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KPA-500 high gain modification?

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LY2IJ

KPA-500 high gain modification?

Hi,

Is it any simple way to modify KPA to drive full power
with KX3? I see VRF2933 have minimum 20 dB gain.
Looks like killer combination.

I know there is some PA gain rectrictions in US, but
many of us are not covered by it ;)

73
Arunas LY2IJ
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Oliver Dröse

Re: KPA-500 high gain modification?

I second that request! Would be really handy ...

Sorrily still no schematics available on the Elecraft website, otherwise I
would already have looked for myself.

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).

Maybe we need to sign a special document freeing Elecraft of all
responsibilities and tighting ourselves to non-disclosure to get the
schematics. ;-))

Vy 73, Olli - DH8BQA
http://www.dh8bqa.de/

----- Original Message -----
From: "Arunas LY2IJ" <[hidden email]>
To: <[hidden email]>
Sent: Thursday, March 15, 2012 7:42 PM
Subject: [Elecraft] KPA-500 high gain modification?

> Hi,
>
> Is it any simple way to modify KPA to drive full power
> with KX3? I see VRF2933 have minimum 20 dB gain.
> Looks like killer combination.
>
> I know there is some PA gain rectrictions in US, but
> many of us are not covered by it ;)
>
> 73
> Arunas LY2IJ
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
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> Post: mailto:[hidden email]
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
>
>
> -----
> eMail ist virenfrei.
> Von AVG uberpruft - www.avg.de
> Version: 2012.0.1913 / Virendatenbank: 2114/4870 - Ausgabedatum:
> 14.03.2012
>

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Alan Bloom

Re: 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

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Oliver Dröse

Re: KPA-500 high gain modification?

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" <[hidden email]>
To: "Oliver Dröse" <[hidden email]>
Cc: <[hidden email]>
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.
> Von AVG überprüft - www.avg.de
> Version: 2012.0.1913 / Virendatenbank: 2114/4872 - Ausgabedatum:
> 15.03.2012
>

W4GRJ

Re: KPA-500 high gain modification?

Another example, MARS operators are not governed by the FCC.

Jack
W4GRJ / AFA4DG

On Mar 15, 2012, at 18:32, Oliver Dröse <[hidden email]> 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" <[hidden email]>
> To: "Oliver Dröse" <[hidden email]>
> Cc: <[hidden email]>
> 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.
>> Von AVG überprüft - www.avg.de
>> Version: 2012.0.1913 / Virendatenbank: 2114/4872 - Ausgabedatum:
>> 15.03.2012
>>
>
> ______________________________________________________________
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Joe Subich, W4TV-4

Re: KPA-500 high gain modification?

In reply to this post by Oliver Dröse

> 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"<[hidden email]>
> To: "Oliver Dröse"<[hidden email]>
> Cc:<[hidden email]>
> 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.
>> Von AVG überprüft - www.avg.de
>> Version: 2012.0.1913 / Virendatenbank: 2114/4872 - Ausgabedatum:
>> 15.03.2012
>>
>
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
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> Please help support this email list: http://www.qsl.net/donate.html

Geoffrey Mackenzie-Kennedy-3

Re: KPA-500 high gain modification?

In reply to this post by Oliver Dröse

Olli,

Would adding a low gain broadband linear amplifier between the KPA500's
input and the "10 watt driver" be a useful alternative to modifying the
KPA500?

I assume that during receive this amplifier would have to be bypassed.

73,

Geoff
LX2AO

On March 15, 2012 at 23:32 +0100, Oliver Dröse wrote:

> But I would buy a second KPA500 in a heartbeat if I knew I could modify
> it for 10 watts drive for full output!

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Oliver Dröse

Re: KPA-500 high gain modification?

Hi Geoff,

sure, could be an alternative. The appeal of NOT needing it would be less
clutter, i.e. not an additional box that needs to be transported, wired,
subject to failure, etc. Just imagine going to an expedition with just a KX3
and KPA500 for a very small but effective powerful station ... couldn't be
easier than that. ;-)) That was what I was thinking about ...

For the K3 there probably is the "money factor" for quite some people, too,
as it would save the cost for the internal 100 W PA (no problem here, needed
it for my tube amp anyway as it requires 50-60 W drive). Needing a "driver
amp" (i.e. from 5/10 to 35/40 W) will add significant cost again for those
not into homebrewing (and to a lesser extend to those homebrewing, too).
Just taking the KPA3 is then probably the better solution again as it also
adds better system integration compared to an additional "driver amp"
between a K3/10 and the KPA500. But I can well understand the K3/10 users'
desires, too. ;-))

73, Olli - DH8BQA

----- Original Message -----
From: "Geoffrey Mackenzie-Kennedy" <[hidden email]>
To: "Oliver Dröse" <[hidden email]>
Cc: "Elecraft Discussion List" <[hidden email]>
Sent: Friday, March 16, 2012 5:09 PM
Subject: Re: [Elecraft] KPA-500 high gain modification?

> Olli,
>
> Would adding a low gain broadband linear amplifier between the KPA500's
> input and the "10 watt driver" be a useful alternative to modifying the
> KPA500?
>
> I assume that during receive this amplifier would have to be bypassed.
>
> 73,
>
> Geoff
> LX2AO
>
>
> On March 15, 2012 at 23:32 +0100, Oliver Dröse wrote:
>
>> But I would buy a second KPA500 in a heartbeat if I knew I could modify
>> it for 10 watts drive for full output!
>
>
>
> -----
> eMail ist virenfrei.
> Von AVG überprüft - www.avg.de
> Version: 2012.0.1913 / Virendatenbank: 2114/4873 - Ausgabedatum:
> 15.03.2012