[AMRadio] 160 meter antenna


JACK C. SHUTT w9gt at verizon.net
Tue Jan 13 09:34:44 EST 2009


Here is some info on the de-tuning process and hardware:
 
http://www.amcoordination.com/detune.htm

--- 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: w9gt at verizon.net
Date: Monday, January 12, 2009, 3:22 PM




Glad to share what Info. I can Jack. 73's
-------------- Original message from "JACK C. SHUTT" <w9gt at verizon.net>: -------------- 






Hey, now that makes sense.  There is an AM broadcast station less than a mile or so from that antenna site.  It uses a four tower directional array. I'll bet they are tuning that monople to look like it is invisible and to not effect the radiation pattern.  I would think that the broadcaster would have to pick-up the tab for that installation.  They apparently incorporated it into the tower safety system design as they are using those cables for climbing as well.   I didn't think it was a radiating antenna in its own right, but ya just never know.

That is really interesting....thanks for the response and input.  It would be cool to have access to that thing to use for a transmitting antenna.
 
73,  Jack, W9GT
--- 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: w9gt at verizon.net
Date: Monday, January 12, 2009, 2:18 PM




Hello Jack, this blog is so interesting....I may never go back to the real life. I have been in communications with a ham whom works for a radio station, describing the reason for what is called a Unipole on towers. In essence, he is saying, this makes nearby communications towers look almost invisible to the nearby AM/FM station/s. Glad to meet you by the way, I worked for Motorola for 20 yrs of which half was spent in their factory troubleshooting Cellular equipment, 5 yrs. for Ericsson doing Nationwide Field work, followed by 9yrs. working for Sprint/Nextel field work and now I am doing contract work for T-Mobile, sweeping antennas on new sites as well as Preventative Maintenance. Here is a comment from him in answer to questions I posed to him. 
Yes Robert
that enclosure box contains  a cap and coil. Just like an ATU(antenna tuning 
Unit)  depending On how many AM stations are in the local area that may be 
re-radiated That box may contain several De-Tuning networks.
an example may Be here in NJ   The State Police decided to install a New 250 
foot tower less than 1/4 from our 930/1480 transmitter site. both stations are 
directional toward NYC. With this new tower installed. and No detuning units. It 
casts a shadow where the signal  cannot be heard behind it.
the Best way to describe this would Be by holding up a flashlight pointing to 
the east. now  place a stick infront of that light.  behind the stick will be a 
shadow... thats where the signal is NOT going where it should.
We Placed 2 De-tuning networks onto that Tower..  
It is now somewhat invisible.. so now replace that stick with a  Glass tube.  
The Light still shines in the Direction of where it should be going..
I dont think I can explain it any Better than that

-------------- Original message from "JACK C. SHUTT" <w9gt at verizon.net>: -------------- 






Well, don't know what the box is, but I have watched them clip on to the cables and climb the tower (s).  One in  particular, here is a monopole tower with three cables spaced out from the pole about 2 or 3 ft.  I watched them using them when they were putting up cell antennas.  I can't imagine that there would be that much demand for HF or MF antennas.  Anyway,  it would be interesting to know what they would be using them for in your area other than for safety cables.  Not debating....just my observation.  I have worked in the telecom industry as an engineer and in management for over 40 years.  Presently working 
at a "retirement" position for a related company.
 
A similar system is installed on our microwave tower here at the C.O.  The safety cable runs up the tower along the ladder.

--- 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: w9gt at verizon.net, "Discussion of AM Radio in the Amateur Service" <amradio at mailman.qth.net>
Date: Monday, January 12, 2009, 1:13 PM




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" <w9gt at verizon.net>: -------------- 






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 <robertcharles at att.net> wrote:

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


> 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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