Hi Helmut, Sorry, it's NOT advanced.
All those folded dipole antenna for commercial VHF and UHF employ the same idea. How to match the folded dipole: Feed the coax into the antenna, inside the tube, around to a point about 1/4 WL from the feed point. Slip a metal collar over the coax inside the tube to ground the coax outer, exposing the coax inner to run inside the antenna tube thus being a higher impedance transmission line, then the inner connects to a plug in the other side of the feed point. Cover the feed area with heatshrink and it's all done. There are many thousands out there. OK then, the cup dipole feed: The cup is 0.7 WL diameter, 0.5 WL deep and the dipoles are about 0.2 WL from the base. The cup is octagonal because it is easy to make that way. As you can see, at the base, folded in tabs to mount the cup sides. At 1300MHz the small capacitance between the tabs to the base are such a low impedance, it may as well be one piece of metal. The crossed dipole dish feed. ======================== Lots of fancy pictures out there requiring Advanced Machining to make them. I built a single patch as per this: http://www.ce5prd.cl/documentos/antenna_handbook/19.pdf page 20 and found the bandwidth way too narrow. I also found problems with the single coax fed patch, two feed points for circular polarisation, fixed that problem with a balanced feed but still, bandwidth too narrow. I then made this and was impressed: The bandwidth I wanted and simplicity of construction. 1/8 in. hardline (or any coax) and 1/8 in. copper wire. The important bit is that three wire line section, 1mm wire, it's just not critical that you get the wires straight and parallel etc.. Good Return Loss at first try! Alan VK2ZIW On Sat, 16 May 2020 13:54:33 +0200, Helmut Oeller wrote > Al, do you have an EZNEC file available of that advanced feed design? > DC6NY > > > Von: Al Beard [mailto:[email protected]] > Gesendet: Samstag, 16. Mai 2020 12:49 > An: [email protected] > Betreff: Re: [Freetel-codec2] Fwd: Microhams Conference, Saturday May 9 - > Live Streamed on YouTube > > How did the talk go? > > > > I've been busy antenna building (and innovating) > > > > > > > > Alan VK2ZIW > > > > On Mon, 4 May 2020 20:14:30 +0000 (UTC), Mark Thompson via Freetel-codec2 > wrote > > Microhams is an excellent digital conference. > > > > > > > It will occur on Saturday, May 9th. > > It has been held at the Microsoft campus in Redmond, WA in the past and will > be live streamed on YouTube again this year. > > > David Rowe, VK5DGR is presenting FreeDV! > > > > > -----Original Message----- > > > > > > > > This year is our 13th annual Microhams Digital Conference. This year has > > required us changing directions too many times to count but we are > > determined to provide a great show. > > > > > One of the virtues of going online is that we were able to invite > > presenters that would be impractical to bring to the Seattle area. We have > > a number of presenters who will be speaking to us from the future. David > > Rowe, the author of Codec2 and FreeDV will be speaking to us live from his > > home in Adelaide, Australia. He's 16 hours 30 minutes ahead of us so it > > will be Sunday morning for him. John Wiseman G8BPQ, the author of BPQ32 > > will be presenting from the UK and we have much of the Winlink development > > team all over the US. This is just a sample and the entire current agenda > > can be found at https://www.microhams.com/ mhdc/mhdc2020/. > > > > > We will be streaming directly to YouTube so we can have an unlimited number > > of attendees. The conference is free but we do request a donation via the > > web site to cover our expenses. There is a chat channel in YouTube to ask > > questions and these will be passed to the presenters (who may wait until > > the end). To provide a more interactive experience, we will have a Zoom > > breakout room available at the end of the session where the presenters can > > hang out and answer questions in person for the next hour. Of course, the > > whole thing will be recorded on YouTube and available for viewing later if > > you miss anything. > > > > > The links to the stream and Zoom breakout room are being finalized and will > > be posted on the MHDC 2020 web site when complete. https://www. > > microhams.com/mhdc/mhdc2020/ > > > > > > See you Saturday, > > > > > Scott N7SS > > MHDC Chair > > > > --------------------------------------------------- > Alan Beard > > OpenWebMail 2.53 > > Virenfrei. www.avg.com --------------------------------------------------- Alan Beard OpenWebMail 2.53
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