Rotatable dipole with spiral capacity hats 1

[TomUnit3]

How well will the antenna work on 40 and 80 meters?

See the attached picture.

Best regards.

Tom
KE6YNH, 73
San Diego, CA

 

[VEBill]

A key distinctive feature of this proposed antenna are the SPIRAL capacity hats (as opposed to simple plates). But the drawing provides almost no information about those spirals. Also, since the transmission lines are not flat, their lengths will have a direct impact on the match.

Anyway - it's not common to have anyone to volunteer to model someone else's design (even if all the details were provided).

But it'll probably work about as well as any other short antenna.

73

 

[TomUnit3]

Hi Jeff, VE1BLL and the Group,

The spiral coil is 1 foot square and has 24 turns of 1/8"
aluminum tubing.

How's that for a starting point?

I would settle for a *rule of thumb* when it comes to flat spiral coils.

I plan on using ladder line rather than coax, since the
SWR may be quite high as a multiband antenna.

Thanks for taking a stab at it.

Tom
KE6YNH, 73
San Diego, CA

 

[TomUnit3]

Hello to the Group,

Here's one more tidbit on the use of flat spiral
loading coils for dipoles.

Apparently, there is a commercial version already
made, that uses spiral, flat, loading coils at:

http://www.tak-tenna.com/

I am not an agent nor am I involved with that firm.

Regards to the Group.

Tom
KE6YNH, 73
San Diego, CA

 

[VEBill]

There are several free NEC programs available on the 'net. Here's one example:

http://home.ict.nl/~arivoors/

 

[TomUnit3]

Hi Jeff, VE1BLL, Thanks for the information!

Tom
KE6YNH, 73
San Diego, CA

 

[Higgler]

The TakTenna has 1.5% bandwidth (2:1 VSWR bandwidth), so that means you will need to have those top loading coils just the right length or your antenna will have very bad VSWR. It's only 40 meters for the link to the Taktenna. 80 meters may be really ugly for VSWR.

If you can see the VSWR while you trim those coil lengths, you could tune it into the right frequency.

to improve your VSWR, if possible, I'd suggest making the tubes (going to the coils on the end) as wide as possible. Or add some metal to make wings, converting the tubes to sheets of metal. VSWR bandwidth is often improved by increasing the antenna size.

kch