[TowerTalk] Antenna Modeling

terry burge ki7m at comcast.net
Wed Jul 11 19:34:53 EDT 2018


Just a quick comment,

I tried to get 40,60 and 80 meters in a fan inverted-V to work for me. NOT! Just could not get them to play although I had just a little luck with 60 meters. And this started with an 80 meter inverted-V that was OK. Gave up quickly on 40 and soon enough on the whole idea. Went back to just the 80 meter inverted V. Strangely enough, when I had that at 70 feet it performed a little better than when I had it up at 104 feet at the apex trying to work Europe SSB. But my advice for trying to get 80 and 40 meters to play together in a fan dipole, inverted V, etc. is don't. I'm not sure if you can even get them spread of far enough apart to make them work. So much for Edward M. Nott, W3FQJ ideas on this one.

Terry
KI7M

> On July 11, 2018 at 4:08 PM Jim W7RY <jimw7ry at gmail.com> wrote:
> 
> 
> I can attest to how difficult it is too!
> 
> I really struggled with my 80-40 fan inverted vee. Secret was to get the 
> wires far apart, (not really in fan style), but that helped the 
> interactions.
> 
> If your going to use a close spaced, each band wire close to the other, 
> better model!
> 
> I would much rather have a resonate antenna than non, I believe that the 
> efficiency is much better with something that is resonate. Unless you can 
> feed it with open wire line all the way.
> 
> 
> Thanks
> 73
> Jim W7RY
> 
> 
> -----Original Message----- 
> From: Grant Saviers
> Sent: Wednesday, July 11, 2018 4:45 PM
> To: towertalk at contesting.com
> Subject: Re: [TowerTalk] Antenna Modeling
> 
> For some good advice on modeling fans see
> https://ac6la.com/aecollection4.html
> 
> Also, they are sensitive to height above ground so modeling at the
> installed geometry is advised.   Using the modeling technique developed
> by Cebik that AC6LA describes has yielded good results for me.
> Otherwise there can be interactions that lead to a lot of cut and try
> frustration.
> 
> Grant KZ1W
> 
> On 7/11/2018 12:12 PM, Jim Brown wrote:
> > On 7/11/2018 10:52 AM, Bruce Jungwirth wrote:
> >> I’m looking for someone in or around St Paul Mn that is fluent in EZNEC.
> >
> > A principal value of EZNEC and other modeling software is as a teaching 
> > tool, and you only learn from it when YOU do it. It's not all that 
> > difficult to learn once you get over the fear factor. The free version 
> > that comes with the ARRL Antenna Book will model simple antennas like 
> > you're thinking about.
> >
> > Here are several studies I've done to help think about problems like 
> > yours.
> >
> > http://k9yc.com/VertOrHorizontal-Slides.pdf
> >
> > http://k9yc.com/VerticalHeight.pdf
> >
> > http://k9yc.com/43FtVertical.pdf
> >
> > http://k9yc.com/AntennaPlanning.pdf
> >
> > I am a big fan of fan dipoles. A good rule is to not try to put more than 
> > three elements in the fan.  80/40 makes a good fan, so does 20/15/10. 
> > Although I haven't done it, i suspect that 30/17 would too.
> >
> > 73, Jim K9YC
> >
> > _______________________________________________
> >
> >
> >
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