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[Amps] SB-220 no output

To: <>
Subject: [Amps] SB-220 no output
From: "Jim Thomson" <>
Date: Wed, 26 Jul 2017 09:35:46 -0700
List-post: <>
Date: Tue, 25 Jul 2017 12:29:59 -0600
From: Warren Volz <>
To: Glen Zook <>
Cc: amps <>
Subject: Re: [Amps] SB-220 no output


<Yes ok, so it's only to give you a general idea on the power not actual
<numbers. That explains it. 


## Correct.  Its just a relative power output meter... used to tweak the
tune and load controls for max output.  It is NOT a wattmeter.  Its a
tuning aid...thats it.  But even with an external wattmeter, the external
wattmeter and the internal.... relative power meter, will both peak..and
dip simultaneously  as the tune and load are rotated. 

##  You just dont know the actual  PO  if the relative power meter is used. 
The relative power meter was used on a lot of amps way back in the day.
Cheap and easy tuning aid that works good, and cheap, vs a real internal
wattmeter.    A good external wattmeter has the advantage that it can be used
on anything and everything, like xcvrS, multiple amps, vhf uhf  gear,
various power levels etc.   Array solutions makes superb wattmeters, with plenty
of alarm features, like high swr shut down, if over a pre-set threshold,  under 
over power.  Also PEP capability, direct swr any power level, etc, 
Several other superb brands that do essentially the same thing.  

## Then the Bird and coaxial dynamics wattmeters, with either single or dual 
line sections,
and optional pep capability. The bird + cd meters read reflected power, and not 
so you have to note down both the frwd and rvs power readings, then use the 
nomograph to depict  actual swr.   The bird and cd meters are sorta going out 
of vogue
these days.  However, they will work on anything from AM broadcast  band to 
uhf,  but
require the correct plug in element...aka slug.   Each slug has a freq 
dependent range, like
2-30 mhz.. or  100-250 mhz etc.  Even then, each can be bought with several 
different max 
power ranges.  Like 5-10-25-50-100-250-500-1000-2500 watts.   The bird + cd 
are most accurate when their readings are in the upper portion of their scale.  
So you end up buying
a mess of expensive elements to cover both various freq ranges..and power 

##  But you dont need  any of that stuff to tune an SB-220.   The simple 
relative power output
internal meter is ample.  Just dont over drive the amp, and or exceed the plate 
and or grid current 
specs laid out in the manual. 

Jim   VE7RF    

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