Owen Duffy wrote:
wrote in
:

...
Even with a 80/1 mismatch, ladder line has low loss.

30m of Wireman 551 with a load of 5+j0 has VSWR=80 at the load end, VSWR=28
at the source end, and the transmission loss is 4.6dB... 65% of the input
power is converted to heat.

Speaks to your meaning of "low loss".

Mythical properties are ascribed to ladder line, some of attributable to
ARRL publications.


Or, I think more properly, to statements in ARRL publications taken with
a different set of underlying assumptions..

For instance, ladder line between a tube amp output tank and a doublet
is probably "reasonably" low loss in most common practical applications..

And in an inappropriate application (reactive load with weird Z to 50
ohm transmitter) it's probably lower loss than RG-58.

Maybe it's that subjective term "low loss"???

Half a dB per foot is low loss at 32 GHz, but you'd be hard pressed to
find a commercially available transmission line with that kind of loss
at 7 MHz. (maybe that funky 1000 ohm Z delay line stuff?)


Ham applications in any case are kind of an odd thing, efficiency-wise,
since the limit is on RF power at the transmitter output connector.
Pretty much every other user of RF power amplifiers sets the system
measurement plane somewhere else.. in space (EIRP or ERP) or at the
power source (power budgets). For instance, you can trade increased
power consumption against lower feedline loss.

Jim Lux wrote in
:

....
Mythical properties are ascribed to ladder line, some of attributable
to ARRL publications.


Or, I think more properly, to statements in ARRL publications taken
with a different set of underlying assumptions..

The ARRL has long published characteristics of "Generic ladder line"
being #18 conductors spaced 1". They publish loss figures better than
theoretical loss for the same size copper conductors in a vacuum (eg at
10MHz, about 0.27dB/100m vs 0.47dB/100m).

The second factor is, I think, the notion that since one-way loss is
relatively low on open wire lines, that it is safe to consider it
*always* insignificant (irrespective of VSWR), then exagerate the point
by talking about it being essentially lossless at extreme VSWR.

I think that the best characterisation we have of ladder line is that of
Wes, N7WS. Similar measurements at lower frequencies might well reveal
whether the stranded copper clad steel versions have inadequate cladding
depth for copper-like performance at low HF.


For instance, ladder line between a tube amp output tank and a doublet
is probably "reasonably" low loss in most common practical
applications..

Perhaps a better concept is "acceptable loss" where acceptable is
influence by the application. The compromises accepted for multiband
operation might well include 3dB of line loss on the lowest band.

....
Ham applications in any case are kind of an odd thing,
efficiency-wise, since the limit is on RF power at the transmitter
output connector. Pretty much every other user of RF power amplifiers
sets the system measurement plane somewhere else.. in space (EIRP or
ERP) or at the power source (power budgets). For instance, you can
trade increased power consumption against lower feedline loss.

Actually, interesting you mention that.

I recently had cause to probe the meaning of the term "transmitter" in
our (VK) regulatory framework. Whilst we are limited in transmitter power
output, the meaning of transmitter is relevant.

From our legislation:

===quote

8 Definitions of radio emission and transmitter

(1) For the purposes of this Act, a radio emission is any
emission of electromagnetic energy of frequencies less than 420 terahertz
without continuous artificial guide, whether or not any person intended
the emission to occur.

(2) For the purposes of this Act, a transmitter is:

(a) anything designed or intended for radio
emission; or

(b) any other thing, irrespective of its use or
function or the purpose of its design, that is capable of radio emission.

=== end quote

It could be argued that an "emission" exists beyond the antenna ("without
continuous artificial guide"), and that everything up to an including the
antenna could be captured as part of a "transmitter" as defined.

Though there is a well understood ordinary meaning to the word
"transmitter", the drafters of the legislation have provided a definition
that should override any ordinary meaning in the context of that law.

Perhaps we (VK) are entitled to apply our limit to radiated power!

Owen

It's a mistake to lump all ladder and window line together as "ladder
line" and draw conclusions about its loss characteristics. There's a
vast difference between punched polyethylene window line and real 600
ohm ladder line made with large diameter conductors and low loss
spacers. Even more so when the line is wet.

Roy Lewallen, W7EL

Roy Lewallen wrote in news:mLadnZ7-05DkY6
:

It's a mistake to lump all ladder and window line together as "ladder
line" and draw conclusions about its loss characteristics. There's a
vast difference between punched polyethylene window line and real 600
ohm ladder line made with large diameter conductors and low loss
spacers. Even more so when the line is wet.

Yes Roy.

I was talking about the commercial "ladder line", and used the example of
Wireman 551 which is of the punched polyethylene window line type you
mention.

The other comparison I made was the ARRL "Generic ladder line" whatever
that means with ideal copper conductors of same dimensions in a vacuum. I
cannot see how adding insulation can possibly halve its dB loss, can you?

Owen

On Jun 13, 12:05*am, Jim Lux wrote:

Ham applications in any case are kind of an odd thing, efficiency-wise,
since the limit is on RF power at the transmitter output connector.

Jim,

That's not the case in the UK. The licence conditions specify "....
power supplied to the antenna by a transmitter ...."

Steve G3TXQ

On Jun 13, 6:54*am, steveeh131047 wrote:
On Jun 13, 12:05*am, Jim Lux wrote:



Ham applications in any case are kind of an odd thing, efficiency-wise,
since the limit is on RF power at the transmitter output connector.

Jim,

That's not the case in the UK. The licence conditions specify "....
power supplied to the antenna by a transmitter ...."

Steve G3TXQ

How interesting, so in both VK and UK (mixing abbreviations).. the
"reference plane" for the measurement is potentially "after" the
transmission line. The 5kW Active Antenna Tuner lives!

Here in the US, I'm sure the rule is interpreted the way it is because
of the heritage of "1kW DC power to the final stage" rule, which in
turn came from pre-ham radio rules for marine transmitters using
sparkgaps, etc... It was simple change from measuring plate current/
voltage to hooking a power meter at the output connector. I wonder if
anyone ever measured RF power on a non-50 ohm transmitter in an
enforcement action?

My father and grandfather both had stories, apocryphal perhaps, about
clever hams having very large "exciters" that fed through a relatively
low power "final stage"... using the final tube as a coupling
capacitor, perhaps, with unity gain.