Search found 227 matches

by Andrew (grayhat)
Mon Sep 29, 2025 8:04 pm
Forum: Questions & Advice
Topic: compact vertical EFHW for 20m
Replies: 0
Views: 4313

compact vertical EFHW for 20m

https://g4tgj.github.io/20m-EFHW-Vertical-Antenna/

it may come handy for POTA/SOTA due to its omnidirectional pattern and low takeoff angle
by Andrew (grayhat)
Mon Aug 18, 2025 9:19 am
Forum: Questions & Advice
Topic: 20 M mag loop advice
Replies: 5
Views: 474875

Re: 20 M mag loop advice

so... did you try that loop then ?
by Andrew (grayhat)
Wed Jul 30, 2025 12:25 pm
Forum: Questions & Advice
Topic: 20 M mag loop advice
Replies: 5
Views: 474875

Re: 20 M mag loop advice

check this loop for the 20m band

http://sm0vpo.altervista.org/antennas/20m_ant_00.htm

:)

HTH
by Andrew (grayhat)
Fri Jul 25, 2025 4:28 pm
Forum: Questions & Advice
Topic: Shortened dipole
Replies: 4
Views: 209128

Re: Shortened dipole

And here's the 3D radiation pattern, as you can see, it's just like the one from a regular size dipole
shortdip14-2.jpg
shortdip14-2.jpg (63.66 KiB) Viewed 207180 times
https://qrper.net/download/file.php?id=194
by Andrew (grayhat)
Fri Jul 25, 2025 2:28 pm
Forum: Questions & Advice
Topic: Shortened dipole
Replies: 4
Views: 209128

Re: Shortened dipole

OK, changed the model so that the folded portion is below, so that the contruction/installation of the dipole is easier, here's the new model optimized for the 20 metters band (centered on 14.175 MHz) CM 20m band shortened dipole CM feed it using a guanella 1:1 CE ' design frequency SY freq=14.175 S...
by Andrew (grayhat)
Fri Jul 25, 2025 7:19 am
Forum: Questions & Advice
Topic: Shortened dipole
Replies: 4
Views: 209128

Re: Shortened dipole

here's a summary, notice the span and the gain
shortdip.jpg
shortdip.jpg (154.05 KiB) Viewed 208724 times
by Andrew (grayhat)
Thu Jul 24, 2025 4:34 pm
Forum: Questions & Advice
Topic: Shortened dipole
Replies: 4
Views: 209128

Re: Shortened dipole

CM shortened dipole CE SY freq=7.100 SY wire=0.0075 SY wave=300/freq SY hfac=0.60 SY lfac=1.2709 SY frac=0.50 SY tlen=(wave*frac)*lfac SY arms=tlen/2 SY hght=wave*hfac SY front=(arms*0.60) SY other=arms-front SY sfac=0.082 SY sides=other*sfac SY back=other-sides SY segs=3 SY segm=21 SY segl=51 GW 1...
by Andrew (grayhat)
Thu Jul 24, 2025 3:32 pm
Forum: Questions & Advice
Topic: Shortened dipole
Replies: 4
Views: 209128

Shortened dipole

Being bored and having some time in my hands I started fiddling with 4NEC2 to explore an idea I had time ago, but let me start from the beginning first of all a fact; if we bend in an U shape the arms of a dipole keeping the "straight portion" (from feedpoint to bend) at 60% of the arm len...
by Andrew (grayhat)
Thu Jul 17, 2025 12:01 pm
Forum: General Discussion
Topic: five bands cobweb
Replies: 1
Views: 427392

Re: five bands cobweb

as for gain and pattern let's start with this image https://www.m0pzt.com/cobwebb_plan.jpg as a reference, the main axis of the radiation solid runs from top to bottom of image and, with the antenna placed at 10m height it offers more than 6dBi of gain, the other axis (left-right) offers more than 3...