[TenTec] Ten-Tec PA design

[Dr. Gerald N. Johnson]

On Fri, 2006-07-14 at 12:42 -0400, Bill Tippett wrote:
> K4KGY wrote:
> 
>  >The question of why TT didn't included a breaker instead
> of a fuse--well in a way they did--it's in their matching power
> supply. This is an electronic breaker not a magnetic and it works
> as good if not better than the magnetic. The fuse in the rig is
> then just a backup to protect the wiring system in case the
> breaker should fail and to protect same if someone uses other
> than a TT power supply. TT has always recommended to use an
> Air-Pax breaker if their power supply was not used and if sized
> correctly it works fine.
> 
>          Thanks Jim!  Someone else responded privately that
> Orion internally has a current limiting circuit (see below):
> The Orion I has a "current limit" circuit in it that limits the PA supply
> current by reducing RF drive to the PA when current exceeds a set level.
> Reference A5 ALC Circuitry  R19  and A0 Input/Output R63 sense resistor.

ALC circuitry!! Just a couple days ago I was told there was NO ALC
circuitry in the Orion. Just after I'd pointed out that ALC could lead
to faster rise times and a sharp transition from rise to level that
could contribute to key clicks...

So there is ALC inside the radio and it can have that effect.

> The SWR forward and reflected signals only drive the display to tell you
> that you have a bad swr. (This surprised me a bit I thought they would be
> using that also in addition  - but the current limit by drive reduction is a
> semiconductor manufacturers dream! ) I can't remember exactly what TT told
> me to set current limit at - but it was something like 20 amps (which pretty
> well fits the max current spec of 23 amps for the radio).My senior moment
> says 21.8 amps but don't believe that without talking to TT.
> 
>          I also checked the most recent versions of both the
> Orion and Orion II manuals under "Power Supply" and there
> is *no* mention of any external circuit breaker.  Maybe
> the circuit above precludes the need for one.
> 
>          Being a paranoid type, I think I'll install
> one just to be safe.  Does anyone know the correct
> Air-Pax model to use with Orion?
> 
>                                          73,  Bill  W4ZV
> 

-- 
73, Jerry, K0CQ,
All content copyright Dr. Gerald N. Johnson, electrical engineer