[OZAPRS] Newb HF questions ;)

Terry Neumann tfneumann at internode.on.net
Wed May 20 09:56:48 EST 2009


G'day Damien,

Yep - try that - experiment around and see what works.   You may not get 
there on all bands, but get one working first.

I'm off to Adelaide for the day as VK5ATN-9.   Good luck , success is 
guaranteed, you just have to get the right combination :-) .

73
Terry



Damien Gardner Jnr wrote:

> 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
>>
>> _______________________________________________
>> Ozaprs mailing list
>> Ozaprs at aprs.net.au
>> http://aprs.net.au/mailman/listinfo/ozaprs
>
>
> _______________________________________________
> Ozaprs mailing list
> Ozaprs at aprs.net.au
> http://aprs.net.au/mailman/listinfo/ozaprs
>
>------------------------------------------------------------------------
>
>
>No virus found in this incoming message.
>Checked by AVG - www.avg.com 
>Version: 8.5.339 / Virus Database: 270.12.35/2123 - Release Date: 05/19/09 17:59:00
>
>  
>

_______________________________________________
Ozaprs mailing list
Ozaprs at aprs.net.au
http://aprs.net.au/mailman/listinfo/ozaprs



More information about the Ozaprs mailing list