Gary,
It could be done that way but you have a capacitor in the mix which are
usually not very resistant to lightning or high static charges, That is why
I like the shunt coil match better.
To each his own.
Jay
-----Original Message-----
From: antennaware-bounces@contesting.com
[mailto:antennaware-bounces@contesting.com] On Behalf Of K9AY
Sent: Tuesday, August 17, 2010 10:58 AM
To: antennaware@contesting.com
Subject: [Antennaware] Fw: Topband vertical matching.
Oops .. sent this from the wrong 'return address' first time.
> Dave,
>
> I started working on problems like this before compuer modeling, so I have
> the habit of separating the antenna analysis and the matching network
> design. L- T- and Pi-networks are very easy to design on a good Smith
> chart program, or just mathematically using one of the matching programs.
>
> Although it's nice to have it all-in-one at times, the "modular" approach
> makes it easy to examine alternate matching schemes -- for example, when
> you want to compare several configurations to maximize VSWR bandwidth of a
> fixed-tuned network. Also, some of the virtual structures required to
> accommodate shunt components can violate NEC design rules and give
> erroneous results.
>
> BTW, I usually match inverted-Ls with a shunt capacitor (8 or 10
> inexpensive high voltage discs), and a slightly long antenna to provide
> phantom inductance. I find capacitors easy to adjust by adding or removing
> small values, and very easy to weatherproof in a small plastic box.
>
> 73, Gary
> K9AY
>
>
>
>> For the last few years I have just been matching my topband vertical
>> or inverted L antennas by using a 1:4 UNUN
>>
>> I have just seen the following article by Jay at Array Solutions..
>> http://www.arraysolutions.com/images/Tuning_160m_Vertical.pdf
>>
>> where he resonates the antenna at 1.9MHz which gives a capacitive
>> reactance at 1.83 (which becomes a phantom part of the L-network) the
>> other part being a real inductance to earth. I like the look of this
>> arrangement because of its simplicity and the fact that there is a DC
>> connection to ground.
>>
>> I would like to try and model this directly in EZNEC, but not quite
>> sure how to define the load components and the source in this case.
>>
>> 1) Can I just specify a load of L+R (where R is the simulated earth
>> loss) and the source in the lowest segment?
>>
>> 2) Should I put the L+R in the lowest segment and the source in the
>> next segment up?
>>
>> 3) Or is there a better way?
>>
>> I would appreciate any advice from anyone with a bit more experience
>> than I have.
>>
>> 73,
>> Dave, G3UEG
>>
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>
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