If you have been following along with my antenna experiments, you know that I always work with temporary outdoor / field antennas and have been searching for a solution I can make more permanent. It needs to be always available, and frequency resilient.

The idea that I’ve harbored for a long time is a multi-band antenna in the attic. Never mind that certain people don’t want me climbing around in an attic which is likely more complex than the simple one we had “up north.”

The very successful EFHW became the ideal candidate. It performs well, even if its signal strength is about 1/2 an S-unit lower than my best verticals. I remade the original with heavier, more durable, wire and field tested it several days. Like the original, it performed well, with no need of a tuner, on 40M, 20M, 15m, and 10m. All I needed was someone to hang it in the attic.

After a good bit of searching, a good guy known as “The Village Tinker” suggested a certain “low voltage” installation firm (cable TV, ethernet, etc. ) They agreed to do it for the simple price of a one hour service call. A couple of guys came out and I described what I wanted, emphasizing that as high as possible was my desire. I handed them the antenna, complete with the 49:1 transformer in a box, and a simple center hanger that I had been using outdoors. They had the job done in about an hour and we exchanged a check for a receipt.

Results: the 4 band antenna that needed no tuner is now a 4 band antenna that needs a tuner for 3 of those bands, doesn’t hear very well, and has an S-5 noise floor! Sigh!!! I have made a few QSOs with it. The signal reports are lower than with other antennas, and the noise, apparently from other things running through the attic, makes it uncomfortable for listening and decoding CW. It certainly will not be an everyday antenna, maybe an alternative on rainy days.

What happened? I asked one of the installers to show me, on a overhead picture of the house, where the antenna ended up. It wasn’t as high as I expected, nor did it run quite as I expected. By that time, we were out of service call time, and I didn’t ask that he go change anything. What had really happened? He put the center hanger, a simple little plastic triangle with a few holes, as high as he could (not very)… when he came to it … If were installing it, I would have scooted the hanger along until I could get it up to the peak of the roof line. Because he didn’t use some of the distance going up, he had more wire left at the far end, and simply routed it around a corner. The antenna is not the inverted vee I wanted, but a bent horizontal that’s not very high. That speaks to the “doesn’t hear well” aspect. The difference in resonance points and in ambient noise floor is most likely due to the nearness of all the other kinds of wires and ducts in the attic space.

Should I ask for another service call to relocate it up to the top of the roof line? With the unpleasantly high noise floor, I think not.

Bottom line: It is a reasonable 3.5 band antenna. It resonates OK on 40M, very well on 20M, OK on 15M, and can be coerced for 18M, and NO-GO on all other bands.

I launched it in the backyard in the usual inverted vee fashion of some of my other wires. Measurements with a NanoVNA produced these SWR values:

It becomes yet another addition to my antenna graveyard / spare parts bin.

This follows the EFHW Fail article. There are a lot of ways to configure an End Fed Half Wave antenna. The earlier article explored a variant that sort of works, but not as well as expected … and certainly not as well as this one.

This EFHW variant is very common, a 49:1 transformer, bridged with a 100pf capacitor, and about 67 feet of wire. It is designed for 40M and higher. Once assembled, the wire is cut to a length that produces the desired resonance points, and there are several with this design.

About design… There’s a well known chart for Random Wire Antenna Lengths. It shows all sorts of lengths to use for antennas that are (1) random length, (2) are not resident on any band, and (3) always require the use of an antenna tuner. There must be some good rationale for such a thing, but it befuddles me why anyone intentionally always wants to use part of their RF output to warm up coils in a tuner. Aren’t antennas resonant at the desired frequencies a lot more efficient? OK, let’s set that aside… the chart is also, maybe unintentionally, helpful for offering the good lengths for EFHW antennas that have multiple natural resonance points. Just use the parts of the chart marked in red that the chart labels “Lengths to avoid.” They are EXACTLY the ones we want.

That blue oval is my addition to the chart, and the starting point for this antenna’s length. The actual length, trimmed as I like it, is 66 feet, 5 inches.

The design is so popular that a number of hams sell kits for building a 40m version. These are the people willing to gather all the parts, package them nicely for us, and save us the effort of finding each individual piece. Just try buying one BNC connector and paying shipping for it, then the wire, then the capacitor, then the torroid, etc. etc. One of those kit packagers is Jason Oleham, KM4ACK. His kit sells for about $40 and is often out of stock because of its popularity. The KM4ACK EFHW kit was the starting point for my EFHW adventures. It worked better than many other wire antennas I experimented with over the past year. As advertised, it is naturally resonant on 40M, 20M, 15M and 10M. With careful trimming, I made mine happy to work very well in the CW portions of those bands. BTW, it works with NO counterpoise, and is not sensitive to feedline length.

Below are NanoVNA screenshots for 3-20Mhz, 40M, 20M, 15M and 10M. In all the charts, the marker shows the QRP hailing frequency in the CW portion of the band.

Interestingly, the tuner built into the Penntek TR-45L can tune this antenna on 80M and 30M, but definitely not on 17M. I haven’t actually made contacts with the tuned results on 80M and 30M, but have on the other bands. I’m very pleased with the results, a good step toward frequency resilience for this HOA ham. Next, let’s see what it does when placed under roof.

Next, let’s look at a couple of WSPR runs for the bands I use most, 20M and 40M. I’ll get to WSPR runs for the other bands soon. In the meantime, I’ll mention that my first contacts on 15M and 10M with this antenna were TX and AZ.

Living in an HOA area, my constant quest is for a stealthy, multiband, effective antenna. When I arrive at a good one, I plan to install it in the attic. That installation will reduce the everyday setup and teardown of the “backyard” portable antennas. Over the past year, I’ve tried many antennas and my antenna junk box is full of “spare parts.” I added more to the pile yesterday. It actually is a workable antenna, but one that fails to be as good as others, and fails to meet my expectations.

The antenna is an EFHW that I found in an issue of CQ magazine from several years ago. I won’t be more specific, because I don’t want to cast blame. The thing might work very well for someone else. Like all EFHW designs, this one is a transformer and a wire. The transformer is 36:1, the wire about 65 feet (later cut to trim for 20M), and has an RC network about 1/3 of the way along the length.

My test rig for such an antenna is putting it up in an inverted vee form using a 17 foot collapsible mast as the center support. That form sort of mimics the roofline of the house, for when I move it into the attic. Measurements are made with a NanoVNA.

There’s another EFHW that does better. We’ll see it shortly…