via Boatanchors" 
<boatanchors at mailman.qth.net>
To: <boatanchors at mailman.qth.net>
Cc: <gtelepko at gmail.com>
Sent: Thursday, June 26, 2014 1:29 PM
Subject: [Boatanchors] GR 1606A RF Bridge question


>I have a question on the  procedure for testing  antenna 
>impedance with
> the General Radio 1606A RF Impedance bridge. I interpreted 
> the  manual as
> saying to do the initial balance with the unknown input 
> shorted  to ground and
> the detector (HF Receiver), and signal generator at 
> frequency of  interest
> connected,adjusting for a null on the receiver. Recording 
> the  reactance dial
> reading. Then connect the unknown,my antenna( A long wire) 
> to the  unknown
> bridge terminal and and adjust the resistance dial and 
> reactance dial  for
> the best null. Is the correct procedure to subtract the 2 
> reactance
> readings,then divide by the frequency in Mhz?This resulted 
> in a lower than  expected
> reactance for the antenna,which I assumed  to be around 
> 1,000 ohms  for an
> end-fed long wire. my example is 3400 ohms initial 
> balance, antenna null  at
> 4200 with r =82. 4200 minus-3400=800. 800 divided by 3.9 
> Mhz =205. So my
> equation  is 82+ j205 (.I found it to be inductive by 
> increasing the
> frequency and seeing a higher null reading) . Does my 
> procedure look correct and  is
> this reading accurate?  73, Al, W4TUK

     I think your procedure is correct.  I read over the 
handbook to make sure my memory is correct.  The reactance 
reading is the difference between the setting for the 
initial balance and the reading for the final balance 
divided by the frequency in Mhz.  The resistance reading is 
constant with frequency.  However, there are some 
corrections to be applied to the raw readings to obtain the 
true values. There are procedures and charts for the 
corrections in the handbook. I am tempted to set this up in 
my shack with my 1606-A but its a little late:-)


--
Richard Knoppow
Los Angeles
WB6KBL
dickburk at ix.netcom.com