China, the long way ’round…and the K3’s APF

de BA7IO

For the second time in a week BA7IO has been putting a potent signal into the US on 10 meters. In the mornings. That means long path – 16,400 miles rather than the “short” path’s 8400.

Sure would like to know what he has for an antoona. I also heard BD7NWF but was unable to work him.

Back to BA7IO:

At 10am my local time I came into the shack after cleaning & tightening the connections on my balun (that I wouldn’t have noticed were needed were it not for my recent 160m antenna work) and saw BA7IO spotted by a handful of US ops, none of whom were near me. Doubting I would hear him, I tuned to his freq and heard him fairly clearly. Definitely workable.

The K3’s APF function gets mixed reviews. Indeed, its capabilities seem inconsistent and it’s hit or miss as to whether a given signal will be enhanced or reduced to indecipherable ringing. I don’t know what the variables are that determine which way it slants a given signal but chosen bandwidth doesn’t seem to be one of them.

After working Yang I opened Audacity and made a recording of him calling CQ. Three seconds into the recording, I turned on the K3’s APF. What can I say – when it works, it works!

Have a listen:



About the 160m “T” I posted about previously…weird problem. I can’t get the SWR below 9:1 no matter what. Further, the MFJ259 doesn’t show resonance anywhere. Should be simple – center conductor of Mr. Coax goes to the feedline, shield goes to my ground system. But nada. No trabaja, señores. It does receive from the north on 40 meters though:

For many nights lately, 4S7NE gets spotted on 7001 kHz by other W stations. I can never hear him on my dipole (which is oriented N-S). Last night he was spotted again and, with the dipole/feedline configured as a vertical, I heard him clearly. Couldn’t work him though – bad SWR.

Fun hobby, ain’t it!


  2 comments for “China, the long way ’round…and the K3’s APF

  1. December 17, 2011 at 5:41 am

    John – for a T antenna, what you really want is the antenna feed coax shorted at the base of the antenna – that makes the “T” or Marconi. From your strike-thru it sounds like you really have sort of an inverted L on the center conductor and another L on the ground shield side!

    I use a shorted G5RV as a 51′ T on 160. I have about the 34′ ladder line shorted together at the bottom, then about 17′ of solid copper wire from there to the ground, where my radial plate and a SO239 bulkhead is. From the SO239 coax back to my tuner.

    I now have about 8 radials out as I slowly add more – the resonant freq drops with each radial – now resonant at about 1850.

    It is a horrible TX antenna anywhere but 160 – if I forget to switch back to my Windom, I’ll be calling stations for hours and they never hear me!

    • December 17, 2011 at 6:59 am

      John, I’m really scratching my head over it. Yep, both sides of the ladder line were tied together as the vertical element; the ground was as described earlier and the minimum SWR with or w/o a tuner was 9:1 across the HF spectrum. It went up at various freqs but 9:1 was the minimum. The tuner was no help. Really odd…

      Out of frustration (and having no more time to spend on it that day) I’ve given up on it for now. I may put up a dedicated inverted L for the band at some time in the future but I still have no idea why something so simple was giving me such a problem…

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