985 Workbench Net - 2024-05-20

My Week in radio

The Vertical EFHW

I Tested my 20m EFHW wire and unun on 2 different POTA outings In an inverted v with a counterpoise, it worked pretty well, but could be shortened. As a vertical, the SWR was higher, and the counterpoise made it worse. I compared the vertical EFHW to the trusty old EFRW in a mostly vertical configuration. That one had exhibited a terrible SWR as well with or without counterpoise. Maybe I needed more radials instead of a counterpoise? I have 2 ARRL antenna books, basic and the big one, so I could read, I suppose. During these experiments, my computer experienced some common-mode interference too.

Custom Antenna Winder

I 3D-printed a nice customized winder with the transformer attached. I modified the code to be parameterized to any size I want.

More VHF

I’ve been discovering I can hear some further repeaters using the spectrum analyzer feature on my Quansheng, so I’ve been adding more repeaters to the scan.

Thoughts on My Vertical Antenna Problem

  • You can tune and end-fed at one angle, and it can have a different swr at another angle.
  • They’re sensitive to objects in their near field. Is the unun near ground or branches? The same goes for the other end of the antenna. Try changing the orientation.
  • The ends are high-voltage, so they’re sensitive to capacitance. The middle is high-current, low-voltage.
  • Vertical antenna will have very different conditions at each end. inverted-V or horizontal will have more similar conditions at each end.
  • RF comes from the current in the middle.
    • Vertical is an inexact science.
    • The tree effects it.
    • 50ft of coax helps provide RF ground, and less can be a problem.
  • Watch height of unun.
  • The Smith chart on the NanoVNA can help evaluate what’s happening.
    • Crossover point on the chart can show the tuning and the swr
    • Is it environmental or the wire?
  • Counterpoise placement can be sensitive.
  • Add radials for vertical.

Interesting Bits from Other People

  • Tim, W3QP, did the W2 SOTA campout: 6 summits and 32 contacts, mostly VHF.
  • Chuck, NA3CW, talked about accomplishing an 75M net using online WebSDRs to hear, because propagation was so bad.
  • Rob, K3VIL, is having fun with his QRP IC-705.

See also