I assume that this "backpack frame antenna" wouldn't be actually used when being worn. The circulating currents in a Hi-Q loop result in strong RF fields along the loop axis which should be avoided in use.
jim ab3cv On Wed, Jan 23, 2019 at 11:21 AM Wayne Burdick <n...@elecraft.com> wrote: > Wish I had time to build one of these myself! A few other things in the > queue.... > > Wayne > N6KR > > > > On Jan 23, 2019, at 6:32 AM, 'Dale Parfitt' pari...@frontier.com [KX3] < > kx3-nore...@yahoogroups.com> wrote: > > > > > > HI Wolf, > > > > VK3YE could have done so much better from an efficiency standpoint > without making the loop any larger. > > > > 1. Flat metal stock is not as efficient as round stock (of the same > circumference) because current crowding at the edges of the rectangular > stock makes it appear smaller in surface area. > > > > 2. A much lower D capacitor such as a dual gang air variable with the > gangs in series (to avoid resistive losses in the bearings) or a butterfly > would also have aided in higher efficiency. > > > > 3. Copper would have helped efficiency somewhat with its lower RF > resistance and ability to be soldered versus mechanical connections, but > that is partially offset by aluminum’s larger skin depth. Of course copper > is heavier and more expensive, but in tube form the weight issue could be > minimized.. > > > > > > > > Just some thoughts. Again, the VK1OD calculator allows one to make > precise efficiency measurements so even small improvements can be > measured. As an example, the difference in efficiency between using > braided coax as the loop radiator versus hardline or copper tubing is > readily apparent. For the same diameter loop and same conductor diameter, a > narrower bandwidth means higher efficiency. > > > > > > > > Dale W4OP > > > > > > > > From: k...@yahoogroups.com [mailto:k...@yahoogroups.com] On Behalf Of > 'Wolf Hoeller, OE7FTJ' wolf.oe7...@gmail..com [KX3] > > Sent: Wednesday, January 23, 2019 4:57 AM > > To: k...@yahoogroups.com > > Subject: Fwd: [KX3] Urban stealth HF: Inside-the-backpack loop antenna? > > > > > > > > > > > > Wayne, > > > > > > > > a really good idea. > > > > Have a look at VK3YE's youtube channel for his experiment to put a loop > antenna in (frame of) a notebook bag. > https://www.youtube.com/watch?v=BC5lFbLqaeg > > > > > > > > Another good idea for a stealth antenna has the spain company Inac. Here > is the suitcase with a loop inside the frame: > https://www.inac-radio.com/MAK721PRO > > > > > > > > I would like the idea, to sit in an urban park with my backpack or > similar on my knees and make some contacts. > > > > > > > > > > Wolf, OE7FTJ > > > > Emergency Communications via Winlink Global Radio Email ®️ > > > > > > > > > > > > > > > > Am Di., 22. Jan. 2019 um 21:57 Uhr schrieb Wayne Burdick > n...@elecraft.com [KX3] <kx3-nore...@yahoogroups.com>: > > > >> > >> > >> I’ve engaged in plenty of ultralight HF pack operation, with a KX2, AX1 > antenna and a dragged counterpoise. In wide open spaces it’s a blast. But > urban settings with dogs, wire-eating cacti and overzealous Neighborhood > Watchers can distract from one’s radio experience. > >> > >> > >> > >> So, just for grins, I’d like to try something completely incognerdo: no > visible antenna. A small remotely tuned loop (say 12” diameter) would seem > to be the best choice, as it would fit entirely inside a small backpack. It > could have modest efficiency while not requiring a counterpoise wire. > Rigid 1” copper pipe formed in a square would be convenient to deploy. > >> > >> > >> > >> The loop would be only 6 to 8” from soft tissue, so you’d want to run > QRP, of course. OTOH, we’re talking about HF. A cellphone by your ear is > probably worse. > >> > >> > >> > >> Any other antenna suggestions? > >> > >> > >> > >> Wayne > >> > >> N6KR > >> > >> > >> > >> > >> > > > > > > __._,_.___ > > Posted by: "Dale Parfitt" <pari...@frontier.com> > > Reply via web post • Reply to sender • Reply to > group • Start a New Topic • Messages in this topic (2) > > > > Have you tried the highest rated email app? > > With 4.5 stars in iTunes, the Yahoo Mail app is the highest rated email > app on the market. What are you waiting for? 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Never delete an email > again with 1000GB of free cloud storage. > > VISIT YOUR GROUP > > • Privacy • Unsubscribe • Terms of Use > > > > SPONSORED LINKS > > > > > > > > . > > > > > > __,_._,___ > > ______________________________________________________________ > Elecraft mailing list > Home: http://mailman.qth.net/mailman/listinfo/elecraft > Help: http://mailman.qth.net/mmfaq.htm > Post: mailto:Elecraft@mailman.qth.net > > This list hosted by: http://www.qsl.net > Please help support this email list: http://www.qsl.net/donate.html > Message delivered to j...@jtmiller.com ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to arch...@mail-archive.com
