[ARC5] Antenna for small yard

Fri Oct 21 02:49:10 EDT 2016

Does this look like your area?

 Wayne
WB4OGM

-----Original Message-----
From: AKLDGUY . <neilb0627 at gmail.com>
To: Kenneth G. Gordon <kgordon2006 at frontier.com>; ARC-5 List <arc5 at mailman.qth.net>
Sent: Thu, Oct 20, 2016 10:44 pm
Subject: Re: [ARC5] Antenna for small yard

On Fri, Oct 21, 2016 at 4:06 PM, Kenneth G. Gordon <kgordon2006 at frontier.com> wrote:

> Neil:
>
> I do antenna modeling here.
>
>First of all, if you can give me a really clear address, I may be able to look your yard up on
Google Map.

3647.85S/17444.94E

> I have no clear idea of your orientation N to S, E to W, and no clear idea of your physical
plant layout there either.

The building is exactly aligned on N,S,E,W. And I mean exactly. Not +/- a few degrees. Exactly. As I walk out my ranchslider into the yard I'm facing due west.

>So, in the meantime, let me see if I have this correct.
>
>Your apartment building is parallel to a fence which is 24 feet long. One corner (the "right"
corner, direction?) of the apt buildfing is 19 feet from the fence and the end of the apt
building is even with that end of the fence.

Yes, the NW corner of the building is 19 feet from the Northern corner of the fence, with everything square.

> At the "left" end of the fence, it makes a right-angle back towards the building and within 6'
runs into a concrete earthquake reinforcement which reinforces that end of the apt building.

Yes, the southern end of my section of the fence makes a 90 degree turn back towards the building. The fence actually carries on even further to the south to enclose the neighbouring yard, so this is really a T-junction. I've just been out to measure more accurately and it's not a 6' turn-back, it's a couple of inches off 9 feet.

> How "deep" does this concrete reinforcement extend towards the "right" end of the apt
building? Is the apt building set back from some end of the concrete slab so that there
remains 13 feet between that point and the building?

The slab is massive. It's a single casting 9m high (3 storeys) x 8 inches thick x 10 feet wide. At least another couple of metres are buried in the ground. It butts up against the building (thin side against the building). It's duplicated on the eastern side of the building but that's irrelevant.

> How high is the apt building? Can you reach the roof easily? How "wide" is the building? Do
you live in all of it, or are there other tenants in the same building?

There are two storeys above mine and no way to reach the roof. There are other tenants on my floor and the other floors.

> Is there similar room on the "other" side of the apt building?

No. The other side of my apartment has the "front door" which leads out into the building's foyer and beyond that there is a similar apartment to mine with its neighbour on its south side. The entire building is exactly square. Four apartments per floor, 12 in all.

> What is the height of the fence at its top above ground?

5 feet / 1.5m.

> Do you wish to operate on both 80 and 40? Higher? Lower?

75m (specifically 3850 KHz for the AM net) is essential. 40m (specifically 7125 KHz) would be a nice bonus for the Sunday afternoon AM net (my BC-230 also has the 6200-7700 KHz coil set). I don't care for any other frequencies since milsurp AM is all I want to do.

>> So, for an approximately balanced antenna, I would have the 24 feet, plus 6 feet at each
>> end right-angled back towards the apartment. Obviously I can make no use of the concrete slab
>> portion, even though more fence is available at the other end.

> What does this mean (more fence available at the other end) in "physical layout" ? Other
end of what?

I meant the 19 feet end (the north facing end). Obviously I can't run wire along the 10 feet wide slab, and that would be pointless since it contains reinforcing mesh. So all I would get out of this portion would be the 8 feet or so of fence, even though the full 19 feet is available in the other right-angled leg. Note: it's now 8-9 feet, not 6 feet after I measured more accurately.

> Where is your operating position with regard to either end of the fence?

A meter or so inside the ranchslider, which is not quite central to the western side of the building. It would be perfectly acceptable to carry the BC-230 on its rack out thru the ranchslider and set it up on my concrete landing, about 18 inches above ground. The next storey's balcony would protect it from rain and dew (never snows in Auckland, ha!). The BC-230 would then be about 15 feet from the 24' western section of fence and offset by about 3 feet from its mid-point.

73 de Neil ZL1ANM

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