vertical dipole against brick?

[rjvalenta]

i built a vertical dipole out of some 102” whips a friend got for cb use and never used. i got a T bracket and bent the arms in, then put a 3/8 base on one side and a 3/8 to pl259 on the other side with a spacer… and laying on the attic floor it’s got a respectable swr at 1.6 when tested with a cb.

id like to mount it to my brick chimney, where i will be able to change out with hamsticks as i choose, or maybe just leave it for cb use, who knows.

the chimney is not seen well from the street and will be less likely to be noticed by HoA neighbors, and with the feed line well tucked into the roof line will hopefully go unnoticed.

but i’m wondering how much having the antenna inches from a brick wall will impact performance, transmission, reception, and swr.

hoping to hear some thoughts before i’m on a ladder with a hammer drill. anyone ever put a vertical up against a brick house?


thanks,

Richard
N0TZC

 

[jaspence]

First concern would be does the chimney have any kind of metal liner? Very possible for water heater or gas furnace. I am running an end fed 10 meter antenna with a G90 transceiver in my 1st floor workroom and worked New Mexico at s9+ with 15 watts USB. Just read an article about buried antennas (used mostly by military). Results vary due to different soils, but some do work.

 

[popnokick]

The answer is..... YMMV. It will work in some manner. But it will work. As well as if it were mounted high and clear on the roof? NO. Better than an antenna that is indoors in the attic? Probably. Even if there was some way to model the performance or get some predictive data... it would likely be subject to a wide degree of variance. So.... get out the ladder and hammer drill... try mounting it that way and see what happens. Perhaps there is a temporary lash-up you could use to hold it in place to see how well it works before you drill.

 

[iMONITOR]

If you can use a strapped chimney mount similar to the one in the picture. Use a short length of mast but as long as possible while keeping it somewhat stealth but at least to get the antenna element above the top of the chimney. Consider painting the mount and the portion of the mast to match the color of the brick and maybe the upper part of the mast with something less bright than the metal like a light gray. Keep all this on the back side of the chimney where it will be less noticeable.

 

[WA0CBW]

Dont forget on a vertical dipole the coax feed needs to leave at a 90 degree angle to the elements for at least a quarter wavelength (or more).

BB