First, don't expect to land exactly where you expect simply by adjusting the lengths to a specific dimension. You really need to place the antenna on a tower to adjust properly and use an antenna analyzer.
The length of feedline from each antenna remains the same. You need to shorten the length of 35-ohm cable that attaches to the tee and heads toward your radio. This needs to be 1/4 wave taking the velocity factor of the cable into effect. Chuck ----- Original Message ----- From: "wa6ifi" <dave_novo...@comcast.net> To: <Repeater-Builder@yahoogroups.com> Sent: Wednesday, November 18, 2009 12:04 AM Subject: [Repeater-Builder] Re: Building Low Band Loop Antennas (DB-212) >I have a 2 loop DB212-2 which is cut for 48 MHz. I want to use it for a 6M >repeater on 53.13. I've shortened the loops to about 53". Do I need to >shorten the length of the coax which runs from the antenna to the "T"? >What should be the length of the cable that runs from the "T" to the >feedline (cable C in instruction flyer. > > Thanks, > Dave Novotny, WA6IFI > > --- In Repeater-Builder@yahoogroups.com, "Jeff DePolo" <j...@...> wrote: >> >> >> I have dimensional data for both Decibel and Celwave lowband folded >> dipoles >> *somewhere*. If there's interest I'll hunt for them. >> >> I think the Celwave design (with the "stingers") would be easier to >> fabricate - no bending involved. >> >> --- Jeff WN3A >> >> >> > -----Original Message----- >> > From: Repeater-Builder@yahoogroups.com >> > [mailto:repeater-buil...@yahoogroups.com] On Behalf Of skipp025 >> > Sent: Sunday, November 15, 2009 10:57 AM >> > To: Repeater-Builder@yahoogroups.com >> > Subject: [Repeater-Builder] Re: Building Low Band Loop >> > Antennas (DB-212) >> > >> > >> > >> > >> > > "Chuck Kelsey" <wb2edv@> wrote: >> > > FYI - Sinclair got the extra bandwidth by stager tuning >> > > the antenna element from the 1/4-wave matching transformer >> > > that is inside the element. The trade-off was a decrease >> > > in return loss (higher VSWR). >> > > Chuck >> > > WB2EDV >> > >> > Maybe... maybe not. I swept one just a short time back and >> > the return loss was about 15.6 dB, which makes it a very nice >> > usable animal. >> > >> > I've also had one in parts and the matching coax length was >> > what I would have expected. Somewhere in my notes I have all >> > the construction information recorded like I did on the Decibel >> > Antennas... >> > >> > I've got a Decibel Loop at the old shop somewhere... if I can >> > easily get it up high enough to throw a sweep on it I can >> > report the results back. >> > >> > I'll have another HP Digital Sender (auto feed pdf scanner) on >> > line within the month... then you'll have more information to >> > chew over. >> > >> > cheers, >> > s. >> > >> > >> > >> > >> > >> > No virus found in this incoming message. >> > Checked by AVG - www.avg.com >> > Version: 8.5.425 / Virus Database: 270.14.61/2498 - Release >> > Date: 11/15/09 07:50:00 >> > >> > >> > >> > > > > > ------------------------------------ > > > > Yahoo! Groups Links > > > -------------------------------------------------------------------------------- No virus found in this incoming message. Checked by AVG - www.avg.com Version: 9.0.707 / Virus Database: 270.14.71/2510 - Release Date: 11/17/09 14:26:00
