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Vertical Antennas - Voltage or current fed
https://www.hamradiodeals.co.uk/forums/viewtopic.php?f=43&t=73200
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Author:  M0SDM [ Fri Jan 15, 2016 7:48 pm ]
Post subject:  Vertical Antennas - Voltage or current fed

Just a couple of questions following on from what I have read on the www and what other have mentioned.

How do you determine if a vertical is current or voltage fed? Are there charts or graphs to look at?

Does the numbers of radials effect the receive performance of vertical?

Thanks Stewart

Author:  G7SSE [ Fri Jan 15, 2016 9:13 pm ]
Post subject:  Re: Vertical Antennas - Voltage or current fed

For a vertical fed at the base:

Odd number of 1/4 waves = current fed.

Even number = voltage fed.

Not sure regarding the radials and RX performance, certainly for TX the more the better.

The image shows current & voltage over a 1/2 wave, cover the bottom half for a 1/4 wave.

Attachments:
Dipole V&I.gif
Dipole V&I.gif [ 4.54 KiB | Viewed 1030 times ]

Author:  M0SDM [ Fri Jan 15, 2016 9:48 pm ]
Post subject:  Re: Vertical Antennas - Voltage or current fed

Perfect, thank you.

Author:  M0GVZ [ Sat Jan 23, 2016 12:26 pm ]
Post subject:  Re: Vertical Antennas - Voltage or current fed

Yes the number of radials affect performance, well not entirely correct. The effectiveness of the radial system affects RX and TX performance. Four quarter wave radials on an elevated antenna perform as well/better than a dozen or more on the ground on a ground mounted antenna.

Author:  M0SDM [ Sat Jan 30, 2016 9:05 am ]
Post subject:  Re: Vertical Antennas - Voltage or current fed

M0GVZ wrote:
Yes the number of radials affect performance, well not entirely correct. The effectiveness of the radial system affects RX and TX performance. Four quarter wave radials on an elevated antenna perform as well/better than a dozen or more on the ground on a ground mounted antenna.


I read that the number of radials can improve the RX, just couldn't understand why.

Author:  G3TXQ [ Sat Jan 30, 2016 9:26 am ]
Post subject:  Re: Vertical Antennas - Voltage or current fed

Increasing the number of ground radials typically reduces the ground losses. That can make a noticeable improvement on Tx, but may not be noticeable on Rx if the S/N ratio is determined by band noise rather than receiver noise.

Steve G3TXQ

Author:  M0SDM [ Sat Jan 30, 2016 12:23 pm ]
Post subject:  Re: Vertical Antennas - Voltage or current fed

Thank you Steve

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