Saturday, April 16, 2016

From the K3 to the Flex 6300 - Part 1

To many people, Elecraft and Flex represent the best of the two disciplines of radio architecture available to hams: knobbed-partial-“depends on your definition of SDR”-SDR and full-fledged, unapologetic, “we digitize just in from the antenna” SDR. These two disciplines generate arguments aplenty over which is “best” with most people belonging to one camp or the other. As a new apostate, I thought I’d share my rationale.

It started out mostly about money.

About a year ago I started seriously looking into adding the 2nd receiver to my K3. I thought (correctly, as it turns out) that being able to listen to the DX on one receiver (left headphone) and the pile-up on the other (right headphone) would offer a significant advantage when working the big DXpeditions. But I also knew that seeing the entire pile-up at once on a pan display would make it easier to find the last station worked and therefore the DX’s listening freq. The cost to add both the sub-receiver, 400  Hz CW filter and panadapter to my K3 would be close to $1600. This is on top of what the K3 already cost.

It was at this point that I started looking at a state of the art manufacturer just down the road from me – Flex Radio.

I subscribed to the Flex user’s forum and read it and the Elecraft reflector daily. User’s opinions, problems, solutions and complaints gave me a good idea of whether I could justify the money for an entirely new rig rather than upgrading what I was already familiar with. A QRP Apache Labs Anan-10E had given me an introduction into the world of SDR operating and I liked it. A lot.

After informing myself as best I could about the Flex’s capabilities, and reading all the opinions on Sherwood Engineering’s rankings, it was time to look at the other numbers – the ones preceded by a dollar sign. When I did, the Flex made more financial sense than pimping my K3. I bought the “entry model” Flex – the 6300 and, after 8 months, I have zero regrets.

For $2500, here’s what it offers along with the price to outfit a K3 in a similar way:

Granted, the F6300 is not the Flex rig that gets top billing in the numbers department. That would be the 6500/6700, one of the main advantages of them over the 6300 being ham band preselectors (the other advantage being 4 receivers - a feature unavailable in the K3 or any non-SDR rig regardless of price). I obsessed over this difference and about the $4300 Flex 6500 but I needn't have worried. Last November's CQWW (CW) contest dispelled any misplaced notions that lacking those preselectors would lead to an inability to copy weak signals next to strong ones - a scenario common in CQWW. The lower-priced '6300 had zero problems in that or any other department.

Many pile-ups for very rare DX have taken place since I bought my Flex - Juan de Nova, Heard, South Sandwich - and the '6300 is doing what I bought it to do. I'm in and done with the pile-ups more quickly that I would have been with my almost-stock K3 - at a much more reasonable price than a "Flex-equivalent" K3.


  1. John,

    This is where I was until mid-Summer 2015. I had been telling everyone at my local club that my retirement radio was going to be a K3 with a 2nd receiver. I was dutifully putting away 100-200 dollars every month for the past 3 years in preparation for "purchase day" just before retirement. Then "one Saturday" happened.

    One of our members was donating a bunch of gear to the Club as he down-sized to move to a smaller home. On the second trip to get "another pickup load", he had bought a shiny new 6500. I spent all of 5 minutes with it and was completely hooked, since I was going to run the K3 via Computer anyway for Digital modes and remote operation. At the end of the day, I bought accessories I would have never been able to have in my budget, upgraded to a bigger/better tuner, Heil headphones, and save about a grand.

    I am utterly at peace with the choice I made (a 6300) and wouldn't go back at all.

    73 de Gary, WB5ULK

    1. Hi Gary,

      I'm trying to decide what to do with my K3 now. If a year goes by without it being used, I'll probably sell it. I know I could never go back to DXing the old-fashioned way, spinning a dial and tuning blindly. As of now, it's packed away in the closet with a bunch of other radio stuff that needs to be put on eBay...

  2. Quite an eye opening comparison! I love my K2 and cannot afford a K3, but have a soft spot for Elecraft and their awesome reflector. Also love my Valiant, Ranger & Hammarlund 100-A, so I lean toward the old-fashioned. Technology marches on, giving me a touch of sadness.

    1. I agree and it was with a degree of sadness that I sold my K3. I felt the same way about a few previous rigs I've owned over the years from other manufacturers. My KX2 eased that feeling and I believe it is one rig I'll never sell.

  3. Great points to consider. I am leaning toward the 6300 as well. Thanks!

  4. Hello John,

    I operate about 90% CW, and have the both the 6300 and the K3 line, but in my case, I find the K3 much more versatile with its true independent 2nd Rx that can use a completely independent antenna for true diversity reception (you'd need the much more expensive Flex 6700 to do that), which I find extremely helpful from 30m down to 160m. I have the original SDR-1000, HPSDR Atlas based system, Flex5000A, and Flex 6300, and have spent considerable time with them all. But for me personally, I can navigate around much faster with knobs, buttons and switches since these can be operated pretty much in parallel, than I can with a mouse where everything needs to be done serially. All are fine products but my preference is for the low-latency very fast t/r turnaround times of the K3.

    Without doubt though, the 6300 is much easier for digital modes since the only connection required is the network cable.


    Dale - WA8SRA

    1. Thanks for your comments, Dale. I guess it depends a lot on how you operate. I've never had diversity reception and ignorance is bliss - if I knew what I was missing, I might sing a different tune. Regarding knobs, buttons & switches I did consider for a while buying the Flex add-on that is a VFO dial and 3 programmable switches but, after looking more closely to how I might use them, decided I didn't need them.

      Most of my operating these days consists largely of waiting for a DXpedition to a Needed One. I then set the rx controls to optimize the signal - after that, the only control I operate is the tx VFO until I work the station. I am getting more and more into digital modes thanks to FT8 and love the clutter-free connectivity of the Flex. It gets along quite well with my Elecraft amp.

  5. I have (had) an Elad Duo SDR
    very nice rig but only 5 watts
    However, a great intro in SDR radios

    I have semi retired but moved to a larger place - with great potential for radio's, aerials and electrically quiet

    I am going for the Flex 6400 and will run it over the home network and will add in a Maestro later when funds/bnds/conditions permit