[TowerTalk] T-match?

[i4jmy@iol.it]

> ---------- Initial message -----------
> 
> From    : jukka.klemola@nokia.com
> To      : i4jmy@iol.it, towertalk@contesting.com
> Cc      : 
> Date    : Thu, 15 Jun 2000 14:40:55 +0300
> Subject : RE: [TowerTalk] T-match?
> 
> Hi,
> 
> I am not looking excactly after higher feedpoint impedance,
> it is one point of interest, yes; but easier construction,
> better balancing and more 'selective' way of feeding the
> antenna are the real targets.

Quite a subjective point. 
Mine are best possible (and balanced) performances in terms of real 
Gain, BW, F/B and F/S in conjunction with a lightweight that still 
insures an excellent mechanical strenght. Feeding system has to be 
symple, free of losses, inherently unaffected by weather or 
temperature, and lightweight.
Feed point impedance is one of the key. 

> For example a cut driven element is far less attenuating at third
> harmonic.

Not really. 
A split dipole behaves exactly like another one that's not.
Eventually it's the feed method that's altering the frequency response 
and actually, most of the typical matching devices behave like high 
pass circuits so leaving just unaffected, or possibly enhanching, 
radiation of harmonics.
An LP filter or a devoted stub work excellent (many times better) to 
reduce harmonics and both can confortably be placed indoor.

> 
> I modelled also with EL & EZNEC, even getting into very short
> lenghts of tubing did not model the impedances right.
> I did not check this with AO, though. I think they use very much
> the same 'engine' to do the simulations so the simulation performance
> should be somewhat similar.

Althought I do not find any more worth the effort to model antennas 
requiring complex matching devices, they can be closely and succesfully 
modeled with wires and loads. Not to have meaningless results it's 
needed to "force" enough segments for the short wires, up to eventually 
consuming all the available computer memory.

73,
Mauri I4JMY


> 
> 73,
> jukka (OH


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