Re: KPA500 active devices!!

Posted by W8JI on Apr 18, 2010; 10:31am
URL: http://elecraft.85.s1.nabble.com/News-from-Visalia-tp4914396p4920398.html

<
The VRF2933 is rated "3:1 Load VSWR Capability at Specifi ed
Operating
Conditions" according to its datasheet; perhaps that's why
there no
built-in ATU.>

.....but that doesn't mean SSB IMD would be acceptable, or
it would be safe in every circuit at that mismatch, so keep
that in mind. :-)

No matter what the data sheets say about device life, the PA
often needs to be kept within 1.5:1 or better SWR to meet
IMD specs. 3:1 is a huge loadline move, depending on the
direction of the impedance move it could really put the PA
into severe flattopping. Use a tuner or fix the antenna, be
safe.

73 Tom

On Sat, Apr 17, 2010 at 6:44 PM, Doug Faunt N6TQS
[phone]
<[hidden email]> wrote:

> There are two VRF2933's in push-pull, so they're not 750
> watts each,
> but per pair.  There are only three amps in existance, and
> no devices have
> been destroyed (yet).  Again, 500 watts is a very
> conservative rating.
> It's been key-down for 10 minutes withy no problems.
>
> 73, doug
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