On Sun, 8 May 2005 15:37:06 -0700, "John Smith"
wrote:

The caps are an attempt to limit "peak reverse spikes" (especially across
the fets drain-to-source) but, only if they (the spikes) are any more than a
figment of my imagination (besides, at this point we only wish DC and rf
dumped to ground is a "good thing")... at the most--they do little harm...

Hi Brett,

Little Harm? It has been quite evident that electronics is quite new
to you (contrary to whatever experience you may feel you have
accumulated). Putting a capacitor at the output of a rectifier
doubles the reverse voltage stress that the rectifier has to tolerate.
If you are worried about FETs (like cutting out cholesterol for the
sake of your appendix), then your lacking equal fear for the LEDs'
breakdown is a bit strange.

Anyway, I doubt you have actually worked through the analysis given
all the gauche designs that lead to this. It is presumed that the RF
will be "spike" free (the FCC frowns on such spurious content); or
that if you are simply speaking about HF in general, then it follows
that you could have simply dumped the RF to ground by shorting the
Caps in the first place (no need for the useless FETs either).

I threw the second fet in because I felt guilty about having too few
parts!!! innocent-look-with-fingers-tightly-crossed-behind-the-back

Uh-huh. As I said, Mad Man Muntz would have a field day.

73's
Richard Clark, KB7QHC

Hmmm, let me think--well, I have--I think I will take that as a complement!
grin

Warmest regards,
John
--
When Viagra fails to work--you are DOOMED!!!

"Richard Clark" wrote in message
...
| On Sun, 8 May 2005 15:37:06 -0700, "John Smith"
| wrote:
|
| The caps are an attempt to limit "peak reverse spikes" (especially across
| the fets drain-to-source) but, only if they (the spikes) are any more
than a
| figment of my imagination (besides, at this point we only wish DC and rf
| dumped to ground is a "good thing")... at the most--they do little
harm...
|
| Hi Brett,
|
| Little Harm? It has been quite evident that electronics is quite new
| to you (contrary to whatever experience you may feel you have
| accumulated). Putting a capacitor at the output of a rectifier
| doubles the reverse voltage stress that the rectifier has to tolerate.
| If you are worried about FETs (like cutting out cholesterol for the
| sake of your appendix), then your lacking equal fear for the LEDs'
| breakdown is a bit strange.
|
| Anyway, I doubt you have actually worked through the analysis given
| all the gauche designs that lead to this. It is presumed that the RF
| will be "spike" free (the FCC frowns on such spurious content); or
| that if you are simply speaking about HF in general, then it follows
| that you could have simply dumped the RF to ground by shorting the
| Caps in the first place (no need for the useless FETs either).
|
| I threw the second fet in because I felt guilty about having too few
| parts!!! innocent-look-with-fingers-tightly-crossed-behind-the-back
|
| Uh-huh. As I said, Mad Man Muntz would have a field day.
|
| 73's
| Richard Clark, KB7QHC

Here are some pics of the prototype I "junkboxed" together--sorry the
quality is so bad...
http://blake.prohosting.com/mailguy2/
or:
http://blake.prohosting.com/mailguy2/index.html
click on the thumbnails for larger pic(s).

The toroid has the winding grounded at center, there are 20 turns total--10
turns per side (way too many!!! I would suggest somewhere between 1-5 turns
for 10 watts or greater!!!)

And, for Richard, BOTH leds share a common current source through the FET...

Later, when I have time, will sketch the schematic and post it here...

PARTS LIST:
1) One aluminum panel to mount SO-239s'
2) Two SO-239's
3) Two hyper-brite LEDs (I would suggest LESS efficient leds--unless for
QRP--these were just handy)
4) One 1K resistor
5) One MPF-102 Fet
6) Hookup wire

If this isn't the most parts-efficient swr indicator in existance, one which
is suitable for QRP thru QRO--then I'll eat this post!!! (well, granted,
Cecils' "Two Lamp SWR Indicator" beats it--but then, this works on coax!!!)

Build one! It works!!!

Anyone know a QRP newsgroup where I can share this design with?

Warmest regards,
John


--
When Viagra fails to work--you are DOOMED!!!

"John Smith" wrote in message
...
| This is a SWR bridge I built using leds and a homemade "directional
| coupler."
|
| ALL critiques on it, and ideas for improvements are welcomed!!!
|
| Please excuse my rough drawing, I am NOT a draftsperson!
|
| Hopefully, the attachment of the .jpg was successful....
|
| Warmest regards,
| John
|
|

Here is the schematic...
http://blake.prohosting.com/mailguy2/final.jpg
I am afraid this is may only good for QRP-one watt or less power...
Here is the link, this should be viewed as a starting design, far from
finished--I would be interested if some QRP'ers would play with it and let
me know of their experiences.

It was pointed out, that this was over-stressing components capabilites (Roy
even made comment)--the FET will just not take the demands put on it at 10
watts (I ran the ten watts through a resistive splitter and sent ~5 watts
too it--with a new FET, it lasted long enough for proof of concept tests...
then FET blew again)

I have fets of 200+ volts (mpf-102 is 25v)--just gotta find 'em... will
stick one of these in when I have time again...

I ended up with total turns of 30 on the toroid (center tapped.)

Warmest regards,
John
--
When Viagra fails to work--you are DOOMED!!!

"John Smith" wrote in message
...
| Here are some pics of the prototype I "junkboxed" together--sorry the
| quality is so bad...
| http://blake.prohosting.com/mailguy2/
| or:
| http://blake.prohosting.com/mailguy2/index.html
| click on the thumbnails for larger pic(s).
|
| The toroid has the winding grounded at center, there are 20 turns
total--10
| turns per side (way too many!!! I would suggest somewhere between 1-5
turns
| for 10 watts or greater!!!)
|
| And, for Richard, BOTH leds share a common current source through the
FET...
|
| Later, when I have time, will sketch the schematic and post it here...
|
| PARTS LIST:
| 1) One aluminum panel to mount SO-239s'
| 2) Two SO-239's
| 3) Two hyper-brite LEDs (I would suggest LESS efficient leds--unless for
| QRP--these were just handy)
| 4) One 1K resistor
| 5) One MPF-102 Fet
| 6) Hookup wire
|
| If this isn't the most parts-efficient swr indicator in existance, one
which
| is suitable for QRP thru QRO--then I'll eat this post!!! (well, granted,
| Cecils' "Two Lamp SWR Indicator" beats it--but then, this works on
coax!!!)
|
| Build one! It works!!!
|
| Anyone know a QRP newsgroup where I can share this design with?
|
| Warmest regards,
| John
|
|
| --
| When Viagra fails to work--you are DOOMED!!!
|
| "John Smith" wrote in message
| ...
|| This is a SWR bridge I built using leds and a homemade "directional
|| coupler."
||
|| ALL critiques on it, and ideas for improvements are welcomed!!!
||
|| Please excuse my rough drawing, I am NOT a draftsperson!
||
|| Hopefully, the attachment of the .jpg was successful....
||
|| Warmest regards,
|| John
||
||
|
|

John Smith wrote:
It was pointed out, that this was over-stressing components capabilites (Roy
even made comment)--the FET will just not take the demands put on it at 10
watts (I ran the ten watts through a resistive splitter and sent ~5 watts
too it--with a new FET, it lasted long enough for proof of concept tests...
then FET blew again)

For a matched Z0=50 ohm system, five watts of forward power
is 15.8 volts. When calibrated, the voltage from the toroid
has to equal that voltage. That means, for the forward power
indication, 31.6 volts must be tolerated for five watts.

For reflected power, the current will be driven by the difference
of the two voltages. When matched at five watts, that difference
will be 15.8v - 15.8v and the LED will be dark. This might be a
hint to eliminate the forward power indication altogether and
go with only a reflected power indication. After all, the reflected
power indication is the most useful and when zero, the system is
matched.
--
73, Cecil http://www.qsl.net/w5dxp


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On Mon, 9 May 2005 13:15:57 -0700, "John Smith"
wrote:

And, for Richard, BOTH leds share a common current source through the FET...

Hi Brett,

And seeing you are tied directly to the feedline, that hosepipe is
going to supply every bit of what that FET can limit.

Hard to imagine they will EVER turn off. This is just a brighter
brake light flasher.

What's the coil for, anyway?

73's
Richard Clark, KB7QHC

Cecil:

Well, these "hyperbrite" leds I am using mask the effect a lot--but since
the FWD and REW run though the same current limiter, if the REV current goes
up though its' led--it starves the FWD from some of its' current--so as you
see one led get brighter--you see the other grow dimmer (kewl to show to cb
buddies grin)

But, seriously, even more desirable, is you don't need to pay any attention
to the direction in which you insert it into the line....

I don't have a RF vtvm Cecil, and too lazy to build a probe... but, under
test conditions something made the FET fail--I suspect too great of
voltage--I have used that fet/led arrangement for "test lamps" on 5~32v with
never a failure (although my datasheet on the mpf-102 says 25v max), I
suspect the voltage went somewhere beyond 32v when it fail (failed in
shorted condition too, both LEDS were "BRIGHT!!!!")...

But, thank you for your time in commenting--I will NOT ignore your input and
keep it in mind--but still, as Roy pointed out--doesn't pay to push
component capabilities to their max and beyond...
in real use at least...

Warmest regards,
John
--
When Viagra fails to work--you are DOOMED!!!

"Cecil Moore" wrote in message
...
| John Smith wrote:
| It was pointed out, that this was over-stressing components capabilites
(Roy
| even made comment)--the FET will just not take the demands put on it at
10
| watts (I ran the ten watts through a resistive splitter and sent ~5
watts
| too it--with a new FET, it lasted long enough for proof of concept
tests...
| then FET blew again)
|
| For a matched Z0=50 ohm system, five watts of forward power
| is 15.8 volts. When calibrated, the voltage from the toroid
| has to equal that voltage. That means, for the forward power
| indication, 31.6 volts must be tolerated for five watts.
|
| For reflected power, the current will be driven by the difference
| of the two voltages. When matched at five watts, that difference
| will be 15.8v - 15.8v and the LED will be dark. This might be a
| hint to eliminate the forward power indication altogether and
| go with only a reflected power indication. After all, the reflected
| power indication is the most useful and when zero, the system is
| matched.
| --
| 73, Cecil http://www.qsl.net/w5dxp
|
|
| ----== Posted via Newsfeeds.Com - Unlimited-Uncensored-Secure Usenet
News==----
| http://www.newsfeeds.com The #1 Newsgroup Service in the World! 100,000
Newsgroups
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Richard:

One important use of the "coil" is a "choke", I'd hate to try to get a
signal though a direct short of the center conductor to the shield...

Warmest regards,
John
--
When Viagra fails to work--you are DOOMED!!!

"Richard Clark" wrote in message
...
| On Mon, 9 May 2005 13:15:57 -0700, "John Smith"
| wrote:
|
| And, for Richard, BOTH leds share a common current source through the
FET...
|
| Hi Brett,
|
| And seeing you are tied directly to the feedline, that hosepipe is
| going to supply every bit of what that FET can limit.
|
| Hard to imagine they will EVER turn off. This is just a brighter
| brake light flasher.
|
| What's the coil for, anyway?
|
| 73's
| Richard Clark, KB7QHC

On Tue, 10 May 2005 09:07:17 -0700, "John Smith"
wrote:

One important use of the "coil" is a "choke", I'd hate to try to get a
signal though a direct short of the center conductor to the shield...

Hi Brett,

So you have a choke.

You have LEDs.

You have a current limiter (that seems to fail).

OK, so why the direct connection then?

73's
Richard Clark, KB7QHC

On Tue, 10 May 2005 09:06:09 -0700, "John Smith"
wrote:

if the REV current goes
up though its' led--it starves the FWD from some of its' current--so as you
see one led get brighter--you see the other grow dimmer (kewl to show to cb
buddies grin)

But, seriously, even more desirable, is you don't need to pay any attention
to the direction in which you insert it into the line....

Ummmm, How do you know which is FWD? Yeah, I know, for CBers, they
can look at the gear shift.

Your description:
but, under test conditions something made the FET fail
is the longstanding suggestion to tune for maximum smoke.

73's
Richard Clark, KB7QHC