Efhw 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.

US-1418: 2025-10-30

Thu, 30 Oct 2025 00:00:00 +0000

I ran out to Sam Lewis, US-1418, to activate when the rain stopped.

I took a few minutes to setup my normal EFHW running North-South to operate more to the East and West, though I did get a contact to Colombia.

I operated mostly low-power FT8, 1-4W, but mostly 2W. I chased and got 1 CW contact before it started getting cold and dark.

setup

antenna north-south

tiny s-biner

key and radio

Camping and POTA

Sun, 31 Aug 2025 00:00:00 +0000

I went camping and operated there and in Michaux Forest, Pine Grove Furnace, and Caledonia. I ran the 40M EFHW in trees at the parks as a sloper and inverted-V for 40M, 10M, and 15M. I did FT8 and a little CW.

At the campground, I contacted NY and ME on CW on 40M in the morning using the Gabil slider coil and whip. I discoverd that the my older Gabil antenna with jumpers on the coil has different thread size for the whip, so not interchangeable.

creek

pine grove setup

pine grove antenna

caledonia antenna

caledonia setup

caledonia inverted-v

High SWR 80m EFHW

Wed, 11 Jun 2025 00:00:00 +0000

I was seeing high SWR on the 80M EFHW: over 3:1+. I found counterpoise was chewed and broken, so I twisted it back together, but I saw no change. I disconnected the counterpoise completely, and that made no difference: still 3:1. I finally unscrewed and re-screwed the rusty alligator clamp and reattached it. That fixed it!

Previously, it seemed I’d sometimes see high SWR for a a moment, then it would recover. It seemed like giving it a little power would “clean up” something.

Broken EFHW

Mon, 26 May 2025 00:00:00 +0000

The home antenna wire comes down every once in a while. I soldered and re-hung it, and it looks good. It seems to need a little power put through it, and then the SWR looks good. I wonder if some static accumulated, and that is causing higher SWR for a moment.

US-1355 French Creek POTA Activation

Sun, 18 May 2025 00:00:00 +0000

I visited French Creek State Park (US-1355).

I deployed my 40-meter EFHW, strung up into a convenient tree. I operated with low power, typically between 1-2 watts, on the 10-meter, 40-meter, and 20-meter bands.

I primary operated FT8, and I also attempted some PSK, but no one responded.

Setup

Pole spike

Antenna

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.

Launched 80M EFHW Antenna

Mon, 12 May 2025 00:00:00 +0000

I launched my 80M EFHW at home, replacing my previous random wire setup. I’ve trimmed it up and folded it back, but it still needs the tuner to touch it up. I’m seeing the expected harmonics near each ham band, which is a good sign. My next step is to build a new 49:1 transformer for it.

POTA US-4567: Marietta Riverfront Park

Fri, 04 Apr 2025 00:00:00 +0000

Rain was predicted later in the weekend, so I headed out to Marietta Riverfront Park (US-4567) for a quick activation to beat the rain. My initial plan was to rebuild my EFHW antenna, but I cut the new wire six inches too short, and I didn’t have enough wire on the spool to start again.

I opted for my 12.5m EFRW instead. It was 7 PM, so I focused my efforts on the 40m. I successfully got about 18 contacts before I packed up for the evening.

Marietta Riverfront

Breakfast and POTA

Fri, 21 Mar 2025 00:00:00 +0000

I went to the 985 breakfast and chatted lots of Vic and Jerry.

After breakfast, I hit the parks for some POTA. I started at Middle Creek where I tested my EFHW vs the Tactical Delta Loop.

Next, I setup at State Game Land 156 down the road with the telescoping antenna for a CB walkie talkie.

Middle Creek

EFHW

Setup at Middle Creek

Tactical Delta Loop

TDL Hub

Setup along the road

POTA US-1356 Gifford Pinchot

Sat, 22 Feb 2025 00:00:00 +0000

I visited Gifford Pinchot State Part, US-1356, and strung up the EFHW from a picnic table to a tree. I managed it in 1 throw to a nice spot. I made 20 contacts:

18 FT8
2 CW, including N4T, the Dry Tortugas DXpedition

Using R1CBU 0.29.1, I knew to pay special attention to undo the AM bug from SWR Scan by switching through modes after an SWR Scan. In this firmware, though, WSJTX would set digital mode (USB-D) and it would bounce back to USB, which doesn’t take sound from the connection to the computer. I had to work around it by disabling WSJTX’s ability to set the mode. Then I could set USB-D and it would stay there.

entire setup

US-1398 Pine Grove Furnace: 2024-10-20

Sun, 20 Oct 2024 00:00:00 +0000

I went camping and activating Pine Grove Furnace, US-1398, and Michaux Forest, US-5471. I stretched the EFHW over the parking lot, because I thought it wouldn’t be busy. I got 21 FT8 contacts and 2 CW contacts to other parks.

park

antenna over lot

setup

efhw

canoe passing by

SPARC Meeting: 2024-07-23

Tue, 23 Jul 2024 00:00:00 +0000

At the previous week’s meeting, many people built EFHW kits and untangled some wire to use with them. No one finished the build and brought them back, so I offered a quick demo of tuning such an antenna.

I connected my 49:1 unun that I’ve been using to a new wire we had hanging. We connected a handful of different analyzers to see how they operated.

POTA US-1743 White Clay Creek

Tue, 02 Jul 2024 00:00:00 +0000

Matt and I activated POTA US-1743, White Clay Creek, DE. I deployed the 20m-long EFHW into a tree, which worked nicely with no SWR. Matt deployed a telescoping dipole on a mast. I worked only 40m, and Matt ran 20m. We didn’t interfere with each other at all. I forgot my 5525 power splitter to run both the laptop and radio off 12V battery, but fortunately I didn’t need it for the computer.

Matt Operating

Matt's Dipole

POTA US-4356

Fri, 07 Jun 2024 23:38:50 -0400

After a bike ride in Harrisburg, I visited US-4356, Boyd Big Tree Preserve. I used the 20m EFHW sloped up into a tree near the main pavilion. I spoke to a park in Western PA, and a museum ship on Great Lakes in Toledo, OH. 15m FT4 was busy with lots of contesting, so I also ran some FT8 on 20m.

The go-box is over-stuffed again with extra rope. I need to slim it down again.

Camping, POTA, and Testing the EFHW

Fri, 07 Jun 2024 22:54:16 -0400

SPARC Elmer Night

I spent the Elmer Night tuning EFHW again with the NanoVNA. I proved that I saw the same graph when the antenna was stretched shallow vs a higher inverted-V.

I tried folding back the EFHW wire. It changed the tuning slower than cutting the wire. DX Engineering has a video about this. I didn’t get it finished at the meeting, since because it got dark.

Memorial Day Weekend POTA US-4361, Kings Gap Environmental Center

Matthew and I setup at Kings Gap Environmetal Center (US-4361) near the campground. I spent the most the time still slowly tuning my EFHW, and then dodging the rain. I barely made any contacts by the time I got the antenna in the air, and then the thunderstorms returned. We bailed, and I put the antenna up back at the campground strung over the site from tree to my fishing pole to telephone pole for the rest of the weekend. The twisted cords I’ve been using started unwinding, so it’s soon time to replace it with braided mason line.

POTA Antenna Test 3

Mon, 20 May 2024 03:19:48 -0400

I compared the 20m EFHW with the 12.5m EFRW at Sam Lewis (US-1418). I threw really high and made both antennas nearly vertical into high trees, not inverted-v.

EFHW could hear pretty well, and the SWR sweep showed again that I could shorten it, so I did lower it and take off a few cm.

The EFHW didn’t seem to like its counterpoise. With the counterpoise, it was giving me an SWR of 2-2.5:1 on 40m when I transmitted. If I removed the counterpoise or kept it coiled up, the SWR was lower. I still made most my contacts on 40m.

I think the radio may have again been interfering with the mouse when transmitting. I already had chokes on both ends of the feed line, but adding the counterpoise helped that common mode interference. It was a rough day.

The EFRW would not tune well at all on 40m with or without its single counterpoise. That surprised me greatly, because I had tested that same unun with my existing EFRW antenna out the front window at home.

I wonder if it had something to do with each antenna being mostly vertical. I wonder if they needed more radials instead of a single counterpoise. K4OGO (Walt of Coastal Waves and Wires) always adds so many radials to his verticals.

This had me questioning everything. I thought I was doing something really good by getting the wires high and vertical. When I brought the radio home and connected to the same old EFRW, it was again performing normally.

I also learned that the POTA website cuts off your activation and starts a new one at 00:00UTC, 8pm, so I ended up with 2 QSOs counting toward a second (incomplete) activation at the park.

EFHW into tall tree

EFHW winder

EFRW winder

EFHW Test 2

Sun, 19 May 2024 00:00:00 +0000

I ran out to Susquehanna Riverlands State Park (US-9719) to test the EFHW again. This time I tied it to a bush and a picnic table and raised the center with the fishing pole mast.

I took the time to sweep all the bands with the X6100’s built-in analyzer app. 40m looked like it could stand to have the wire slightly shorter, but when I transmitted, the SWR looked fine. I saw about 1.5:1 SWR on 40, 20, and 15. 10 was a little off, so I guess I’ll add the 100pf capacitor that most people use.

The tuner made 12m and 17m work, so I made FT8 contacts on 40m, 20m, 15m, and 17m.

I was also trying out some of the combo winder/unun I 3d printed and made some notes. I’ll post my remix soon of another person’s OpenSCAD code. I like the all-in-one designs that wrap up into one package, but I wonder how much that will hinder my random experimentation with antennas.

While transmitting, I noticed the Evolve 3 laptop’s mouse would stop responding. I had seen this on other laptops using the 1/4 wave HF vertical. I added the common mode choke to the feed line near the radio, and that cleared up. There was already a choke near the antenna, but I guess it wasn’t enough. I love when I can see a clear cause and effect or problem and solution.

Riverlands Sign

Riverlands Rain

Riverlands Operating

EFHW Test

Wed, 15 May 2024 21:36:49 -0400

Ben and I took the radio gear for a walk to Hawk Point overlooking the river in Susquehannock State Park (US-1425) for a POTA activation. We threw the 20m EFHW into the trees in an inverted-V. I checked the SWR on 15M, and it came in about 1.5:1 or so.

I could hear really well with it, and I contacted Argentina, Texas, California, and Italy among other closer places on 15M FT8. I spun the dial down to 20M SSB to hear a park in Illinois, but it was busy and the sun was setting quick, so I didn’t wait to try to make contact.

I’ll have to try the other bands next, but my randomly starting up on 15M worked great.

Using the little box as a winder for the wire didn’t work out so well. It became an immediate tangle as I tried to unwind it. I’ll switch to a 3d-printed winder instead.

Hawk Point

New Wires

Sat, 11 May 2024 15:41:09 -0400

The bands were dead with the terrible geomagnetic storm this weekend, so HF is very limited. I was only able to contact Lititz from Mountville.

With the downtime, I built some new EFHW antennas. I tied some wires to trees, stretched them out, and tuned each of the 2 20m EFHW antennas with the NanoVNA: one speaker wire, and the other lightweight silicone wire. I built new ununs and mounted them in plastic gum cases and a 3D-printed winder.

I also cut a lightweight EFRW, 12.5m, from the silicone wire and gave it a gum case as a winder.

I’ll test the new antennas soon when the bands are better.

EFHW Gum Case

EFHW Winder

EFRW Gum Case in Use