"Dave VanHorn" wrote in message
...
Have you looked at the collinear antenna on the web written by "Brian

Oblivious"?

No, I googled on it but didn't hit anything.

He cuts the coax into equal lengths 1/2 wave each.

The articles I have seen are 1/2 wave * the velocity factor.

Each one connecting center to shield.

I can't picture how the elements all end up resonant, and in phase.

Seems like one of those can't be true.

And that

1/2 wavelength accounts for the velocity of propagation inside the coax.

So, each length is somewhat shorter than the free space halfwave It shows

how he connected lengths of coax to make a collinear array. In my
opinion,

that would be a waste of that good coax you have.

Why? It's nice rigid coax, and takes that sort of soldering well.


Dave

I didnt mean to imply that your good coax wouldnt work well. I (perhaps
wrongly) assumed that some garden variety coax might work OK for that
staggering of lengths of coax, inner conductor to outer conductor.

My web service thru Google, gets me that Brian Oblivious + Capt Kaboom
site on their 802.11 2.4 GHz antenna. They indicate that the "elements" are
1/2 wave long minus the Vp inside the coax. That will put the feed points
along that 'staggered' array, in phase.

You have probably already considered that there will be some beam squint
with this type of collinear. The "corporate fed" collinear will a
maintain a main beam broadside, even though sidelobes do increase with
bandwidth.

Jerry