February 21, 2018
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It took several days of off and on work to debug the problems with the EFHW matchbox. I had to disassemble and rewire this several times before finding the issue. I noticed initially that the toroidal inductor seemed sensitive to motion. I ended up completely rewinding the coil then used some hot melt glue to pin down the winding. Ultimately the problem was with the capacitor. I ended up modifying it so that the capacitance range was maxed out. Seems to be working now and the antenna tuned to 2:1 SWR across all but a small portion of the CW portion of the band. I made some SSB calls and completed the QSO’s however the signal reports were in the 56 to 57 range. I am running WSPR now and will collect some data as a comparison.
February 19, 2018
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It started off well, I had previously measured the wire 35.4 feet for the horizontal section and 17 feet for the initial cut of the two vertical sections (full wave total wire length for 20m). I used the new longer fishing poles and managed to fit them in the yard. As expected there was significant sag on the horizontal section but was manageable. I hooked up the EFHW matchbox from the linked EFHW project to one end to voltage feed it. It tuned up nicely with a 1m counterpoise:
Going inside the shack I made a few domestic Phone contacts with 55 57 signal reports. I did notice SWR was swinging a bit and started to check on it. That is when the real fun started. Suddenly the SWR lock up very high across the band. I thought there might be a bad antenna switch or loose coax connector. I built another ugly balun. Checked the match box with a 3.9K Ohm resistor and started seeing the weirdness. Sometimes is worked, sometimes it didn’t. I opened it up and checked the connections but couldn’t find a definitive wiring problem. I basically rewired it from top to bottom after checking the capacitor and inductor verifying they still worked. It behaved while I set it up but the minute I stepped back in the shack….sky high SWR. Check just the matchbox and it is not responding. Re-wired it a second time. Pretty much the same behavior.
So I have narrowed it down to the toroid. I may have a subtle solder issue one one end as well as shifts due to movement. I’ll debug this some more this afternoon. So far:
The Good: Easy to setup with potential for good gain.
The Bad: somewhat narrow banded
The Ugly: the EFHW matchbox wackiness tying up most of my antenna time this weekend.
December 11, 2017
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WSPR results o 40m and 20m WSPR look good with the EFHW. here is 40m during nightime hours:
And 20m for just a few hours yesterday and so far this morning:
On 40m there have been 103 unique heard vs 106 heard by (@1/2 W). On 20m, this is 124 unique heard vs. 74 heard by (also @1/2 W). These numbers indicate good overall performance.
I found a great write up on how to build one of these antennas titled “A Shortened Multi-band End-Fed half Wave (EFHW) Antenna for 80-10m” by Steve Nichols, G0KYA.
I am going to do some work on how to best deploy this in the field given my typical situation (i.e. lack of tall trees). this could be a great Field Day antenna.
December 10, 2017
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There were some things bothering me about the EFHW matchbox. I would run a scan using the RigExpert with a 3.9K Ohm resistor from the antenna line across to the ground and sometimes get a good reading and sometimes not. I suspected a poor solder connection or the el cheapo binding posts I was using. Well I am done with the el cheapo binding posts! From now on I am using stainless steel machine screw hardware. I replaced the binding posts with these and the readings settled out.
I made a few other changes for round 2 with this antenna today. First up, I wrapped the end of the RG-58 cable eights times around an FT240-43 core to act as a choke at the feedpoint. I added about six feet of counterpoise. I went back to setting this up a a low inverted V of sorts. The feedpoint is over a tree branch on one end about 6 feet off the ground. The other end is supported by a fishing pole. Unfortunately, this configuration had a huge amount of sag in the middle. I placed another pole in the middle so the apex is up about 16 feet. Not happy with this configuration. I will use a sturdier pole and set this up as a true inverted v next time around. meanwhile, I am running some test in this configuration. SWR was good on 40m and 20m but a bit high on 15m:
Initial WSPR results on 20m look promising. 1/2W signal is showing a good ratio to received spots. I tried a few SSB contacts but none were closed. I’ll run WSPR on this over night on 40m and 20m and see what the data shows. I’ll then switch to a 10m pole to support the middle of the wire into an inverted V.
One more thought is that I’ll add a 110uH coil to the end of the wire then about 2m more of wire, the idea that it can trap 40m and then act as a loading coil on 80m. I have worked out the coil dims for this using a 1-1/4″ PVC pipe coupler as a coil form. 110uH works out to 52 turns of #20 magnet wire.
December 5, 2017
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Here are the 24 hour WSPR results on 40-20-15m receive using band hopping. They appear to be pretty consistent with current band conditions and while not as good as the 1/4 wave vertical it is a very respectable and very portable multi-band antenna.
The SWR plot is as follows:
These antennas are increasingly popular and many quality antennas sell for ~$140. Building your own is very simple and I would estimate my cost to build this would not be greater than $30. This will work out to be a good antenna for portable or field day use. It is not especially sensitive to mounting or orientation.
December 2, 2017
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Back in late August, I had a post regarding a broadband auto transformer for an EFHW antenna. I finally got around to cutting 66ft of wire (1/2 wave on 40m) and did some basic tests. It is only up about 10 ft and stretched out north-south across the back yard. The RigExpert Zoom showed dips in the 40m, 20m & 15m bands. SWR is below 2:1 across each band. Twenty-five feet of coax forms the counterpoise. Very promising. One SSB contact on 20m yielded a 57 report on this antenna and the 1/4 wave vertical. I am running WSPR now on 40m. Tomorrow I will raise this up to a least 20ft and run some more tests. If I add another 66ft it will be a 1/2 wave on 80m and should get me a match on all bands (except 60m) between 80m and 10m.
August 31, 2017
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First up is a broadband EFHW using an auto-transformer wound on an FT240-43 Ferrite toroid. I used 18 gauge doorbell wire (had to remove the outer jacket of the wire pair first. The basic wiring looks like this (thanks to PA3HHO):
What is not shown here is a 150pF capacitor across points A & B. Here is the completed toroid:
Here I test the matching by connecting a 3.9KOhm resistor across point B & C along with the 150pF capacitor across A & B. Here is the SWR plot:
SWR is below 2:1 across nearly the entire band 80m to 12m 10m is 5:1 well within range of a tuner. I will mount this in a box with a UHF connector and two banana jacks, One for the antenna wire and the other as a ground connection. Once complete I’ll try first with 40m 1/2 wave wire. That should give me a good match on 40m, 20m, and 15m. The wire will be around 66 ft long. I should be able to add 80m by adding a loading coil and an additional 2.5m piece of wire. Planning to un the first 10m of wire up the travel mast then bring the rest down as a sloper.
August 23, 2017
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I am going to build a matching transformer for a multiband EFHW antenna. The idea is to use a 1/2 wave wire and not have to use a tuner across several bands. More details to come. Also will build an inverted V for 20m to use as a reference antenna.
June 28, 2017
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I got a late start to field day this year due to a late breaking family commitment. Our club tried to setup at the local weather station but cancelled operations due to a large noise source crashing the bands at that location.
I started operating about 19:30 UTC. I started at 5W on SSB but over the first hour only made one contact. The band conditions were not good on 20m with lots of QRM and QSB. I added the amplifier and started to work on 45W. My power draw was significantly higher but my Q rate increased. The solar panel kept up with the power consumption even though there was quite a bit of cloudiness. I continued to operate on 20m until dusk when I switched to 40m. Overall I made 60 Phone contacts over the course of about 8 hours. My score this year will be lower even with more Q’s due to the higher power I ran. I did not get a chance to run digital.
- Digital logging – netbook needed one charge cycle during this period. The 12V to 18V DC-DC converter was running at abou 2.2A during the charging cycle. I used a 7Ahr for this through a spare Solar Charge controller. I am going to look at a tablet for next year.
- The EFHW antenna worked great on 20m.
- SOTAbeams travel mast + TV tripod worked great to support antenna with no guy lines.
- Solar generator box had enough juice to supply the day’s activity even at the higher power consumption and had some power to spare.
- Tube Tarp came in real handy as shade. Luckily no rain on Saturday. I’ll do better with the depolyment next time as I figured out how to guy it better.
What did not work so good:
- Can’t run digital mode while using an amp. The amp uses the ACC port on the radio but provides no pass through. I am looking at how I can accomplish this for next time.
- I don’t have the battery budget to run 45W phone for 24 hours. I figure I would have run out of power after about 12 hours. Partly cloudy day didn’t help.
- Didn’t take advantage of more 6 stations to raise Q count.
- Calling CQ consumes a lot of power. Need to refactor the power budget.
So I figure my score this year for 60 SSB QSO’s + bonus points for emergency power will work out to 310 for my 1B station. I am convinced now that I have to finish learning CW so that next year I can run 5W on CW and up my point count. A more directional antenna would be nice but a portable beam antenna remains elusive. For some reason I seemed to be doing better with stations in California than on the more densely populated east coast.
In summary, A great afternoon of outdoor radio fun and already looking forward to next year.
June 21, 2017
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I purchased the following for $1 at Home Depot yesterday to form links for the EFHW I plan to use for Field Day:
These are buckles to make paracord bracelets. Here is how the resulting link looks like using these, a couple of cable ties and a pair of Anderson Power Poles:
I have made initial wire cuts for 15m, 17m, 20m and 40m. I also cut 1/10 wavelength counterpoise wires for each band. I have also prepped the Travel Mast and the TV Tripod so I will hopefully setup later this afternoon (when it cools off a bit) and tune the wires. I’ll run 15m-20m as a vertical and 40m as an inverted V.
The only other prep I am working on today is I’ve taken the solar generator box I built last year and set it up outside with the two 15W panels to charge them up.
Update: Just did the calculations on the 40m inverted V and found that I probably don’t have enough space to lay that out in the backyard due to obstacles. Will configure the first half as a vertical and then the remaining half as a sloper which I’ll aim towards the north and terminate 4 feet off the ground. Only need a radius of about 16ft. A quick run on EZNEC show the following pattern: