******* Copied from uk.radio.amateur newsgroup. ********

Reg spoke of the SWR meter as a resistance bridge. It is possible to
build a
meter that is a bridge
===================================

The so-called SWR meter is ALWAYS a resistance bridge (although it may
be described in other terms).

In the HF, 100 watt models, the little ferrite ring is a current
transformer. The turns ratio on the transformer allows the bridge
resistors to be changed to values other than 50-ohms.

For example a bridge resistor which is across the transmitter changes
to 5000 ohms. And a bridge resistor in series with the load changes
to 0.5 ohms. In both cases the power lost in the resistors falls to
the order of 1% of the power which would be lost in 50 ohm resistors.

The meter becomes far more power efficient. With 50-ohm bridge ratio
arms the power lost in the bridge would be 75 percent of Tx power
output.

The 0.5-ohm resistor does not exist. Very cleverly, the input
resistance of the one turn primary winding on the current transformer
becomes the 0.5-ohm bridge arm.

The DC seperation between primary and secondary windings on the
current transformer allows the diode rectifier and moving coil DC
microameter circuit to be operated very nicely all at ground
potential.
----
Reg, G4FGQ

The term 'meter' is incorrect. It does not 'measure' anything. It
merely 'indicates'.

Reg,
You said,"The term 'meter' is incorrect. It does not 'measure'
anything. It merely 'indicates'." ... Sounds a lot like a definition
of a politician. What comes out is what was fed in, with about
10% accuracy...
'Doc

You said,"The term 'meter' is incorrect. It does not 'measure'
anything. It merely 'indicates'." ... Sounds a lot like a definition
of a politician. What comes out is what was fed in, with about
10% accuracy...
'Doc

Same over here except that it's only 5%. I have more faith in SWR
meters with bent needles.
---
Reg.

Reg Edwards wrote:

You said,"The term 'meter' is incorrect. It does not 'measure'
anything. It merely 'indicates'." ... Sounds a lot like a definition
of a politician. What comes out is what was fed in, with about
10% accuracy...
'Doc


Same over here except that it's only 5%. I have more faith in SWR
meters with bent needles.


A man with a watch knows the time.

A man with two watches is never sure......



- Mike KB3EIA -

This is getting a bit far from antennas, but the way to know the uncertainty
in knowing time is to have multiple clocks. NBS (whatever it now calls
itself) has a bunch of clocks that are compared to each other.
When I was young (and WWV was back East) the uncertainty indicated from
multiple clocks was a few parts in ten to the eighth power. Today, that
uncertainty is a few parts in ten to the 13th power! It takes multiple
clocks to know the uncertainty.

73 Mac N8TT

--
J. Mc Laughlin; Michigan U.S.A.
Home:
"Michael Coslo" wrote in message
...

snip


A man with a watch knows the time.

A man with two watches is never sure......



- Mike KB3EIA -

Even a broken clock is quite accurate, TWICE a day (the 12 hour
variety)! Jim NN7K

J. Mc Laughlin wrote:
This is getting a bit far from antennas, but the way to know the uncertainty
in knowing time is to have multiple clocks. NBS (whatever it now calls
itself) has a bunch of clocks that are compared to each other.
When I was young (and WWV was back East) the uncertainty indicated from
multiple clocks was a few parts in ten to the eighth power. Today, that
uncertainty is a few parts in ten to the 13th power! It takes multiple
clocks to know the uncertainty.

73 Mac N8TT

--
J. Mc Laughlin; Michigan U.S.A.
Home:
"Michael Coslo" wrote in message
...

snip


A man with a watch knows the time.

A man with two watches is never sure......



- Mike KB3EIA -

Reg Edwards wrote:
******* Copied from uk.radio.amateur newsgroup. ********

Reg spoke of the SWR meter as a resistance bridge. It is possible to
build a
meter that is a bridge
===================================

The so-called SWR meter is ALWAYS a resistance bridge (although it may
be described in other terms).

Utter nonsense.

There are numerous ways to measure SWR without using a bridge of any
kind.

A bridge implementation is mearly a simple and cheap way to do it and
hence the most likely to be found in use by a hobbiest.

snip remainder

--
Jim Pennino

Remove .spam.sux to reply.

Reg spoke of the SWR meter as a resistance bridge. It is
possible to
build a
meter that is a bridge
===================================

The so-called SWR meter is ALWAYS a resistance bridge (although it
may
be described in other terms).

Utter nonsense.

There are numerous ways to measure SWR without using a bridge of any
kind.

A bridge implementation is mearly a simple and cheap way to do it
and
hence the most likely to be found in use by a hobbiest.

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

I'm sorry to say you are all banging your heads against a brick wall.

The so-called SWR meter does NOT measure SWR.

For starters, there is no transmission line on which to measure
anything. Can you find one? It is NOT the one which goes between
tuner and antenna.

To measure SWR on THAT line the meter has to be located in the air at
the antenna end of the line and has to be read using an astronomical
telescope mounted on a tripod. But it would still give the wrong
answers.

Go and think about it some more.
----
Reg, G4FGQ

Reg Edwards wrote:
Reg spoke of the SWR meter as a resistance bridge. It is
possible to
build a
meter that is a bridge
===================================

The so-called SWR meter is ALWAYS a resistance bridge (although it
may
be described in other terms).

Utter nonsense.

There are numerous ways to measure SWR without using a bridge of any
kind.

A bridge implementation is mearly a simple and cheap way to do it
and
hence the most likely to be found in use by a hobbiest.

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

I'm sorry to say you are all banging your heads against a brick wall.

It feels that way when trying to discuss SWR with you.

The so-called SWR meter does NOT measure SWR.

Depends on what you call a SWR meter and what you mean by measure,
but this has already been hashed to bits.

For starters, there is no transmission line on which to measure
anything. Can you find one? It is NOT the one which goes between
tuner and antenna.

It depends on how you implement the hardware to measure SWR, but you
are so obsessed with bridge circuits you have little chance of
understanding there is more in the world.

What do tuners have to do with anything? Tuners are irrelevant to
the original post. Are you deliberately trying to confuse the issue
or do tuners confuse you?

To measure SWR on THAT line the meter has to be located in the air at
the antenna end of the line and has to be read using an astronomical
telescope mounted on a tripod. But it would still give the wrong
answers.

Go and think about it some more.

I did in EE class about 30 years ago and numerous times since. Guess
what, the physics hasn't changed.

You are so obsessed on this issue that the small nugget of information
you have to offer is swamped by the enormous amount of arm waving
and babble.

----
Reg, G4FGQ



--
Jim Pennino

Remove .spam.sux to reply.

You are so obsessed on this issue that the small nugget of
information
you have to offer is swamped by the enormous amount of arm waving
and babble.

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

I'm afraid your reduction to personalities is a positive indication to
bystanders you have lost the argument and have accepted defeat.

No hard feelings! Have a good day!
----
Reg, G4FGQ