[SECC] 160M Ant Question

[K4SAV]

An inverted vee at 50 ft for 160 won't be a very good antenna for DX.  
You can work some but it will be a struggle, especially in a contest.  
It will be OK for stateside contacts.  I used exactly that antenna for 
the ARRL 160 in 2006.  With 1500 watts, in 20 hours I worked 47 states, 
9 VE provinces, and 24 countries.  It was fun but you are at the bottom 
of the pile when calling DX with this antenna, and they don't call you.

A 70 ft tower is very short for 160 and you will have trouble with the 
matching network and the shunt-feed wire, but it is still possible.  
Typically a tower like this will resonate somewhere between 80 and 160 
meters.

If the 80 and 40 meter inverted vees have the coax lines brought down 
the tower or close to it, those vees will act as loading on 160 when 
feeding the tower.  That will bring the resonant point down a lot, but 
the bad part is currents in those wires will cause a lot of loss on 160 
due to the fact they are close to the ground. 

If the tower is fed, you will need some radials at the bottom in 
addition to your lightning ground system (which won't be a lot of help 
at reducing RF loss on 160).  Also all wires exiting the tower should 
have shields connected at the bottom of the tower (sounds like you have 
that already).  Guy wires must also be insulated.  If the guys are 
connected to the tower at the top, they will act as loading (same as the 
inverted vees) and they will cause a lot of ground loss, even if they 
are insulated at the bottom.  In practice when the guys are connected at 
the top, the lowest set of guys will have the most current, and those 
are the ones closest to the ground.  The SWR may be good, but it will 
act like a large dummy load.

So  I don't have the answer as to which is best, without seeing exactly 
what you have to work with.  Sounds like some changes are in order to 
use the tower, but I don't know what options you have.  Do you have 
enough room to erect a couple of Rohn H50 push up masts for a long 
inverted L?  I just put one up and it is working well. I'm using it for 
the CQWW 160 this year, 837 Q's and 55 countries so far.  Maybe you 
could just put up only one and use the tower to hold the other end.  You 
need to keep that horizontal wire as high as possible (not sloping back 
down).

Jerry, K4SAV

Jeff W4DD wrote:

> I've had great luck using a 160M quarter wave vertical shot up over 
> some tall trees.  It's a pain putting it up each fall.  I don't leave 
> it up all year because the moving branch tend to destroy it over the 
> summer.
>
>  
>
> So I've been considering two other approaches to get (stay) on 160M;
>
>  
>
> 1) Inverted Vee off the tower at 50ft (simple)
>
>  
>
> 2) Shunt feed the tower (more complex)
>
> Tower is 70Ft with A-4 tribander at the top, and 80 and 40M Inv Vees.
>
> All antennas terminate in an RCS-8V antenna switch mounted on the 
> bottom of the tower along with rotor control lines.
>
> Tower currently has 4 in-ground radials (20-60 ft) with 10 ground rods 
> every 16 ft on the radials
>
>  
>
> Any advice as to which approach is best and the performance of only 
> using a 70ft tower?
>
>  
>
> Thanks,
>
> Jeff, W4DD
>
>  
>
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