[OZAPRS] Newb HF questions ;)

[Craig Turner]

Hmm,

Actually the standard VHF antennas on the aircraft I fly are about the 
length of a knitting needle. Are the V shapped horizontal antenna often 
found on the empennage a diploe? I had thought they might be as there is 
one element either side of the empennage? Actually those ones look more 
like wire coat hangers than knitting needles

Craig
VK3LCT



David and Justine Olsen wrote:
> No but I did think to myself, that is a short dipole for 120 MHz- I am a 
> pilot.
> 
> 
> 
> On 24 May 2009, at 08:10, Ray Wells wrote:
> 
>> Ben,
>>
>> Nope, not a knitter, but my wife is.
>>
>> Didn't anybody spot my "mistake"?
>>
>> If one needle when used as a quarter wave, and the frequency is 
>> 240MHz, two of them used as a dipole will still be 240MHz, and not 
>> 120MHz.
>>
>> Ray vk2tv
>>
>> Ben Lindner-VK5JFK wrote:
>>> Well done Ray. Were you a knitter from way back ? having those 
>>> needles hanging around. Not that there is any thing wrong with that, 
>>> a lot of men knit :-)
>>>
>>> Ben vk5jfk
>>>
>>> Ray Wells wrote:
>>>> Looks like it's time to get technical, heaven forbid!
>>>>
>>>> I've just measured a typical aluminium knitting needle at 300mm. If 
>>>> we assume it is a quarter wavelength and the length to diameter 
>>>> ratio is 0.96 we can divide 300000 by (1200/0.96) to arrive at 
>>>> 240Mhz. This is a reasonably thin needle so an appropriate 
>>>> adjustment needs to be made for fatter needles. The metal end-cap 
>>>> would add slight capacitance to slightly lower the resonant frequency.
>>>>
>>>> Since knitting needles are usually used in pairs, a dipole would be 
>>>> resonant at about 120Mhz which is great for the aircraft band.
>>>>
>>>> Ray vk2tv
>>>>
>>>>
>>>> Tony King wrote:
>>>>> I had to ask.... What band are knitting needles resonant on??
>>>>>                                        Regards Tony VK3API
>>>>>
>>>>> Ben Lindner-VK5JFK wrote:
>>>>>> "Have you thought about trading in your radios for knitting 
>>>>>> needles :-) "
>>>>>>
>>>>>>
>>>>>> Ray,  I believe that Scrap Booking and Quilting have taken over 
>>>>>> from knitting now. :-)
>>>>>>
>>>>>> Ben
>>>>>> VK5JFK
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