This is the exact combination I use. I also have the MFJ-998 High Power autotuner for a rather simple "push button" station, albeit with less "automatics" than with my Kenwood rigs. It works just as well as my friend's Icom 7800/PW1 station, which is where my inspiration came from :)
First, I agree with Jim concerning ALC. I have never used this connection with my ALS-600 (the version 2 kind) and any rig. I set the rear apron ALC pot to 50 % and with around 95 watts out from the K3 on 80m, with the front ALC pot set to 50%, I see the red ALC LED flicker every once in a while on peaks, especially during contest times when I run more dense modulation. DO NOT put more than 100w into the ALS600 input for any apreciable length of time unless you want to constantly replace the swamping resistor! You *will* fry it, even with the "fast" fan mod! Its a very simple hookup. Wire RCA cables thusly: K3 PTT out to, in my case, a Ameritron ARB704 key in (You dont *need* this box at all, but I owned it, and it has a nice big red light on it, and I have two rigs on my bench with two of these boxes in line, it they are to the left and right of my wattmeter and tell me which rig is keyed at a glance, so I use it!) then from the ARB key out to the 998's "tuner enable" then from the tuner key out to the ALS600 key in. Press on the footswitch, the red light goes on the K3 panel, the ARB704 and the ALS600. My Kenwoods have an interface to the Autotuner that forced a low power tune cycle from the front panel of the rig. The K3 doesnt have this feature, but I can get close to this with the K3/MFJ998/ALS600 combination. The ALS600 hates SWR above 2.0. I set the SWR bypass limiter on the MFJ998 to 1.9. If the SWR is above 1.9, the amp automatically bypasses driven by the tuner circuitry. If the tuner doesn not notice (sometimes it forgets), the amp will auto bypass on its own at 2.0. But, if I attempt to tune my antennas with the ALS600 being driven at full power, the tuner gives up and sends "QRP"! I dont want to bypass the amp all the time to tune, so to get around this, I use this proceedure: Bypass the K3 Internal tuner Set Tune Power out to exactly 10 watts globally on the K3 Set the MFJ998 to "Sticky Tune" Set the MFJ998 to autotune when SWR exceeds 1.5 Then, to emulate my Kenwood radio's tune cycle I do this: Memorize your antenna system into the tuner by starting a manual tune cycle every 10kHz across all the bands you operate by pressing and holding the Transmit button on the K3 then hitting the Tune button on the MFJ998. This sets the tuner's memories up for all the bands you plan on using with all the antennas you use for those particular bands. Dont worry, there is LOTS of memory space in the 998! In normal QRO operation, I do this: Go to a band, switching the K3 bandswitch then switching the ALS600 bandswitch (soon to be replaced by auto band switching from the K3 BCD outputs), then press and hold the Transmit (tune) button on the K3. This outputs a 10w carrier from the radio to the amp, which then outputs aproximately 40-50 watts to the tuner, which then looks up the frequency you are transmitting on in its memory and snaps the L/C combinations in line with your feedline in less than a second. Release tune by pressing and holding the Transmit button again. Youre all set to go! I have found that, with my "Version 2" ALS600, I can get full 500w cw - 600w PEP output with no more than 75-80w from the K3 (95w on 80m, where the ALS600 is traditionally soft). On RTTY, keeping the K3 around 70w and switching the ALS600 into RTTY mode gives me a cool 300w out and the amp never trips off for overtemp. I may develop a more elegant "autotuner interface" to the ALS600 using ideas and a couple of resistors plus a small reed relay from information gathered in the Kenwood AT300 manual... But I bet Phil AD5X beats me to this (I have his ALS600 QSK relay mod installed and it is WONDERFUL!) Regards Lu - W4LT Message: 6 Date: Mon, 21 Dec 2009 10:02:31 -0800 From: "Jim Brown" <j...@audiosystemsgroup.com> Subject: Re: [Elecraft] K3 to ALS600 Amplifier To: "Elecraft List" <elecraft@mailman.qth.net> Message-ID: <20091221180232.15b6658...@gw1.nlenet.net> Content-Type: text/plain; charset="us-ascii" On Mon, 21 Dec 2009 08:20:32 -0800 (PST), w4grj wrote: >I am hooking up my new K3 to a ALS600 and would appreciate comments from >anyone with this combo concerning connecting without ALC control and any >relay delay settings in the K3 In general, ALC should NEVER be used to set drive level -- doing so will generally cause MASSIVE splatter and clicks. I have no experience with the ALS600, but I've used my K2/100, K3/100, TS850, and Omni V to drive Ten Tec Titans (tubes), Herc I (solid state), and Herc II (solid state) power amps. 1) There IS a delay built into the K3's circuitry that keys the power amp. The delay is adjustable, and the defalut settings work very well with most amps. You can easily change the delay with a menu setting. 2) To set the power level, simply start with low output from the K3 (I'd start with 10-20 watts) and bring up the output power of the K3 (using the Power knob) until you hit the recommended power output of the amp. My Ten Tec amps all produce full power with less than 50 watts drive. 73, Jim K9YC ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
