Broadband Terminated Dipole Antenna for ALE

Hello Operators.
This week I'm looking at an ALE (Automatic Link Establishment) compatible broadband terminated dipole antenna for HF. When putting together my test ALE station for emergency communications, I realized the unique frequency hopping functionality of ALE, created challenges for operators using PC-ALE or MARS-ALE software, with an HF rig having no ALE compatible antenna tuner. To solve this problem, I needed to find some sort of rapid tuning or no-tuning antenna system.

In the video, I briefly explain the frequency hopping aspect of ALE, how the broadband terminated dipole addresses this problem, finally I do some SWR measurements on the antenna, to see if it really is a "no tuner" antenna meeting ALE requirements.

de oh8stn

 

I skipped past all of the SWR testing for individual bands. Good to know if you want documentation, but not very interesting The charts of communications with Europe and Asia are very impressive. EmComm'ers should be check this out.
AF4RK

 

Whenever I see "broadband terminated antenna," I automatically think "very lossy." Are there computer models available of the antenna that show how the loss figures vs. frequency? I'm not saying that the antenna is necessarily lossy, but it is certainly something to consider when considering a broadband terminated antenna.

 

Thanks for the feedback. I'll keep that in mind for the next video
73 de oh8stn

 

Yeah, I think that it is pretty inefficient. And not much of a NVIS antenna. But it is broadband and provides a fairly simple solution to the ALE problem. I prefer either a Maypole arrangement of resonant dipoles or perhaps a tuner option like this from KQ6XA at hflink.com:

 

I can see the advantage of the multiple resonant antennas with a common feedpoint. A busy station using the auto-tuner is going to do a lot of high-SWR key-ups for the initial link establishment while the tuner does the memory recall step.

 

I don't know if it's lossy, but it solves the ptoblem I had. Remember this can also be configured in any of the typical T2FD configurations which are not considered lossy . A little food for thought.

I was definitely hoping for something that was basically a dipole or could be configured in a variety of different ways. I do like the T2FD antennas from HFLINK.NET, but there's no chance I'm going to deploy one of those other spider web octopus monsters.

I think I mentioned it in the video that I ultimately want to deploy this in the field, using one of those spider beam 12-meter mests. Those multi-element dipoles just don't work at 65 degrees north, when it's so cold you can't take your mittens off.
About NVIS. This is surprisingly good. I have an excellent station near by SM3FXT, I've been testing NVIS with.

If we're really looking for something to criticize about the antenna, I would say the weight. It is awesome deploying from a car with my 10-meter Surplus Russian Army antenna mast. Of course it has a 300 watt rating, but I would be happy with a 20, 50 or maximum of 100 watt version, if that would reduce the weight and increase portability.
73 de oh8stn

 

If it works, it works. Perfect is the enemy of good enough. Tactical comms isn't about the 100% solution.

EDIT: I admit that I shot from the hip BEFORE watching the video, which was stupid of me. My comments were regarding the Terminated Folded Dipole, which is another antenna that I have experience with. Sorry about that.

 

Check out the T2FD dipole. http://www.packetradio.com/t2fd.htm . It will be 3-6dB down from a resonant dipole but is definitely broadband; it is considered a transmission line radiator.

 

This is definitely the top goal on the list of goals for any antenna installation.

While you are on the subject of power ratings, this is one way to estimate the efficiency of the antenna if you get an opportunity to do some testing at a later date. If you ever use high-duty-cycle data modes, you can use the heating of the termination resistor to get an idea for how much of the transmitted power is dissipated in the termination resistor. Being happy with your antenna's performance is of course the primary goal, as you noted, but if you are curious about efficiency, this is one way you could experiment with respect to performance.

 

On a related note, I have listened to a lot of military HF communications, and there are many of them who couldn't care less about efficiency.

 

Roger that.

 

Hi Julian,

Good informative video as always.

I ran a broadband terminated dipole as an inverted V at my workshop for the last two years. It was of my own design and directly connected the resistors to ground rods rather than counterpoises. It had a similar wideband SWR plot and worked really well. OK a dipole cut for a particular band would be more efficient on that one band but it's not wideband.

I learned a lot using that antenna and when I moved house to one with a tiny yard developed the terminated inverted U. I've written that antenna design up on my web site:
http://www.crosscountrywireless.net/terminated_inverted_u.html

In the wide open spaces you operate in the broadband terminated dipole will be an excellent choice. In the tight urban spaces surrounded by RF noise generating gadgets the Terminated Inverted U works well.

73,
Chris, G4HYG

 

My dummy load is very broadbanded, essentially flat from DC to 1gig.
It's also very efficient, it coverts nearly 100% of the RF energy to heat.,
It is however a lousy antenna.

 

Thanks Chris. Its always nice to hear from you.
I'll have a read, and also link your antenna to my ALE pages.

73 de oh8stn