[Antennas] 80m EDZ for NVIS

Thu Sep 18 20:46:51 EDT 2025

The original design uses 450 ohm open wire line to match the impedance of the EDZ to 50 ohms. You can’t use a balun for this since the impedance is not a pure resistance at the design frequency (it is capacitive). It’s probably possible to use 300 ohm line, but you wouldn’t be able to use the dimensions in the calculator. It’s likely that both the length of the OWL and the dipole would need to be tweaked to match 50 ohms, but then the dipole wouldn’t be quite 5/8 wl on each side and the gain might be slightly lower.
Let me know if you’re still interested, and I can run this in an optimized EZNEC model with the 300 ohm line. Let me know your wire diameter and insulation type plus the height above ground you can achieve. Getting near 1/4 wave (~ 63 feet) is great for NVIS.
Even better, use two of these EDZs in phase, spaced 5/8 wave apart for another 3-4 dB gain! (Won’t fit in my yard!!!)
73, Terry N6RY
> On Sep 3, 2025, at 9:04 PM, Raymond Brown <kb0stn at sbcglobal.net> wrote:
>> 2 1/4 wave dipoles would be sufficient for an EVIS antenna. 
> Interesting concept, I never entertained the idea of running 5/8-wave dipoles in a horizontal mode. Each element would be 50 m long! Have you done any modeling of a 5/8-wave dipole? It sounds interesting, but as I said, you gotta have a lot of real estate to run that! That’s like 310 feet!
>>> Sent from AT&T Yahoo Mail for iPhone
>>> On Wednesday, September 3, 2025, 1:38 PM, Rob Matherly, W0JRM <w0jrm at jrobertmatherly.com> wrote:
>> So just skip the balanced line and run a balun with two 5/8 wl wires on 
> the poles?
>> On 2025年09月03日 13:19, Raymond Brown wrote:
>> The 300 ohm twin lead would just be the feedpoint up to the balun. If 
>> you select the right Balun, you can feed it with coax. So basically you 
>> need to bring up a 80 m dipole 10 feet off the ground. 
>>> -- 
> Thanks,
> Rob Matherly, W0JRM
> Centerville, Iowa - EN30nr
> http://w0jrm.jrobertmatherly.com
> NAQCC #7688, FPQRP #-330, FISTS #19246, QRP ARCI #16952
>>>> ______________________________________________________________
> Antennas mailing list
> Home: http://mailman.qth.net/mailman/listinfo/antennas
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:Antennas at mailman.qth.net
>> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html