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.

It’s not actually *that* heavy, but heavy enough I wouldn’t want to stress the top of my fiberglass poles.

I should note here that Eric (WD8RIF), who originally provided inspiration for this build, only used the center fixture as a winder for this very reason. He crafted a center insulator out of a discarded 35mm plastic canister. Here’s Eric’s doublet:

At Lake Norman, I found a  picnic table with ample space to deploy the doublet. Admittedly, there were a couple small branches I had to finagle the antenna around, but it wasn’t terribly difficult to set up.

I paired the doublet with my Elecraft KX2 mainly because it has an internal antenna tuner, thus I could simply connect BNC binding posts to the rig, then use the two pre-installed pins on the feedline to connect the antenna to the binding post adapter. Very easy.

This doublet requires an antenna tuner to find an impedance match. With a good ATU (like the one in the KX2) I’ve found that this doublet will find matches anywhere from 60 meters up to 6; ideal for field activations!

Gear:

On the air

I found out later that propagation conditions were pretty poor during the activation. Nevertheless, the doublet performed very well–especially in such a short period of time.

I also decided I’d stick to the higher bands in this activation as a few readers/subscribers have asked for me to do a little more 20 meter park work so my signal might reach the west coast more frequently.

In 19 minutes on the air, I logged 13 contacts–all on 20 meters. Quick and easy!

Honestly, though, had I moved down to 30 meters, or 40 meters, I’m sure I could have logged a couple dozen more in short order.

Frankly, though, I felt a bit of time pressure as another goal at Lake Norman was to hike their Lakeshore Trail before sunset. The previous day, I ran out of time to fit in a good multi-mile hike; I didn’t want that to happen again.

QSO Map

Here’s what 5 watts into the doublet yielded on the 20 meter band:

Activation video

Here’s my real-time, real-life, activation video at Lake Norman. As always, there are no ads in my YouTube videos:

Click here to view on YouTube.

Lakeshore Trail

The hike post-activation was beautiful. Here are a few photos:

Thank you

I always get a small thrill out of taking a new antenna to the field. It’s that much more fun when it’s one I’ve built! You’ll definitely be seeing this doublet in future activations. I’m really looking forward to using it on the 60 meter band.

As always, I’d like to send a special thanks to those of you who have been supporting the site and channel through Patreon and the Coffee Fund. While certainly not a requirement as my content will always be free, I truly appreciate the support.

I hope you have some time this week to play a little radio. If you’re considering doing your first park activation, get a little in-shack experience by hunting a few parks in advance!

I’ve been so impressed with the number of operators who’ve contacted me to tell me they’re learning CW–keep up the good work! You’ve got this!

72/73,

Thomas (K4SWL)

13 thoughts on “Field Activation Antenna Challenge #1: Military Fixture Homemade Multi-band Doublet!”

  1. I got one of those doublets and set mine up for 80 meters. It’s 132 feet long using SOTA beams antenna wire. The whole thing cost less than 30 bucks and weighs about a pound. I used it during winter field day (QRP) and had good results. The antenna will tune down to 160 meters using my AH-705 (2:1) . It is my go to low band activating antenna.

  2. I was lucky enough to get several of these prc-74 antennas BNIB

    The feeder works great for portable ops

    Add radio and go qso

  3. Thomas.
    Thanks again for this great article. When you mentioned this antenna before, I bought 2 of them, though I haven’t used them yet. My QRP rigs are not operational currently due to some time constraints and of course the KX2 is further delayed.
    When I get one of the other 2 up and running I’ll attempt an activation and try it out. Thanks again for showing us the way!

    73
    Wb8yxf

    1. You may find you can configure the second one for a different type of antenna, too. I thought about doing a delta loop (vertical) with one of those fixtures. The only issue is keeping the feedline off the ground. 🙂 Haven’t figured that out yet!

      Cheers,
      Thomas

  4. I love the fact that QRP and any type of field activation is more active now than in recent years. And while there is more products for all this activity now than ever before. I still would like to see more people building HB antennas, be they wire fiber etc. get away from the “Appliance operator” syndrome and back to the “experimental builder” mode. It is so gratifying to build an antenna take it out to the field or even at your home station and watch it perform. a great sense of pride and satisfaction. goes with it and it teaches the newcomers that opening their wallets is not always needed to enjoy this hobby. Ok my 2 cents worth. de Wa1RKS

    1. I get a real thrill out of building antennas and, frankly? It’s actually quite easily. Antenna building is well within the capabilities of most new hams–especially if you go QRP.

      Cheers,
      Thomas

  5. Tnx for the contact, Thomas.

    Watching your video reminds me of one of the things that frustrates me when making POTA activations: the need to use both hands to send CW. I’m beginning to think that lightweight portable paddles may not be the best way to go after all. I have brought my heavier home-station paddles on a few activations and I’m beginning to realize that the ability to send CW with one hand is worth the heavier weight.

    73,
    John

    1. It’s funny you mention that. Recently, I’ve decided that I need a way to do one-handed CW. Instead of a heavier base (which frankly? Is 100% fine for POTA) I’ve thought about finally attaching a paddle to my clipboard/kneeboard.

      But honestly? For POTA there’s no reason we can’t go for a heavier key.

      Cheers,
      Thomas

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