Topband: Cage wire performance

[Kenny Silverman]

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 at 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 at 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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