[OZAPRS] Newb HF questions ;)

[Damien Gardner Jnr]

Hey Terry,

Cheers, will pull the balun out, and see how it goes - I was 99% sure  
it was just a really bad idea on a vertical, but lee @ andrews was  
pretty adamant it was needed, and I figured he's been in the business  
a long time so knew what he was talking about..  I'll make sure to ask  
an actual ham next time I go buying gear ;)

Re 'pretty darned close to 50 ohms', that was from ray's workings  
earlier showing it was 40 ohms on 30m - I figured that's a hell of a  
lot better than the 10ohms being presented to the ATU at the moment ;)

Cheers,

Damien

On 20/05/2009, at 9:11 AM, Terry Neumann wrote:

> 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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