[TenTec] 160 M antenna

[Ken Brown]

>> What kind of bandwidth do you get with your inverted L, 50 kHz?  
>> Would I still be able to use a tuner in the shack if I want to bend 
>> it for more coverage on 160?
>
> Define bandwidth.  Do you mean SWR bandwidth?  Do you mean you can get 
> it to load?
A very good question. And it brings up a couple of points that are worth 
mentioning.

If your antenna has a wide SWR bandwidth, it may seem like it works 
really good, because it is so convenient. Operate the whole band without 
making any adjustments as you go from top to bottom of the band. Very 
convenient! Beware though that a wide low SWR bandwidth is often a sign 
of inefficiency. How wide is the 1.5:1 SWR bandwidth of a Heathkit 
Cantenna? Pretty wide. How much DX are you going to work with it? Not much.

A quarter wavelength vertical over an excellent ground counterpoise 
system has an impedance of about 37 ohms. If you don't need a matching 
device to get a 1:1 SWR at the resonant point, then it is likely you 
have about 13 ohms of loss resistance (the kind that produces heat, 
versus radiation resistance, the kind that produces a radiated signal) 
that added to the 37 ohms of radiation resistance makes a perfect match 
to your 50 ohm coax. Very convenient. Not very effective. What would you 
rather have? A low SWR or a stronger signal? Many hams have chosen 
(perhaps unwittingly) a low SWR.

A quarter wavelength that is folded over into an inverted L, instead of 
going straight up, has an even lower radiation resistance. You will (or 
at least you should) need a matching device to get the SWR down, unless 
you have a lot of loss. You are likely to have high ground losses, 
because your ground resistance is high and radial field is lacking. You 
could have a low SWR, and a wide bandwidth. It could be very convenient. 
Or you could reduce your ground losses and make your SWR worse. Not as 
convenient, but much more effective as an antenna.

Yes there are antenna designs that have wide low SWR bandwidths, without 
being outdoor dummy loads. Discones, biconical dipoles, log periodics, 
etc. A fatter inverted vee "cage" will be an improvement, but you will 
still want to do whatever you can to reduce your ground losses.

Have fun!

DE N6KB