[TowerTalk] 4 square for 80

[jimlux]

On 9/25/16 11:35 AM, Joe Subich, W4TV wrote:
>
> On 9/25/2016 12:48 PM, jimlux wrote:
>> One could of course make the transmission lines 3/4 wavelength long,
>
> Which would, in turn, reduce the bandwidth of the cables by a factor
> of three

I don't know that the bandwidth is the right term here.  Between 3.5 and 
4.0, assuming you cut for 3.75, for quarter wave you'd be 84 to 96 
degrees, for 3/4 wave, it would be 252 to 288.

For exactly 90 and 270, I at the far end is proportional to E at the 
near end.  As you go away from those, how much does it change - that is, 
how much "current forcing" do you lose.


and similarly increase losses in the cables which operate at
> significant SWR both of which would negatively impact operation of the
> 4 square on a "wide" band like 80/75 meters.

Do they really have that much loss? I've done the calculations in the 
past, but I don't remember how much there is.  And loss is tricky to 
calculate when you've got less than a wavelength - the "loss in a 
transmission line" equation assumes uniform current/voltage along the 
line, which is not the case here.  The voltage losses are small at HF, 
so the losses come from the current.



>
> 73,
>
>    ... Joe, W4TV
>
>
> On 9/25/2016 12:48 PM, jimlux wrote:
>> One could of course make the transmission lines 3/4 wavelength long, and
>> have plenty of length to wrap dozens of turns on however many cores
>> spaced however frequently along the length of the cable.
>>
>>
>>
>>
>> On 9/25/16 9:25 AM, Jim Brown wrote:
>>> I see.
>>>
>>> 73, Jim
>>>
>>> On Sun,9/25/2016 5:41 AM, Joe Subich, W4TV wrote:
>>>> Jim,
>>>>
>>>> The problem is that, in that application, the cables must be 1/4 wave
>>>> long electrically.  That already makes them shorter than desired and
>>>> "wound" chokes on each end would shorten them by another 5-7 feet
>>>> making the spacing of the 4 square much too small.
>>>
>>> On Sun,9/25/2016 6:49 AM, Steve London wrote:
>>>
>>>> What problem(s) are we attempting to solve with chokes on the 4-square
>>>> feedlines ?
>>>>
>>> Noise.
>>>
>>
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