> Ken,
>
> Actually, the feedpoint impedance for a half wave center fed dipole is 70 ohms if it is "in the clear". The proximity to earth and other physical objects will lower that impedance. For antennas typically used at HF, yes, the feedpoint impedance will be closer to 50 ohms than the ideal of 70 ohms.
>
> 73,
> Don W3FPR
>
> On 12/8/2011 8:14 PM, Ken wrote:
>> On Dec 8, 2011, at 6:47 PM, Jim Brown wrote:
>>
>>> Virtually all the loss in transmission lines at HF (and even VHF) is due
>>> to copper (that is, I squared R). Open wire line (and window line) has
>>> much lower loss than coax because it has much higher impedance, so the
>>> current for the same transmit power is much less than for coax.
>>
>> The impedance of the feedline does not change the impedance of the antenna. A half wave length dipole at the proper height is still a 50 ohm feed regardless of whether it's fed with 50ohm line or 600 ohm line.
>>
>> Ken WA8JXM
>>
>>
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