If the length is that restricted - about 40 inches - you are probably out of luck.
The ground plane is about half the length of a folded dipole, so it is actually substantially shorter. The other issue is nearby obstructions. If the reason for the limited height is due to another antenna platform above, even a "shortened" antenna may not work due to influence of nearby metallic components. A base-loaded mobile antenna is not all that much shorter than a 1/4-wave. The one on my car is overall 50". A 1/4-wave antenna would be 54". Chuck WB2EDV ----- Original Message ----- From: "cruizzer77" <[email protected]> To: <[email protected]> Sent: Wednesday, February 03, 2010 10:31 AM Subject: [Repeater-Builder] Re: Space-saving 6m repeater antenna? > > > I know they probably won't, but up to now this has not been an issue. > Touch wood... > > Obviously the folded dipole antenna is not much smaller than the normal > quarterwave vertical, but it's an interesting design. It depends on how > this size thing turns out, I can't tell yet how long it can be exactly. > Probably it must not be longer than 1m, then this would still be too long. > > 73 > Martin > > > > > > --- In [email protected], "Chuck Kelsey" <wb2...@...> > wrote: >> >> A DB212 must be mounted with a metallic mast (or tower) parallel to, and >> extending beyond, the element. It sounds like you may have rules this >> antenna out as a possibility. >> >> A ground plane antenna is typically not side mounted on a tower. >> Depending >> on the distance of the platform rail to the tower, it may work. >> >> One option: >> http://www.krecoantennas.com/fgplane.htm >> >> If it's a commercial site, they may not permit a home-brew. >> >> Chuck >> WB2EDV >> >> >> >> >> ----- Original Message ----- >> From: "cruizzer77" <atlant...@...> >> To: <[email protected]> >> Sent: Wednesday, February 03, 2010 9:34 AM >> Subject: [Repeater-Builder] Re: Space-saving 6m repeater antenna? >> >> >> > >> > >> > You're right, the mounting location is on the lowest platform of this >> > particular mast at a height of about 15m. The antenna is to be mounted >> > sideways to the rail of the platform. Probably it would be possible to >> > mount 2 antennas on the opposite sides of the platform, but this is not >> > clear yet (was a question for the DB212 also). >> > >> > Is there somebody on this list who has built a shortened (i.e. base >> > loaded) 6m antenna, probably for mobile use? I'd be interested in the >> > design and the experiences with it. Not much is to be found on the net >> > regarding 6m designs in particular. >> > >> > 73 >> > Martin >> > >> > >> > >> > --- In [email protected], "Chuck Kelsey" <wb2edv@> >> > wrote: >> >> >> >> You haven't given us a clue as to the mounting location. >> >> >> >> A ground plane antenna is going to be about 54" high and would be >> >> about >> >> the >> >> shortest configuration I can think of. A base-loaded mobile antenna >> >> mounted >> >> on a ground plane would be a few inches shorter. >> >> >> >> Chuck >> >> WB2EDV >> >> >> >> >> >> >> >> ----- Original Message ----- >> >> From: "cruizzer77" <atlantis7@> >> >> To: <[email protected]> >> >> Sent: Wednesday, February 03, 2010 8:25 AM >> >> Subject: [Repeater-Builder] Space-saving 6m repeater antenna? >> >> >> >> >> >> > For our 6m repeater project I had planned to use a DB212 clone as an >> >> > antenna. But the repeater is to be located at a commercial site >> >> > unfortunately and it turned out lately that antenna height is >> >> > restricted >> >> > so much that the height of about 2.5 meters of a single DB212 may >> >> > already >> >> > be too much. >> >> > >> >> > Can anybody tell me something about a 6m repeater antenna which is >> >> > optimized for reduced vertical space but is still polarized >> >> > vertically? >> >> > I >> >> > guess if the DB212 is too tall the height of another antenna will >> >> > need >> >> > to >> >> > be half that size or even less. I'm interested in a homebrewable >> >> > design >> >> > primarily, I was also going to build the DB212 clone myself. >> >> > >> >> > 73 >> >> > Martin >> >> > >> >> > >> >> > >> >> > ------------------------------------ >> >> > >> >> > >> >> > >> >> > Yahoo! Groups Links >> >> > >> >> > >> >> > >> >> >> >> >> >> -------------------------------------------------------------------------------- >> >> >> >> >> >> >> >> No virus found in this incoming message. >> >> Checked by AVG - www.avg.com >> >> Version: 9.0.733 / Virus Database: 271.1.1/2664 - Release Date: >> >> 02/02/10 >> >> 14:35:00 >> >> >> > >> > >> > >> > >> > ------------------------------------ >> > >> > >> > >> > Yahoo! Groups Links >> > >> > >> > >> >> >> -------------------------------------------------------------------------------- >> >> >> >> No virus found in this incoming message. >> Checked by AVG - www.avg.com >> Version: 9.0.733 / Virus Database: 271.1.1/2665 - Release Date: 02/03/10 >> 03:09:00 >> > > > > > ------------------------------------ > > > > Yahoo! Groups Links > > > -------------------------------------------------------------------------------- No virus found in this incoming message. Checked by AVG - www.avg.com Version: 9.0.733 / Virus Database: 271.1.1/2665 - Release Date: 02/03/10 03:09:00
