Swr on John Flinchbaugh KD3EE

High SWR on HF

Tue, 03 Feb 2026 00:00:00 +0000

I was seeing high SWR and started needing the tuner for the 80M EFHW. I checked/reseated connections at the wire and un-un with no change. I started testing down the line, and found that the outside connection to the pass-through cable was bad: it started pulling apart. I replaced the window pass-through, and now SWR is good again without the tuner.

64:1 Unun for 80M EFHW

Tue, 13 May 2025 00:00:00 +0000

Today I experimented with building a 64:1 unun for an 80-meter EFHW.

My initial attempt involved 3 primary / 24 secondary windings, but I quickly found that this took up too much space on the small toroid I was using.

After some adjustments, I settled on a 2 primary / 16 secondary windings, adding a 100pF capacitor. This configuration was inspired by resources like KM1NDY’s DIY linked EFHW 64:1 antenna guide.

I’m now successfully running my home EFHW antenna on 40 meters without needing a tuner. On 17 meters, the SWR is a bit high, so I engage the tuner for that band.

This setup reminds me a lot of my previous 71-foot random wire antenna with a 9:1 balun. I’m noticing a significant increase in the number of signals I’m receiving, which suggests this new EFHW might be a considerable improvement over my old 107-foot EFRW.

SWR with the Long Wire

Tue, 31 Dec 2024 00:00:00 +0000

I was using the 71-foot (21.64m) EFRW antenna at home, and I noticed SWR was surprisingly low as measured by the X6100 with the tuner disabled. I suspected loss on the feed line, but I also found this video of another person not using a tuner with the same antenna.

I disconnected my feed line at different places to find SWR jumps way high, so the measurement is working:

inside window
outside window
at the antenna

Does a very long wire have low SWR for everything? Is the 9:1 giving low SWR? The antenna’s working fine, and FT8 shows far-flung signals like always. Disconnecting antenna wire raised SWR above 1.5:1, but not much. Even with wires disconnected from the balun, it’s receiving a very few FT8 signals on 10m, and I can still transmit, but it’s folding back power with SWR just below 2. The tuner is definitely needed for 6m.