2020-07-22 Someone asked in a Facebook Group whether you could add a coil to the DS-1 to make it work on 80 meters? That reminded me that I had wound an 80 meter coil for my DIY PAC-12 several years ago. So I dug around in my stuff and found it.
To my surprise, when I added it on top of to this DIY DS-1 and checked it with my nanoVNA, it was resonant with a reasonable SWR just below the 80 meter band. And by shortening the whip a few inches it was in the band. I didn't have time to experiment further but I suspect if I used a somewhat longer counterpoise than the 16 ft one, the SWR would have been "perfect."
Will it be an effective antenna? Likely not due to it's short length. But it does resonate. The coil is about 115uh, and consists of 50 turns of #20 wire, 2 inch diameter. I gave some thought to winding one on 3/4 PEX to match the rest of the antenna but my calculations indicate it would require between 200 and 300 turns and would be almost 10 inches long! I don't think I could count that far, so I'll stick with this one for now!
I'll do some more testing just for fun! Maybe even try for a contact. The coil is wound on a retired pill bottle! Nothing like recycling!
Well, after dinner and some other responsibilities it still wasn't dark and the mosquitoes hadn't swarmed in the yard yet, so I set up the antenna with the 80 meter coil, connected it to my nanoVNA and adjusted it to resonate in the middle of the 80 meter band. SWR was reported as 1.21:1. I then connected my x5105 and did some more checks checks, one with the 16 ft counterpoise and one with a 33 ft counterpoise. The SWR trace by the x5105 showed no difference at all as the two photos show. That doesn't say they won't make a difference on radiation effectiveness.
I tuned around and there was a strong signal on 3.055 sending a seemingly unending string of numbers and letters in groups. I was hoping he would take a breath and I could give him a call, but no, he just kept going, pausing only briefly for "the other guy" to acknowledge. Neither ever sent a call sign. Not sure what that was all about. I also heard fairly strong FT-8 signals. But I had to give up for now. At least it was encouraging that I could hear something.
2020-07-13 As with all my antennas, I can't leave them alone! I keep thinking of ways to make them better, or at least different. This paragraph is about how I "added" 30 meters to my 20/40 meter short vertical I raved about yesterday. Tap the 40 meter coil! I had a good experience building my kw4jm 20m 1/4 wave vertical with tapped coil for 30 and 40 meters. So why not apply what I learned there to this?
Some quick experimentation with a pigtail between the 20 and 40 meter coils and a straight pin quickly identified that I needed a tap at 26 turns from the top. Since I've been mulling this idea over for a couple days I had ordered some very small jewlrey silver screw eyes from Amazon which came today. Five hundred of them they say - looks like 1000 to me! But they are tiny, which is what I wanted since my application is to screw them through the center of the 24 gauge RCA speaker wire that the coil is wound with.
Using a Push Pin, I made a tiny hole through the wire and into the PEX coil form just right to carefully screw one of the silver screw eyes through the 26th turn from the top and into the coil form. A quick SWR check showed it was perfect! and simply disconnecting the pig tail from the screw eye returned the coil to resonance on 40 meters. So now it is a tri-band short vertical. 30 meters is dead quiet so no on-air checks yet! It strikes me that a tapped-coil vertical is the vertical equivalent of a link dipole! The down side to both is that you have to visit the antenna to change bands. In exchange you get pretty solid performance on each band, accepting the limitation of any loaded vertical. By the way, the black splotches on the coils is where I've put a little Liquid Tape on to either hold the coil in place or seal up a damaged spot on the wire.
2020-07-12 Well, I've now logged ten QSOs with this "completed" antenna in its 40 and 20 meter configurations pictured above. Three of those were at 5w. the rest were at 20 watts. and all but three were on 20 meters. I compared antennas on a number of signals and the vertical is consistently a couple S units lower on receive. But it really does work pretty well. I'm pleased overall. It is so small and easy to set up that it's hard to be disappointed in those couple S units. If propagation is any good at all it can get you on the air.
2020-07-11 This evening I added a couple turns to the 40m coil so it now has 76 turns. Then I set it up and did some fairly careful SWR checks.
- With the whip fully extended to 57", SWR is 1.35 @ 7.00mhz, 1.00 @ 7.06mhz & 1.94 @ 7.3mhz.
- With just the 20m coil and the whip fully extended it reads 1.09 @14.070 and is below 1.15 across the whole band
I decided to see what it would take to use it on 30 meters. The whip has to be shortened to 19" resulting in an SWR 1.09. I can't believe it would be an effective antenna with such a short vertical element. I did the same check with the 20m coil and shortening the whip for 15 meters. It was again very short and not a feasible option.
I believe it really should have either taps on the coils or different coils for these "off-design" frequencies. I'm curious how QRPGuys has one set up DS-1 for the whole range of 40-10 meters which they advertise.
Having gotten to this point, I find myself thinking about a single, tapped coil version. My quick calculations are it would take a 7" coil form with the 105 turn winding taking up about 6". That would require about 23' of speaker wire. The whole concept is the same as for both the Pac-12 and my 17' DIY KW4JM wire vertical, just with a shorter vertical radiator and more turns to compensate. I guess a vertical is a vertical! It takes me a while but I get there!
2020-07-10b (about 8:00pm CDT) This evening after a relaxing KYC dinner in a park in town I quick erected the 40 meter short vertical described below and connected it to my g90 inside wiht a 25' coax. The band was alive with CW signals. I quickly heard W2RPW (754 miles) calling CQ FISTS on 7.028 and answered him. He came back immediately and gave me a 599 report. He was 559 in here. Then I called CQ SKCC on 7.055 and W8CMK (587 miles) answered me with a 579 report. He was 559 here. To say I'm a happy camper would be an understatement. Below is the RBN report on my two times calling CQ.
I compared a couple signals on both the short vertical and my EFHW inverted vee. signals were similar in strength but there was more background noise on the vertical.
2020-07-10a So, I decided to make a 40 meter extension coil. I calculated it would need 75 turns but ran out of space on the form at 74 turns. And that took a bit of creativity! Then I assembled the whole, extended the whip to its full 55 inches, attached the 16 foot radial and connected it to my nanoVNA. I was pretty surprised when It immediately showed it was in the 40 meter band! Narrowing the sweep range on the nanoVNA I found it was resonant at exactly 7.100mhZ! I couldn't believe it so attached my x5105. It showed the same thing! And the SWR at that frequency was 1.16:1! tuning around I heard a couple very weak signals until I hit W1AW at 7.047.5. It was registering S5! I tried to see if I could get any response out of the RBN network but alas, none! I wish I had a couple more turns on the coil so I would have a bit of room to adjust the whip but that will have to wait for the next iteration! For now, I'll just enjoy the success! Everything but a feedline weighs 10 oz.
2020-07-10 One thing that has concerned me about this antenna from the beginning is how the SWR seemed kind of erratic when I would adjust the length of the whip. Small changes had somewhat unexpectedly varying result. This morning as I was looking at it I noticed that the whip was slightly loose in the 1/4-20 coupling that attached it to the coil. After investigating that I decided to solder a small piece of wire from the whip to the coupling. When I set it up again it was stable as a rock! I could easily make very fine adjustments to the length and change the resonant frequency and equally small about exactly as I intended. Also, the SWR is 1:1 at resonance! clearly I had both resistive loss and a poor connection which is not solved. I did manage to get one difficult QSO with AA5VE in Texarkana, TX on 14.060, a little over 600 miles. He was about 439 in here QSBand gave me a 339 also with QSB. But that is now two QSOs! Whoopee!
2020-07-09 If you follow my web site at all you know I'm crazy when it comes to antennas! But it's a happy crazy! I've now been playing with making a short vertical for three days. I was "set off" by a post in a Facebook group that mentioned QRPGuys new 40- 10 meter short vertical kit. As mentioned below I ordered one. I really like their stuff. It's simple in concept and to build and inexpensive. And best of all their kits work when you're finished! All that said, as the paragraph and pictures below chronicle, while waiting for the kit I downloaded the instructions and then decided to build my own version. Inevitably one has to do some things differently as you may not have some particular parts that a kit builder provides and that was the case with this one.
Not exactly sure why but my first attempt, below, was to make a 30 meter version. It worked, I made one decent contact with it at 5 watts. But with all such projects there were some things I wasn't happy with. For one thing, 30 meters doesn't have a lot of activity. Also I didn't like the way I had cobbled together the BNC coax connector. QRPGuys use a male connector and then provide a PCboard mounting bracket to which it attaches. That then handles the counterpoise connection, etc. My first iteration included a make-do male connector which was quite elegant, if I do have to say so myself as chassis mount male BNC connectors were not in my junk box. When I switched to a chassis mount female connector I couldn't get a nut on it. And how to provide for the counterpoise connection was a quandary.
So today I set about to make a 20 meter version and do a better job of dealing with the counterpoise. As you can see I failed on the counterpoise thing. i totally forgot that I needed the shield of the coax to connect to counterpoise, even thought I made a provision of the counterpoise. Imagine my surprise when i set it up to find that the SWR was off the roof and that my hand capacitance on the x5105 had a huge influence on it! Then it hit me... no connection between the ground spike, 16' radial and the coax! Dumb, I know! The temporary solution? One of my little banana jacks to male BNC adaptors and a BNC Tee connector to the rescue!
Time to retest. When I re-deployed it and turned the radio on with great anticipation.... The SWR was about 5:1! Connecting and disconnecting the counterpoise made no difference. I even added an extension to the counterpoise making it 33' long. No change. At this point I remembered a statement I've read and made many times, "If the results are not what you expect, something is wrong." And it is usually something simple. But what? It's very hot and muggy here so I had the antenna in the front yard about 20 feet from the door and the x5105 inside on our bay-window-seat. As i stood at the door looking at the antenna contemplating this unexpected turn of events, there it was. I had failed to extend the whip! It was about 10 inches long when it should have been about 53 inches long. Easy fix and all WAS as I expected it.
Tuning around the 20 meter band, W1AW was about s3. My G90 showed about s5 connected to my EFHW base antenna in comparison. There were a few signals on but they were all weak and QSB was fairly bad. I called one but got no response. Than suddenly AD5US called CQ at 14.35mhz. He was running about s5. So anxiously I responded. It took a bit of work on his part but he stuck with me and we got the details across! Wow! Exciting! Time to take it down and relish a success! What fun! I love antennas. Now to do something with that crazy counterpoise connection! Which I did by adding a banana jack. The result is pictured above. I love antennas.
20 Meter Details
- Coil form is a 4 inch piece of PEX plumbing pipe
- Coil is 27 turns 34 gauge RCA speaker wire with an inductance of 8uh.
- Plugs in both ends are 3/4 inch LF PEX Bronze Plugs drilled and tapped for a 1/4-20 bolt
- The ground spike for is an 8 inch piece of 1/4 aluminum rod threaded 1/4-20 on one end and sharpened on the othe end.
- The whip is a 53 inch collapsible whip from the original Miracle Whip antenna. It collapses down to 10 inches including the 1/4-20 coupling I fabricated onto it.
- The counterpoise is 16 ft of 18 gauge stranded wire.
- Finished antenna weighs 5-1/4 ounces.
2020-07-08 This morning, in spite of the heat and humidity, yes even here in Wisconsin, I took my antenna outside, poked the spike in the ground connected the counterpoise and a 25' RG-174 feedline and double checked that it still worked! And it did, if you count good SWR at the frequency you want it! If you need a contact or even an RBN report to "know" it works, well it failed. But I'll give it a bit of grace, I came inside turned the power down to 5w on my ic7300 and did the same check with my EFHW antenna. I did get a couple RBN hits at 4db but that's it. So I'm not discouraged conceptually. I may be discouraged about the usefulness of this cute little thing!
Wanting to be scientific, I took every measurement I could think of. Set for 30 meters, the whip was 52" long. The coil consists of 50 turns and measures 16uh. The radial was 15' long. The SWR as reported on my x5105 and my nanoVNA was very close to 1:1.
Then I got to wondering what it might look like on 20 meters. I'll spare you of all the hoops I jumped through to electrically shorten the coil but I got it to resonate in the 20 meter band with 26 turns which measure 7.2uh. The whip was 53" long and I had the same 15 ft radial. But, the SWR was 1.7:1. And sadly, neither RBN or anyone else heard me, though RBN heard my ic7300 set to 5w and using the EFHW antenna.
I've been scratching my head about the 1.7:1 SWR on 20 meters. It occurred to me as I was typing this that the counterpoise length may be an issue. But I think I'm done with this until my QRPGuys kit arrives. I want to learn from them.
I learned some things about making this kind of antenna. Not so much about the wisdom of making this type of antenna! Such is the life of an antenna junkie!
2020-07-07 I have been mulling over this antenna now for a day. Once conclusion, even without having it in my hand, is that the QRPGuys one is worth the money! It's possible to make something similar but it is a lot of work. Even just taping the 1/4-20 hole in the end of the PEX Brass Plug can be a project, particularly if your tap is dull! And though I was "proud" of my solution to not having a chassis mount male BNC connector, in the end a BNC connector on the bottom without the mounting hardware and PC board that QRPGuys supplies it is not the simplest approach. having said that I have enjoyed the project and learned from it. And I may have a useful antenna!
All that said, pictured below is my "re-engineered" version. The changes are, 1) The coil is shortened to resonate in the 30 meter band with the whip almost fully extended. I say almost as i purposely shortened it about three inches so I'd have room to fine tune it in the field. 2) I moved the BNC connector from the bottom end of the coil form to the side. 3) I replaced the copper cap and BNC connector on the bottom with a secnd brass PEX plug and a 1/4-20 mounting coupling. My plan was to drill and tap a 1/4 hole so I could simply screw a 1/4-20 mounting bolt into it. But my tap was so dull I couldn't tat the hole! So I took the cheap and easy way and drilled the hole out so a 1/4-20 bolt will slip through it and tightened a coupling nut on the protruding bolt. I have a 1/4 sharpened aluminum stake which will thread into that coupling. So to erect the antenna, simply attach the spade and whip and poke the spade in the ground. Then attach the coax and counterpoise and you are on the air.
Does it work? That I can't say definitively. It has excellent SWR across the band. At resonance it shows near 1 to 1:1. I haven't had time to do an on-air test yet. So we'll have to wait and see.
Based on the experience I've gained with this project, I'll likely convert this coil to the 40 meter add-on coil for my 20m QRPGuys antenna when it comes. if I buy a new 1/4-20 tap!
2020-07-06 Yesterday I ordered QRPGuys new DS1 short portable antenna. Can't wait to get it! In fact after downloading and looking at their instruction manual I decided to do a take off on it. I have a 55 inch collapsible whip that is part of my Pac-12 antenna. I have lot's of RCA 24 gauge speaker wire. All I needed was a piece of 3/4 inch PEX plumbing pipe, a 3/4 inch brass stopper or plug and a 3/4 inch copper cap. So i went to the hardware store and about $8 poorer had them! The semi-finished result is shown in the three photos below.
I knew mine wouldn't be exactly as theirs so I wound as much of one strand of the speaker wire as I could on the 8 inch piece of 3/4 PEX I had cut off. It took some fiddling and my drill press to get the 1/4-20 bolt in the brass stopper but I finally got it. Then I realized didn't have a chassis mount male BNC connector in the house. Checking online I found that they are actually kind of rare. So I dug through my drawer of adapters again and came up with one with a UHF female on one end and a male BNC on the other end. And I happened to have a couple of nuts that fit the UHF end from some feed-through connectors I wasn't using. It was quite a chore to drill and file a hole in the end of the copper cap but I finally got it and with more fiddling got the connector mounted.
Knowing I would have to experiment to find the number of turns needed for 20, 30 and 40 meters I decided to use the technique described in my page on building the KW4JM vertical. So I wound the coil, connected a pigtail to the BNC UHF adapter with a banana plug and put straight pins in every 20th turn of the coil. Now to test it!
My wife is at a ladies meeting at church tonight so I took it to the living room and mounted it in my test jig, the gap between the cushions on the sofa! They press together tightly so held it firmly upright! I also clipped a 12 foot wire onto the screw that holds the copper cap on the bottom and tossed it across the floor. Then screwed the extended whip on the top, grabbed my nanoVNA, clipped the pigtail to the pin in the bottom turn and turned on the nanoVNA.
It was resonant with a very low SWR at 7.6mhz! Going up to each of the 20 turn taps it was also resonant at 8.4, 9.5, 11.6, 14.8 and 15.6 mhz. It showed a second resonant point on the top tap of 21mhz! Those measurements are all with the whip fully extended. Clearly it needs more turns or a longer whip for 40 meters. The whip can be adjusted and the tap points can be changed to cover precise band frequencies, including up to ten meters, I'm guessing. I also noticed that moving around with the nanoVNA changed the SWR some and maybe the resonant frequencies. That's not surprising as the counterpoise was lying on the floor about four feet above ground level over our crawl space.
But that was enough to make me get my xiegu x5105 and connect it. It's SWR sweep function verified those numbers! Well, it was connected so I had to see if it had ears! I could hear a few signals on 40 meters but it was way too far off for that. I changed to 30 meters and played with the tap location until I had a near 1:1 SWR at 10.100mhz. Tuning around I heard K2M, one of the 13 Colonies stations calling CQ at 10.113. Dare I answer? I did! It took a couple tries but he heard me and gave me the obligatory contest 599! He was about 539. I came into the shack and turned on my IC7300 connected to my EFHW inverted vee and he was about 559 there.
I'm happy and my wife just drove in! Time to destroy the evidence and return the living room to its primary purpose. I love antennas!