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Re: KPA500 active devices!!

Posted by Joe Subich, W4TV-4 on Apr 18, 2010; 1:09am
URL: http://elecraft.85.s1.nabble.com/News-from-Visalia-tp4914396p4919366.html


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: [hidden email]
> [mailto:[hidden email]] On Behalf Of juergen
> Sent: Saturday, April 17, 2010 7:50 PM
> To: [hidden email]
> 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 <[hidden email]> wrote:
>
> > From: Joe Subich, W4TV <[hidden email]>
> > Subject: Re: [Elecraft] KPA500 active devices!!
> > To: "'Doug Faunt N6TQS +1-510-655-8604'" <[hidden email]>,
> > [hidden email]
> > 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: [hidden email]
> >
> > > [mailto:[hidden email]]
> > On Behalf Of Doug
> > > Faunt N6TQS +1-510-655-8604
> > > Sent: Saturday, April 17, 2010 6:45 PM
> > > To: [hidden email]
> > > 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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