> But I would buy a second KPA500 in a heartbeat if I knew I could
> modify it for 10 watts drive for full output!
I think you're being optimistic about full output with 10W drive.
The VRF-2933 is rated for 23 dB gain (typical). With perhaps 1 dB loss
in the low pass filter, a dB or so in the output transformer, roughly 3
dB in feedback to improve linearity one dB in the input transformer,
bias decoupling, gate balancing, and two dB in the input matching comes
very close to the roughly 15 dB gain limit in the US regulations.
Some of those values are based on application notes from Motorola,
MicroSemi and APT for similar MOSFET designs while some values are
from Elecraft designers. In any case, the inescapable conclusion is
that there is no "magic modification" to get the additional 2 - 3 dB
of gain necessary to get 600W with 10W of driver from the KPA-500.
73,
... Joe, W4TV
On 3/15/2012 6:32 PM, Oliver Dröse wrote:
> Great Alan, nice idea with the manual! ;-))
>
> Anyway, a very big part of this world's ham population is not bound to FCC
> rules. So no need to make it public how to modify, just publish the
> schematics or send them out on request without pointing out something and
> Elecraft should be safe?
>
> My KPA500 is serving me very well on my remote station so also no chance to
> take the PA apart again and have a look myself and just buying a second one
> without knowing it is possible might be a bit too expensive to find out.
> ;-)) But I would buy a second KPA500 in a heartbeat if I knew I could modify
> it for 10 watts drive for full output!
>
> 73, Olli
>
>
>
> ----- Original Message -----
> From: "Alan Bloom"<n...@sonic.net>
> To: "Oliver Dröse"<dro...@necg.de>
> Cc:<elecraft@mailman.qth.net>
> Sent: Thursday, March 15, 2012 10:58 PM
> Subject: Re: [Elecraft] KPA-500 high gain modification?
>
>
>> On Thu, 2012-03-15 at 21:54 +0100, Oliver Dröse wrote:
>> ...
>>> Three big reasons I can think of that Elecraft does not want to release
>>> the
>>> schematics:
>>> a.) To keep them hidden for the competition (quite understandable).
>>> b.) It would probably put down sales of the KPA3 a bit (hmmm).
>>> c.) If somebody modifies it themselves it will be almost impossible to
>>> support it in case of problems (quite understandable, too).
>>
>> The other reason is they might get in trouble with the FCC if they make
>> it too easy to modify.
>>
>> Many years ago when the CB craze was at its height, a manufacturer who
>> shall remain nameless came out with a new transceiver. On page 1 of the
>> manual was an illustration of the underside of the chassis with a big
>> arrow pointing to a certain wire. "Do not cut this wire or the
>> transceiver will transmit on 11 meters."
>>
>> They didn't get away with it. :=)
>>
>> Alan N1AL
>>
>>
>>
>>
>> -----
>> eMail ist virenfrei.
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>> Version: 2012.0.1913 / Virendatenbank: 2114/4872 - Ausgabedatum:
>> 15.03.2012
>>
>
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