[Antennas] log periodic design article; a few questions

[Gary Lee]

Could someone on this list please take a look at the following url and do a 
thing or two for me?

http://www.conformity.com/0005emc.html

I looked at this, and tried working out there math as best I can.

I am totally blind, and all their formulas are shown as embeded graphics, 
so can only guess.

However, I can't get the math to work.

Could you please pull out the formulas, send them to me in text form, and 
maybe tell me what I've missed?

For example, the first element of the antenna is calculated with the 
traditional 492/freq formula for a half wave excluding velocity factor.

The next element looks to be el-1 * (tau) selected as 0.8 in their example. 
However, I get 23.616, not 23.64.
Help!!