Hi Dave, thanks for the analysis. I was using your number 3 model, though I
had a small slope in the top wires. When I flattened the top wires I too was
getting about 100kc at 24 ohms.
I will to do a sensitivity analysis to see what works best for me. Where I set
down the 60 radials (laying on the forest floor) I can’t get the top wires flat
due to overlapping tree canopies. The only place with a clearing is above my
house and I can’t put the vertical there.
Also thanks to all the input on and off the reflector! I will look at the
relay option if my idea doesn’t work. I’m running low power so my rig’s tuner
can help if I don’t get 100 kc
Regards , Kenny K2KW
> On Jan 4, 2021, at 1:18 PM, Dave Cuthbert <telegrapher9@gmail.com> wrote:
>
>
>
> Kenny, your model might have a problem with the acute antenna between the two
> vertical wires. I ran EZNEC simulations to test this and compare against a
> single vertical wire T reference antenna. Your antenna shows similar
> bandwidth, but a different input resistance.
>
> Antenna 1 reference antenna
> 75' vertical wire
> from there extend two horizontal 35'wire
> SWR bandwidth normalized to the antenna input resistance of 23 ohms
> SWR bandwidth is 118kHz
>
> Antenna 2 your antenna
> perfect GND, #12 bare wire, current segments are 1'
> 1' vertical wire from GND
> from that wire two wires extend to 75' separated by 4' at the top
> At 75' the two wires are joined
> From each 75' wire extends a 48' wire
> SWR bandwidth normalized to the antenna input resistance of 16 ohms
> 2:1 SWR bandwidth is 100kHz
>
> Antenna 3 your antenna modified to conform to the NEC included angle rule
> perfect GND, #12 bare wire
> 1' vertical wire from GND
> from that, 2' horizontal wires extending opposite one another
> two wires extend from the ends of those two wires to 75'
> at 75' the two wires are joined
> from each 75' wire extends a 52' horizontal wire
> SWR bandwidth normalized to the antenna input resistance of 25 ohms
> SWR bandwidth is 106kHz
>
> Antenna 4 single vertical wire with a horizontal flat top wires
> perfect GND, #12 bare wire
> 75' vertical wire from GND
> from that, 2' horizontal wires extending opposite one another
> two wires extend horizontally from the ends of each of those two wires to 22'
> SWR bandwidth normalized to the antenna input resistance of 23 ohms
> SWR bandwidth is 72kHz
>
> Dave KH6AQ
>
>
>> On Mon, Jan 4, 2021 at 5:07 AM Kenny Silverman <kenny.k2kw@gmail.com> wrote:
>> Hello and HNY!
>>
>> I will be converting a wire inverted-L to a T top loading on a 75’ tall wire
>> hung from a tree. To improve the bandwidth, I was wondering about going to a
>> 2-wire “cage” for the vertical section. I’m actually modeling a skinny
>> triangle where the wires connect at a point on the top, but with a 4 foot
>> spread of the wires near the ground. This adds about 15-20 kc to the 2:1
>> bandwidth per the model.
>>
>> Will a 2-wire section like this always behave as a wide/fat conductor or do
>> I have to worry about voltage/current in Each wire?
>>
>> Regards , Kenny K2KW
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