[TenTec] Airpax circuit breaker for Orion

[Robert & Linda McGraw K4TAX]

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 at ptd.net>
To: <tentec at 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 at contesting.com>
> Subject:  Re: [TenTec] Airpax circuit breaker for Orion
> From:  "ROBERT CARROLL" <w2wg at comcast.net>
> Reply-to:  Discussion of Ten-Tec Equipment <tentec at contesting.com>
> Date:  Fri, 2 Dec 2005 13:03:00 -0500
> List-post:  <mailto:tentec at 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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