A term I had not even heard of until recently – primarily meant for contesting, but applicable for anybody who has 2 HF radios and wants to maximize usage of both at the same time. SO2R is a technique of managing two radios with a single computer and audio interface (1 set of headphones and 1 microphone or boom-mic). I got interested in the technique in order to monitor two BANDS simultaneously, or while calling CQ on one radio and listening for band openings on another band with the 2nd radio.

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My interest in SO2R stemmed from the fact that I have an Elecraft K2, along with a full-house Elecraft K3. Each now has an amplifier, so each can be a fully capable QRO station – yet, I only have 1 microphone and 1 set of ears. SO2R, using the appropriate hardware and software, will allow me to hear the K2 in my LEFT ear, whilst the K3 is in my RIGHT ear. The microphone or boom-mic will follow the radio which needs to transmit, based on computer software settings (I’m using WriteLog for contests). It’s all made seamless with the right equipment and software, but here’s an example of what can be done (my plan) :

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Let’s use the example of the K2 on the LEFT and the K3 on the RIGHT. The K2 has an Alpha-99 legal-limit amplifier connected to it, so we’ll use that radio as our RUN radio and try to “own” the frequency for some period of time due to high power and a good antenna. The K3 only has 650w (only.. ) or nearly QRO, so we’ll just use it for search-and-pounce.

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The SO2R controller has a built-in Sound-Card interface for each of LEFT and RIGHT radios. We pre-record  a set of contest exchanges in the left side for the K2 – such as : “CQ Contest, CQ Contest, CQ Contest – this is WB6RTH calling CQ and standing by”  - but we also have responses like “Roger, 59 Florida, 73′s” or whatever the contest exchange needs to be. We then have the SO2R controller “play” the recordings as necessary, such that human intervention is hardly ever required during the contest (except for unusual exchanges). This allows us to concentrate on logging the station (call-sign only, since the SO2R controller transmits all of the frequency, mode, power and other radio information to the logging software). Aside from logging, we would be listening for DX or band openings in the RIGHT ear, using the K3 – and if a multiplier was found, pounce on it with 650w of SSB or CW power.

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In normal situations, having both radios online and in different ears would maximize chances of running into DX, since we’d be listening to multiple bands at the same time. Oh – in case there’s any concern about transmitting and receiving on the same band (or harmonics), the SO2R controller automatically prevents that, since it always knows the frequencies of both radios – and will inhibit PTT if the adjacent radio is on the same band. Most of the better controllers can also control Bandpass Filters, as well as other peripheral controllers and equipment – at a cost, of course.

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I’ll be SO2R in the next few weeks, using the MicroHam MK2R+ controller and will write about my experiences during October. The MK2R+ is the BMW of SO2R controllers in that it has a SINGLE USB interface to the computer, but has 2 Sound cards, radio interfaces for two radios and can do CW, PSK, FSK, RTTY and Voice simultaneously – remarkable.

WOW….!!!  Another great product from Elecraft – this time, an HF amplifier rated at 500w CW but which actually goes to 650w easily without any significant IMD increase.

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This “kit” was received in a single box, with the typical Elecraft care in packaging. The largest component was the toroidal transformer which weighs-in at about 15 pounds and which contributes to the majority of the overall 26 pound completed unit. Everything went together without a hitch – there are no super-tight-clearances involved in this kit, so if you get one of these units, take your time, go slow and enjoy the build process.

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I completed the build in about 5 hours – at a casual pace. Started at about 4pm after my last conference call of the work-day and completed by 9:30pm with a quick dinner break in-between. The unit powered-on on the first try and passed all of the routine start-up checks. High Voltage reading was well within the normal parameters at 76v and all the band-switching worked flawlessly as expected.

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Unit can be operated on 95-245vac – switching from 120 to 240 is easy – simply change the position on the switch and you’re ready to go. If you have non-standard voltages (under or over-voltage), adjustments in the inside transformer taps will be required, but it’s both easy to accomplish, and simple to understand.

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Elecraft KPA500 front panel – clean and all automatic, currently on 60m

Entire unit is the size of the K3 and weighs 26 pounds

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Update – Day-2
Had the opportunity to get back to the KPA500 this afternoon and was able to test the new MAC software for the KPA500. Worked flawlessly, as in all of the software that I’ve used from David Fleming (he writes software for Elecraft). Was able to check the firmware versions, as well as download the most current version of the KPA500 firmware and change any of the parameters on the KPA500. Also did the full transmitter integration test with the K3 this afternoon – using a purchased KPAK3 cable (crazy to make one yourself, considering how inexpensive the cable is from Elecraft). Works like a champ. One thing unexpected – the ACC cable between the K3 and the KPA actually signals PTT, so there is no separate KEY line required (unless you’re NOT using the ACC line). Obviously, there are some cases where you might actually WANT to use the key-circuit – in that case, Elecraft provides a mod (an “interrupter”) which disconnects pin-10 of the ACC cable so that you can use the external KEY circuit. A curious tid-bit of information.