[OZAPRS] Newb HF questions ;)

Wed May 20 12:17:31 EST 2009

Hi All,

All I can say is WHOA!@#!  Very temporary replacement for the balun 
(buggered if I can find my heatshrink box, OR my self-amagamating tape 
:( ) : 
http://photos-f-0.ak.fbcdn.net/photos-ak-snc1/v4704/250/124/506862762/n506862762_1874629_2686781.jpg

Turned on the transceiver, hit tune on the AT-897, which took it about 
two clicks, then TX on AM, and my current 50mv of 50hz ripple turns into 
a fun 120mv of 10mhz with 50mv ripple, but I'm pretty happy with that..  
Pressed send beacon on UI-View, she TX'd happily without messing up my 
monitors, killing my mouse, or dumping crap to the serial ports, and by 
the time firefox had loaded up, there was my packet sitting on aprs.fi!

VK2TDG-15>APU25N,GATE,WIDE2-1,qAR,VK4UN-4:=3312.35S\15130.12E-Testing on 
HF {UIV32N}

Now I'm even *hearing* other stations! (well its either that or pagers.. 
there's plenty of somethingorother that sounds like a machine gun.. ) 
Though the DCD light on the MFJ isn't coming on, so I'll have to grab a 
couple of recordings and shove them through the spectrum scope in 
audacity and see what shows up :)

So one more question ;) What's a 'good' but not overly expensive antenna 
for 30m, which will happily be mounted on one of the roof racks on a 
commodore wagon, or on a boot side-mount on a commodore sedan? :)

Cheers,

Damien

Terry Neumann wrote:
> 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
>>>
>>> _______________________________________________
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>>> Ozaprs at aprs.net.au
>>> http://aprs.net.au/mailman/listinfo/ozaprs
>>
>>
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>
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