Yes Ken you are correct about the detuning skirt. In fact mono pole here has a detuning skirt around the tower. I am also familiar with the climbing safety lines. You can tell the difference in that most detuning skirts I have seen on Cell mono poles had several wires around the pole coming down. Also you will see quite a bit of insulators and hardware compared to a simple safety line. However that last time I was there the fiberglass housing the vacuum capacitor had been damaged by hail. So it was full of water. Very sad deal. However I don't think they need it any more. The AM station was right next to this moved across the river. After they put on the mono pole it caused a problem with the AM station's pattern. So up went the detuning skirt that looks much like the Folder Unipoles, hi.
73 de jay/w5jay.. >I would bet that the Skirt type antenna that you describe is actually a >detuning system on a cellphone tower that is within two miles of a >Directional AM Broadcast array. If the Cell tower is within the two mile >range, the company who owns it must have a partial proof of performance >done on the AM directional array before and after the tower is built. If it >is shown to distort the pattern, then the detuning network that you see is >added and tuned to make the cell tower invisible electrically to the AM >array at the broadcast frequency. It actually is an "untenna" I guess. > Ken Zuercher KC8QO > > > --- On Mon, 1/12/09, [email protected] <[email protected]> wrote: > >> From: [email protected] <[email protected]> >> Subject: Re: [AMRadio] 160 meter antenna >> To: "Discussion of AM Radio in the Amateur Service" >> <[email protected]> >> Date: Monday, January 12, 2009, 3:36 PM >> Bill, I wasn't aware the broadcast towers were sitting >> atop of a insulator on the base...is this considered the >> norm? What type of material would you suppose the insulator >> is made with? >> -------------- Original message from BILL GUYGER >> <[email protected]>: -------------- >> >> This is a skirt type antenna it's a fairly common >> "trick" used at some AM b'cast sites. This way >> the tower can be grounded rather than sitting on a base >> > insulator. >> > >> > Bill AD5OL >> > >> > >> > >> > >> > ________________________________ >> > From: "[email protected]" To: >> [email protected]; Discussion of AM Radio in the Amateur >> Service >> > >> > Sent: Monday, January 12, 2009 12:13:42 PM >> > Subject: Re: [AMRadio] 160 meter antenna >> > >> > Hello Jack. I am familiar with the lynards that the >> climbers use as a safety line while climbing the tower. >> Their are however 3 vertical lines made out of what looks >> like guy wire with a circular ring near the base being fed >> by a box >> > at the base. Just a FYI -------------- Original >> message from "JACK C. SHUTT" : >> > -------------- >> > >> > >> > Hi Robert, >> > We have several of those wireless towers and monopoles >> around here, as well Those side wires are safety cables >> that climbers can clip on to with >> > fall-arresting lanyards and harnesses, they are not >> radiators. >> > Anyway, the folded unipole is a worthwhile antenna to >> try. I have had excellent >> > results with an inverted L running up the side of my >> 80' tower and the >> > "horizontal" portion sloping out to a tree. >> The "L' perhaps looks more like a >> > vee with one short leg. Total length is about 135 ft. >> I use a coil and >> > capacitor parallel network at the base of the tower >> feeding the end of the >> > antenna wire then coax back to the shack. As always, >> a good radial system >> > really helps. >> > >> > 73, Jack, W9GT >> > >> > --- On Mon, 1/12/09, [email protected] wrote: >> > >> > From: [email protected] >> > Subject: Re: [AMRadio] 160 meter antenna >> > To: [email protected], "Discussion of AM Radio in >> the Amateur Service" >> > >> > Date: Monday, January 12, 2009, 7:23 AM >> > >> > >> > Neal. Thanks for the link on building the Unipole. I >> had worked for Sprint for >> > some time and I noticed they were using that same >> concept on many of their >> > towers. The link was exceptionally helpful >> > -------------- Original message from neal Newman : >> > -------------- >> > >> > >> > > Jim you only need 50 feet of verticle space. >> > > why not just build yourself a Folded Unipole >> antenna if you Dont know how. >> > Ask. its really easy. Just Run 3 lengths of #12 wire >> or if you have it #6 wire. >> > short them up at around the 50 foot point and use >> 1" PVC >> > > Tubing as Insulators with clamps Down the side of >> the Tower. >> > > at the bottom Each wire is isolated with PVC from >> the Tower. >> > > BTW Each wire should be about 12" or more >> off the tower. then Tie all 3 wires >> > together with a ring of #12 and take that as the Lead >> to the antenna tuner. Run >> > at Least 4 ground radials 50 feet long If you can get >> > > the space make them 120 feet... >> > > and you will have a Killer 160 antenna. if not >> make an inverted L Run a wire >> > thats 130 feet long. as far vertically as >> > > you can then run the rest out horizontally... >> again you need at least 4 ground >> > radials.... the unipole is what we use for >> > > Broadcast stations when we are tight for height >> or space on a grounded Tower. >> > > >> > > Neal-KA2CAF >> > > CE- WTTM/WHWH/WJDM/WIBG/WFYL >> > > >> > > >> > > --- On Sun, 1/11/09, Jim Miller WB5OXQ in Waco >> wrote: >> > > >> > > > From: Jim Miller WB5OXQ in Waco >> > > > Subject: [AMRadio] 160 meter antenna >> > > > To: "Discussion of AM Radio in the >> Amateur Service" >> > > > Date: Sunday, January 11, 2009, 11:28 PM >> > > > I always wanted to try am on 160 but like >> most do not have >> > > > enough room for a full size antenna, so, >> > > > I am considering building a 160 meter >> antenna at our >> > > > clubhouse because there is a 80' tower >> there and over an >> > > > acre of land to spread out a 1/2 wave >> dipole. Question is; >> > > > 1 Is a 1/2 wave wire dipole the best antenna >> for the band >> > > > considering there is room for it. >> > > > 2 Is 80' high enough for the center of >> the inverted V? >> > > > 3 How high do the ends need to be off of the >> ground? >> > > > 4 Should I feed it with coax or ladder line >> to the 10' >> > > > level (or other) then a balun to coax to the >> tuner (coax is >> > > > the only acceptable line into the shack)? >> The shack is a >> > > > metal building 30X60' and directly below >> the tower. >> > > > There is no way to get ladder line to the >> operating position >> > > > since all cables have to run through a >> 3" conduit for >> > > > at least 30'. >> > > > >> > > > The tower is a free standing commercial >> tower made of 4 >> > > > 20' sections bolted together with a 2 >> meter and a 440mhz >> > > > antenna at the top, all ham antennas. >> > > > >> > > > Thanks for any advice. Jim >> > > > >> wb5oxq______________________________________________________________ >> >> > > > Our Main Website: http://www.amfone.net >> > > > AMRadio mailing list >> > > > Searchable Archives: >> > > > >> http://www.mail-archive.com/[email protected]/ >> > > > List Rules (must read!): >> http://w5ami.net/amradiofaq.html >> > > > List Home: >> http://mailman.qth.net/mailman/listinfo/amradio >> > > > Help: http://mailman.qth.net/mmfaq.html >> > > > Post: mailto:[email protected] >> > > > To unsubscribe, send an email to >> > > > [email protected] with >> > > > the word unsubscribe in the message body. >> > > >> > > >> > > >> > > >> ______________________________________________________________ >> >> > > Our Main Website: http://www.amfone.net >> > > AMRadio mailing list >> > > Searchable Archives: >> http://www.mail-archive.com/[email protected]/ >> > > List Rules (must read!): >> http://w5ami.net/amradiofaq.html >> > > List Home: >> http://mailman.qth.net/mailman/listinfo/amradio >> > > Help: http://mailman.qth.net/mmfaq.html >> > > Post: mailto:[email protected] >> > > To unsubscribe, send an email to >> [email protected] with >> > > the word unsubscribe in the message body. >> > >> ______________________________________________________________ >> >> > Our Main Website: http://www.amfone.net >> > AMRadio mailing list >> > Searchable Archives: >> http://www.mail-archive.com/[email protected]/ >> > List Rules (must read!): >> http://w5ami.net/amradiofaq.html >> > List Home: >> http://mailman.qth.net/mailman/listinfo/amradio >> > Help: http://mailman.qth.net/mmfaq.html >> > Post: mailto:[email protected] >> > To unsubscribe, send an email to >> [email protected] with >> > the word unsubscribe in the message body. >> > >> ______________________________________________________________ >> >> > Our Main Website: http://www.amfone.net >> > AMRadio mailing list >> > Searchable Archives: >> http://www.mail-archive.com/[email protected]/ >> > List Rules (must read!): >> http://w5ami.net/amradiofaq.html >> > List Home: >> http://mailman.qth.net/mailman/listinfo/amradio >> > Help: http://mailman.qth.net/mmfaq.html >> > Post: mailto:[email protected] >> > To unsubscribe, send an email to >> [email protected] with >> > the word unsubscribe in the message body. >> ______________________________________________________________ >> Our Main Website: http://www.amfone.net >> AMRadio mailing list >> Searchable Archives: >> http://www.mail-archive.com/[email protected]/ >> List Rules (must read!): http://w5ami.net/amradiofaq.html >> List Home: http://mailman.qth.net/mailman/listinfo/amradio >> Help: http://mailman.qth.net/mmfaq.html >> Post: mailto:[email protected] >> To unsubscribe, send an email to >> [email protected] with >> the word unsubscribe in the message body. > ______________________________________________________________ > Our Main Website: http://www.amfone.net > AMRadio mailing list > Searchable Archives: http://www.mail-archive.com/[email protected]/ > List Rules (must read!): http://w5ami.net/amradiofaq.html > List Home: http://mailman.qth.net/mailman/listinfo/amradio > Help: http://mailman.qth.net/mmfaq.html > Post: mailto:[email protected] > To unsubscribe, send an email to [email protected] with > the word unsubscribe in the message body. ______________________________________________________________ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/[email protected]/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Help: http://mailman.qth.net/mmfaq.html Post: mailto:[email protected] To unsubscribe, send an email to [email protected] with the word unsubscribe in the message body.
