Search found 225 matches

by Andrew (grayhat)
Mon Aug 18, 2025 9:19 am
Forum: Questions & Advice
Topic: 20 M mag loop advice
Replies: 5
Views: 457119

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: 457119

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: 200471

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 198523 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: 200471

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: 200471

Re: Shortened dipole

here's a summary, notice the span and the gain
shortdip.jpg
shortdip.jpg (154.05 KiB) Viewed 200067 times
by Andrew (grayhat)
Thu Jul 24, 2025 4:34 pm
Forum: Questions & Advice
Topic: Shortened dipole
Replies: 4
Views: 200471

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: 200471

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: 422502

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...
by Andrew (grayhat)
Tue Jul 15, 2025 8:45 pm
Forum: Questions & Advice
Topic: Svalbaard Islands activation
Replies: 1
Views: 152423

Re: Svalbaard Islands activation

the activation is ongoing, snd aside some issues wirh FT8, the SSB and CW contacts are just fine. at least looking at the log https://www.mdxc.support/jw0v/log-oqrs/ and the main page carries the updates https://www.mdxc.support/jw0v/ if interested, just start from the log above and the bandplan fou...
by Andrew (grayhat)
Wed Jun 25, 2025 8:51 pm
Forum: General Discussion
Topic: five bands cobweb
Replies: 1
Views: 422502

five bands cobweb

suitable for portable operations https://www.m0pzt.com/cobweb-aerial/ and being omnidirectional may be useful for POTA the antenna offers a gain around 6dBi with low takeoff angle and an almost omnidirectional pattern it can be built using stuff found in most "home improvement" stores, so....