[TowerTalk] Wind Load Spec Differences Between Tower and Antenna

[Steve Dyer W1SRD]

Thanks Steve.

It's El Dorado country. From Champion, it's a 75 MPH windspeed county.

Current specs for a Tashjian:
1. LM470 is 18 sq ft @ 72' for 85 MPH w/ 3 sec gust per TIA-222-G.
2. WT51 is 13 sq ft @ 53' for 85 MPH w/ 3 sec gust per TIA-222-G.

I have some older Tri-Ex documentation that lists the LM-470 at 16 sq ft 
in 60 MPH and the WT51 at 9 sq ft in 50 MPH.

Current specs for SteppIR:
1. DB36 17.5 sq ft for 100 MPH per EIA-222-C
2. 4 EL 9.7 sq ft for 100 MPH per EIA-222-C

Can I assume the antenna wind loading is less at 70/75 MPH?

Again, looking to be safe, not get a permit.

73,
Steve W1SRD

> >  Would like to be confident my LM-470 can handle a DB36 (17.5 sq ft 
> using
> 100 MPH EIA-222-C) .
> I believe the 4 El SteppIR (9.7 sq ft) is fine on the WT51
> >  Usual caveats about crank it down in the wind already noted. Also, the
> Tashjian specs are for a *new* tower. I don't know the vintage or
> history of the LM-470 I have. It came with the property.
>     What do the current specs say? In the old days - pre-EIA-222 - 
> crank-ups were rated @ 50MPH. Your tower might be that vintage.
>     You didn't include enough specifics. What is your local windspeed 
> rating? You can find an older EIA-222 windspeed rating for all US 
> counties at http://www.championradio.com/county.windspeed.data.html. 
> San Mateo County, CA, is a 70 MPH windspeed zone. Not a high wind area 
> (70 MPH is the minimum windspeed rating) but crank-ups have to be 
> treated with much care wind-wise.
>     You could probably get away with it but if you need to get a 
> building permit, forget it.
> Cheers,
> Steve    K7LXC
> TOWER TECH -
> Professional tower services for hams