[Elecraft] OT: Small Patio Vertical:

[Vic Rosenthal]

Martin AC6RM wrote:

> 1.  nine-or-so-foot home-made "whip" ...  with
> a SGC239 providing matching services at the base;
> 
> 2.  same as above, but with one of the buddipole coil forms performing
> antenna "tuning" duty.  Essentially a centre-loaded vertical;
> 
> 3.  a screwdriver-driven centre-loaded vertical (high sierra hs1500). 
>    I am able to a/b test #1 and #2 and I found that #1 seems to have
> better receive (more S-meter action on my K2 on any given signal) but
> not by much.  

Theoretically, a center-loaded vertical should be more efficient than a 
base-loaded one.  Since it's not, I suspect that the Buddipole coil is 
lossy enough to make up for it.  Another possibility is that there is a 
lot of resistance in the joints of the Buddipole parts.  Since the 
radiation resistance of a shortened vertical is low, any ohmic 
resistance in the antenna or ground connection will have a large effect 
on efficiency.

Note that adding a capacity hat to any shortened vertical will improve 
efficiency, since it will increase the radiation resistance and also 
allow you to have a much smaller coil.

> My recall tells me that #3 performed better than either
> #1 or #2, 

I would expect it to be better than 1 and 2 because it is about the same 
height with a much better center-loading coil.  The wire size and form 
factor (length/diameter ratio) of the coil affect its Q.  If you have 
seen the large diameter "Texas bug catcher" coils that are popular, this 
is why.

>    Thoughts / references?  I am really interested in why one design -- #1
> would be better or worse than #2 or #3 for receiving.  

Almost certainly what gives a louder signal on receive will be more 
efficient or transmitting.  See above for why 2 was better than 1.

>    And is the idea of putting the matching components (inductor, etc.) in
> the middle of the antenna section better than at the base, from a
> "receive" perspective?

Yes, for both receive AND transmit.

Vic K2VCO
Fresno CA