nick smith wrote:
Is this a fairly correct understanding of what is going on, Reg / Cecil ?

Yep, Nick, all I was doing was taking a tongue-in-cheek poke
at the idea that "The tuner doesn't reduce efficiency."
--
73, Cecil http://www.qsl.net/w5dxp


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"Cecil Moore" says -

There's no such thing as a 100% efficient tuner.
====================================

Cecil, not a very surprising statement.
There's nothing which is 100% efficient.

What is the typical efficiency of a typical tuner with a typical
antenna.
Does it differ significantly from 100% ?
Yes or no?
----
Reg.


Well, at the risk of David going into conflict with the Goliaths of
the
newsgroups, I would reckon that a tuner (matcher ?) must be a pretty
efficient
device as it doesn't get very warm from wasting energy as heat - or
perhaps my
aerials are a reasonably good match and the tuner isn't doing any /
much work.
Also a tuner, I would suggest, is a fairly useful bit of kit in that
it enables
the transmitter to see the sort of load it wants to and allows it to
deliver
more power to the antenna system without the internal protection
devices
limiting the power it produces (to avoid self destruction) even if
not all
arrives at the antenna.......

Is this a fairly correct understanding of what is going on, Reg /
Cecil ?

Nick

====================================

Nick, your response indicates a 'perfect' understanding of what goes
on inside tuner boxes. If it runs cold or cool with 100 watts there's
nothing to worry about.

Most Guru's over-exaggerate the importance of tuner losses. But in a
practical case they never state what the efficiency actually is. Such
omissions illustrate their ignorance of the subject.

From the frequency of occurrence at which 'tuner loss' appears in
these columns, novices and even experienced amateurs can gain the
frightening impression that tuner loss is the most serious loss in the
system and is to be avoided at all costs, even to the extent of
dispensing with the tuner.

In answer to my own question, the efficiency of a typical tuner when
used with a typical antenna does not differ significantly from 100
percent. Even if it is as poor as 90% this corresponds to an
undetectable loss in signal strength of 0.5dB or 1/13 of an S-unit.
Less than the thickness of the S-meter needle. So forget it.
----
Reg, G4FGQ

"Reg Edwards" wrote in message
...

"Cecil Moore" says -

There's no such thing as a 100% efficient tuner.
====================================

Cecil, not a very surprising statement.
There's nothing which is 100% efficient.

What is the typical efficiency of a typical tuner with a typical
antenna.
Does it differ significantly from 100% ?
Yes or no?
----
Reg.


Well, at the risk of David going into conflict with the Goliaths of
the
newsgroups, I would reckon that a tuner (matcher ?) must be a pretty
efficient
device as it doesn't get very warm from wasting energy as heat - or
perhaps my
aerials are a reasonably good match and the tuner isn't doing any /
much work.
Also a tuner, I would suggest, is a fairly useful bit of kit in that
it enables
the transmitter to see the sort of load it wants to and allows it to
deliver
more power to the antenna system without the internal protection
devices
limiting the power it produces (to avoid self destruction) even if
not all
arrives at the antenna.......

Is this a fairly correct understanding of what is going on, Reg /
Cecil ?

Nick

====================================

Nick, your response indicates a 'perfect' understanding of what goes
on inside tuner boxes. If it runs cold or cool with 100 watts there's
nothing to worry about.

Most Guru's over-exaggerate the importance of tuner losses. But in a
practical case they never state what the efficiency actually is. Such
omissions illustrate their ignorance of the subject.

From the frequency of occurrence at which 'tuner loss' appears in
these columns, novices and even experienced amateurs can gain the
frightening impression that tuner loss is the most serious loss in the
system and is to be avoided at all costs, even to the extent of
dispensing with the tuner.

In answer to my own question, the efficiency of a typical tuner when
used with a typical antenna does not differ significantly from 100
percent. Even if it is as poor as 90% this corresponds to an
undetectable loss in signal strength of 0.5dB or 1/13 of an S-unit.
Less than the thickness of the S-meter needle. So forget it.
----
Reg, G4FGQ


Well, I was actually pretty sure I was right, but its good to have it confirmed
and hope
this was useful to others in their understanding or otherwise of the job a
tuner (matcher) does.

Thanks Gentlemen,

Nick

On Mon, 06 Jun 2005 07:40:49 GMT, "nick smith"
wrote:

...

"Cecil Moore" says -

There's no such thing as a 100% efficient tuner.
====================================

Cecil, not a very surprising statement.
There's nothing which is 100% efficient.

What is the typical efficiency of a typical tuner with a typical
antenna.
Does it differ significantly from 100% ?
Yes or no?
----
Reg.


Well, at the risk of David going into conflict with the Goliaths of the
newsgroups, I would reckon that a tuner (matcher ?) must be a pretty efficient
device as it doesn't get very warm from wasting energy as heat - or perhaps my
aerials are a reasonably good match and the tuner isn't doing any / much work.

Let me refer to you to this link:

http://users.triconet.org/wesandlinda/ladder.htm

and suggest that you also follow the imbedded link to my letter to
Dean.

There you will find an analysis if what tuner losses can be.

But let's also answer this issue of "It doesn't get hot, so it must
not be lossy."

First let's say that, unless the op is a real blabbermouth, the
transmit duty cycle will be 50%. Transmit half the time, listen half
the time.

If the op is on CW then the duty cycle of the transmit cycle is ~44%.
(The standard word "PARIS" sent repeatedly with 1:3:7 spacing. So for
CW operation, the overall duty cycle is .5 * .44 = 22%.

On SSB it's more complicated. Without speech processing, the peak to
average ratio is variously given, but 14:1 (11.5 dB) is typical. Most
rigs have some form of speech compression or clipping these days (most
used to excess). Really effective clippers, (ahem)

http://users.triconet.org/wesandlinda/s_proc.pdf

can improve this quite a bit so let's say that it's 6 dB. So the
average power is 6 dB below the peak or 25% of the peak. Our overall
duty cycle is .5 * .25 = 12.5%

Of course the digital modes and FM are full carrier so the duty cycle
is 50%. Not many using FM on hf where tuners are the norm, the PSK
guys pride themselves on QRP, which leaves only the special case RTTY
contesters running full power.

So back to the guy running 100 W CW through a tuner driving a ladder
line fed antenna. If his tuner burns up half of the power will it get
hot? Are 11 W (22% of 50) going to smoke most components? What if
the tuner loss is 6 dB? The average power dissipation climbs to a
whopping 16.5 W. (22% of 75) Is this a big thermal management issue?

Certainly, KW rigs running RTTY are going to be a bigger concern, but
the tuners (and component parts) are commensurately bigger and can
dissipate more power without "getting hot".

Let's put this an easier way, how many of you have a low pass filter in
line. Most manufacturers claim a .25dB or less insertion loss. These filters
consist of a boat load of coils and caps.

A tuner normally has 2 varible caps and a single silver plated coil.

While any device indeed has loss, here we are picking fly crap out of
pepper.


Let me refer to you to this link:

http://users.triconet.org/wesandlinda/ladder.htm

and suggest that you also follow the imbedded link to my letter to
Dean.

There you will find an analysis if what tuner losses can be.

But let's also answer this issue of "It doesn't get hot, so it must
not be lossy."

First let's say that, unless the op is a real blabbermouth, the
transmit duty cycle will be 50%. Transmit half the time, listen half
the time.

If the op is on CW then the duty cycle of the transmit cycle is ~44%.
(The standard word "PARIS" sent repeatedly with 1:3:7 spacing. So for
CW operation, the overall duty cycle is .5 * .44 = 22%.

On SSB it's more complicated. Without speech processing, the peak to
average ratio is variously given, but 14:1 (11.5 dB) is typical. Most
rigs have some form of speech compression or clipping these days (most
used to excess). Really effective clippers, (ahem)

http://users.triconet.org/wesandlinda/s_proc.pdf

can improve this quite a bit so let's say that it's 6 dB. So the
average power is 6 dB below the peak or 25% of the peak. Our overall
duty cycle is .5 * .25 = 12.5%

Of course the digital modes and FM are full carrier so the duty cycle
is 50%. Not many using FM on hf where tuners are the norm, the PSK
guys pride themselves on QRP, which leaves only the special case RTTY
contesters running full power.

So back to the guy running 100 W CW through a tuner driving a ladder
line fed antenna. If his tuner burns up half of the power will it get
hot? Are 11 W (22% of 50) going to smoke most components? What if
the tuner loss is 6 dB? The average power dissipation climbs to a
whopping 16.5 W. (22% of 75) Is this a big thermal management issue?

Certainly, KW rigs running RTTY are going to be a bigger concern, but
the tuners (and component parts) are commensurately bigger and can
dissipate more power without "getting hot".

Unfortunately, simply counting the number of coils and capacitors isn't
even an approximate way to judge loss. What counts, mainly, is how much
current is flowing in those inductors and how large their wire is (and,
if the capacitors have other than air dielectric, perhaps how much
voltage is across the capacitors)(*). If you do an analysis of a tuner,
you'll find that for a given applied power, the inductor current can
vary a huge amount depending on the load impedance. Consequently, the
loss can vary a greatly.

Lowpass filters are invariably specified when in a circuit with a fixed,
specified impedance load. It's not hard at all to design a lowpass
filter which has low loss under that condition. Likewise, it's not hard
to design a matching network (tuner) which has low loss when the load
isn't too far away from 50 ohms resistive. The trick is to maintain
reasonable loss when the impedance transformation is extreme.

Roy Lewallen, W7EL

Fred W4JLE wrote:
Let's put this an easier way, how many of you have a low pass filter in
line. Most manufacturers claim a .25dB or less insertion loss. These filters
consist of a boat load of coils and caps.

A tuner normally has 2 varible caps and a single silver plated coil.

While any device indeed has loss, here we are picking fly crap out of
pepper.

Fred W4JLE wrote:
Let's put this an easier way, how many of you have a low pass filter in
line.

Most commercial rigs already meet the FCC spec so
usually no low pass filter is needed.
--
73, Cecil http://www.qsl.net/w5dxp

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In article ,
Fred W4JLE wrote:

Let's put this an easier way, how many of you have a low pass filter in
line. Most manufacturers claim a .25dB or less insertion loss. These filters
consist of a boat load of coils and caps.

A tuner normally has 2 varible caps and a single silver plated coil.

While any device indeed has loss, here we are picking fly crap out of
pepper.

I think you're making an inapplicable comparison.

The low-pass filters you're referring to have a relatively low loss
when used as directed, it's true... but the "use as directed"
condition usually mandates having the proper source and sink
impedances on either side. The loaded Q is usually modest.

A transmatch being used to match a difficult load can be in a
distinctly different situation. If the load is a harsh one (low R,
high magnitude of X), tuning up can create a situation with a high
network Q and high circulating currents in the tuner components.

The April '95 QST has an article which shows some actual calculations
(and if I recall correctly the Handbook has a bunch of tuner loss
tables).

One example in the QST article shows the results of using a T tuner to
tune an antenna which is just too darned short. The tuner sees a load
of 4.40 - j35 ohms. Although a match can be established with the
specified tuner components, the estimated power loss in the tuner is
almost 2/3 of the input (4.54 dB!). The transmission line eats enough
11.6 dB, in their example.

Granted, this is a rather pathological situation, but it does occur
from time to time in the real world. I've heard numerous reports of
people "burning up" their tuners by trying to match a low-resistance,
highly-reactive load, and frying the coil. Some of the MFJ tuners
seem to have a reputation for suffering from heat damage to the coils
(the plastic coil form melts).

--
Dave Platt AE6EO
Hosting the Jade Warrior home page: http://www.radagast.org/jade-warrior
I do _not_ wish to receive unsolicited commercial email, and I will
boycott any company which has the gall to send me such ads!

Can you give us a typical loss for a tuner matching a G5RV?



"Roy Lewallen" wrote in message
...
Unfortunately, simply counting the number of coils and capacitors isn't
even an approximate way to judge loss. What counts, mainly, is how much
current is flowing in those inductors and how large their wire is (and,
if the capacitors have other than air dielectric, perhaps how much
voltage is across the capacitors)(*). If you do an analysis of a tuner,
you'll find that for a given applied power, the inductor current can
vary a huge amount depending on the load impedance. Consequently, the
loss can vary a greatly.

Lowpass filters are invariably specified when in a circuit with a fixed,
specified impedance load. It's not hard at all to design a lowpass
filter which has low loss under that condition. Likewise, it's not hard
to design a matching network (tuner) which has low loss when the load
isn't too far away from 50 ohms resistive. The trick is to maintain
reasonable loss when the impedance transformation is extreme.

Roy Lewallen, W7EL

Fred W4JLE wrote:
Let's put this an easier way, how many of you have a low pass filter in
line. Most manufacturers claim a .25dB or less insertion loss. These
filters
consist of a boat load of coils and caps.

A tuner normally has 2 varible caps and a single silver plated coil.

While any device indeed has loss, here we are picking fly crap out of
pepper.

Fred W4JLE wrote:
Can you give us a typical loss for a tuner matching a G5RV?

No, sorry, I can't, and I don't believe there is such a thing. It's
possible of course to find the input impedance of any wire antenna like
the G5RV at each of the frequencies of interest. But transmission line
lengths and impedances vary, which transforms the impedance seen by the
tuner. Those impedance changes can be dramatic, and can result in widely
varying tuner efficiency. On top of that, you have the variations in
tuner topology and construction which makes a "typical" tuner also an
elusive beast. I'd be very suspicious of any "typical" tuner loss
figure, and wouldn't expect to see it in practice unless the conditions
are spelled out really well and my setup was very similar.

You see, I'm not a true Guru. A real one wouldn't waffle like this, but
would give you a positive answer, and you'd very probably never have
reason to doubt it.

Roy Lewallen, W7EL