[600MRG] Free standing verticals

Fri Feb 16 12:22:24 EST 2018

Thats a great suggestion. I will experiment and (eventually) share my
results.

On Fri, Feb 16, 2018 at 9:21 AM, Brian, WA1ZMS <wa1zms at att.net> wrote:

> Ben-
> I had an added idea of putting a foot of
> small shock cord on the bottom end of
> the wire inside to keep it in tension. The
> voltage will likely be lower at the bottom
> although a tiny homebrew insulator will
> be best. And you have the most room
> inside at the bottom anyway.
>
> -Brian, WA1ZMS
> iPhone
>
> On Feb 16, 2018, at 11:49 AM, Ben Gelb <ben at gelbnet.com> wrote:
>
> Many thanks for all of the replies.
>
> I just ordered an 18m spiderbeam pole, and going to try to fashion some
> kind of base (with either large dia ABS or a wooden post sunk into the
> ground) to secure it at the bottom. Will experiment w/ varying height and
> see how far I get w/ minimal guying.
>
> I really liked the suggestion of running the wire inside of the pole - I
> think this will help keep it balanced, and if it can support a little bit
> of tension, maybe even help keep it vertical. Will experiment and see.
> Still have to figure out the top wire(s) but if making pole stay vertical
> goes well, can probably figure out something, esp if they're relatively
> light gauge. Maybe sloping to the house, or another pole.
>
> On Thu, Feb 8, 2018 at 10:38 AM, W2XJ <w2xj at w2xj.net> wrote:
>
>> let me add a twist. Consider utility poles. It is not an obvious choice
>> unless you’ve worked with them (I have) They are not that expensive and
>> very wind resistant while capable of carrying a fairly substantial load. A
>> 40 footer typically provides about 34 feet above ground height while a 60
>> footer can provide 50 feet or more. I have used them in the past and the US
>> military built many 50 watt AM radio stations with those as masts along
>> similar lines of Mr. Smith’s designs  While not an option for everyone, it
>> is worth consideration in certain situations.
>>
>> Sent from my iPad
>> _____________________________
>> From: Mike Irizarry <michael.irizarry29 at gmail.com>
>> Sent: Thursday, February 8, 2018 10:50 AM
>> Subject: Re: [600MRG] Free standing verticals
>> To: Brian Pease <bpease2 at myfairpoint.net>
>> Cc: <600mrg at mailman.qth.net>
>>
>>
>>
>> Check this design out. You good use a 40 foot fiberglass push up mast to
>> build something similar. Picture is in the link. Looks like 43 foot mast.
>>
>> Carl E. Smith has now described (IEEE Trans. on Broadcasting, June 1989,
>> pages 237-240) a modified short low-loss AM antenna and explores ways in
>> which the performance of relatively small transmitting or receiving antenna
>> systems can be improved. He writes: "Small AM antennas are useful for
>> standby use when the regular antenna fails for some reason. With some
>> modification of a short tower by using top loading, low-loss loading
>> inductances and an insulated counterpoise, the performance can be made
>> quite acceptable. The counterpoise is connected as shown in the
>> illustration. The inductance +jx4 is tuned so as to maximise the field
>> strength radiated by the antenna into the far field... Top loading raises
>> the current loop on the tower and, by adding a low-loss inductance at the
>> top of the tower, the current loop is raised still higher on the tower. A
>> low-loss inductance at the top of the tower can be achieved by insulating a
>> suitable conductor inside the tower and shorting it to the tower to
>> simulate a short-circulated coaxial line with the open and inner conductor
>> connected to the top loading hat at the top of the tower... At the bottom
>> of the tower, more series inductance can be added by insulating a conductor
>> up inside the tower to a shorting point. It may also be necessary to add a
>> low-loss base loading-coil to resonate the top hat with the counterpoise..
>> The counterpoise potential is adjusted to minimize ground losses."
>>
>> Dr James F. Corum of Corum & Associates Inc. believes that "The
>> Smith/Musselman low-loss tuned-counterpoise structure is a remarkable
>> addition to the technology of electrically-small antennas... it represents
>> a significant contribution to this branch of antenna engineering. We think
>> that anyone requiring a vertical stub with an abbreviated ground system
>> should seriously consider this technology." It is clear from the paper that
>> results are highly dependent upon correct tuning of the counterpoise
>> system, preferably while observing the far-zone field strength. At the
>> Corum test facility at Windsor, Ohio, a Smith/Musselman radiator resonating
>> on 1330kHz had a tower height of 43ft, a top hat of 24 horizontal radials
>> 50ft long, a counterpoise of 24-50 radials 12ft above ground and soil
>> conductivity of 8 millimhos per metre, producing a field strength at 1 mile
>> of 1.1mV/m with 250mW input with the counterpoise tuned, dropping to
>> 605p.V/m without the tuned counterpoise.
>>
>> http://www.robkalmeijer.nl/techniek/electronica/electronicab
>> laden/ew_ww/1990/02/page169/index.html
>>
>> On Thu, Feb 8, 2018 at 9:23 AM, Brian Pease <bpease2 at myfairpoint.net>
>> wrote:
>>
>>> One cheap method to get some height is to mount a 10-12 ft piece of Sch
>>> 40 large dia PVC pipe on your post with a short adapter or shimming on top
>>> to fit a tall (say 30 ft) lightweight carbon fiber fishing pole/kite pole
>>> on top, which just drops in.  The trick is to run a wire INSIDE the kite
>>> pole attached at the top and run right out the bottom and through the PVC
>>> pipe.  A light horizontal wire can run to your other pole.  This should be
>>> self supporting although it will bend towards the house.  I think the main
>>> problem would be breaking of the horizontal wire in high winds.  An light
>>> guy line (or wire) run from the top to the neighbor's house might help.
>>> I also have used electrical tape on each joint when extending the kite
>>> pole to prevent collapsing.
>>> Depending on soil conditions, I would consider enlarging the bottom of
>>> the post hole and packing in a bag (80 lbs) of mixed QuickCrete.  I
>>> installed >20 8 ft sign posts this fall.
>>>
>>>
>>> On 2/8/2018 12:10 AM, Ben Gelb wrote:
>>>
>>> Thanks all for the replies.
>>>
>>> Yard is 30' wide by perhaps 45' deep behind my rental house in San
>>> Francisco. There is one tree of substantial height (the one thats going
>>> away) on one corner of the yard (up against mine and my neighbor's house on
>>> the east side of me). That currently gives me about 30' of vertical for my
>>> inverted L, and then I have a fiberglass fishing pole supporting the end of
>>> the top-hat about 30' away from the vertical. (this inverted L is my only
>>> transmitting antenna currently, but for MF and HF - I also have a couple of
>>> small receiving loops on a rotatable base at ground level)
>>>
>>> With the tree gone will need to provide my own structure, and I would
>>> prefer to avoid a lot of guying if possible, as there's not a lot of room
>>> for it, and it will really consume the entire yard. I was thinking to sink
>>> a 4x4 or 6x6 post into the ground (i have a post-hole digger) and then
>>> maybe attach some sort of mast to it, hopefully stiff enough to not need
>>> any guying (or at least not much). Alternatively, the DX Engineering
>>> MBVA-5A looks like it might be a reasonable option, albeit perhaps a bit
>>> more expensive than some home-depot option (ostensibly it doesn't require
>>> guying).
>>>
>>> If I were to kludge up some set of metal pipes and tubes, I wonder how I
>>> might mount it to a wooden post - I'm thinking a wooden post might not be a
>>> great dielectric (tree sure wasn't) and might lead to some burning. Anybody
>>> tackled that problem?
>>>
>>> I do have some of the 4' military mast sections (mine are aluminum not
>>> fiberglass though) but I think they'll get pretty floppy over 15-20' or so
>>> w/o some guying...
>>>
>>> Neighbor mentioned being open to draping a wire over his house if it
>>> helped.... but I think more useful would be expanding the radial field
>>> throughout his backyard... haven't broached that subject. He might be less
>>> excited about that.
>>>
>>>
>>>
>>> On Wed, Feb 7, 2018 at 5:35 AM, Dave Riley <dave.riley3 at verizon.net>
>>> wrote:
>>>
>>>> Hello Ben,
>>>>
>>>> Can you give us more info concerning your real estate plot such as
>>>> square footage, relationship to power lines, existing antennas, size and
>>>> height of your home, any neighbors who would allow you to span their
>>>> property, or any obstructions that would be in the way of an antenna and
>>>> lastly what you have for antennas for ham use at this time?
>>>>
>>>> Are you presently using any sort of loop or probe antenna for receive?
>>>>
>>>> All the answers to your quest so far sound workable so maybe a mix or
>>>> some kind of a modification could allow you to enjoy the new band.
>>>>
>>>> Thanks from DaveR @ aa1a
>>>>
>>>>
>>>>
>>>> On 2/4/2018 7:11 PM, Ben Gelb wrote:
>>>>
>>>>> My neighbor is taking down my antenna tree ... possibly this week :(.
>>>>>
>>>>> Its actually the right thing - the tree is very unbalanced and needs
>>>>> to go. But it means my undersized antenna will be even smaller (gone)
>>>>> soon...
>>>>>
>>>>> Seems like I may need to try to get something in the air that doesn't
>>>>> require a tree or permanent support structure. I can probably fashion some
>>>>> kind of vertical pole out of cheap materials, but imagine it will require a
>>>>> lot of guys to remain vertical - which I'd kind of like to avoid since I
>>>>> don't have a lot of room for guys.
>>>>>
>>>>> Any suggestions from this group?
>>>>>
>>>>>
>>>>
>>>
>>>
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>>
>>
>>
>>
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