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Old March 31st 05, 05:27 PM
John Smith
 
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Default SWR meter, inline, non-resistive, led

I am looking to construct a SWR meter which can be left in line and consumes
negligible power (just to light a led or two and associated, minimal, losses
of transmitter power.)

I had seen such a schematic years ago. Drawing a mental picture, from what
I can remember, a wire ran down the center of a tube on a couple of
insulating spacers (washers) in a concentric configuration.

A small hole in each end of the tubing allowed an insulated pickup turn to
be run adjacent to the wire in the tube--exiting the holes in the sides of
the tubing, this picked up sufficient reflected power to drive the led(s)
and give an indication of SWR (led(s) dim or out at 1:1, or near.

Anyone got that schematic/construction details or, one of a similar unit to
construct?

This unit was inserted in the coax line to the antenna.


Warmest regards,
thanks in advance
--
Hay, if'n ya'll cun't konstructivly partecipete in this har disscusion, haw
aboot speel-checkin it fer me?




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Old April 2nd 05, 07:05 PM
andreas magun
 
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Default

Have a look at http://www.qsl.net/iw3hev/ where a simple
non resistive broadband coupler (used in an antenna analyzer)
is described.

Andreas



John Smith wrote:
I am looking to construct a SWR meter which can be left in line and consumes
negligible power (just to light a led or two and associated, minimal, losses
of transmitter power.)

I had seen such a schematic years ago. Drawing a mental picture, from what
I can remember, a wire ran down the center of a tube on a couple of
insulating spacers (washers) in a concentric configuration.

A small hole in each end of the tubing allowed an insulated pickup turn to
be run adjacent to the wire in the tube--exiting the holes in the sides of
the tubing, this picked up sufficient reflected power to drive the led(s)
and give an indication of SWR (led(s) dim or out at 1:1, or near.

Anyone got that schematic/construction details or, one of a similar unit to
construct?

This unit was inserted in the coax line to the antenna.


Warmest regards,
thanks in advance

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Old April 8th 05, 02:12 PM
Highland Ham
 
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Default

I had seen such a schematic years ago. Drawing a mental picture, from
what
I can remember, a wire ran down the center of a tube on a couple of
insulating spacers (washers) in a concentric configuration.

A small hole in each end of the tubing allowed an insulated pickup turn to
be run adjacent to the wire in the tube--exiting the holes in the sides of
the tubing, this picked up sufficient reflected power to drive the led(s)
and give an indication of SWR (led(s) dim or out at 1:1, or near.

Anyone got that schematic/construction details or, one of a similar unit

to
construct?

========================
As an alternative to the above you might consider a piece of 'air-spaced'
coax (10 mm OD) as used for sat TV ,say 100 mm long ,connecting the centre
conductor to the sensor's in- & output connectors, earthing 1 side of screen
only.
By inserting a (possibly teflon) insulated wire through one of the 'air
gaps' you create a suitable pick-off for forward/reflected power (SWR)
measurement. The 75 Ohms impedance of the short piece of coax is of no
concern in a 50 Ohms environment.

Frank GM0CSZ / KN6WH




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