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Re: perpendicular primary

At 08:22 PM 03/20/2000 -0500, you wrote:
>Hi Dan and all,
>I have a question--just for a change:
>Why is the flat spiral SOP for a TC primary? Has anyone experimented with a 
>solenoid
>of sufficient diameter to avoid the arcover problem?
>
>I made a perpendicular primary for the 3.5 inch diam secondary on my 1/2 wave
>bipolar. It is a huge deadly spider web nearly 18 inches in diameter. I have 
>ten turns of
>3/16 Cu tubing with a 0.75 inch spacing. Well, that's what I tried to get.  
>:-)) I find a very
>sharp f res at 74 kHz and a very broad tuning with lateral adjustment along 
>the secondary.
>I guess the flat coil at the electrical center produces sort of an 
>ellipsoidal field. Is that good? That is why I ask the question on the flat 
>spiral use with a regular TC. Unlike the large solenoid, there is no arcing. 
>Perhaps this is a good clue to the 
>poor coupling.  Aside from the mechanical problems of safely supporting this 
>monster, I'm not overly impressed by the results compared to the performance 
>of a 6 inch diam -12 turn
>solenoid. I will try another flat coil wound to 0.50 spacing and a few more 
>turns to 
>increase the inductance.
>
>Does anyone have any ideas?
>
>Happy day,
>Ralph Zekelman
>

Hi Ralph,

	I think the real key is what is the primary to secondary coupling.  I
don't think it makes any difference what the shape of the primary is as
long as the coupling is optimal.  Conical primaries do have more coupling
available than flat primaries if you really need it.  You may want to
contact me off list and we can be sure your new primary will have the right
properties.

Cheers,

	Terry