Theoretically a circle is the best but in actual practice it would be only a fraction of a dB over a square or delta.
It's best to use the loop shape that you can build especially something that can stay up in high winds rather than trying to attain theoretical perfection.
I use 4NEC2 for antenna modelling.
I find that the editors are easier to use. You can program values as a text item so that say you can use the value "height" for the height of the antenna elements above ground. You can then just change the value of "height" to raise and lower your antenna in the model. It also has an optimising tool that can vary the text values for best gain, VSWR or front to back ratio.
The graphics output is one of the best with colour 3D visualisations of the antenna pattern making it very easy to understand especially when explaining an antenna pattern to non-technical people.
A circular loop with a circumference of 2.5 m so that it's resonant as a full wave loop around 125 MHz would be best for VHF airband use with the LAA++.
Other loop configurations such as a square or delta as long as the circumference is the same.
So what would your recommendation be Chris, a circular loop or other form?
From: CrossCountryWireless@groups.io <CrossCountryWireless@groups.io> on behalf of Chris Moulding <chrism@...> Sent: Thursday, June 23, 2022 10:43:30 AM To: CrossCountryWireless@groups.io <CrossCountryWireless@groups.io> Subject: Re: [CrossCountryWireless] LAA++ For Airband
Hi Michael,
There are pros and cons to doing that.
The pro is that the vertical folded dipole will have an omni-directional pattern over the figure of eight pattern for the loop.
The con is that the impedance of the folded dipole is a lot higher than the loop and would not efficiently match the input impedance of the LAA++ at VHF airband frequencies.
It's worth trying to see if the performance is adequate for airband listening.
When I test the next batch of LAA++ head units I'll reconfigure the test loop to try it out.
The pro is that the vertical folded dipole will have an omni-directional pattern over the figure of eight pattern for the loop.
The con is that the impedance of the folded dipole is a lot higher than the loop and would not efficiently match the input impedance of the LAA++ at VHF airband frequencies.
It's worth trying to see if the performance is adequate for airband listening.
When I test the next batch of LAA++ head units I'll reconfigure the test loop to try it out.
I have a couple of projects I want to do with the two LAA++ amps that are due to arrive tomorrow (one replacement and one new one) and one of those projects is an airband antenna. If I use the supplied loop cable and form it as a folded dipole with the amp head located midway in the vertical plane will this provide any benefit over any other form of loop, i.e. circular, delta etc.?
