[Elecraft] External RF Amp T-R relay driver for the BASIC K2...

[Tom Hammond]

Hi Fellas:

At 07:51 AM 6/19/2005, walter renner wrote:
>I have used my K2 with and SB1000 Heathkit amp (3-500 single) with good 
>results, about 120 watts out on SSB and have had good reports.  I have 
>also used it with an Ameritron AL811 (3 811As) and this gives  about 135 
>watts out with 15 watts drive, again with good reports. This has been on 
>75 meters where I check in to local nests.
>K0ARO
>Kurt

For what it may be worth...

Several YEARS ago, Elecraft posted to their web site that I was working on 
a PC board adapter for the BASIC K2 (e.g. 15W, no K60XV installed) to add 
the ability for it to key an external T-R relay such as those in QRP RF 
Amplifiers.

Well, I think a PC board design was posted somewhere, but it never breathed 
the light of day as far as ever going into production. Additionally, 
another reflector member had a small run of T-R PC boards run off and they 
found their way to Elecraft for sale. Once those boards (and associated 
parts) went out the Elecraft door, they (Elecraft) continued selling 'kits' 
of parts only (no PC board) with which you could wire your own external T-R 
relay driver, but no PC board was available as far as I know.

Recently, I have redesigned the PC board for my external T-R relay driver. 
I've sent out three Field Test (prototype) boards three builders. Tow of 
the boards are still awaiting the builders to complete their RF amplifiers, 
BUT the third board HAS been installed and is merrily keying an Alpha 
amplifier... I don't recall the specific Alpha model however.

The PC board design uses two resistors, one 2N7000 MOSFET in the 
pre-driver, and either one 2N7000 MOSFET (60VDC and 150mA keying current) 
or a heavier-duty
HexFET (200VDC and 5A keying current) at the output. You can choose which 
output device to use.

I will place the documentation for this PC board design on my web site at:

    www.n0ss.net

The file will be in (1.4MB) PDF format and will be located in the section 
entitled "K2 RELATED FILES", but you can use the QuikLinks at (almost) the 
top of the page go directly to that section by clicking on the "K2-SPECIFIC 
FILES" link. By the way, the pix on the docs show the heavy-duty HexFET 
model of the adapter.

Parts for this project ARE already available (I think) available at 
Elecraft, and they can also be ordered from Mouser (both Elecraft and 
Mouser part #'s are included in my docs). And I'm hoping that Elecraft will 
decide to have some of these boards made and include them as part of the 
'kit' of parts they currently offer. I sent a design to Eric at Elecraft on 
Friday, but I used a drafting program I'm not familiar with (ExpressPCB), 
so I may have botched the design enough that I'll have to re-do it before 
they can use it (IF they decide to use it). In the meantime, if there's 
enough interest, I'll consider making some PC boards up (it's a 'kitchen 
sink operation' here, so they're not quite as 'pretty' as those 
commercially made, but they do look quite nice and work just as well). 
Price of the PC boards will probably by $6 ppd to your (US) doorstep with 
another $1 for DX orders. Please contact me directly if you are the least 
bit interested... I do NOT have any boards made at present, and am hoping 
that Elecraft will pick them up BEFORE I have to drag out the light box, 
developer and etchant... <G>

Just thought someone might be interested.

   ONE MORE ITEM... If you use this device you WILL have to have
   one of the more current PIC firmware versions.. once which
   allows you to set the MENU item "T-R" to "8r hold" using the
   [DISPLAY] button once you are in the T-R edit mode. I don't
   recall what firmware revision first offered this feature, but
   it is a requirement if you wish to use the K2's 8R line to key
   an external T-R device.

73,

Tom Hammond    N0SS