[Elecraft] KPA500 active devices!!

[Joe Subich, W4TV]

John, 

It's not shown on the datasheet.  However, the VRF2933 is 
specified as a communications product (not a repurposed 
switching device) and is from the same family as the VRF150 
(upgraded MRF150) which is specified at -32dBc (-38 dB to 
ARRL standard).  Since the VFR2933 is a higher gain part 
(20 dB minimum gain) than the MRF150/VRF150, I would guess 
the IMD performance might be a bit worse at maximum output. 

Still, with the VRF2933 rated for 300W minimum - 375 typical 
at 50V - the KPA-500 is not pushing them at 500W.  I'd look 
for IMD numbers on the mid to high 30's (ARRL spec). 

73, 

   ... Joe, W4TV 
  
 


> -----Original Message-----
> From: elecraft-bounces at mailman.qth.net
> [mailto:elecraft-bounces at mailman.qth.net] On Behalf Of juergen
> Sent: Saturday, April 17, 2010 7:50 PM
> To: elecraft at mailman.qth.net
> Subject: Re: [Elecraft] KPA500 active devices!!
> 
> 
> 
> Hi Joe
> 
> Have you seen  any IMD data on these devices?
> 
> 
> John
> 
> 
> --- On Sat, 4/17/10, Joe Subich, W4TV <lists at subich.com> wrote:
> 
> > From: Joe Subich, W4TV <lists at subich.com>
> > Subject: Re: [Elecraft] KPA500 active devices!!
> > To: "'Doug Faunt N6TQS +1-510-655-8604'" <faunt at panix.com>,
> > elecraft at mailman.qth.net
> > Date: Saturday, April 17, 2010, 4:45 PM
> > 
> > The VRF2933 is rated for 300 Watts each according to the data
> > sheet on the manufacturer's web site (Microsemi) ... That
> > makes 
> > their use in a 500 W amplifier reasonable from an IMD
> > perspective. 
> > 
> > The VRF 2933 minimum gain is also 20dB (23 dB typical) so it
> > would appear that the KPA-500 should be capable of clean 
> > operation with 5 W of drive (e.g., K3 in low power mode). 
> >  
> > 73,
> > 
> >    ... Joe, W4TV
> >  
> >  
> > 
> > 
> > > -----Original Message-----
> > > From: elecraft-bounces at mailman.qth.net
> > 
> > > [mailto:elecraft-bounces at mailman.qth.net]
> > On Behalf Of Doug
> > > Faunt N6TQS +1-510-655-8604
> > > Sent: Saturday, April 17, 2010 6:45 PM
> > > To: elecraft at mailman.qth.net
> > > Subject: [Elecraft] KPA500 active devices!!
> > > 
> > > 
> > > 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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> 
>       
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