Thierry wrote:
the built-in SWR of my RTX TS-570D read SWR 1:1. If my external SWR
displayed an SWR 4 that means that it read the info AFTER it, what looks
in contradiction with what ARRL website states in his technical columns...
Who's right ?

The SWR between the transmitter and the antenna tuner is usually adjusted for
1:1. The antenna tuner doesn't affect the SWR between the antenna tuner and the
antenna. It can be almost any value. Nothing strange at all about a 4:1 SWR
after the antenna tuner.
--
73, Cecil http://www.qsl.net/w5dxp



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The install was : RTX +50 cm RG58 + AMP + 1m Aircom (like RG213) + SWR +15m
Aircom + G5RV. the built-in SWR of my RTX TS-570D read SWR 1:1. If my external
SWR
displayed an SWR 4 that means that it read the info AFTER it, what looks
in contradiction with what ARRL

Thierry, If your external SWR meter is after the amplifier, in a 50 ohm
system, and it read 4 it could possibly destroy your amplifier output devices.
The fact that the built-in SWR meter in the Kenwood read 1:1 only means the
input match to the Amplifier was good. If the 570 has a built-in tuner, it
will try to get a 1:1 match, no matter what is downstream. It doesn't mean the
output the Amp sees is good.
As for the ARRL, I haven't had the time to look, but I hope they are not
stating that a 50 ohm output Amp operating into 4 mismatch is a good thing.

73 Gary N4AST

The TS 570D is driving the amplifier which shows an excellent load for
the TS 570D!!

The amplifier is driving a different load with a 4:1 VSWR. This is a 36%
reflection of the power. If your Amplifier is vacuum tube with tuning
controls it is not a serious condition. You can vary the loading
controls for reasonable output without damage. If your amplifier is
solid state then you have to do something to correct the VSWR because it
presents a load to the amplifier that is outside the designed load range.

Deacon Dave, W1MCE

Cecil Moore wrote:

Reg Edwards wrote:

I wonder why most commercial finals are protected from a high SWR
by foldback circuitry to avoid damage to the finals?


They don't. There isn't an SWR meter on the station.


Reg, I'm talking about commercially manufactured ham radio
finals. Virtually every single one of them has protection
circuitry and virtually every one of them has a built-in
SWR metering system.

I'll stand to be corrected because my RF design activity, C-Band and
S-Band satellite circuits, ended in the mid 80s. Back then, an antenna
load outside of the design range causes higher emitter currents in the
bi-polar solid state devices. These higher currents are the damage
producers. So, circuits were added to control the maximum emitter
current. Today's semiconductor technology is different but I still
suspect that localized voltage or current stresses are a function of the
load.

We used to design for a plasma enhanced environment with an intrinsic Zo
range between 120 to 377 ohms, or, slightly more than 3:1 VSWR at the
antenna. BTW, the circuits continued to operate at almost 10:1 VSWR!!

"JGBOYLES" wrote in message
...
The install was : RTX +50 cm RG58 + AMP + 1m Aircom (like RG213) + SWR
+15m
Aircom + G5RV. the built-in SWR of my RTX TS-570D read SWR 1:1. If my
external
SWR
displayed an SWR 4 that means that it read the info AFTER it, what
looks
in contradiction with what ARRL

Thierry, If your external SWR meter is after the amplifier, in a 50 ohm
system, and it read 4 it could possibly destroy your amplifier output
devices.
The fact that the built-in SWR meter in the Kenwood read 1:1 only means
the
input match to the Amplifier was good. If the 570 has a built-in tuner,
it
will try to get a 1:1 match, no matter what is downstream. It doesn't mean
the
output the Amp sees is good.
As for the ARRL, I haven't had the time to look, but I hope they are not
stating that a 50 ohm output Amp operating into 4 mismatch is a good
thing.

No no, they only tell that a SWR-meter place this way read the SWR "between
itself and the RTX"...
I am not agree with this sentence... as my SWR 4:1 was well read AFTER it,
thus between itself as they state and the antenna rather !

Thierry


73 Gary N4AST

"Dave Shrader" wrote in message
news:ri_Ob.101568$8H.152471@attbi_s03...
The TS 570D is driving the amplifier which shows an excellent load for
the TS 570D!!

The amplifier is driving a different load with a 4:1 VSWR. This is a 36%
reflection of the power. If your Amplifier is vacuum tube with tuning
controls it is not a serious condition. You can vary the loading
controls for reasonable output without damage.

Hi,

Correct. This is well what I did, rotating the amplifier load knob (a
kenwood TL922) to reduce the SWR as I could not reduce it another way
(antenna side) due to my defect balun.

73
Thierry

If your amplifier is
solid state then you have to do something to correct the VSWR because it
presents a load to the amplifier that is outside the designed load range.

Deacon Dave, W1MCE

"Thierry" To answer me in private use http://www.astrosurf.com/lombry/post.htm wrote in message ...
"Cecil Moore" wrote in message
...
JDer8745 wrote:
It's funny that this old wive's tale about the high SWR "burning out the
finals" still exists. I guess it depends on what the meaning of "high"
is.

If high SWR and the attendant mismatch cannot burn out a final,
I wonder why most commercial finals are protected from a high SWR
by foldback circuitry to avoid damage to the finals?

Indeed.
I always hear and read that a high SWR can destroy the PA final of TX,
cranck coils, etc.

Thierry

I may be confused now after reading all the posts, but if you have a
good SWR on the rig that is driving an amp, this is normal, even with
a mismatch to the amp. The amp probably has a tuned input circuit.
It's not going to change much if any, if the SWR to the amp goes high.
Or I don't believe anyway...You should run a meter before the amp, on
the antenna side, to also measure the SWR to the amp. The meter in the
rig is just looking at the tuned input circuit of the amp. You need
another one if you want to keep the amp happy. A solid state amp is
much more critical than the tube amps as far as SWR. But I still
prefer to keep a tube amp under 2 to 1, unless I lower the power
level. But I've run 3:1 or worse many times with my henry 2K classic,
and it never complained. As long as you are within the loading range
of the amp, it's perfectly fine. I think the tubes do run a bit hotter
if the SWR is excessive. Thats why I'll drop the power a bit. When I
do run the amp, I almost always have a good match, IE: coax fed
dipoles, yagis, etc... and I almost never use a tuner. I haven't
actually run my amp in about 4 years. I have it dismantled, and have
been too lazy to order new caps and out it back together. I really
don't need it most of the time. It's handy if I want to brown the food
in a certain area.
MK

"Mark Keith" wrote in message
m...
"Thierry" To answer me in private use
http://www.astrosurf.com/lombry/post.htm wrote in message
...
"Cecil Moore" wrote in message
...

Thierry

I may be confused now after reading all the posts, but if you have a
good SWR on the rig that is driving an amp, this is normal, even with
a mismatch to the amp. The amp probably has a tuned input circuit.
It's not going to change much if any, if the SWR to the amp goes high.
Or I don't believe anyway...You should run a meter before the amp, on
the antenna side, to also measure the SWR to the amp. The meter in the
rig is just looking at the tuned input circuit of the amp. You need
another one if you want to keep the amp happy.

Is this really necessary Mark ?
My config is TX (+built-in ant.tuner and SWR) + AMP + SWR + antenna.
The TX antenna tuner can match the load upo to 2.5:1 to get SWR 1:1 on its
terminal, not further.
The AMP load/plate knob are tuned in the proper band in order to get the
lowest SWR (read on the external one, place just after him)
The SWR, the exernal one placed between the amp and ant, read, in my
opinion, the SWR towards the antenna, not toward the RTX conrrarily to what
state ARRL in its Q&A column.
You speak of inserting another SWR between rtx and amp ? why for ? I do not
understand its utility from the moment I can fine-tune the the amp with the
SWR placed just after it, toward the antenna (in practice in adjusting the
plate on the right band and then the load, in adjusting with accuracy this
latter the SWR increases or descreases). It enough.

NB. at the time of my tests all worked fine, my amp gave all its 850W
although much reduced due to high SWR 4 (I emitted about 300 W) and no one
rig was damaged. Of course I never worked longtime this way but I did some
SSB QSO (thus theoretically enough to burn something) and I had to tune my
RTX to reduce the SWR the best I could. Of course I do never suggest to
proceed this way to nobody but instead to find a solution to get the lowest
SWR (say below 2:1 or even 1:1 if you antenna permits).

Thierry
ON4SKY
http://www.astrosurf.com/lombry

A solid state amp is
much more critical than the tube amps as far as SWR. But I still
prefer to keep a tube amp under 2 to 1, unless I lower the power
level. But I've run 3:1 or worse many times with my henry 2K classic,
and it never complained. As long as you are within the loading range
of the amp, it's perfectly fine. I think the tubes do run a bit hotter
if the SWR is excessive. Thats why I'll drop the power a bit. When I
do run the amp, I almost always have a good match, IE: coax fed
dipoles, yagis, etc... and I almost never use a tuner. I haven't
actually run my amp in about 4 years. I have it dismantled, and have
been too lazy to order new caps and out it back together. I really
don't need it most of the time. It's handy if I want to brown the food
in a certain area.
MK

Cecil, why do you insist on deliberately missing the point?

There is NO SWR meter!

It is a misnomer.

It is a TLI.

This misrepresentation continues to confuse, mislead people trying to
understand what is really a very simple application of an antenna tuner.

In this application the phrase SWR should be banned from the dictionary.
---
Reg, G4FGQ

.................................................. ..........
Regards from Reg, G4FGQ
For Free Radio Design Software go to
http://www.btinternet.com/~g4fgq.regp
.................................................. ..........

Reg Edwards wrote:
Cecil, why do you insist on deliberately missing the point?
There is NO SWR meter!

Reg, my name "Cecil" means "blind" but I'm not blind. Should
I change my name? A rose by any other name smells just as sweet.
The thing is named an "SWR Meter". It's written right on all of
mine. Never mind that all it does is a phasor addition between
a voltage proportional to the voltage and a voltage proportional
to the current.
--
73, Cecil http://www.qsl.net/w5dxp



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