Quoted from the Omni VI Plus manual.
"NOTE: When operating the transmitter into an SWR higher than 2:1, adjust
the RF "PWR" control to a collector (Ic) current not to exceed 20 amps as
indicated on the front panel meter."
Now with that said, in looking at my Omni VI Plus operation into various
load conditions, I find that a 1:1 SWR and 90 watts output, the Ic current
is ~14 amps. With a 100 ohm load, thus a 2:1 SWR the Ic is ~12 amps and
power output is 90 watts. With a 25 ohm load, thus a 2:1 SWR the Ic is ~ 18
amps and power output is still 90 watts. The point being a 2:1 SWR does not
tell you if you have a 100 ohm load or a 25 ohm load. In my case, if the
load gets down to 12 ohms the Ic is 20+ amps and power output is still 90
watts On the other side of the slope with a 200 ohm load, the SWR is 4:1
and power output is still 90 watts bit Ic is now only 10 amps.
Thus using a supply with unlimited current above 20 amps can be dangerous
unless you know your load Z and can control the power to such extent as not
to exceed 20 amps Ic. It must be done either manually or automatically by
the power supply or some other fast acting current interrupt device.
Failure to do this will cause excessive investment in output transistors.
73
Bob, K4TAX
----- Original Message -----
From: "Vic Klein" <vhklein@ptd.net>
To: <tentec@contesting.com>
Sent: Friday, December 02, 2005 9:48 PM
Subject: Re: [TenTec] Airpax circuit breaker for Orion
Ten Tec design philosophy for radio finals is to run them full power into
any load, rather than folding back the power as SWR increases. The only
potential for damage then is if the finals draw too much current, so their
power supplies feature a current limit that protects the transistors. When
using another brand of supply, then, it is just a safety measure to
include
a fast acting breaker to do what TT supplies provide internally.
=Vic=
WA4THR
----------------------------------------------------------------------------
---------------------
To: "'Discussion of Ten-Tec Equipment'" <tentec@contesting.com>
Subject: Re: [TenTec] Airpax circuit breaker for Orion
From: "ROBERT CARROLL" <w2wg@comcast.net>
Reply-to: Discussion of Ten-Tec Equipment <tentec@contesting.com>
Date: Fri, 2 Dec 2005 13:03:00 -0500
List-post: <mailto:tentec@contesting.com>
I missed some of the earlier messages on the Orion Airpax issue. Is the
Orion or Ten Tec rigs in general more susceptible to whatever fault causes
the problem? I suppose ignorance may be temporary bliss, but being in
that
state I have been running all my rigs from various Astron supplies--with
appropriate caution about the Astron grounds.
What causes the Orion to inhale current, what specific Airpax is
appropriate, and about how much do they go for?
Bob W2WG
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