Tag Archives: Doublets

Field Activation Antenna Challenge #1: Military Fixture Homemade Multi-band Doublet!

I mentioned in a previous post that my personal “Activation Challenge” for 2022 was “to build a new antenna each month and deploy it at least once that month during a field activation.”

On Thursday, January 27, 2022 I took my first antenna–the military fixture doublet–to Lake Norman State Park for a Parks On The Air activation!

For more information about this doublet and how it was constructed, check out this post.

Lake Norman State Park (K-2740)

I picked Lake Norman knowing that it had numerous spots to set up a doublet.

Unlike an end-fed wire antenna, doublets need a little more clear space to deploy both legs; the idea is to avoid as many low tree branches and other obstacles as possible.

Many (if not most) of the operators I know who regularly deploy field doublets actually use a telescoping mast for the center support to make the whole process easier.  I didn’t take either of my fiberglass masts on this outing because, frankly, the winding fixture on this doublet acts as the center insulator, and is “heavy” compared to most of my field antennas. Continue reading Field Activation Antenna Challenge #1: Military Fixture Homemade Multi-band Doublet!

Portable Doublet-Building Party & my 2022 Activation Challenge!

This past weekend, my good friend Vlado (N3CZ) and his wife came over to the QTH for the afternoon. It’s been a while since our families got together, so it was fantastic to hang with them.

I’ve been trying to tempt Vlado to do more field activations–we’ve done a number together in the past and it has always been loads of fun. Thing is, both of us have pretty active family/work lives, so it’s challenging to make schedules work out.

Nonetheless, our 2022 goal is to do at least one activation per month as a team!


If you recall, a couple months ago, I posted an activation report and video using my buddy Eric’s 40-10 meter doublet. I called it a “stolen” antenna because it had been on loan to me for so long, I think Eric forgot it even existed.

Exhibit A: The stolen antenna.

Eric’s doublet was build around a Hughes Aircraft MK-911 Dipole Fixture that was designed and manufactured for the US Military and appears to have been part of the PRC-74 manpack radio-set.

I had assumed Eric found this as a one-off at a military surplus sale. Turns out Eric (and a few readers) made me aware that it was available at Fair Radio Sales in Ohio for $10.

Image of the MK-911 from Fair Radio’s product catalog.

In fact, here’s a link to the MK-911.

I decided to buy two of them: one for me, and one for Vlado. The temptation was strong to purchase a few more just for the 30 feet of 72-ohm military-surplus twinlead, however I understand that there’s a limited inventory and wanted others to be able to purchase this gem.

I was also thinking this antenna fixture would pair beautifully with Vlado’s Yugoslavian RUP-15/PD-8 manpack or even his IC-703 Plus.

Doublet time!

While our wives were catching up, Vlado and I made our way to the storage shed and opened my antenna parts boxes.

I did a little digging and found what I was looking for: some wire I purchased at a thrift store many years ago.

This wire has a black jacket that’s quite slick. Guessing it might be 20 gauge and might even be teflon coated. It was ideal for antennas and eyeing it, I thought there might be enough for two doublets.

For a Norcal-inspired doublet–which covers 40-10–we would need two 22′ legs. I decided (prior to cutting) that I wanted our doublets to go as low as 60 meters (5,332 kHz) and cover everything above. 60 meters is such a useful band. Thing is, I hadn’t done research into suggested leg lengths in advance.

We decided to pick a longer non-resonant length and just give it a go. If it worked, great–if not, we’d cut them down to 22 feet and be happy with 40M and up.

We cut the legs to 31 feet, so there’d be a total of 62 feet of wire in each doublet. Many thanks to my daughter Geneva (K4TLI) for helping stretch, measure, and cut the antenna wire with us!

Assembling the antennas was incredibly simple as there are built-in binding posts attached to the twin lead on the winding fixture.

Vlado and I both decided to use the winder as the center-insulator of the antenna. This is actually how this military fixture was designed to be used. The negative, of course, is that the center insulator is relatively heavy. This isn’t a problem for me at all since I use super strong arborists throw lines to deploy my antennas.

From WD8RIF’s website.

Eric (WD8RIF), by the way,  actually detached the twin lead from the fixture and posts on his unit and built a new center-insulator from a discarded 35mm film canister (see photo above). He wanted to keep the weight down so he could support the center of the doublet on his fiberglass masts.

Testing QRV!

I had planned to hook up the doublets to my RigExpert antenna analyzer, then I realized it was essentially an unnecessary step.

The big question for me was, “Will my Elecraft KX2 find impedance matches on 60M and above?”

Vlado and I connected the doublet to the KX2 and tuned to 5,332 kHz. After confirming the frequency was clear, I pressed the ATU button. The KX2’s internal ATU churned for a couple of seconds and confirmed a 1.4:1 match.


We checked all of the bands above 60M and the matches were even better.

Standing in the middle of my driveway, I asked Vlado to load the POTA.app website and look for CW spots.

I couldn’t put the antenna away without chasing some parks!

We then proceeded to work about three stations on the air in CW with 5 watts. All of them gave us 599 reports!

Vlado chasing a POTA activator.

It was serious fun.

As I mentioned to Vlado, it might have been the first time I’ve ever used an HF “Handy Talky” with a doublet antenna!

In the end, we both walked away with two effective military-grade field doublets. A perfect antenna for our monthly “Team Baklava” activations.

2022 Activation Challenge

Last year, my personal challenge was to validate all of my park and summit activations with 5 watts or less.

Since I’m very much a QRPer and primarily a CW op these days, this turned out to be low-hanging fruit; lower than I would have guessed in this part of the solar cycle.

For 2022, I plan to continue the 2021 five watt challenge and add another layer…

This year, my challenge will be to build a new antenna each month and deploy it at least once during that month during a field activation. 

The MK-911 doublet will count as January’s antenna.

I’m going to allow myself to build these antennas from anything and everything. I might even cannibalize a few of my broken/worn-out antennas.

I do want to keep these projects quite simple and easy for anyone to build in one sitting. I’ve gotten so much positive feedback from the super-simple speaker wire antenna I built in the field last year no doubt because it was so easy to build and super cheap.

I already have enough ideas to take me through the summer months, but I plan on dusting off some of my antenna books for more ideas!

With that in mind, I welcome your input! If you have a suggestion, feel free to comment!

POTA Field Report: Pairing the Elecraft KX2 with a stolen doublet at Table Rock Fish Hatchery!

Someone asked me recently which activity I prefer more: Summits on the Air (SOTA) or Parks On The Air (POTA)?

Truth is, I like both.

I like SOTA because I love hiking and playing radio on the summits of some pretty impressive mountains.  I’m often treated to amazing views and the DX can be spectacular. I love the sense of accomplishment when the activation goes well and I’m back home later feeling a bit tired from a long hike. Good stuff!

I like POTA because it’s incredibly accessible (thus fits in my tight schedule easily). Many of the parks have great hiking trails, and there’s almost always a picnic table available making set up so much easier.  Here in western North Carolina it’s almost a given that park picnic tables are surrounded by large trees and have a reasonable amount of space, thus POTA sites can be ideal for antenna experimentation.

I don’t typically experiment with antennas during SOTA because after hiking 2-3 hours to a summit, I feel pretty invested in the activation and the last thing I want to do is roll the dice with my antenna.  With POTA, I can bring a few extra supplies or “plan B” antennas if something goes sideways.  Plus, unlike parks, summits are often lacking in tall trees so I stick with shorter wire antennas and self-supporting verticals.

On the morning of October 20, 2021, I decided that I wanted to try a new antenna or an antenna I hadn’t used in quite some time. My intention was to dig out my Wolf River Coils TIA vertical, but when I reached into my antenna bag, I pulled out a nondescript Shure microphone pouch. I scratched my head for a moment…

For the life of me, I couldn’t remember what this was, so I opened it up and discovered a doublet inside! Not just any doublet, either–based on the use of a 35mm film canister in the antenna’s construction, I knew it had to be a creation of my buddy Eric (WD8RIF).

Then my memory kicked in. Continue reading POTA Field Report: Pairing the Elecraft KX2 with a stolen doublet at Table Rock Fish Hatchery!