985 Workbench Net

My Week in Radio

  • I’ll miss field day.
  • POTA around Harrisburg, York, and Lancaster.
    • Mostly FT8/FT4
    • Also have been chase some phone park-to-park, and have been getting good reports with my little QRP radio
    • Exclusively testing the 20m-long EFHW I built.
  • Upgrading firmware from a 3rd party for my x6100, and my own patch to show me band boundaries by privilege
  • Moved the 1/4 wave ground-plane antenna higher in the tree.
  • Always get perplexing interference at start of this net, otherwise clear all day. It’s a net on the big repeater over in York that’s 15khz lower. Maybe I need to build a yagi next, so I can get more directional.

Other Discussion

  • Vic (KC3TYX) was making contacts with VARAC, not for winlink. The software let’s you beacon on 14.105MHz, and has 15 slots (channels) near the calling frequencies for conversation. Fire a beacon or 2, and check pskreporter to see if anyone’s listening.
  • Lots of digital modes have conventional calling frequencies.
  • WB8NUT website has sounds of digital modes. http://wb8nut.com/digital/
  • Jim (AF3Z) suggests a 5khz shift to help alleviate interference from W3HZU’s net on 145.970, so I redefined 985 as 146.990MHz with a -605MHz offset. That works in a test after the net.
  • Trying to move things around in the radio blew away the offset and PL when I saved the new 990 frequency. The computer works better or that programming.

New Firmware for X6100

There’s a new person building onto Oleg’s R1CBU firmware. He first made a patch TGZ available, and then an entire image.

He has a repo for this work, and it includes some build instructions which reference the buildroot and submodules. I think I’m close to being able to build it, but I’m seeing some errors trying to find the xkbcommon headers.

I did patch his source with my DB changes. I built the DB: sqlite3 params.db < params.sql, mounted the DATA partition, and copied my custom params.db to it.

It’s looking nice so far. I can use flrig and have wsjtx and fldigi both talk to it simultaneously. That’s the main improvement in my mind, but it includes some other fixes:

  • volume encoder can be spun quickly now
  • smoothing of the TX/SWR graphs
  • finer detail in the waterfall

POTA US-4356

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.

pota  efhw 

Camping, POTA, and Testing the EFHW

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 WeekendPOTA 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.

efhw  pota  camping 

Antenna on the Car

I removed the magnet from the inexpensive mag-mount antenna that I had stuck to a baking sheet in the back of the BMW i3 (which is all plastic). The bike rack is always on the car, so I cobbled together some scrap metal parts and clamped the antenna onto the rack. It’s got a screw knob, so I can loosen and reorient it when I flip the bike rack.

It works great now with the antenna outside the car and attached to the metal of the rack.

antenna  vhf  uhf  mobile 

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.

POTA Antenna Test 3

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.

pota  efrw  antenna  efhw 

EFHW Test 2

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.


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.

efhw  pota