K7ITM wrote:

(Excellent summary and explanations!)

. . .

-- Copper loss (I^2*R loss) goes down as the impedance of the line
increases. Loss in dB/unit length is inversely proportional to
the impedance.

What a lot of people miss is that this is the real reason open wire line
is less lossy than coax -- it inherently has higher characteristic
impedance than coax because of its geometry. (The I^2*R loss is lower
for high impedance lines because I is lower for a given power level.)

But dielectric loss can be significant with twinlead. Water is lossy and
has a very high dielectric constant, so wet ladder line or TV twinlead
can actually have greater loss than moderate size coax.

. . .

Roy Lewallen, W7EL

Roy Lewallen wrote:
K7ITM wrote:

(Excellent summary and explanations!)

. . .

-- Copper loss (I^2*R loss) goes down as the impedance of the line
increases. Loss in dB/unit length is inversely proportional to
the impedance.

What a lot of people miss is that this is the real reason open wire line
is less lossy than coax -- it inherently has higher characteristic
impedance than coax because of its geometry. (The I^2*R loss is lower
for high impedance lines because I is lower for a given power level.)

But dielectric loss can be significant with twinlead. Water is lossy and
has a very high dielectric constant, so wet ladder line or TV twinlead
can actually have greater loss than moderate size coax.

. . .

Roy Lewallen, W7EL
From
http://www.k6mhe.com/n7ws/

http://www.k6mhe.com/n7ws/Ladder_Line.pdf talks about measurements on
wet and dry ladderline
http://www.k6mhe.com/n7ws/LadderLineUpdate.PDF

Jim Lux wrote:
From
http://www.k6mhe.com/n7ws/

http://www.k6mhe.com/n7ws/Ladder_Line.pdf talks about measurements on
wet and dry ladderline
http://www.k6mhe.com/n7ws/LadderLineUpdate.PDF

Also see http://eznec.com/Amateur/Articles/Po...Feed_Lines.pdf.

Roy Lewallen, W7EL