On Wed, 4 May 2005 16:13:10 -0700, "John Smith"
wrote:

And, that current source works, I have used it many times (makes an
excellent test lamp for 5-30V)... will with stand at least 30V+ across drain
and source and maintain ~10ma... when the REV current to its' led drops to
zero, max flows though the FWD--all other cases they must share that 10ma...

Hi Brett,

I've no doubt, but in your circuits - never. Doesn't make sense
unless you need parts ballast. It's like when the watchmakers
advertised watches with 60 jewels, and there were only half a dozen
points that actually used them.

73's
Richard Clark, KB7QHC

Richard:

If I use that at QRP levels, then go to QRO, that constant current source
will be used! I have a couple of burnt leds which offer proof... at a KW
the fet would wave bye-bye (even before I suspect)...

Regards,
John

"Richard Clark" wrote in message
...
| On Wed, 4 May 2005 16:13:10 -0700, "John Smith"
| wrote:
|
| And, that current source works, I have used it many times (makes an
| excellent test lamp for 5-30V)... will with stand at least 30V+ across
drain
| and source and maintain ~10ma... when the REV current to its' led drops
to
| zero, max flows though the FWD--all other cases they must share that
10ma...
|
| Hi Brett,
|
| I've no doubt, but in your circuits - never. Doesn't make sense
| unless you need parts ballast. It's like when the watchmakers
| advertised watches with 60 jewels, and there were only half a dozen
| points that actually used them.
|
| 73's
| Richard Clark, KB7QHC

If you would send it to me, I will post it on my website so all may
peruse...

"John Smith" wrote in message
...
Oh great!!!

Can I just rename it?

What is a workaround? Or, do I have to get a free host and setup a
webpage?

Regards,
John

"Cecil Moore" wrote in message
...
| John Smith wrote:
| Hopefully, the attachment of the .jpg was successful....
|
| The usenet gods will not allow .jpg files since this is
| specified as a text only newsgroup.
| --
| 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

Richard:

I just climbed up and pulled the SWR meter off the pole--DUH!!! Those 50
ohm resistors are actually 1500 ohm 2 watt metal oxide.... sorry, as usual,
your post was relevant.... I just couldn't see it till I opened up the
box....
I could have sworn I stuck 50 ohm ones in there--getting old here... but now
I can see it, if they had been 50 ohm, power to the ant would have been
really limited.... and I would have "smoked" that winding and resistors...

Anyway, will try to get sometime to toy with it tomorrow, and paste the
"real" schematic of it on the webpage....

Warmest regards,
John

"Richard Clark" wrote in message
...
| On Wed, 4 May 2005 16:13:10 -0700, "John Smith"
| wrote:
|
| And, that current source works, I have used it many times (makes an
| excellent test lamp for 5-30V)... will with stand at least 30V+ across
drain
| and source and maintain ~10ma... when the REV current to its' led drops
to
| zero, max flows though the FWD--all other cases they must share that
10ma...
|
| Hi Brett,
|
| I've no doubt, but in your circuits - never. Doesn't make sense
| unless you need parts ballast. It's like when the watchmakers
| advertised watches with 60 jewels, and there were only half a dozen
| points that actually used them.
|
| 73's
| Richard Clark, KB7QHC

Cecil, W5DXP wrote:
"Knowing the current at one point tells you absolutely bothing about
SWR."

The reflection coefficient depends on a mismatched load at the end of
the line. Reflection coefficient is more or less constant in a low loss
transmission line.

Bird`s Model 43 does not contain a toroid, but it does sample the
current at a single spot.

Just as its forward and reverse watt indications can be scaled to SWR
readings, it could be calibrated to indicate SWR and scaled to give
watts.

Forward and reverse power flows on a line are nearly constant, except
for slight line loss, no matter where the line is sampled.

The design trick in the Model 43 is making samples derived from amps and
volts exactly equat to each other. So, when their polarity is the same,
their total is double the value of either by itself. When their
polarities are reversed from each other, they cancel completely.

It so happens that a reflected wave always undergoes a reversal of
polarity of either its volts or amps, but never both. This is the
distinguishing difference between the forward wave and the reflected
wave.

The phase reversal of the reflected wave, makes its sample of volts and
amps in the 43`s directional coupler (sampling unit) cancel, while the
sample of the forward wave has double the magnitude of either sample,
volts or amps, by itself. This permits a reading proportional to forward
power only.

To get an indication of the reflected power alone, it is necessary ro
flip a switch (in the Model 43, this is reversal of the slug`s
direction). This switch reverses polarity so that now the forward power
samples cancel and the reverse (reflected) power samples produce a
double of either of their values alone.

Bird gets very satisfactory results without a toroid. Using only a small
pickup loop inside the sampling element to sample the line current is
enough. Line voltage is sampled by this tiny coil`s capacitive coupling
to the precission short 50-ohm line segment inside the meter case.

In normal low-loss transmission lines the forward power is the same at
either end of the line. Same for reflected power. So it makes no
difference where they are measured in the transmission line.

Best regards, Richard Harrison, KB5WZI

John - KD5YI wrote:

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

I think he thinks his toroid is a directional coupler.

But it is a current transducer, not a directional coupler.
--
73, Cecil http://www.qsl.net/w5dxp

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Richard Harrison wrote:

Cecil, W5DXP wrote:
"Knowing the current at one point tells you absolutely nothing about
SWR."

Bird`s Model 43 does not contain a toroid, but it does sample the
current at a single spot.

It also samples a voltage which John's design does not.

I left out a word that I thought was implied. I should have said:
Knowing *only* the current at one point tells you absolutely nothing
about SWR. He is sampling *only* the current and *only* at one point.
Either two current samples, a current and voltage sample, or two
voltage samples are required for an SWR reading.
--
73, Cecil http://www.qsl.net/w5dxp

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"John Smith" wrote in message
...
Well, can't remember where I seen that "directional coupler", but will be
willing to give the designer credit if he makes himself know...

The led indicating circuit is my design...

It seems to work, all I have is another SWR with analog meter I
constructed
myself to compare it with, soon as I locate someone with a commercial
meter--I will compare both of mine to it... Only real apparent problem is
the REF led changes brightness slowly (and here it is hard to "judge" SWR
by
brilliance), until right at, or near, match, when it will plunge to
darkness
rather quickly...

Well, show me what is wrong and suggest an alternative circuit or mods to
set it proper (or explain in text, I will see how good I am at word
problems
here)--I am all EARS Cecil... smile

Regards,
John

"Cecil Moore" wrote in message
...
| John Smith wrote:
| OK, one... more.... time!!! there is no time yanno!
| Please someone, see if you can view the page he
| http://blake.prohosting.com/mailguy2/JS-swr.jpg
|
| You have a number of problems. Where did you get that design?
| In order to separate the forward power from the reflected
| power, you need to use phasor addition/subtraction of voltage
| and current. You only have current sampled. Where is your
| voltage sample? Where is your phasor addition/subtraction?
| --
| 73, Cecil http://www.qsl.net/w5dxp
|
|
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I found this while tidying my bookshelf last night:
CQ Amateur Radio magazine October 1997 "N7VE's One LED SWR Indicator".

73 Roger ZR3RC

"Richard Harrison" wrote:
Forward and reverse power flows on a line are nearly constant,
except for slight line loss, no matter where the line is sampled.
____________

Average power is nearly constant, but for every value of SWR 1:1, peak
power along the line is not. I have seen many examples in FM broadcast
stations where their transmission line was damaged at intervals of 1/2
wavelength due to a high mismatch at the antenna, or a precipitating failure
in the line itself.

RF