Welcome to the new FlexRadio Community! Please review the new Community Rules and other important new Community information on the Message Board.
If you are having a problem, please refer to the product documentation or check the Help Center for known solutions.
Need technical support from FlexRadio? It's as simple as Creating a HelpDesk ticket.

Receiver Shootout at NX6T Corral - Contest Station

KY6LA_Howard Member ✭✭✭
edited June 2020 in SmartSDR for Windows
John W6JBR reported on 10/30/2014



On Friday, before the CQ WW SSB Contest, I had the great pleasure of assisting Dennis N6KI, **** K6NAL, and Howard KY6LA, in setting up a receiver shootout at the NX6T Contest Club Superstation between 4 current state of the art transceivers:

ICOM 7800
Elecraft KX3
Elecraft K3
FLEX 6700

All rigs were fed by switch from the same antenna, and all rigs had their audio fed to a line level mixer, which fed a headphone amplifier system.

Howard was extremely gracious to supply his very latest developer version SOTA Flex 6700 with overkill power supply, and a pair of large display monitors. Dennis most graciously supplied the Elecraft K3, KX3, ICOM 7800, and audio mixer/headphone amplifier.

All 4 rigs are highly regarded, and have a variety of approaches, 

a) electronically, for the task of receiving HF signals, 

as well as 

b) ergonomically, for accessing their deep feature sets.

While we were setting up, a major solar flare wiped out the HF bands, but they seemed to come back fairly quickly.

The contest had begun, giving us lots of signals and QRM, so we began listening tests on 20 & 40 meters.
Very weak stations were located in the vicinity of very strong adjacent signals.

First test:
Dennis adjusted the K3 for optimum reception of the target signal, then Howard adjusted the 6700 to receive the same signal. These adjustments consisted of RF and audio levels, AGC settings, passband filters (crystal and DSP/bandwidth), notch filtering, etc. DSP Noise Reduction was not used or evaluated at this time.

At this time, I felt that I heard the signal on the K3 very slightly clearer than on the 6700 during maximum QSB and QRM. If I was adjusting the radios myself to my hearing/preferences, such difference may have been minimized, as I think it would be if Dennis himself was adjusting both receivers at once.

Further listening was done with the KX3, and 7800.

All these fine radios seem to be doing an excellent job, with no one clearly beating out the others for pulling the weak ones out of the QRM, although we are not specifically testing NR or DSP yet.

Howard mentioned hearing 'phase noise' in the K3 audio. The K3 did sound a little 'brighter' in terms of audio frequency, but I attribute this to filter settings/characteristics, which are excited by the band noise impinging upon it.

My understanding of phase noise as pertaining to local oscillators in HF receiver circuitry, would lead me to believe that one would not directly 'hear' phase noise, but would hear the result of such phase noise as an ambiguity in signals perceived near the noise floor of the receiver. Since the signals we were receiving, and the band noise itself, were well above the system noise floor of the receiver, I do not believe that the intrinsic phase noise specifications of these radios would have created a perceptual difference in the target signal intelligibility. I would appreciate further discourse with Howard in this regard, to better learn from his obvious expertise in this area.

The biggest relevant factor to these tests, IMHO, would be the dynamic IMD caused by intermixing of strong near-in signals to the target signal. IMD manifests as a complex non-harmonic distortion of signals, which creates difficulty in psychoacoustic perception of the desired audio information.

The Sherwood receiver tests indicate that the 3rd order dynamic range, narrow spaced, is led by the 6700, with the KX3, and K3 quickly following, so I would think that there should be little perceptual difference between them. The 7800 is substantially down the list here, so might be more susceptible than the others to this issue.


I was not able to participate in Saturday's test, and do hope to hear more about that.


Now, regarding "contestability" of the K3 vs the 6700: this is, of course, Dennis' area of expertise. Even if the radios perform equally, he appears to feel that the ergonomics of a full 'black box' SDR transceiver are not yet workable for serious contesting, and that may be true.

The K3 seems to be the most popular radio for contesting, for many good reasons.

Is it perfect? Is anything?! 


All radios, no matter how good they are, need to have an operator develop a serious rapport with the system controls for effective utilization.


I do believe that the 6700 has superlative specs, and amazing possibilities for feature access and control. I see that SDRs are the future, and the future is almost here. An ergonomic setup with appropriate physical controls, use of macros, and proper operator training, should allow the flexibility of an advanced SDR to enhance a fixed contest situation. The need for a large amount of display real estate may hamper it's feasibility for portable and DXPedition use.

With all the features and computational horsepower in these modern transceivers, comes more responsibility, as one can easily shoot oneself in the foot with so much complexity. I have seen it happen with large scale digital film dubbing consoles of 128 to 256 channels, where huge feature complexity vs communication of parameter status (or lack thereof) contributed to major operator meltdown! And let's not even factor in the inevitable software glitches.


So, there may not be one ultimate radio to please every operator's needs and desires, but there are certainly a variety of excellent products available, so that an operator should be able to find something very close to his 'dream' radio. Also, 3 of the 4 radios we heard are all-American designed and manufactured! Go USA!


I hope this information is helpful. If not, at least enjoy the pictures!

FLEX 6700 System (the little black box between monitors!) courtesy of Howard KY6LA:


Diminutive but full featured Elecraft KX3 QRP XCVR on top of the titanic ICOM 7800


N6KI doing final system tests with K3:


Howard, Dennis and **** evaluating the signals.


70' tower SteppIR and shorty 40m

40' tower C31XR


Hope you did well in the contest! 

See you in the Sweepstakes!



de W6JBR's Amazing iPad Air!

--...  ...--

-.. .  .--  -....  .---  -...  .-.


  • Ken - NM9P
    Ken - NM9P Member ✭✭✭
    edited June 2020
    Howard, I just checked my LOTW Confirmations, and I have worked NX6T on 4 occasions...

    August 16, 2015 - 40 SSB - NAQP SSB
    Feb 28, 2015 - 160 SSB - CQ 160 SSB test
    Dec 15, 2013 - 10 CW - ARRL 10 M Contest
    March 31, 2013 - 15 SSB - CQ WW WPX

    The ones in 2013 may have been with my 1500
    The ones in 2015 are certainly on my 6500.

    Just thought it interesting.  I had been wondering if I had worked you before.

    Ken - NM9P
  • Ernest - W4EG
    Ernest - W4EG Member ✭✭
    edited October 2019
    Several years ago the members of the San Diego DX Club conducted a similar test during the SSB Sweepstake weekend.

    We compared and evaluated the following radios: K3, Yaesu, Icoms etc... See "Flex-6x00 side by side comparison to K3, Icom, Yaesu Kenwood..." on this forum.

     Howard was not able to provide the radio and I volunteered my Flex-6700 which I had received 2 weeks earlier. I barely knew how to turn it on, using SmartSDR v.1.0 the original release for these radios.

    The results are much better than the one I had previously, but I see the skeptical; or the "doubting Thomas" are still around and not willing to accept reality. "Even if the radios perform equally, (t)he(y) appears to feel that the ergonomics of a full 'black box' SDR transceiver are not yet workable for serious contesting."

    I assume that this will be an ongoing annual side by side test, until some big DX group steps up and start using the Flex radios.

    Maybe then the SDDXC and many of the member's will eventually see the light at the end of the tunnel.

    W4EG - SDDXC Member - Amelia Island, FL

  • KY6LA_Howard
    KY6LA_Howard Member ✭✭✭
    edited September 2015
    Likely all the SSB contests except for WPX, All Asia and JIDX which we run from my QTH. Never the CW contests where Dennis N6KI would never even let me into the station.
  • Ken - NM9P
    Ken - NM9P Member ✭✭✭
    edited December 2016
    I guess you can serve chips & dips to the CW team!
  • KY6LA_Howard
    KY6LA_Howard Member ✭✭✭
    edited September 2015
    Not even that. Dennis considers me too distracting during a C W contest so I am officially banned. But I am required to sit in First Chair for SSB and various digital contests.
  • Ken - NM9P
    Ken - NM9P Member ✭✭✭
    edited December 2016
    I would be interested in hearing their comparison of major rigs specifically for CW competition.  Have them comment upon QSK smoothness, filtering.  Using the RX EQ to enhance receive audio, etc.  I have a theory that most of the folks who have difficulty with CW modes haven't learned to effectively adjust AGC-T, RX EQ, and the other DSP features to maximum effect and are missing the major power of the 6000 series.  

Leave a Comment

Rich Text Editor. To edit a paragraph's style, hit tab to get to the paragraph menu. From there you will be able to pick one style. Nothing defaults to paragraph. An inline formatting menu will show up when you select text. Hit tab to get into that menu. Some elements, such as rich link embeds, images, loading indicators, and error messages may get inserted into the editor. You may navigate to these using the arrow keys inside of the editor and delete them with the delete or backspace key.