80M Vertical = 70 khz Bandwidth

The Elecraft KAT-500 can handle pretty high SWR for most of the ham bands, but I noticed that on 80M especially, and when the power is higher than about 300 watts, things get a little “touchy”. With the KPA-500 in line, I have had a constant battle of amp faults – and I have tried all kinds of antenna matching circuits – in the shack and at the base of the antenna. I think the real issue was – I was trying to use the antenna in the 80M CW band and also at 3.857.5 for The Mission Trail Net. If I only could choose one, I would take 80M, and since at 1.8:1 or less (I don’t like higher SWR because of the amp situation), I’d just cut the antenna for 3.15 mhz and be done with it. In fact, right now, I could just shorten the antenna by at most a foot and I’d be done. At 100 watts up at 3.857.5, the KAT-500 is fine, and the net notices how much better this 60′ antenna is over the old Inverted L where I had to switch in an LC circuit so it could work on 160M and 80M. In fact, on 160M – the “real” was ALWAYS CW for me – SSB was a non starter. Something to think about.

The antenna as it is right now – is resonant in the 80, 30, 17 and 12M bands. This really is a great thing, especially because I am getting 30M out of this deal. A while back, Tom, N6BT told me that my radial field is good with a vertical when the bandwidth is narrow – that a wide bandwidth means there is a problem with the radial field. So – the antenna and radial field are good – I just need to “behave” in my use of it.

I need to do some serious A – B testing between the UrbanBeam and this 60′ vertical on 30M – that will be fun. There is always some kind of fun little antenna experiment going on here at KY6R! I guess its true – its always been about the antenna – WAY more than DXCC – although DXCC is a great “leveler” – a thing to give you structure and drive – a goal and a purpose to guide one through this antenna “adventure”. An Antenna-Spedition? Antenna-Palooza?

I started building the switchable 80 / 75M circuit, but I’m wondering if I had a direct and a linear loaded loop at the base if the RF would follow one or the other path depending on frequency that I am on. I bet the answer is no – that it will always find the shortest path – which would be 75M. The difference in wire length is several feet – up to 7 in fact.

I checked with Bob at Balun Designs and he recommends his 1:1 Current Choke (I have one) plus my idea to switch in different stubs. He thinks my amp faults are due to common mode at high power.

That makes total sense.

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