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I recently sat down and calibrated my antenna, going through the bands
and recording the antenna tuner settings required to reach 1:1 on all
the bands my rig can run.

I'm thinking about another calibration I'd like to perform with the
tuner bypassed, trying to determine where on the bands I can use the
antenna without a tuner and still be within a reasonable SWR range.

I am hoping to preserve the lifetime of my tubes and maximize the
power available to me.

My question is: what is an acceptable SWR range? I know that 1:1 is a
desirable SWR, but when does SWR become undesirable to the point that
it shortens the lives of my tubes?

I am using a Kenwood TS-520 and an MFJ Versa Tuner II.

Jack.
=2D --=20
Jack Twilley
jmt at twilley dot org
http colon slash slash www dot twilley dot org slash tilde jmt slash
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Jack Twilley wrote:
My question is: what is an acceptable SWR range?
I am using a Kenwood TS-520 and an MFJ Versa Tuner II.

Your transceiver manual should specify a maximum SWR.
For my IC-706, it is 3:1. I consider anything below
2:1 to be perfectly safe. That's about 11% reflected
power. Most modern transceivers are equipped with
foldback circuitry to protect the finals.
--
73, Cecil, W5DXP

A TS-520 has vacuum tube output stages --
Vacuum tubes are very forgiving of SWR --- unlike solid states rigs.

I operated a TS-830S (tube outputs) with swr's well over 3:1 for years (no
tuner) and never had to change the finals.

Not desireable but in my case had no choice as I didn't have a tuner and the
SWR was high on one end of the band for my junior beam.

Caveat -- your tube life may vary !!!!!

--
73 From
"Cecil Moore" wrote in message
...
Jack Twilley wrote:
My question is: what is an acceptable SWR range?
I am using a Kenwood TS-520 and an MFJ Versa Tuner II.

Your transceiver manual should specify a maximum SWR.
For my IC-706, it is 3:1. I consider anything below
2:1 to be perfectly safe. That's about 11% reflected
power. Most modern transceivers are equipped with
foldback circuitry to protect the finals.
--
73, Cecil, W5DXP

"Jack Twilley" wrote in message
...

I am hoping to preserve the lifetime of my tubes and maximize the
power available to me.

My question is: what is an acceptable SWR range? I know that 1:1 is a
desirable SWR, but when does SWR become undesirable to the point that
it shortens the lives of my tubes?

Impedances of 25ohms, 50+j39ohms, and 100 ohms all represent loads that
could present a 2:1 SWR to the transmitter. Which is worse depends on
how the matching and filtering networks reflect the load back to the
transistor.
With a networks that look like a half wavelength of transmission line, the
25ohm
load would cause more transistor stress than the 100 ohm load. Adding
another
quarter wavelength of transmission line wouldn't change the SWR, but would
make
the 100ohm load more of a problem than the 25ohm load.

I am using a Kenwood TS-520 and an MFJ Versa Tuner II.

You may be in luck. You can calculate the plate power (plate current*plate
voltage).
Subtract the power output and you have a very good idea on how much the tube
is
stressed. You can then measure the SWR and see if how much of a correlation
there
is between SWR and tube stress. Another useful measurement may be to
measure
the temperature of the tube with one of those non-contact IR thermometers.

73--Zack Lau W1VT

On Fri, 10 Oct 2003 11:07:53 -0700, Jack Twilley
wrote:

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I recently sat down and calibrated my antenna, going through the bands
and recording the antenna tuner settings required to reach 1:1 on all
the bands my rig can run.

I'm thinking about another calibration I'd like to perform with the
tuner bypassed, trying to determine where on the bands I can use the
antenna without a tuner and still be within a reasonable SWR range.

I am hoping to preserve the lifetime of my tubes and maximize the
power available to me.

My question is: what is an acceptable SWR range? I know that 1:1 is a
desirable SWR, but when does SWR become undesirable to the point that
it shortens the lives of my tubes?

I am using a Kenwood TS-520 and an MFJ Versa Tuner II.

Jack.

Jack,

The 520 has a pi-network output. When properly adjusted, the pin-net
work will match the finals to the load. So if you are able to adjust
your plate and loading controls to the recommended grid and plate
current values everything will be just fine reguardless of the SWR.
Now if your SWR is so high as the 520 will not load properly then you
should think of bringing the tuner on line. Otherwise just leave it in
the by-pass position. Nothing is gained using the tuner if it isn't
needed.

73
Danny, K6MHE

Also the tank circuit in vacuum tube finals will allow loading into a
mismatch -- just watch that the
plate and grid current values are in limits.

--
73 From El Martillo
------------------
"El Martillo" wrote in message
news:UiDhb.67228$Ms2.27006@fed1read03...
A TS-520 has vacuum tube output stages --
Vacuum tubes are very forgiving of SWR --- unlike solid states rigs.

I operated a TS-830S (tube outputs) with swr's well over 3:1 for years (no
tuner) and never had to change the finals.

Not desireable but in my case had no choice as I didn't have a tuner and
the
SWR was high on one end of the band for my junior beam.

Caveat -- your tube life may vary !!!!!

--
73 From
"Cecil Moore" wrote in message
...
Jack Twilley wrote:
My question is: what is an acceptable SWR range?
I am using a Kenwood TS-520 and an MFJ Versa Tuner II.

Your transceiver manual should specify a maximum SWR.
For my IC-706, it is 3:1. I consider anything below
2:1 to be perfectly safe. That's about 11% reflected
power. Most modern transceivers are equipped with
foldback circuitry to protect the finals.
--
73, Cecil, W5DXP

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"Cecil" =3D=3D Cecil Moore writes:

Jack My question is: what is an acceptable SWR range? I am using a
Jack Kenwood TS-520 and an MFJ Versa Tuner II.

Cecil Your transceiver manual should specify a maximum SWR. For my
Cecil IC-706, it is 3:1. I consider anything below 2:1 to be
Cecil perfectly safe. That's about 11% reflected power. Most modern
Cecil transceivers are equipped with foldback circuitry to protect
Cecil the finals.

I don't have my manual at work, but the following URL

http://www.qsl.net/sm7vhs/radio/kenwood/ts520/specs.htm

doesn't show any kind of maximum SWR.

This transceiver isn't "modern" by any stretch of the imagination -- I
wouldn't be surprised to learn that the radio is older than I am.

Jack.
=2D --=20
Jack Twilley
jmt at twilley dot org
http colon slash slash www dot twilley dot org slash tilde jmt slash
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Jack Twilley wrote:

etc. etc.

I run a TS-520S and do a lot of antenna experimentation. I have never
really concerned myself with SWR as tube rigs are very forgiving. In the
military we always considered 1.5:1 or better as 'mil spec'. I never worry
about 3:1 or less, and wouldn't even care about greater SWR's as long as
the finals are properly tuned and within current specs.

I think that a very high SWR might cause problems with the tuner well
before it would do anything to the rig.

Irv VE6BP

--
--------------------------------------
Diagnosed Type II Diabetes March 5 2001
Beating it with diet and exercise!
297/215/210 (to be revised lower)
58"/43"(!)/44" (already lower too!)
--------------------------------------
Visit my HomePage at http://members.shaw.ca/finkirv/
Visit my very special website at http://members.shaw.ca/finkirv4/
Visit my CFSRS/CFIOG ONLINE OLDTIMERS website at http://members.shaw.ca/finkirv5/
--------------------
Irv Finkleman,
Grampa/Ex-Navy/Old Fart/Ham Radio VE6BP
Calgary, Alberta, Canada

Yep you are correct.

--
73 From
"W7TI" wrote in message
...
On Fri, 10 Oct 2003 11:57:56 -0700, "El Martillo"
wrote:

Vacuum tubes are very forgiving of SWR --- unlike solid states rigs.

__________________________________________________ _______

I think you mean "vacuum tube rigs", not "vacuum tubes". The tubes
themselves don't care what the SWR is, assuming the tank circuit is
properly tuned.

--
Bill, W7TI

On Fri, 10 Oct 2003 11:07:53 -0700, Jack Twilley
wrote:

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snip

My question is: what is an acceptable SWR range? I know that 1:1 is a
desirable SWR, but when does SWR become undesirable to the point that
it shortens the lives of my tubes?

I am using a Kenwood TS-520 and an MFJ Versa Tuner II.

The 520 uses tubes for finals and a Pi Network for matching. As long
as the network tunes and loads without exceeding the tube ratings it
should run just fine.

All that the tuner does is extend the matching range, so it matters
little whether the external tuner, or the built in Pi network does the
matching. (as long as it does match)

Roger Halstead (K8RI EN73 & ARRL Life Member)
www.rogerhalstead.com
N833R World's oldest Debonair? (S# CD-2)


Jack.