[OZAPRS] Newb HF questions ;)

[Terry Neumann]

Damien Gardner Jnr wrote:

> Hey Norm
>
> I'm a little confused by the balun too ;)
>
> 50 ohms u/b from the rig to the atu
> atu is u/b (50 ohm?) to the PL259 on the bottom of the balun.
> balun balanced side has one terminal to the bottom of the TEV-1, and  
> one side to the 'radials' terminal on the mounting plate for the  
> TEV-1, which is bolted directly to the mast.  I can see why you'd 
> have  the 4:1 balun if you were feeding a dipole, but as ray said 
> earlier,  on 30m, the TEV-1 is pretty damned close to 50 ohms, so I 
> would have  thought putting the balun in there would completely screw 
> the vswr??   (it'd be giving me ~11 ohm on 30m yeah?)

It certainly should, and would most probably produce problems similar to 
those you are seeing. 

Take the balun out as a first step.   The presence of the balun on the 
TET Emtron web site is a real puzzle.  It could be useful at some out of 
the ball park frequency, but flies in the face of everything one reads 
about the feeding of vertical antennas elsewhere.     If you use the 
balun at all, put it right at the transceiver /atu and run a balanced 
line  (300 ohm ribbon?)  from there to the feed point of the antenna and 
the ground system at that point.

The TEV-1 at a length of 8.5 metres  calculates out as a quarter wave 
vertical at approx. 8.8 Mhz.   This is a very long way from any amateur 
allocation and as such  in a "ideal" ground plane antenna would exhibit 
a feed impedance of 50 ohms only at that frequency (8.8Mhz).    
Something is very seriously wrong if it "is pretty damned close to 50 
ohms" on 30 metres as is.  Something else in the system is doing the 
most of the radiating - or absorbing the RF energy as heat somewhere - 
or both.

73
Terry

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