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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