Topband: T-antenna dimensions?

[Herbert Schoenbohm]

Mike Waters W0BTU wrote:
> I have some trees picked out for a T antenna, between a section of pasture where it's easy to lay down a lot of radials. I can have a 50' vertical section.
>
> But I'm having trouble finding what the approx. dimension of the horizontal portion at the top should be. Any advice would be appreciated!
>
>   

Mike, Assuming a 50 foot vertical drop...... 100 foot horizontal section 
or more to make the feed point have some inductive reactance which you 
can tune out with a series cap to get a reasonable VSWR.  If you have an 
MFJ 259B you can check the base impedance and reactance right at the 
bottom of the drop and put in a fixed mica transmitting cap close in 
value to the inductive reactance you read.  Or use a bread slicer to see 
what you may require and replace with a fixed cap after measurement  You 
might also want to use a choke to decouple the feedline run from the 
vertical T.  If you can drive the base impedance up to 40-50 ohms by 
adjusting the equal length of the top. 

See you in the contest.


Herb, KV4FZ