Anyone got 2m end fed antenna experience?
Posted: Sun Sep 18, 2011 9:13 am
G'day,
Yesterday I had a crack at building some HF end fed antennas using the matching circuit described in this article: http://www.w7dk.org/10%20meter%20vertical%20project.pdf
It's basically your standard end fed half wave but uses an autotransformer for impedance matching and a short run of RG58 as the capacitor which tunes out the magnetising inductance.
So far I've managed to build matching units which get good results on 40m (33T on 20mm PCV pipe, 70cm of RG58 capacitance) and 10m (13T with ~15cm of RG58) and was wondering if anyone has experience scaling this design to work on the 2m band. The 15cm length of RG58 has a capacitance of about 10-15pF. With a capacitance this size the transformer inductance would need to be 120nH. This is all well and good, but I've got no idea what the physical dimensions of an inductor that size would be. If anyone's got a ballpark figure that'd be great .
The end goal is to build a 1/2 wave end fed antenna for use where ground planes are hard to come by (backpacks, push bikes etc). I'd heavily prefer not to use a J-pole simply because they're 50% longer (or the 1/2 wave 33% shorter, depending on your point of view).
Yesterday I had a crack at building some HF end fed antennas using the matching circuit described in this article: http://www.w7dk.org/10%20meter%20vertical%20project.pdf
It's basically your standard end fed half wave but uses an autotransformer for impedance matching and a short run of RG58 as the capacitor which tunes out the magnetising inductance.
So far I've managed to build matching units which get good results on 40m (33T on 20mm PCV pipe, 70cm of RG58 capacitance) and 10m (13T with ~15cm of RG58) and was wondering if anyone has experience scaling this design to work on the 2m band. The 15cm length of RG58 has a capacitance of about 10-15pF. With a capacitance this size the transformer inductance would need to be 120nH. This is all well and good, but I've got no idea what the physical dimensions of an inductor that size would be. If anyone's got a ballpark figure that'd be great .
The end goal is to build a 1/2 wave end fed antenna for use where ground planes are hard to come by (backpacks, push bikes etc). I'd heavily prefer not to use a J-pole simply because they're 50% longer (or the 1/2 wave 33% shorter, depending on your point of view).