A better material for ground screens might be expanded aluminum mesh.
I've seen 50' rolls of 6" wide mesh for use as gutter screens. I did
some googling and found painted Al gutter mesh, but I have seen it in
the past unpainted at my local hardware store. Check Sears also.
Expanded metal mesh is not particularly expensive since it has a 4 to 7x
expansion. Also, the grass and weeds can easily grow through it. Al
metal flashing is another choice if you don't mind stripes in the lawn ;-) .
Two other materials I came across are Al artist modeling mesh, used as a
framing structure to build sculptures in clay, paper mache, etc. I only
found 24" wide by 10' lengths, but some company is making these small
rolls out of big ones. There is also a rodent block woven copper
material that comes in 100' rolls by 6". I haven't seen this material
so would be cautious about its RF continuity. I know that woven Cu
residential screening isn't very good for RF screening if not soldered
or welded periodically. The wires don't make good enough contact.
http://www.pestmall.com/stuf-fit-rodent-proofing-copper-mesh.html
http://www.dickblick.com/products/amaco-wireform-mesh/ see "gallery mesh"
I've also purchased expanded galvanized steel from McNichols in sheet
form. see
http://www.mcnichols.com/products/expanded/standard/material/aluminum/
I don't know if they have/can get rolled material. They have warehouses
in many cities.
In addition to salt water being a great antenna ground, I've operated
mobile from an alkali lake bed (Black Rock Desert Playa) that mostly
dries out in summer and that worked very well. Next time I'm there I'll
measure the conductivity.
Grant KZ1W
On 9/25/2011 10:23 AM, Jim Lux wrote:
> On 9/25/11 9:41 AM, Kevin Normoyle wrote:
>>> From ON4UN's Low-Band DXing regarding ground enhancements using mesh
>> screening... "Steel is a very poor conductor at RF"
>>
>>
>> Looking at VK1OD's table here, zinc is pretty good
>> http://vk1od.net/antenna/conductors/loss.htm
>>
>> so zinc-plated steel, or Al would be fine, it's just the corrosion issues.?
>>
> I think so. It sort of depends on a whole cost/benefit analysis... If
> you're rolling out wires for a weekend or a couple weeks, cheap and
> light might be the ticket (go aluminum!). If you're installing a ground
> field for your 160m full wavelength vertical to reduce losses so you can
> beat the guys operating in the middle of a salt marsh for the Stew Perry
> for the next 20 years, then copper might be a better choice.
>
> ANd the corrosion thing will be highly site specific. If you're out in
> the desert (where soil conductivity is really, really low), practically
> anything will help. If you're in that salt marsh, galvanized fence
> wire's probably not a good choice. (I remember seeing a big AM
> broadcast tower in Japan in the middle of a lagoon or marsh on the way
> from Nara to Osaka and thinking: yes, they have a great location. The
> lagoon served as field for a golf driving range, too. I don't know how
> they recovered the balls, though)
> _______________________________________________
>
>
>
> _______________________________________________
> TowerTalk mailing list
> TowerTalk@contesting.com
> http://lists.contesting.com/mailman/listinfo/towertalk
>
_______________________________________________
_______________________________________________
TowerTalk mailing list
TowerTalk@contesting.com
http://lists.contesting.com/mailman/listinfo/towertalk
|