[TowerTalk] Why did adding a radial make the input Z of my inverted L go ...

[Jim Smith]

Hey guys, thanks for taking the time to formulate these responses.

Yuri -

1.  Yes, everyone has been telling me that the BCI is messing up my 
measurements.

2.  Yep, aware of that.  Where is K7GCO?  Haven't seen him on here for 
ages.  Last I heard he was in the process of moving.

3.  I hadn't thought of the possibility of not being in the centre of 
the "dipole". 

4.  3/8 wave.  Wish I could but lot is only 33 x 120 ft and 6kV power 
line is only 18 ft or so from top of tower.  Hence tower top 
deliberately no higher than power line at 30 ft.  Originally wanted to 
go to 50 ft.  Maybe I can convince everyone that the power lines should 
be underground.

5.  I understand that I'll get some horizontally polarized radiation.  
This is not a bad thing.  This antenna's purpose is to enable me to 
increase my mults in contests where domestic mults count.  I'm hoping to 
be able to work the Carib guys too.  If I get any DX beyond that, I'll 
consider it a real bonus.  If it performs as I hope I will be real 
happy, knowing that I've probably done the best I can, given the 
constraints of my QTH.

6.  Very impressive performance.  Bet you lit a big Cuban cigar after 
that one.

7.  Being the typical ham in a hurry, I thought I'd model it after I get 
it working!  Given my entry level modelling skills and that there really 
wasn't much in the way of options for 160, this may not be quite as dumb 
as it sounds.  i.e. I now have an antenna, the rest of the radials went 
in today, I just have to trim it to length.  Had I gone the other route, 
in the same amount of time I might have a model that I have confidence 
in but I wouldn't have an antenna that I can use in WPX.  I also 
wouldn't have worked XF4IH on 40 ssb.  40?  Yes, the L works better on 
40 than my 40 dipole.


Lee -

I tried the GDO, an FB old Millen 90651.  I connected the tower to the 
ground plate with a length of wire.  I wrapped 3-4 turns of the wire 
around the GDO coil.  I was unable to get a discernible dip anywhere in 
the freq range covered by the coil so then I tried the Autek RF1 with 
results as described. 

I just looked at the GDO coil I used and see that its range is 1.7 to 
4.5 MC (I said it was old - we didn't have MHz then).  Now I realize I 
might have had better luck with the 925 to 2000 KC coil.  I'll have to 
try it out.

I was planning on making the antenna slightly long and putting a 
variable C in series so I could resonate the antenna anywhere in the 
band.  Maybe even motorize it.  From what you say, maybe the MkV tuner 
will be good enough.

As always, a learning experience.  TT is such a great resource of people 
helping people.

73 de Jim Smith   VE7FO