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".

Reg Edwards wrote:

Chuck Olson wrote:
The tuner doesn't reduce efficiency - -

"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?

Some ARRL publication said the losses in a tuner average about
0.5 dB. If true, a tuner indeed reduces efficiency by about 12%.
--
73, Cecil http://www.qsl.net/w5dxp


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"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.


I did some measurments on a MFJ tuner into a dummy load. While I am not
sure if the losses would be more or less than to an acutal antenna, I would
assume it should be the best case . The losses were around 5 to 10 watts
starting with 100 watts input depending on the band. I think 80 meters was
the worse from 80 to 10 meters. This is a small tumer rated around 200 or
300 watts and has a built in wattmeter. This may account for a small
aditional loss. I did not use this meter but did use 2 Bird meters , one on
the input and one on the output to keep the input power constant at 100
watts.

On Sun, 05 Jun 2005 19:21:27 -0500, Cecil Moore
wrote:

Chuck Olson wrote:
The tuner doesn't reduce efficiency - -

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


I realize that a tuner is not 100% efficient, but when I hook up my 80
meter dipole and listen on 20 meters (the wire is fed with coax), the
signals are stronger when tuned thru the tuner rather than direct from
the antenna. Not to mention that when I transmit, the radio is
operating on reduced power with the dipole direct. I realize that
there is considerable loss in my coax (I am using garbage and know it)
and that I am taking a loss thru the tuner, but it is a better option
than direct thru the coax alone.




--
73 for now
Buck
N4PGW

Of Course you are, all horror stories aside.

Don't confuse the angels dancing on the pinheads around here with practical
world experiences. The best solution is to increase the length of your
dipole to 130 feet and feed it with 100 foot of 450 Ohm ladderline. Connect
a piece of coax with a ferrite bead choke to the 450 Ohm line. Your tuner
will love you and you can use all bands from 80 on up.

The electrical plug on your rig has losses that are about as meaningful real
world..

"Buck" wrote in message
...
On Sun, 05 Jun 2005 19:21:27 -0500, Cecil Moore
wrote:

Chuck Olson wrote:
The tuner doesn't reduce efficiency - -

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


I realize that a tuner is not 100% efficient, but when I hook up my 80
meter dipole and listen on 20 meters (the wire is fed with coax), the
signals are stronger when tuned thru the tuner rather than direct from
the antenna. Not to mention that when I transmit, the radio is
operating on reduced power with the dipole direct. I realize that
there is considerable loss in my coax (I am using garbage and know it)
and that I am taking a loss thru the tuner, but it is a better option
than direct thru the coax alone.




--
73 for now
Buck
N4PGW

On Tue, 7 Jun 2005 14:55:25 -0400, "Fred W4JLE"
wrote:

Of Course you are, all horror stories aside.

Don't confuse the angels dancing on the pinheads around here with practical
world experiences. The best solution is to increase the length of your
dipole to 130 feet and feed it with 100 foot of 450 Ohm ladderline. Connect
a piece of coax with a ferrite bead choke to the 450 Ohm line. Your tuner
will love you and you can use all bands from 80 on up.

The electrical plug on your rig has losses that are about as meaningful real
world..


Thanks for the encouragement and antenna.

I have two dipoles up right now. One is a 20 meter mono-bander that
was setup specifically for 20 meters and to test a test design for a
PVC 'cobra head' (whatever the generic name).

The other is a piece made of junk that I put up using parts I already
had available. (#14 electrical wire, PVC insulators and TV Coax). It
started as a 20 meter dipole, I added 40 and then 80 meters. It
wasn't supposed to be anything but a temporary antenna until I made a
new one, but weather, timing and money won't cooperate with me. I
have patched and patched it. Ice tore down one leg this winter and
destroyed half the PVC insulators I was using for spacers. Yesterday I
rewired the PL-259, cut the connection to the wires and re-wired it
and cut off the 40 and 20 meter elements. It tunes and hears much
better now.


I have always wanted antennas that would cover all bands without a
tuner. This was practical as a novice when all I could work was 80,
40, 15, and 10 meters. Three parallel dipoles hanging from one
antenna feed worked well. When I advanced to General, I used two
parallel dipoles and an antenna switch. (CW: 80, 40-15, 20, &10; and
SSB: 75, 40, & 10).

Today, my idea isn't as practical as it was. I now have a rig that
covers 160-6 meters on one HF connector. That's eleven bands!!
That's a lot of parallel dipoles on a feed even with the bands split
up into two antennas.

I acquired an antenna tuner recently and it tunes very quickly. I
still don't like it, but I can operate anywhere from 160-6 meters on
it (not that I have heard anyone on 6 yet.)

I would like to build a portable antenna using 300 ohm TV- twin lead
for the feed for the tuner. Is there a recommended length and feed
point for all bands?

Thanks

Buck
N4PGW

--
73 for now
Buck
N4PGW

GeorgeF wrote:
I would have started making the loop shorter to bring up the resonate
frequency to 80 meters however I’m concerned as to why the lowest SWR I
can find anywhere on the HF band is still over 3:1. Is it because the
loop low to the ground (20’)? Or do I need a balum? 1:1 balum? 4:1
balum? Looking for any suggestions.

Common mode current could be upsetting your measurements as you
are feeding a balanced antenna with coax. Your loop seems to be
too long to resonate on the 75m band. By shortening it, you can
probably move that 3.4:1 point into the 75m band. But why not just
feed it with 450 ohm ladder-line through a balun at a tuner output
and alleviate most of your problems?
--
73, Cecil http://www.qsl.net/w5dxp

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My 2 cents on the subject of tuner loss.
A tuner will Always introduce more loss to the system.
If the total power output of the transmitter is not improved(ie, at
2:1 SWR), then using the tuner to reduce SWR to 1:1 is counter
productive, isn't it?
In other words, getting the SWR down to 1:1 from anything = 2:1, will
always cause a reduction in total power out.

Pat W0OPW

On 7 Jun 2005 04:35:50 -0700, wrote:

My 2 cents on the subject of tuner loss.
A tuner will Always introduce more loss to the system.
If the total power output of the transmitter is not improved(ie, at
2:1 SWR), then using the tuner to reduce SWR to 1:1 is counter
productive, isn't it?

For me, not so. The manual for my Icom 735 says it is designed to
handle 1:1.5 swr, but to try to get it as close to 1:1 as possible.

I just tried an experiment on 20 meters with my 80 meter dipole and an
MFJ 989c tuner. At 1:1 swr, the meter measures 110 watts out; raising
the swr to 2:1 lowers the metered output to 20 watts. So I'm not sure
what the advantage of running a higher swr is.

bob
k5qwg


In other words, getting the SWR down to 1:1 from anything = 2:1, will
always cause a reduction in total power out.

Pat W0OPW

If you can't get the internal SWR meter on an Icom 735 (or similar
rigs) down to exactly 1:1 then either there's something wrong with the
tuner or with the tuner operator.

The tuner either works or it doesn't. There's no half-way house.
Without a tuner anything can happen. And it usually does.

There are far too many sleepless nights unnecessarily caused by the
SWR meter not being in the right imagined ballpark. Just ask
yourselves is the transmitter loaded with roughly 50 ohms or isn't it.
The SWR on the feedline hardly matters two hoots - the so called SWR
meter doesn't measure it anyway.

Do G5RV addicts realise that under even the best conditions the SWR on
the feedline is as high as 10-to-1 regardless of what the meter says.
But it doesn't seem to worry them.
----
Reg.