Johnson High Power Attenuators

Glen Zook gzook at YAHOO.COM
Thu Jan 12 16:00:37 EST 2006

For a while I have been making a "modern" equivalent
of the "low power" attenuator (approximately 6 dB)
that was originally sold by Johnson to use with the
Ranger when driving the Thunderbolt, etc.  In fact,
the one that I am making has twice the power
dissipation that the original has.  The pricing and
description can be found on the Zcomco website the URL
of which is listed at the end of this message.

I am occasionally asked about building the higher
powered version, the one with the 75 watt light bulb
included in the circuit.  As such, I am "toying" with
adding the attenuator that will allow the Viking I,
Viking II, Apache, DX-100, etc., transmitters to be
used with the Thunderbolt.  Since I already use a
resistive network that has twice the dissipation
capabilities I would probably increase the size of the
light bulb to at least 100 watts (maybe 150 watts if I
can find bulbs that are physically small enough).

Because of the larger sized housing and additional
work that is going to be required to make the higher
powered attenuator the cost in going to have to be a
"bit" more than for the lower powered one.  Probably
in the $110 - $120 range.  These are not a high volume
item.  I am wondering if there is enough interest to
make it worth my while to go ahead with this project. 
A volume of between 10 and 20 units would be all that
is required to make the project worthwhile.  Not
trying to make a "mint" from them, just wanting to
cover my time in construction.

Glen, K9STH

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