antenna – Page 7 – WB3GCK QRP Amateur Radio

The Doublet – Revisiting a Classic Antenna

I was recently going through my stash of portable wire antennas and came across one of my old favorites—the doublet. I don’t see too many references to this type of antenna these days, but the doublet provides a great portable antenna option.

What is it?

The doublet, simply put, is just a dipole. The difference is that you feed it with a balanced feeder, rather than coax.

Hams have been using doublets for many years. The earliest reference I could find in the ARRL QST archives was from September of 1929.[1] In this write-up, Clair Foster W6HM describes a 40M doublet fed with twisted wire lamp cord used for receiving.

Advantages of the Doublet

The balanced feeder provides some advantages. Depending on how it’s constructed, it can withstand higher SWR with lower losses than coax. Because of the low losses at high SWR, you can use the doublet as a multi-band antenna.

As a portable antenna, it’s hard to beat, especially as an inverted vee. Use a tree branch or telescopic pole to hoist up the center, tie off the ends, and you’re in business. [2]

Some Disadvantages

This multi-band capability comes with some disadvantages, though. Fortunately, none of them are insurmountable.

First, you’ll need a transmatch that can handle balanced feedlines. Typical commercially-available feedlines have either 300 or 450-ohm characteristic impedances. For open-wire feedlines, the impedance can sometimes be 600 ohms or more.

I’ve had success using a homebrew Z-match tuner. Companies like Pacific Antenna and QRP Guys sell Z-match tuner kits that will handle balanced lines. They offer tuners that are small and light enough for QRP-portable use.

You can also use a balun to transition from the balanced feedline to 50-ohm coax. While this isn’t an optimum approach, it works. Textbooks often recommend a 4:1 balun, and that’s a good starting point. If you go this route, I recommend keeping the coax as short as practical. If you run into matching problems on some bands, try another balun ratio (e.g., 1:1), or change the length of your feedline.

The second drawback is that you need to be careful of how you route balanced lines. You need to avoid getting it too close to metal or laying it on the ground. Both can upset the line’s balance. This can cause it to radiate or introduce losses. If you have excess line, don’t coil it up. Operating outdoors, I found these restrictions aren’t very difficult to work around; you just need to be mindful of them.

Construction

Building the doublet is pretty simple. Many folks suggest making the doublet a half-wavelength long at the lowest band you intend to use. I’ve built one for 40M and it worked well on 40M and higher. Depending on your tuner, it may also be usable on the next lower band.

L. B. Cebik W4RNL (SK) popularized the 44-foot doublet for 40M-10M. According to Cebik’s analysis, this length produces a more consistent radiation pattern across the bands.

Doublet diagram. One rule-of-thumb suggests avoiding combinations of feedline electrical length (L1) and one leg of the radiator (L2) that are odd multiples of an eighth-wavelength.

Regardless of the size of the doublet, you should try to avoid certain feedline lengths. One rule-of-thumb suggests avoiding combinations of feedline electrical length plus one leg of the radiator that are odd multiples of an eighth-wavelength. [3] If you run into matching problems, you can try adjusting the length of either the feedline or the radiating elements.

Feedline Options

You have several options here:

Commercial 450-ohm or 300-ohm ladder line. These are commonly available, and they work great.
Homebrew open-wire feeders. This is the most efficient option. If you do some Internet searching, you’re likely to find lots of ways to build open-wire feeders. SOTABEAMS has a great example on their website.
TV twin-lead. I’ve used the cheap, brown stuff quite a bit for portable doublets. Unfortunately, it’s nearly impossible to find these days. If you come across it somewhere, stock up!
Lamp cord or speaker wire. This works and I’ve seen folks use it for portable antennas. However, it can be lossy, compared to window line or open-wire feeders.

More Later

If you want more technical details on this antenna, information abounds on the Internet and in antenna books. In particular, Cebik wrote some great articles that are worth searching for.

In a future post, I’ll cover some practical examples that I have come across or used in the field.

73, Craig WB3GCK

References:
[1] Foster, C. W6HM (1929, September). Experimenters’ Corner: The “Doublet” for Receiving. QST, p. 39.
[2] DeMaw, D. W1FB (1991). Technical Bits & Pieces. In W1FB’s QRP Notebook (2nd Ed., pp. 157–161). Newington, CT: QST.
[3] Heys, John D., G3BDQ (1989). Center-fed antennas using tuned feedlines. In Practical Wire Antennas. Bedford, UK: Radio Society of Great Britain, p 7.

Dollar Store Special

[NOTE: This is an updated version of an old article from my QSL.NET website. In the interest of full disclosure: My local dollar store no longer sells the speaker wire I used. While it’ll probably cost you a few more bucks to build one, it’ll still be a cheap antenna. Although the original article has been on my website for 15 years, I still get the occasional email from folks who have built one.]

I love rummaging through our local dollar store. One of the biggest bargains in our local dollar store is speaker wire. You can get 50 feet of two-conductor speaker wire for a buck. Not too shabby. I always keep a bunch of the stuff on hand for antenna experimentation.

Diagram of the Dollar Store Special. See the text for other counterpoise options. — Diagram of the Dollar Store Special. See the text for other counterpoise/radial options.

Using a single 50-foot roll of dollar store speaker wire, I made a simple 50-foot random wire antenna with counterpoise wires to cover the 40, 30 and 20-meter bands. I stashed the whole kit in a zip-lock sandwich bag and always keep it on hand as a backup antenna system whenever I operate in the field. With a simple antenna tuner of some sort, this will get you on the air in a pinch, should your primary antenna fail.

This is the 20 AWG speaker wire I used. Sadly, my local dollar store no longer carries it. I wish I had bought a ton of it while it was available. — This is the 20 AWG speaker wire I used. Sadly, my local dollar store no longer carries it. I wish I had stocked up while it was available.

Here’s all you have to do:

Separate the conductors so that you now have two separate 50-foot wires.
For the radiator, take one of the 50-foot wires and crimp a small ring lug to one end—right over the insulation. This gives you someplace to tie a line to hoist it up. On the other end, just strip off a half-inch or so of the insulation. You can leave it bare or add whatever kind of connector you want; whatever works best with your tuner.
For the counterpoise wires, take the remaining 50-foot wire and cut it so that you have a 33-foot wire and a 17-foot wire. If you only want to work 40 and 20 meters, you can stop right here. You now have counterpoise wires for both of these bands.
To provide a counterpoise wire for 30 meters, take the 33-foot wire from Step #3 and cut it so that you now have a 23-foot wire and a 10-foot wire. Strip off about 1/2-inch of insulation from one end of the 23-foot wire. Install a quick-disconnect connector of some sort on the other end, so that you can join the 23-foot and 10-foot wire sections together. The idea here is that, with the two wires connected, you have a 33-foot counterpoise wire for 40 meters. With the two sections separated, you now have a 23-foot counterpoise wire for 30 meters.

I used a ring terminal to terminate the 50-foot wire. Note that the terminal is crimped over the wire's insulation. The metal ring terminal is electrically-isolated from the antenna wire. — I used a ring terminal to terminate the 50-foot wire. Note that the terminal is crimped over the wire’s insulation. The metal ring terminal is electrically-isolated from the antenna wire.

This is the quick-disconnect connector I used on the original version of the counterpoise wire. I used some Goop® adhesive to provide some strain relief.

[Note: If you only plan to operate with the radials laying on the ground, cutting them to resonance isn’t too important. You can simplify things a bit by going with just the 33 and 16-foot wires. I think two 25-foot wires would be sufficient, as well. Three 16.6-ft radials is another option to consider. Feel free to experiment here and see what works for you.]

In operation, just hoist one end of the 50-foot radiator up in a tree or other suitable support. Connect the other end to the hot side of your tuner. Connect the 33-foot and 17-foot counterpoise wires to the ground connection on your tuner and lay them out on the ground. When you want to work 30 meters, just disconnect the quick-disconnect on the longer counterpoise wire. Pretty simple, eh? Any type of simple L-tuner should work fine for this.

Please note that I wouldn’t recommend using this wire for a permanent outdoor antenna. It’s not suited for that kind of use. But for temporary outdoor use, it’ll do just fine. Besides, if the wire goes bad, you can always replace the whole thing for a dollar!

73, Craig WB3GCK

Amazing GOOP for Ham Radio

You have probably seen Amazing GOOP® in your local hardware store. This product with the funny-sounding name has been around for decades. I’ve been using it for ham radio applications for the past 25 years or so.

I recently did some extensive research on Amazing GOOP. (Full disclosure: OK. I lied. My “extensive research” merely consisted of a quick Google search and reading a Wikipedia article.) Back in 1972, a senior executive in the aerospace industry created a product called “Shoe GOO®.” Shoe GOO was intended to repair rubber-soled shoes. In fact, I first used it many years ago to repair a pair of rubber fishing waders. The original Shoe GOO is still produced by Eclectic Products. They also produce a wide variety of waterproof, flexible adhesives for a host of applications and environments. The Amazing GOOP® product line is what I’ve been using for ham radio applications.

Here are some of the uses I’ve found for it:

Sealing portable antenna connections. This was my original use for Amazing GOOP. After soldering the connections between the feedline and dipole elements, I seal them up with Amazing GOOP. I’ve never had any corrosion problems like you can run into with RTV.

This is the center connector of the doublet that I use for my "Up and Outer" antenna. I used Amazing GOOP to seal the soldered connections and help anchor the wires in place. This particular antenna was built about 15 years ago and is still holding up well. — This is the center connector of the doublet that I use for my “Up and Outer” antenna. I used Amazing GOOP to seal the soldered connections and help anchor the wires in place. This particular antenna was built about 15 years ago and is still holding up well.

Wire end loops. Instead of end insulators for my portable wire antennas, I just form small loops. I twist the wire to form a loop and use Amazing GOOP to hold the wire twists in place. (This works very well for my lightweight portable wire antennas but I would use end insulators for permanent antennas.)

End loop on one of my (many) wire antennas for portable use. I attach my throwing line directly to the loop, foregoing an insulator. With smaller diameter wire, I sometimes put some shrink wrap over the GOOP.

Powerpole® connectors. I’m a “belt and suspenders” kind of guy. So, I crimp and solder my Powerpole connectors. After I assemble and test them, I apply some Amazing GOOP where the wires enter the connector housing. This provides strain relief and makes them very rugged. I also place a dab of GOOP on both ends of the roll pin. This keeps them from popping out in the field.

Miniature audio connectors. I’m hard on the little 1/8″ audio plugs I use on my CW keys. So, after soldering and testing them, I put some GOOP on the connections before screwing on the plastic housing. Then, I put some GOOP on the wires where they enter the connector to add strain relief. I also apply GOOP to spade/ring lugs after they are crimped and soldered.

A 3.5mm plug and Anderson Powerpole connector after I have applied GOOP as a strain relief. Sure, they look a bit ugly but these connectors are pretty much bomb-proof. These items have seen heavy use in the field over the past 3 or 4 years.

My CW Clipboard. I used GOOP to attach the steel washers to the clipboards I use in the field. The washers are how I attach the magnetic bases of my portable paddles and straight key to the clipboard.

I used GOOP to attach the steel washers to the clipboards I use in the field. The washers are used to attach the magnet bases of my portable paddles and straight key. — I used GOOP to attach the steel washers to the clipboards I use in the field. The washers are used to attach the magnetic bases of my portable paddles and straight key.

My rainspout antenna. I use a liberal amount of GOOP to seal the connection to my trusty rainspout antenna. GOOP holds up well to the continuous exposure to the elements.

Hopefully, the pictures will clarify my descriptions.

If I can find it, I use one of the GOOP varieties intended for outdoor use for my rainspout and portable wire antennas. Right now, I’m using Amazing GOOP Max. Regular old household variety of Amazing GOOP is fine for most uses, though. For all applications, I like to let the GOOP cure overnight before use.

A few disclaimers are in order:

This stuff is permanent. Be sure whatever you’re using it on works before sealing it up with GOOP.
This stuff works for me, as described. I don’t know what you’re using it for or how you’re using it, so your results may vary.
I have absolutely no financial interests in this product. I’m just a satisfied consumer.

So, that’s it. I hope you found it useful.

73, Craig WB3GCK

Reference Links:

Portable Antenna Ground Mount

Here’s yet another quick little hack. I raided my junk box to cobble together a ground mount for my portable vertical. While this solved a couple of specific issues I had, it might only be of interest to a few of you folks out there.

I often support my 19-foot vertical with one of those inexpensive fishing poles from eBay. (I paid around $10 USD for my 7.2M pole.) I had been using a simple method for ground mounting. I shove a screwdriver in the ground, take the bottom cap off of the pole, and place the pole over the screwdriver. Voila!

While the screwdriver technique is a useful way to support my vertical, there are two issues with it. First, the screwdriver method places the bottom of the pole in direct contact with the dirt. This can gunk up the threads on the bottom of the pole. (Ask me how I know.) Next, since my homebrew 19-foot vertical takes up the entire length of the pole, the matchbox ends up too close to the ground for my liking. I made a simple little gizmo that addresses both of these issues.

Antenna ground mount in use with my 19-foot vertical

From some scraps and junk I had on hand, I used the following:

5 inches of 1/2-inch PVC pipe
Approx 6 inches of 3/4-inch PVC pipe
3/4″ x 1/2″ PVC reducer
(2) 3/4″ PVC end caps (with flat ends)
Stainless steel toilet float rod (1/4″ diameter x 10″ long. 1/4-20 threads on each end of the rod)
(2) 1/4-20 nuts
1/4″ lock washer
Duct tape (optional, for a better fit between the 1/2-inch PVC and the bottom of the pole)
A dab of Lock-Tite thread locker

[Note: The PVC pipe I used works with the particular pole I use. If the bottom of your pole has a different inside diameter, you might need to use a different size pipe.]

I joined the two pieces of PVC pipe together with the PVC reducer. Then I glued the two end caps together, back-to-back. Next, I drilled a 1/4-inch hole through the center of the two end caps. I fastened the stainless steel rod with two nuts and a lock washer. I also used a dab of thread locker for good measure. I had to do some sanding on the 3/4-inch pipe to allow the end caps to slide on and off easier. At this point, you might want to put a layer or two of duct tape on the 1/2-inch pipe for a snug fit inside the pole.

The two main assemblies of the antenna ground mount

Stainless steel rod bolted through the two back-to-back PVC end caps

In the field, I place the end cap assembly on the 3/4-inch pipe and shove the rod into the ground. The pole goes over the 1/2-inch PVC pipe, of course. This places the bottom of the pole about 8 inches above the ground. With lightweight poles, guying is unnecessary. For travel, I flip the end cap assembly around so that the bolt stores inside the pipe. This prevents poking holes in my backpack or bicycle pannier bags.

Antenna ground mount configured for travel. The stainless steel rod is stored safely inside the PVC pipe assembly.

The threads on the end of the stainless steel rod pick up some dirt in use. It’s not a major problem but I might cut the rod off just above the threads. I haven’t decided yet.

That’s all there is to it. I’m hoping the accompanying pictures clarify how I built it.

72, Craig WB3GCK

(Almost) Gone with the Wind

I was long overdue for some outside QRP-portable operating. Although we had some heavy rain overnight, it looked like it would be gone by mid-day. So, yesterday I headed out to nearby Towpath Park to take advantage of some milder temperatures.

I had a couple of objectives for today. First, I was hoping to make some QRP to the Field (QTTF) contest QSOs. I also wanted to test a new ground mount I put together for my cheap eBay telescopic pole.

When I got to the park, the rain had stopped. Unfortunately, last night’s heavy rains left the park a bit on the swampy side. That, coupled with some gusting winds, would make for an interesting test of my new ground mount. I was a bit leary but went ahead and set up the antenna anyway.

As I was setting up, a Pennsylvania Fish & Boat Commission officer got out of his car and walked up the path towards me. While it’s true that I was using a fishing rod (for my antenna), I was about 50 yards away from the river! As he approached, I told him that I was a ham radio operator. He said, “I know.” As it turns out, he was also a ham and had spotted my callsign on my license plate. He was just stopping by to say hello. As we talked a bit, we also found out that we also had some former employers and co-workers in common. Small world!

As we were chatting, the gusting wind blew my antenna over to a 45-degree angle. The ground was too soggy to hold my antenna mount. It never fell over, so I gave my antenna mount a passing grade for this extreme test. Unfortunately, in my rush to straighten out the antenna, I never took a picture. Pity. It put that tower in Pisa to shame. I moved the antenna a few feet to a somewhat drier spot and that did the trick. I’ll show a closer look at my ground mount in a future post.

My vertical ground-mounted in the soggy ground. This picture was taken while Mother Nature was on a brief break from trying to blow my antenna over.

When I finally got on the air, I found the bands dominated by Michigan and Ontario QSO Party stations. I didn’t hear any QTTF stations at all. So, I spent some time handing out points to some of the QSO Party stations.

After a while, I had had enough of the wind and packed up my gear. As I was packing up, the sun came out and the wind subsided. Go figure!

72, Craig WB3GCK

A Slippery Sloper

I spent the weekend with my grandkids out near Harrisburg, Pennsylvania. My XYL and I watched the kids while my daughter and son-in-law took a little anniversary get-away. Of course, there was some time for ham radio, too.

By the time I got around to setting up an antenna on Friday, it was dark and the temperature was well below freezing. Oh yeah, there was about 4 inches of snow in the backyard to boot. So, I was in need of a real quick and dirty antenna.

I decided to toss a 29.5-foot wire out of a 2nd-floor window. I then went out to the backyard to secure the other end of the wire. I used some shock cord to tie it off to the top of a 6-foot wooden fence. My total time outside in the cold and dark was about a minute.

Back inside, I fed the wire through a homebrew 9:1 UNUN with 18 feet of RG-8X coax. This particular wire and UNUN served me well as a vertical during many National Parks on the Air (NPOTA) activations. I commandeered one end of the dining room table for my KX3 and powered up for a test. The KX3 was able to get a match on 80M through 10M. Then, I went back to hanging out with the kids.

My impromptu sloper's feedpoint. The wire from the 9:1 UNUN is just pinched in the window. — My impromptu sloper’s feedpoint. The wire from the 9:1 UNUN is just pinched in the window.

By now I’m sure you’re wondering where the “slippery” part of the this post’s title comes in. Well, the next morning I looked out the window and saw that some ice had accumulated on the wire. The wire was dragged through the snow during installation and it froze overnight. The KX3 didn’t mind at all; the internal tuner loaded up the frozen wire without problems.

I got on the air for a bit on Saturday afternoon. On the air, my impromptu antenna far exceeded my low expectations. I started off working N2CX on 40M. Joe was activating a park on the Eastern Shore of Maryland. I followed that up with a nice two-way QRP chat with WK2J in North Carolina.

I worked a couple of QRPers in the FYBO contest sponsored by the Arizona ScQRPions. I also worked some Minnesota and Vermont QSO Party contesters. An assortment of SKCC, POTA, and SOTA stations also made it into my log over the weekend. The best “DX” of the weekend was VE7ST in the British Columbia QSO Party on 20M.

I didn’t expect much from this quickie antenna configuration but I was happy with the way it got out. Plus, set up/tear-down was easy and only took a few minutes. This sloper will likely be my go-to antenna for future visits to see the Harrisburg grandkids.

72, Craig WB3GCK

Revisiting the Rybakov 806 Vertical

Some recent Internet discussion got me thinking about the Rybakov 806 Vertical antenna. This easy-to-build antenna has served me well over the years. So, I went back and revisited some of the ways I’ve used it.

What the heck is a Rybakov anyway?

The Rybakov 806 Vertical appears to be the brainchild of Enrico IV3SBE from Italy (now 5Z4ES in Kenya). The term, Rybakov, is Russian for “fisherman.” That’s right… It’s an antenna with a Russian name designed by an Italian who lives in Africa — truly an international creation. From what I could glean from exhaustive Internet searches, this design dates back to the mid to late 2000s. I found numerous references to it from 2009.

The classic Rybakov configuration is a 7.6m or 8m (~25 or 26 feet) wire fed through a 4:1 UNUN. The length isn’t critical, as long as you avoid resonance on the bands of interest. It’s often supported by a telescopic fishing pole (hence, the name, “Rybakov”). Being a non-resonant antenna, you need to use an antenna tuner to make it work. You also need to use radials or some other type of ground.

The antenna can cover 80M through 6M (the “806” part of its name, I suppose). The band coverage depends on the wire length used and the capabilities of your tuner. With a 7.6M wire, you can cover 40M and up without problems. For 80M coverage, plan on using a longer radiator.

The only thing you need to build is the 4:1 UNUN. The IW7EHC website provides detailed instructions for building one. Beyond that, you just need to cut some wire to length for the radiator and radials. Easy peasy!

My experience with the Rybakov

I had been using this type of antenna before I even knew it had a name. Rick KC8AON had a version of this type of antenna he called, “The Untenna.” That’s where I found it.

My first experiment with it was in a “stationary mobile” setup. I rigged up a 26-foot vertical wire and grounded the UNUN to the body of my truck. My Z-817 tuner was able to load it up with no difficulty. I had no problem making contacts and I liked the multi-band coverage.

I next used the Rybakov at a Boschveldt QRP Club Field Day. I set up a 26-foot ground-mounted vertical and used about six 16-foot radials with it. Again, the performance seemed decent and I remember doing well on 10M that year. The only shortcoming was that it wouldn’t load up on 80M.

The next year, I solved the 80M problem by using a 50-foot wire in an inverted L configuration. For the ground, I used six 16-foot radials and two 33-foot radials. This configuration gave me full coverage from 80M to 10M and it worked great. This antenna configuration became my “go to” Field Day for several years. In later years, I used a 53-foot radiator re-purposed from another antenna project.

My typical implementation of the Rybakov 806 antenna. A length of 25 to 27 feet does well from 40M and up. I go with a 53-foot radiator for 80M coverage. — My typical implementation of the Rybakov 806 antenna. A length of 25 to 27 feet does well from 40M and up. I go with a 50 or 53-foot radiator for 80M coverage.

I used another version of the Rybakov with the pop-up camper that I used to own. I strapped a 31-foot Jackite pole to the camper and used it to support a 27-foot wire. I grounded the UNUN to the body of the camper. This antenna worked great on 40M to 6M and, best of all, I didn’t need to go outside at night to change bands. I used this antenna with good results for several years until I sold the camper.

I also built a Rybakov that I use as a backup antenna in the field. I built a small 4:1 UNUN that I use with a 25-foot radiator and a 25-foot radial. The antenna, along with a short length of coax, is easy to carry in my pack.

The bottom line (for me, at least)

I’ve had good luck with the Rybakov Vertical over the years. Is it the best antenna? Nope. Purists will argue about UNUN, ground, and coax mismatch losses. Yep, there are those. Yet, its simplicity and “no gap” band coverage are hard to beat. It’s easy to deploy in the field and it really does work.

If you’re in the market for a simple portable antenna project, the Rybakov 806 is an easy one.

[Update 4/3/2019: I’ve always wondered about the rationale behind the 25-foot radiator often used with the Rybakov antenna. An article in QST [1] by Joe Reisert W1JR shed some light on that for me. Joe’s article discusses the 3/8-wave vertical antenna. According to the article, the 3/8-wave antenna has a low take-off angle and its 200-ohm feedpoint is easily matched with a 4:1 transformer. Its higher radiation impedance provides good performance with just four 1/4-wave radials. For 20M, a 3/8-wave radiator is about 25-ft. Similarly, for 40M, it would be 50-feet. So, my guess is that’s the concept behind the Rybakov design.]

73, Craig WB3GCK

Reference Links:

Reference Articles:

Reisert, Joe W1JR, “The 3/8-Wavelength Vertical — A Hidden Gem,” QST, April 2019, pp. 44-47.

MFJ-1820T Whip

I made an impulse buy this week. After reading an old Elecraft mailing list post from Wayne Burdick N6KR where he made a strong recommendation, I ordered an MFJ-1820T whip antenna. I need another portable antenna like I need a hole in the head but I figured it might be fun to give this little whip antenna a try.

If you aren’t familiar with it, the MFJ-1820T is a 4-foot, telescopic, loaded whip for the 20M band. It collapses down to a tiny 10-inches. It will handle 25 watts but my whip will never see that much power. It sells for around $30 (U.S.). Wayne recommended using at least one 13-foot radial with it. I went with two 13-foot radials made from some cheap speaker wire I had on hand.

This morning, while operating from a local park, I connected the whip to my KX3 with a BNC right angle adapter. I connected my radials to one of the knurled nuts on the KX3 with an alligator clip. To keep the whip from swiveling, I used a small, plastic spring clamp.

The MFJ-1820T whip connected to my KX3. The plastic spring clamp was used to stabilize the whip. You can also see the alligator clip for the radials.

The KX3’s internal tuner loaded up the whip with no problems. I heard W8SVC calling CQ from Michigan and gave him a call with 5 watts. He got my callsign on the first call but he wasn’t sure he had copied it correctly. I upped my power to 10 watts (gasp!) and called again. He gave me a 559 and we exchanged our basic information. Unfortunately, I lost him when the band faded.

Moving up to the 20M QRP calling frequency, I called CQ a couple of times. AA8WQ (QRP at 5W) responded from Ohio and gave me a 569 report. Again, we were able to exchange our basic info before I lost him completely.

Frankly, I wasn’t really expected much from a 4-foot whip but I was surprised that I was able to make two contacts this morning. It certainly isn’t the best antenna for 20M but, when the band is in good shape and you need something that sets up in an instant, the MFJ-1820T is certainly a usable antenna. I’ll probably be carrying the MFJ-1820T in the field as a backup antenna.

72, Craig WB3GCK

Quick End Insulator

Here’s another quick hack that took longer to write up than to actually build. I recently built a portable vertical antenna using some #26 Stealth Wire. I needed some sort of end insulator that would facilitate pruning the wire to resonance. Here’s my quick and dirty solution.

Using scissors, I cut a piece of plastic from a used up gift card I had in my wallet. The piece I cut is about 1 inch by 0.5 inches. Then, I drilled 3 holes in it. Two of the holes were just slightly larger than the #26 Stealth Wire (The Wireman Product #534). These holes hold the wire in place. I drilled a larger hole for attaching to a light line or, in my case, a small clip at the top of my telescopic pole. I also rounded off the corners a bit.

The end insulator and the gift card from which it was cut. (Disclaimer: I have no financial interest in the Wawa company, except that I have consumed untold quantities of their coffee over the years.)

So far, this is working out well for my portable vertical antenna. If I was using heavier gauge wire, I would definitely use something more substantial than the gift card. I also wouldn’t use it for a permanent installation. But for an ultralight antenna that is only used for portable excursions, it’s perfect.

If I ever need to replace it, I have enough of the original gift card left to make a bunch more!

72, Craig WB3GCK

Antenna Testing in the Park

Today was fun. I had a little time this afternoon, so I headed out to a nearby park to test a new antenna and ended up making a couple of interesting contacts.

I spent a couple of hours in Towpath Park, a nice little park along the Schuylkill River. It’s usually not very crowded, so it’s been one of my favorite places to test new antennas. Today, I was doing some initial testing and tuning on a Tri-Band Vertical from QRPGuys.

My "outdoor shack" overlooking the Schuylkill River — My “outdoor shack” overlooking the Schuylkill River

I set up the antenna and spent some time taking SWR plots on the antenna. The 20 and 30 meter bands were great without any adjustments. The 40M band is resonating too low, so I need to do some tweaking on one of the loading coils. I’ll do a separate post on this antenna when it’s finished.

My antenna today. My $9 telescopic pole from eBay is mounted on a screwdriver shoved in the ground.

I put the antenna analyzer away and got out my KX3. I made a few “CQ SKCC” calls on 20M and was answered by CT7AFN in Portugal. There was some QSB but we managed to exchange SKCC numbers. A few minutes later, I got a call from another station in Portugal, CT1BQH. Wow! Back-to-back Portuguese SKCC stations. This new antenna definitely has some mojo.

I worked stations in Texas and Florida before wrapping up. I neglected to bring gloves today and the wind chill was taking a toll on my fingers. I packed up my equipment and headed out happy with the contacts I made in a short period of time.

I have a little work to do on this new antenna but so far it looks like a keeper.

72, Craig WB3GCK