[Elecraft] K3 with linear amp?

Don Wilhelm w3fpr at embarqmail.com
Mon Dec 24 19:08:50 EST 2012


Gerry,

As with any amplifier ---

Connect the K3 output coax to the AL82 input coax, and connect the K3 
KEYOUT to the AL82 PTT IN (or whatever they call it).
Forget the ALC cable - instead, adjust the K3 power output to drive the 
AL82 to its full output (or whatever you want below that level), and use 
that as the maximum when driving the amplifier.  The amplifier 
instructions may tell you to connect an ALC line too.  Be aware that 
using the amp's ALC to control the drive power is a recipe for 
distortion no matter what the amplifier may be.  If you do choose to 
connect the ALC line, use it only as an amplifier fault control - adjust 
the drive power as I stated, and all will work fine.

A word on keying the amplifier (yes, even in semi QSK).  Ameritron 
amplifiers are famous for their slow open frame relays (there are QSK 
mods to change those relays and eliminate the problem), but the K3 semi 
QSK mode does not increase the time between KEYOUT and the onset of RF.  
(There is a K3 menu parameter to increase that timing).  Semi QSK does 
extend the cessation of RF keying to the time the K3 goes back to 
receive mode, and can eliminate relay chatter in the amplifier.

If you can extend the K3 TX DLY parameter sufficiently to assure that 
you will not hot switch the amplifier, then all will be fine, but if the 
delay time provided is not sufficient, you will be forced to use a 
footswitch (or other means) to activate keying of the amplifier before 
you start CW keying or SSB audio.

Note that I have not looked up the time from keying the amp to the relay 
settling, but that time is typically greater than the K3 8 ms. default 
KEYOUT to onset of RF timing.

In other words, semi QSK controls the training edge of the KEYOUT 
signal, but does not change the leading edge.  TX DLY will control the 
leading edge up to the limit of its range.

If you increase TX DLY significantly, listen to your signal to be 
certain that leading CW elements (or SSB syllables) are not truncated by 
the delay parameter.

73,
Don W3FPR
On 12/24/2012 6:21 PM, Scott James wrote:
> I do not have my K3 yet. I have been reading about it.
> I would like to use it with an Ameritron AL82 in semi QSK  (vox on).
> I do not see an amp connection mentioned in  the manual
>
> What is the hook up for a non QSK amp to the K3?
>
> Tks very much
>
> Gerry
>



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