Trapping the EFHW?

Do you have a question about choosing a radio, installing an antenna, or are you simply seeking advice about getting started in QRP and field radio? This is a place where you can ask your questions and seek guidance from a wide variety of radio enthusiasts. No questions are too simple. You will be treated with respect here.
KL7MJ
Posts: 27
Joined: Mon May 15, 2023 9:06 pm

Re: Trapping the EFHW?

Post by KL7MJ »

Rich,
The kite sounds like a great idea, just not in my backyard - too many trees!

Why not use an EFHW instead of a center fed dipole? They're essentially the same antenna (half wavelength), but a center fed dipole is only resonant on odd multiples where the EFHW is resonant on all multiples. An 80m EFHW should work on all multiples of 3.6MHz (maybe with a tuner, maybe without). You could still fly it at 200 feet, but you wouldn't have to pull the coax to change bands!

My desire to add traps was to get 30m and 17m on a 40m EFHW. I lost 10m and 15m as resonant bands, but I have the bands I prefer - 17/20/30/40, so it works for me.

73,
Mike, KL7MJ/4
NJ6FNJ6F
Posts: 2
Joined: Sun Jul 09, 2023 6:00 pm

Re: Trapping the EFHW?

Post by NJ6FNJ6F »

Mike,

I agree with you on fixed setups and convenience factor. The kite is a out of norm example where just pulling on the coax and bringing the kite straight down fast, to clip on another antenna if needed might offer according to some articles less of a small loss penalty to pay versus a proper transformer to feed a EFHW at its highest impedance point with a result of estimated 1.6dB lower radiated power than a standard half wave dipole per JPEG attached. A bit of increase in efficiency as per JPEG attached helps when using (low power, it all counts). I was generally coming from a increase in efficiency as per JPEG when using low power, using a straight dipole and the (gain in height of 200 feet) or so away from the noise floor with the increase in signal you could work many more stations (faster) on whichever band hi.
Regards
Rich / NJ6F
center-fed_vs_end-feds_magfield.png
center-fed_vs_end-feds_magfield.png (85.82 KiB) Viewed 730 times
KL7MJ
Posts: 27
Joined: Mon May 15, 2023 9:06 pm

Re: Trapping the EFHW?

Post by KL7MJ »

Rich,
I started down the trap path when I realized that having to drop my antenna to open or close a link dissuaded me from using the unlinked band. With my trapped antenna, I can operate both my KX1 and QCX mini (17m) without having to change the antenna out. I realize that trapped antennas may have slightly less gain than their full length brethren, but the convenience factor wins for me.

Having said that, I think I need to add a kite to my kit...

73,
Mike, KL7MJ/4
Post Reply