[Amps] Time for New Power Meter

[Jim Thomson]

Date: Tue, 5 May 2015 23:57:15 -0400
From: "robrk at nidhog.net" <robrk at nidhog.net>
Cc: AMPS submit <amps at contesting.com>
Subject: Re: [Amps] Time for New Power Meter

There?s a chart in the manual for the Bird 43 that shows what change in reading is, outside the freq range of the slug

Page 4-5?.

http://www.repeater-builder.com/test-equipment/bird/pdf/bird-43-wattmeter-old.pdf <http://www.repeater-builder.com/test-equipment/bird/pdf/bird-43-wattmeter-old.pdf>


A few years ago, when the Kenwood TS 940 was hot, a guy went through six of them and a wife trying find one that the meter would ?talk up? to the right power.

"?Scopes were not good for anything?.

Might have been the same guy who needed an antenna tuner to ?get them swr?s out of his antenna."

##  problem with the charts is..they are not for 2-30 mhz slugs.  Another issue with bird 43 meters is they dont read  swr directly.  Suffice to say that
11% reflected is = 2:1  swr.   And 25%  reflected = 3:1 swr.    To aid with the mental maths.... as long as reflected = 10%  or less,  u are in the ballpark. 

## another issue is with any amount of swr, the frwd reading is not true power at all...but is on the high side.   To get real power,  you have to subtract rvs power
from the frwd power to obtain...net power.   You also  have yet  another issue....esp with single line sections. Since rvs power is typ low, the element  is gonna be way outa
whack, trying to read low rvs power.   With any dual line section, the rvs slug is typ only 10% of the power rating of the frwd slug.   IE: if a 2.5 kw frwd slug is used, the rvs slug will
be a  250 w element.   If a single section is used, like the bird 43, then u have to remove the 2.5 kw slug, and insert a 250 watt slug..in the rvs direction. 

##  The array solutions   power master display  reads swr directly, down to 2 decimal places..and doesn’t change regardless of applied power.   5 watts or 2 kw, it will still read say 1.23:1 swr. 
It also has an option to display ..net power..which is just  frwd power minus  rvs power.  Problem solved, no screwing around.   If swr is above a pre-set threshold, amp kicks offline. 
You just cant do any of this stuff with a bird 43. 

Jim  VE7RF