[Amps] SB-220 no output
jim.thom at telus.net
Wed Jul 26 12:35:46 EDT 2017
Date: Tue, 25 Jul 2017 12:29:59 -0600
From: Warren Volz <warren at warrenvolz.com>
To: Glen Zook <gzook at yahoo.com>
Cc: amps <amps at contesting.com>
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 power,
over power. Also PEP capability, direct swr readout..at any power level, etc, 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 swr,
so you have to note down both the frwd and rvs power readings, then use the supplied
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 meters
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 levels.
## 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.
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