driving external PA with K2

[Mike W-12]

Hi Folks,
Using a basic K2 with no options other than SSB. How can I drive
an external PA and have PTT and ALC controlled by the K2 ?.
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[johnny-52]

Hi Mike,

There is a amp-key kit provided by elecraft at a cost of USD5.

There is no ALC communication between the external PA and K2.  I use my K2
with my ICOM ICPW-1.  With an input of 15 watts, I shall get an output of
about 300 watts.

The output of the PA is controlled by the input power from K2.

73

Johnny Siu VR2XMC
----- Original Message -----
From: "Mike W" <[hidden email]>
To: <[hidden email]>
Sent: Thursday, July 08, 2004 7:19 PM
Subject: [Elecraft] driving external PA with K2


> Hi Folks,
> Using a basic K2 with no options other than SSB. How can I drive
> an external PA and have PTT and ALC controlled by the K2 ?.
> _______________________________________________

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[Gernot Trautmann]

Hi Mike,
I've formerley using a PA with PTT connection only, no ALC.
For the connection see:
http://www.qsl.net/df5rf/k2_2nd.html

Hope that helps,
Gernot
DF5RF

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[G3VVT]

 
Within the Elecraft application notes there are details of a  partial mod kit
available for an external PTT feed:  http://www.elecraf
t.com/Apps/Amp_keying_ckt.htm
 
This uses a 2N70000 and a 2N2222 transistor plus two resistors, and two  
connectors mounted on a perf board pcb. The transistors are  available in the UK
though having problems finding the correct mating 8 pin  and 2 pin connectors
here. Elecraft can supply a partial kit listed  at US$5 on the Elecraft
website. This includes the transistors,  resistors and the 8 pin connectors. You have
to provide the perf board, 2 pin  connectors and an external phono or
whatever connector you decide to  use. I intend using this mod to hard key my
Spectrum TRC4-10iL 4m transverter  which at present is working on RF keying. The PTT
mod plugs in at the rear of  the K2 RF board at J13 location (if available)
 
Regards,
Bob, G3VVT
K2 #4168

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Mike,
 
You already have all the info you need, but I would like to say you will need no ALC at all.  If you keep the rig linear and not over drive the amp...there is no need for ALC.  This feature is kind of a left over from when tubes were tubes and men were men (sorry Ladies, trying to make a bad pun)  Of course, you will not over drive a typical amp with 15 watt of mighty mojo.  Now, if you have a KPA100, that is a different story altogther, but I do not want to digress.  The main point here is keep the rig linear and do not over drive the amp.
 
Have fun building the keying interface.  Works like a champ.
 
Lee - K0WA
 
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[johnny-52]

To supplement Lee's email, I would say that ALC is a way to protect the PA
from overdrive.

For example, if I set proper ALC level at my ICPW-1 to get only 500 watts
(the full output of PW-1 is 1 kw), even when I turn the RF power control on
my IC756pro2 to full scale, the ALC feedback voltage from PW-1 will
automatically limit my pro2 to an output power of less than 30 watts.

In the case of K2, the output power is less than 15 watts.  I do not see any
danger to overdrive a PA.  Clearly, K2/100 is a different story.

73

Johnny Siu VR2XMC
----- Original Message -----
From: "Lee Buller" <[hidden email]>
To: "Mike W" <[hidden email]>
Cc: "Elecraft Reflector" <[hidden email]>
Sent: Friday, July 09, 2004 6:46 PM
Subject: Re: [Elecraft] driving external PA with K2


> Mike,
>
> You already have all the info you need, but I would like to say you will
need no ALC at all.  If you keep the rig linear and not over drive the
amp...there is no need for ALC.  This feature is kind of a left over from
when tubes were tubes and men were men (sorry Ladies, trying to make a bad
pun)  Of course, you will not over drive a typical amp with 15 watt of
mighty mojo.  Now, if you have a KPA100, that is a different story
altogther, but I do not want to digress.  The main point here is keep the
rig linear and do not over drive the amp.
>
> Have fun building the keying interface.  Works like a champ.
>
> Lee - K0WA

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