My first 9:1 unun for an End Fed Antenna

Well hello there little guy! Welcome to Planet Earth! Say hello to my first born 9:1 unun. He was born last night, at around 8:30 p.m., weighing in at just...

Well hello there little guy! Welcome to Planet Earth!

wp-1488378112731.jpg

Say hello to my first born 9:1 unun. He was born last night, at around 8:30 p.m., weighing in at just over 10 ounces! I’ve named him Old Glory, after good ole’ red, white & blue! 😛 Take a look at my color combination for the 3 wires 😛 Was purely coincidental though, I needed a third wire of the same gauge and it just so happened to be blue!

wp-1488373724557.jpg

What is this little guy? Well it’s called a Transmatch/Matchbox/Matching Network (take your pic) if you will. Since most modern transceivers are designed to operate at 50 ohms, the ‘matchbox’ will bring the impedance down enough for you to be able to use multiple bands on a single wire antenna (with an antenna tuner). Very popular with folks in an HOA or for portable use. I’ve probably seen more end fed antennas in use than anything in my first couple of years!

I may have gone a little fancy on this one by using banana plug terminals instead of wingnuts, but it was extra hardware that wasn’t being used, and the banana plug terminals are a nice touch because the banana plugs can be easily inserted into another insulated length of wire while your finding the ‘right’ lengths that work with the matchbox instead of adding a new terminal to each piece of wire you try.

wp-1488369396689.jpg

I followed the EARCHI plans for a 40m-6m end fed antenna. I tested continuity between all the wires inside the matchbox with a multimeter. I soldered a 470 ohm resistor on between some alligator clips (need to shorten the leads) to test between the antenna & ground lead and came back with a graph that was a tad bit on the high end.

wp-1488369583460.jpg

Though this may be typical for a T130-2 toroid analyzer sweep? There is so much information (a lot of which is conflicting) on Powdered Iron Toroids & Ferrite Toroids on the internet. So I’ve invested in several other types, including the T200-2 & FT-240-43 to see what different kinds of results I get with different toroids. As you can see SWR for 20 meters is around 1.6, but the impedance value was still a little high (about 90).

Surprisingly, the best length that I’ve found yet has been a 21′ piece of wire for 40 meters, but gets worse as you go higher in  bands. Initially I had thrown a 31′ piece on there to compliment the 31′ Jackite pole in my backyard, but that was more resonant towards the 60 meter band! So I tried others, including a 28.5′ piece & a 43.5′ piece (suspended as a sloper from roof). When I added the counterpoise wires, it seemed to make things worse (generally speaking – on most bands). So I left them off & used a 50′ piece of RG213 to the analyzer, with shorter pieces of coax, the SWR shot up a bit, still need to try a 25′ piece though. I’m still baffled as to why the counterpoise wires would make the situation worse.

I’ll admit I tried setting all this up in my cramped backyard up against the fence, where the radials may have been interacting with the current radials laying under the sod for my Hustler vertical. Need to get into an open space, but need to develop a stand or stake of some sort to hold the Jackite pole up.

Here’s some useful articles from ARRL on Transmatching & Antenna Tuners if you are so inclined to learn more about them : ARRL Transmatch/Antenna Tuners. If you’re thinking about trying an End Fed antenna, build it! You’ll save a lot of dough & learn some in the process! I’m guilty though, I’ve used commercial end feds, nothing wrong with that, sometimes you just need to get on the air! I’m not sure how I would do this without an analyzer though, I know some have said they did manual SWR plotting, I can’t imagine how much of a pain in the butt that is though!

More to come……

Happy Hump Day!

73

K5ACL

 

 

 

 

 

Categories
End Fed AntennaHF Antennas
No Comment
  • Andrew VK1AD
    1 March 2017 at 11:51 AM
  • Andrew VK1AD
    1 March 2017 at 11:48 AM
    • K5ACL
      1 March 2017 at 1:18 PM

      Lots of useful info there, thanks. I was ‘hoping’ to keep it under 40 feet, but that might not be possible!

    RELATED BY