Spark Plug Antenna: setup and first try

Here I am trying out the Spark Plug Antenna.

Trying out my new Spark Plug Antenna. It's another EFHW.

 

That is a neat form factor for a bnc mounted 1:49/1:64 autotransformer used with an EFHW. For POTS/SOTA use, this is really nice as it's compact and tidy. It's great to see the experimentation and the market for this part of the hobby is alive and well.

Chaz

 

The end fed half wave has a very high impedance at the feedpoint, so the 49:1 un-un on this 'spark plug' transforms the impedance of the wire from about 2500 ohms to about 50 ohms that the radio is looking for.

Thanks for watching.

 

That's not an antenna, that's a balun. Not that wire is hard to come by, but if they're going to call it an antenna they should at least supply the wire with it. It is a pretty neat design, though, and I wouldn't mind trying it out.

 

Here is one of a similar form factor, courtesy of N5JLD:

 

It is also available as a full kit with wire and winder. They weren't available when I bought mine.

 

I like the idea of using a kite string holder to wind an antenna on.

 

K9KMV said it correctly. It is a transformer that takes the high impedance of the voltage max and takes it to about 50 ohms. You still may need to further choke the coax .

This particular transformer won't do well with high power, but that is so noted.

End feeding dipoles, for example, is a fairly modern approach brought on by lower loss materials and the availability of ferrite for chokes. The downside is the high voltages can make things burn up with overheating or even wet conditions. BUT this is rare...

 

bien vu , bien dis... je vais essayer les bougies de ma tondeuse...et regarder si YL va aimer... Hi

 

You mike try some 26g Poly Stealth wire as it has a 25lbs weight rating. What did you feed it with like RG 174u?

 

si c’est le cas, c’est une bougie d’allumage vraiment coûteuse HI HI

 

I received one as a gift from a buddy of mine a while back. I believe somebody on QRZ was selling them at some point. With my G90, I have had amazing results with that antenna system once I got the wire trimmed and tuned up. I’ve worked all over the US and Europe with mine.

 

I use one that came in kit form from KM4ACK, similar to this except the toroid and capacitor is mounted on a 3D printed kite winder. Easy 30 minute build, winding the toroid takes some care but the rest is easy. I got similar results to you, the kit included about 68 feet of the 26 gauge polystealth wire and I ended up trimming about a foot and a half to bring it into resonance on 40. 20, 15 and 10 looked good too. I had it running from a 25 foot fiberglass pole sloping down to about 10 feet to our back deck. I made contacts right away with my 705 at 10 watts SSB. Haven't been to the park yet, but that's next.

 

The EFHW antenna can be quite effective - I use one here at home with very good results. In the interest of correctness, the matching transformer is actually a UNUN - UNbalanced-to-UNbalanced rather than BALanced-to-UNbalanced.

But who cares? So long as it works well!