grin
Ahhhh, Richard, your armour and weapons rattle as you come down the hall...

Well, it doesn't flash, and it does seem to work... albeit in a bit of a
"sloppy" fashion (tuning is sloppy as to light changes in the REF led)...
and you are correct, the 100k (and the 1k is there in series too) is barely
enough to keep from burning out the leds and a kludge...

If you HAD to make this circuit work, I am interested, and certainly I think
you of an intellect capable--what changes would you make--keeping as much of
the original circuit as possible?

Warmest regards,
John

"Richard Clark" wrote in message
news | On Tue, 03 May 2005 22:12:31 -0700, Richard Clark
| wrote:
|
| an emergency flasher weakly lighting the alternate LEDs at an HF rate.
|
| On review of the circuit (having neglected the capacitors) it looks
| more like a lower rate in a somewhat haphazard logic race of a
| relaxation oscillator whose RC (1K-101K times 0.01µF) still makes this
| wobbulate at higher than visible rate (or lower than perceptible
| brightness, take your pick).
|
| 73's
| Richard Clark, KB7QHC

On Tue, 3 May 2005 22:31:29 -0700, "John Smith"
wrote:

Well, it doesn't flash,

Hi Brett,

How could you tell? Everything about this is far too fast for the eye
to perceive. But we let that pass.

and it does seem to work... albeit in a bit of a
"sloppy" fashion (tuning is sloppy as to light changes in the REF led)...
and you are correct, the 100k (and the 1k is there in series too) is barely
enough to keep from burning out the leds and a kludge...

Barely enough? The problem is it is far too much. You would have to
pump 3KW (matched) through this SWR meter to run the forward LED at
rated current.

The eye is a miserable detector of absolutes, and what you perceive as
bright with whatever current is eking its way through the circuit, is
a sad comparison to what the LED could support. The proper comparison
is done by what is called optical pyrometry, but then that is the
wrong kind of balance for this application.

If you HAD to make this circuit work, I am interested, and certainly I think
you of an intellect capable--what changes would you make--keeping as much of
the original circuit as possible?

Research the "Bruene SWR meter" to find out where you went wrong in
the circuit topology. If you are going to substitute LEDs for meters,
take heed that they are power indicators, not current indicators.
This is some advantage in one sense, and a divergence from the
standard presentation in another sense. Not keeping track of the
sense can get your necktie wrapped around the axle. Mixing LED types
like for Green forward power and Red for reverse power (or t'other way
'round) can really gum up the works when it comes to sizing other
component values.

A simple test of how confounding the eye can be is found in the
question:
"How bright can the Red be in proportion to the Green?"
By the simple electronics, this is a slam dunk. By appearance from
those same electronics, you are off by two orders of magnitude. By
conversion efficiencies there are still major errors of appearance.
Once you get all these balanced out, you still have to answer the
question whose psychology will still perturb most users. Try writing
the answer for a User's Manual (the ultimate test of functionality).

73's
Richard Clark, KB7QHC

John (Smith), all you have is a circuit which might light up a couple
of light-emitting diodes from an RF source via a current transformer.
What purpose is served by the 100K resistor is anybody's guess. But it
has nothing to do with SWR.

As Cecil implies, you should go right back to square one and think
about it.

Actually, you are in good company. Most people don't know how their
SWR meter works or what it does. Most people and Tx manufacturers
don't connect it in the correct place for it read SWR on the
transmission line. Consequently it doesn't even indicate SWR and its
name is a very misleading misnomer.

All it indicates is the magnitude of the reflection coefficient of the
load on the transmitter relative to the impedance the transmitter is
designed to see. And it only does THAT provided the meter has itself
been designed to cater for the same impedance. It is fortunate there
exists a standard impedance of 50 ohms.

But don't allow me to put you off. Just obtain a circuit diagram of a
so-called SWR meter (an HF version) from a handbook and, with little
more than Ohm's Law, you can see and work it out for yourself.

Reg, G4FGQ.

The resistance in the anode circuits of the LEDS only serves as an attempt
at limiting the current through the FWD LED to full brightness (and a
constant current source would best replace this)--and to keep it from
"burning out."

My goals are this:
1) CHEAP!!
2) Cheap!
3) Fewest possible parts...
4) Marginal functionality...

I want to be able to cover the world with these devices (put one on every
single antenna project of mine (even the EH Antenna!!! grin)

I will continue to toy with the design as my time permits....

I am quite willing to suffer the slings and arrows of others, education is
expensive yanno!!! And, I do see most, if not ALL, are saying there is much
more to SWR than at first it seems...

Thanks Reg...

Warmest regards,
John

"Reg Edwards" wrote in message
...
|
| John (Smith), all you have is a circuit which might light up a couple
| of light-emitting diodes from an RF source via a current transformer.
| What purpose is served by the 100K resistor is anybody's guess. But it
| has nothing to do with SWR.
|
| As Cecil implies, you should go right back to square one and think
| about it.
|
| Actually, you are in good company. Most people don't know how their
| SWR meter works or what it does. Most people and Tx manufacturers
| don't connect it in the correct place for it read SWR on the
| transmission line. Consequently it doesn't even indicate SWR and its
| name is a very misleading misnomer.
|
| All it indicates is the magnitude of the reflection coefficient of the
| load on the transmitter relative to the impedance the transmitter is
| designed to see. And it only does THAT provided the meter has itself
| been designed to cater for the same impedance. It is fortunate there
| exists a standard impedance of 50 ohms.
|
| But don't allow me to put you off. Just obtain a circuit diagram of a
| so-called SWR meter (an HF version) from a handbook and, with little
| more than Ohm's Law, you can see and work it out for yourself.
|
| Reg, G4FGQ.
|
|

On Wed, 4 May 2005 11:23:39 -0700, "John Smith"
wrote:

The resistance in the anode circuits of the LEDS only serves as an attempt
at limiting the current through the FWD LED to full brightness

It, in fact, serves to reverse bias the other LED, turning it OFF
(until the first LED depletes the capacitor which then reverses the
situation - the original RDL flip-flop running asynchronously). Which
one lights up is a matter of an indeterminate logic race, not some
proportionality of powers.

(and a constant current source would best replace this)--

If you think about this statement, you would recognize that
either/both LEDs would always be ON and equally bright. [the word
"constant" should be a dead give-away]

and to keep it from "burning out."

Then you put a current limiter (not constant current device) in EACH
LED lead (not sharing). To select a 1KOhm limiter presumes a 20V drop
across it for a 20mA LED excitation current (a typical current
specification). You may achieve the 20mA limit, but it will come at
the cost of more than 40V across 100 Ohms backing through the current
transformer (it is NOT a directional coupler) which can only be
supplied by a transmitter excitation of several KW to a matched load.
If you did nothing other than simply connect an LED across the current
transformer's terminals and adjust the transmitter for 20mA through
the LED, you would need 8W into a matched load.

To put it simply, you are fixated on a problem so remote from your
goal, that solving it basically accomplishes nothing towards measuring
(or even indicating) SWR. As several suggestions have been offered to
research a real topology, you might want to pursue that first.

73's
Richard Clark, KB7QHC

John Smith wrote:
I want to be able to cover the world with these devices (put one on every
single antenna project of mine (even the EH Antenna!!! grin)

http://www.qsl.net/kb7rgg/heath/sche...chema_hm11.gif
--
73, Cecil http://www.qsl.net/w5dxp

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Well, that is how my "meter SWR" which I constructed looks all right--but I
wished to get away having to construct a directional coupler from tubing and
pickup loops...
Only, my (metered) SWR meter uses just ONE pickup loop, I switch terminating
50 ohm resisistor and take-off ends and use the single loop for BOTH "FWD"
and "REF", with a physical switch--my thinking was it would keep the device
more "balanced" using the same pickup...

Warmest regards,
John

"Cecil Moore" wrote in message
...
| John Smith wrote:
| I want to be able to cover the world with these devices (put one on
every
| single antenna project of mine (even the EH Antenna!!! grin)
|
| http://www.qsl.net/kb7rgg/heath/sche...chema_hm11.gif
| --
| 73, Cecil http://www.qsl.net/w5dxp
|
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John Smith wrote:
Well, that is how my "meter SWR" which I constructed looks all right--but I
wished to get away having to construct a directional coupler from tubing and
pickup loops...
Only, my (metered) SWR meter uses just ONE pickup loop, I switch terminating
50 ohm resisistor and take-off ends and use the single loop for BOTH "FWD"
and "REF", with a physical switch--my thinking was it would keep the device
more "balanced" using the same pickup...

A toroidal pickup samples the current at one point. Knowing the
current at one point tells you absolutely nothing about SWR.
--
73, Cecil http://www.qsl.net/w5dxp


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I am thinking, that is ok, long as there is none reflected...

Regards,
John

"Cecil Moore" wrote in message
...
| John Smith wrote:
| Well, that is how my "meter SWR" which I constructed looks all
right--but I
| wished to get away having to construct a directional coupler from tubing
and
| pickup loops...
| Only, my (metered) SWR meter uses just ONE pickup loop, I switch
terminating
| 50 ohm resisistor and take-off ends and use the single loop for BOTH
"FWD"
| and "REF", with a physical switch--my thinking was it would keep the
device
| more "balanced" using the same pickup...
|
| A toroidal pickup samples the current at one point. Knowing the
| current at one point tells you absolutely nothing about SWR.
| --
| 73, Cecil http://www.qsl.net/w5dxp
|
|
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Cecil Moore wrote:
John Smith wrote:

Well, that is how my "meter SWR" which I constructed looks all
right--but I wished to get away having to construct a directional
coupler from tubing and pickup loops...
Only, my (metered) SWR meter uses just ONE pickup loop, I switch
terminating 50 ohm resisistor and take-off ends and use the single
loop for BOTH "FWD" and "REF", with a physical switch--my thinking was
it would keep the device more "balanced" using the same pickup...


A toroidal pickup samples the current at one point. Knowing the
current at one point tells you absolutely nothing about SWR.

Hi, Cecil -

I think he thinks his toroid is a directional coupler.

John