multiband vertical on the roof... how long for the radials?

[mr_fx]

Planning to build something like this (the vertical)

but I am wondering since I plane to mount this on the peak of the roof and anchor it to the chimney, how would I determine home long toe make the radials?

I am planning to use and old A99 with the matching section out (perfect for 20m), then a an element for 6m/10/15m (maybe 12m?)

So this will be a 20/15/10/6 vertical

My homebrew vertical multiband hf antenna | ON3JT

 

[Beetle]

Planning to build something like this (the vertical)

but I am wondering since I plane to mount this on the peak of the roof and anchor it to the chimney, how would I determine home long toe make the radials?

I am planning to use and old A99 with the matching section out (perfect for 20m), then a an element for 6m/10/15m (maybe 12m?)

So this will be a 20/15/10/6 vertical

My homebrew vertical multiband hf antenna | ON3JT

Quarter wavelength vertical antenna needs a quarter wavelength radial (actually at least two per band, arranged 180 degrees apart, and more than two per band will not hurt anything). Make the radials part of a guying system.

 

[mr_fx]

Quarter wavelength vertical antenna needs a quarter wavelength radial (actually at least two per band, arranged 180 degrees apart, and more than two per band will not hurt anything). Make the radials part of a guying system.

it will be mounted at roof level, and bolted to the chimney, no guying will be needed

the radials will be laid out on the roof following the slope of the roof

 

[Beetle]

In that case, delete the last sentence of my previous post.

Be really sure your chimney can stand the leverage of the antenna in the worst wind you've ever seen in your area (whatever/wherever). Many chimneys on older houses are just brick and mortar, with no reinforcement and just relying on gravity pulling straight down.

The chimney on my parents' old house in Las Vegas was built before Isaac Newton invented gravity... ... so it was exempt from this.