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[Amps] About LP100A

To: <>
Subject: [Amps] About LP100A
From: "Jim Thomson" <>
Date: Mon, 19 Jun 2017 10:21:12 -0700
List-post: <>
Date: Mon, 19 Jun 2017 04:36:43 -0400
From: "Roger (K8RI)" <>
Subject: Re: [Amps] About LP100A

<Be careful of the scope across a known load.  Accuracy depends on the 
<precision of the resistor and on many bands may require compensation.  
<If you have a good dummy load, there is the calibration of the load.My 
<DL5K requires compensation above 40 meters. It's great on 160, 75, and 
<40, but the SWR goes up in a hurry from there.

<73, Roger (K8RI)

##  so why didnt palstar include a simple compensation cap ?   Thats no
different than using a small cap to achieve 1:1  swr on any amp...including
6m.....when on bypass mode.  Cap goes from hot to ground on the dummy load. 
The XC of the cap just cancels out the XL of the wiring on the resistors.  Its
typ just a few pf.  Tweak cap value for 1:1 swr on 10m...or 6m  if you use the
load on 6m. 

##  IF the scope is off by say 10%...the calculated power will be off by 20%.
IE: calculated power is always off by double the scope calibration.    If the 
is dead on..and the dummy load is 50 ohms, and no reactance, the calculated 
power should be dead on.... but thats a lot of ifs. 

##  On a side note, a buddy across town has a large dummy load used for
AM broadcast.   Consist of  an array of air cooled coils...similar to what you
see in a clothes dryer.  It looks very similar to what we used at the telco I 
at... for  load testing large emergency diesel generators... like the 
50-500 kva variety. 

## The AM broadcast  load  had  a vac variable cap across it.   Used to tune out
the XL  of the heating coils...which are obviously inductive.  But they had 
the array of coils, such that the Z  was close to 50 ohms...when driven.   At 
the original
AM site,out in the bush there was no water available for a water cooled load.   
It was 
a cost effective load for 600 khz usage. 

Jim  VE7RF

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