[AMRadio] 160 meter antenna


Ken Zuercher hepcatrevival at yahoo.com
Mon Jan 12 17:13:32 EST 2009


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, robertcharles at att.net <robertcharles at att.net> wrote:

> From: robertcharles at att.net <robertcharles at att.net>
> Subject: Re: [AMRadio] 160 meter antenna
> To: "Discussion of AM Radio in the Amateur Service" <amradio at mailman.qth.net>
> 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
> <bguyger at sbcglobal.net>: -------------- 
> 
> 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: "robertcharles at att.net" To:
> w9gt at verizon.net; 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, robertcharles at att.net wrote: 
> > 
> > From: robertcharles at att.net 
> > Subject: Re: [AMRadio] 160 meter antenna 
> > To: cozy659 at yahoo.com, "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 
> > > >
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