[stampeder]

I was just going to say the same thing - the arsenic got banned, so copper quat is the standard now.

BTW, if anyone is going to mount a metal pole on or against some pressure-treated lumber that uses copper quat the metal pole must be galvanized and the fasteners must be hot dipped galvanized, or else corrosion will happen relatively rapidly.

 

[antenfan]

Wood works good on M-4

I've been using McClapp's M-4 design with 9 3/4" spacing and 10" elements for better than a year. I used steel, wood & cpvc. It receives 2-edge channels that have co-channel and adjacent interference better than any other antenna I've used. Please see pictures in my profile.

 

[300ohm]

Very nice job on the reflector.

I think you would find that if you replaced that piece of wood holding the elements with a plastic, it would perform better. And it looks like from the pictures the bowtie feed point gaps are a bit too close together. Having them at spec would also improve performance.

 

[stampeder]

Nice build!

The wood in the second photo is already cracking and gray, so it would also be good to replace it for structural reasons as well as what 300ohm said.

 

[overunity]

I know this is an old thread at this point, but still referenced I'm sure. I just wanted to throw in my two cents that in an indoor environment where humidity doesn't get out of control, kiln-dried wood, especially laminated plywood, is essentially identical to a plastic. The moisture content is negligible and the wood is electromagnetically inert. That's why antennae work from the inside of wood-framed houses with wood sheathing. The same wouldn't hold true for either outdoor environments or indoor environments that suffer high humidity, where the porous wood might absorb moisture and become an electrolytic medium. For my ideal antenna paradigm, which is to embed it within a wood-framed wall and thus eliminate any outward appearance of it, wood is an ideal building material. But for an even further, probably superfluous, measure to prevent interference, I've used nylon bolts and rubber washers to completely insulate the antenna connections from the wooden substrate.

 

[300ohm]

that in an indoor environment where humidity doesn't get out of control, kiln-dried wood, especially laminated plywood, is essentially identical to a plastic. The moisture content is negligible and the wood is electromagnetically inert.

Not really. The moisture content of kiln dried wood can vary from 6% to 12% as bought. (more if the lumber was stored outside in the rain, like a lot of places do. My local Lowes has a habit of getting in a shipment of lumber, then leaving it outdoors for a while. Then they wonder why when they bring it indoors and unbundle it, its mostly curved boat lumber, heh. )
http://www.fpl.fs.fed.us/documnts/fplrn/fplrn226.pdf

Wood also eventually acquires the prevailing moisture content of the environment, so in an attic, kiln dried wood may get to 20% or more moisture content like air dried wood, depending on the climate.

I've used nylon bolts and rubber washers to completely insulate the antenna connections from the wooden substrate.

Indoors, nylon bolts and rubber are fine. Outdoors, white nylon and a lot of rubber types don't last long. For outdoors, you want to use UV resistant black nylon and fiberglass or UV resistant gray or black plastic.

 

[Stereocraig]

I agree w/ the part about the plastic and rubber washers/shims/ sleeves, but could never be certain of their benefits, if they were inside a building, where the antenna would be subject to electrical interference, reflections and attenuation from building materials.

 

[overunity]

Wood also eventually acquires the prevailing moisture content of the environment, so in an attic, kiln dried wood may get to 20% or more moisture content like air dried wood, depending on the climate.

If your attic averages 20% or more moisture, then the limiting factor will be your rafters, roof sheathing, floor joists, etc., not the small strip of wood used to mount your antenna. But in most cases, all of this wood is virtually transparent to radio waves.

 

[overunity]

Can't find the function to delete accidental double-post.

 

[zdcyclops]

More info on woods water content: when wood is cured at 220 degrees F its water content can be reduced to O%, it can then be sealed with a marine grade varnish to prevent water
uptake. Here's another link on the dielectric properties of wood, lots of facts and figures for the technically competent. http://www.fpl.fs.fed.us/documnts/fplrp/fplrp245.pdf

 

[300ohm]

At 220F working temps, youre much better off dipping the bone dried FINISHED piece of wood into paraffin, which has a lower dielectric constant than shellac or varnish. This is what they used to do in the early days of radio.

 

[holl_ands]

Paraffin isn't used anymore because of the FIRE HAZARD, whether in original block or finished coated form....and it does NOT cancel out the Conductive Element effect of the the material contained inside.