Elecraft RF Probe
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I forgot to mention that I put a 1N4148 in and it seems to have
taken it out too. I put too much voltage on my poor probe. Is there a heavier diode that will take a little more voltage, say around 70v, that I can replace the 1N31A with? Stan Rife W5EWA Houston, TX K2 S/N 4216 _______________________________________________ Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
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Hmmmm. That means you need more than 100V. Maybe a pair if 1N5711s in series with balancing resistors? Larry N8LP Stan Rife wrote: > I forgot to mention that I put a 1N4148 in and it seems to have > taken it out too. > > > I put too much voltage on my poor probe. Is there a heavier diode > that will take a little more voltage, say around 70v, that I can replace the > 1N31A with? > > > Stan Rife > W5EWA > Houston, TX > K2 S/N 4216 > > > _______________________________________________ > Elecraft mailing list > Post to: [hidden email] > You must be a subscriber to post to the list. > Subscriber Info (Addr. Change, sub, unsub etc.): > http://mailman.qth.net/mailman/listinfo/elecraft > > Help: http://mailman.qth.net/subscribers.htm > Elecraft web page: http://www.elecraft.com > > > > Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
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In reply to this post by srife
Funny you should mention that -- just in the past few days I was browsing
through an old [1968 edition] ARRL "Hints and Kinks". In an article titled "Diode Protection for the Heath R.F. Probe" the author suggested adding a NE-51 neon lamp across the diode (a solution he came up with after frying "three or four" 1N34s). This should work for the Elecraft probe as the schematic shown in H&K for the Heath probe is virtually identical to the schematic in the K1 manual (the only difference is a .005 vs. .01 cap for the input coupling and the polarity of the diode). 73 es GL, Al On Mon May 22 2006 06:53 pm, [hidden email] wrote: > Date: Mon, 22 May 2006 17:22:23 -0500 > From: "Stan Rife" <[hidden email]> > Subject: [Elecraft] Elecraft RF Probe > To: <[hidden email]> > Message-ID: <007701c67dee$339355a0$6401a8c0@stansdesktop> > Content-Type: text/plain; charset="US-ASCII" > > I forgot to mention that I put a 1N4148 in and it seems to have > taken it out too. > > > I put too much voltage on my poor probe. Is there a heavier diode > that will take a little more voltage, say around 70v, that I can replace > the 1N31A with? > > > Stan Rife > W5EWA > Houston, TX > K2 S/N 4216 Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
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Now, that solution shows the power of the group!
All this piker could do was look up a 200V diode or suggest connecting two in series. When the NE-51 lights you know you have exceeded the diode reverse voltage! And it's time to add a resistance pad. Mike Scott AE6WA Tarzana, CA Elecraft KX1 40M Inverted V 20M Dipole -----Original Message----- From: [hidden email] [mailto:[hidden email]]On Behalf Of Al Gulseth Sent: Monday, May 22, 2006 5:44 PM To: [hidden email]; [hidden email] Subject: Re: [Elecraft] Elecraft RF Probe Funny you should mention that -- just in the past few days I was browsing through an old [1968 edition] ARRL "Hints and Kinks". In an article titled "Diode Protection for the Heath R.F. Probe" the author suggested adding a NE-51 neon lamp across the diode (a solution he came up with after frying "three or four" 1N34s). This should work for the Elecraft probe as the schematic shown in H&K for the Heath probe is virtually identical to the schematic in the K1 manual (the only difference is a .005 vs. .01 cap for the input coupling and the polarity of the diode). 73 es GL, Al On Mon May 22 2006 06:53 pm, [hidden email] wrote: > Date: Mon, 22 May 2006 17:22:23 -0500 > From: "Stan Rife" <[hidden email]> > Subject: [Elecraft] Elecraft RF Probe > To: <[hidden email]> > Message-ID: <007701c67dee$339355a0$6401a8c0@stansdesktop> > Content-Type: text/plain; charset="US-ASCII" > > I forgot to mention that I put a 1N4148 in and it seems to have > taken it out too. > > > I put too much voltage on my poor probe. Is there a heavier diode > that will take a little more voltage, say around 70v, that I can replace > the 1N31A with? > > > Stan Rife > W5EWA > Houston, TX > K2 S/N 4216 Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com _______________________________________________ Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
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Interesting solution. Be aware that neon lamps fire at about 60-70
volts. At that voltage you have _definitely_ exceeded the PRV of a 1N4148! You might want to consider a heavier diode in this application - the 1N4007 should take quite a bit higher PRV, allowing the neon lamp to illuminate with extinguishing the diode. On May 22, 2006, at 6:25 PM, Mike Scott wrote: > Now, that solution shows the power of the group! > All this piker could do was look up a 200V diode or suggest > connecting two > in series. > > When the NE-51 lights you know you have exceeded the diode reverse > voltage! > And it's time to add a resistance pad. > > Mike Scott > > AE6WA > Tarzana, CA > > Elecraft KX1 > 40M Inverted V > 20M Dipole > > > -----Original Message----- > From: [hidden email] > [mailto:[hidden email]]On Behalf Of Al Gulseth > Sent: Monday, May 22, 2006 5:44 PM > To: [hidden email]; [hidden email] > Subject: Re: [Elecraft] Elecraft RF Probe > > > Funny you should mention that -- just in the past few days I was > browsing > through an old [1968 edition] ARRL "Hints and Kinks". In an article > titled > "Diode Protection for the Heath R.F. Probe" the author suggested > adding a > NE-51 neon lamp across the diode (a solution he came up with after > frying > "three or four" 1N34s). This should work for the Elecraft probe as the > schematic shown in H&K for the Heath probe is virtually identical > to the > schematic in the K1 manual (the only difference is a .005 vs. .01 > cap for > the > input coupling and the polarity of the diode). > > 73 es GL, Al > > On Mon May 22 2006 06:53 pm, [hidden email] wrote: >> Date: Mon, 22 May 2006 17:22:23 -0500 >> From: "Stan Rife" <[hidden email]> >> Subject: [Elecraft] Elecraft RF Probe >> To: <[hidden email]> >> Message-ID: <007701c67dee$339355a0$6401a8c0@stansdesktop> >> Content-Type: text/plain; charset="US-ASCII" >> >> I forgot to mention that I put a 1N4148 in and it seems to >> have >> taken it out too. >> >> >> I put too much voltage on my poor probe. Is there a >> heavier diode >> that will take a little more voltage, say around 70v, that I can >> replace >> the 1N31A with? >> >> >> Stan Rife >> W5EWA >> Houston, TX >> K2 S/N 4216 > _______________________________________________ > Elecraft mailing list > Post to: [hidden email] > You must be a subscriber to post to the list. > Subscriber Info (Addr. Change, sub, unsub etc.): > http://mailman.qth.net/mailman/listinfo/elecraft > > Help: http://mailman.qth.net/subscribers.htm > Elecraft web page: http://www.elecraft.com > > _______________________________________________ > Elecraft mailing list > Post to: [hidden email] > You must be a subscriber to post to the list. > Subscriber Info (Addr. Change, sub, unsub etc.): > http://mailman.qth.net/mailman/listinfo/elecraft > > Help: http://mailman.qth.net/subscribers.htm > Elecraft web page: http://www.elecraft.com -Jack Brindle, W6FB ======================================================================= _______________________________________________ Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
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My brain got got a little ahead of my fingers.
That should be _without_ extinguishing the diode... Oops... On May 22, 2006, at 6:47 PM, Jack Brindle wrote: > Interesting solution. Be aware that neon lamps fire at about 60-70 > volts. At that voltage you have _definitely_ exceeded the PRV of a > 1N4148! You might want to consider a heavier diode in this > application - the 1N4007 should take quite a bit higher PRV, > allowing the neon lamp to illuminate with extinguishing the diode. > > > On May 22, 2006, at 6:25 PM, Mike Scott wrote: > >> Now, that solution shows the power of the group! >> All this piker could do was look up a 200V diode or suggest >> connecting two >> in series. >> >> When the NE-51 lights you know you have exceeded the diode reverse >> voltage! >> And it's time to add a resistance pad. >> >> Mike Scott >> >> AE6WA >> Tarzana, CA >> >> Elecraft KX1 >> 40M Inverted V >> 20M Dipole >> >> >> -----Original Message----- >> From: [hidden email] >> [mailto:[hidden email]]On Behalf Of Al Gulseth >> Sent: Monday, May 22, 2006 5:44 PM >> To: [hidden email]; [hidden email] >> Subject: Re: [Elecraft] Elecraft RF Probe >> >> >> Funny you should mention that -- just in the past few days I was >> browsing >> through an old [1968 edition] ARRL "Hints and Kinks". In an >> article titled >> "Diode Protection for the Heath R.F. Probe" the author suggested >> adding a >> NE-51 neon lamp across the diode (a solution he came up with after >> frying >> "three or four" 1N34s). This should work for the Elecraft probe as >> the >> schematic shown in H&K for the Heath probe is virtually identical >> to the >> schematic in the K1 manual (the only difference is a .005 vs. .01 >> cap for >> the >> input coupling and the polarity of the diode). >> >> 73 es GL, Al >> >> On Mon May 22 2006 06:53 pm, [hidden email] wrote: >>> Date: Mon, 22 May 2006 17:22:23 -0500 >>> From: "Stan Rife" <[hidden email]> >>> Subject: [Elecraft] Elecraft RF Probe >>> To: <[hidden email]> >>> Message-ID: <007701c67dee$339355a0$6401a8c0@stansdesktop> >>> Content-Type: text/plain; charset="US-ASCII" >>> >>> I forgot to mention that I put a 1N4148 in and it seems >>> to have >>> taken it out too. >>> >>> >>> I put too much voltage on my poor probe. Is there a >>> heavier diode >>> that will take a little more voltage, say around 70v, that I can >>> replace >>> the 1N31A with? >>> >>> >>> Stan Rife >>> W5EWA >>> Houston, TX >>> K2 S/N 4216 >> _______________________________________________ >> Elecraft mailing list >> Post to: [hidden email] >> You must be a subscriber to post to the list. >> Subscriber Info (Addr. Change, sub, unsub etc.): >> http://mailman.qth.net/mailman/listinfo/elecraft >> >> Help: http://mailman.qth.net/subscribers.htm >> Elecraft web page: http://www.elecraft.com >> >> _______________________________________________ >> Elecraft mailing list >> Post to: [hidden email] >> You must be a subscriber to post to the list. >> Subscriber Info (Addr. Change, sub, unsub etc.): >> http://mailman.qth.net/mailman/listinfo/elecraft >> >> Help: http://mailman.qth.net/subscribers.htm >> Elecraft web page: http://www.elecraft.com > > > -Jack Brindle, W6FB > ====================================================================== > = > > > _______________________________________________ > Elecraft mailing list > Post to: [hidden email] > You must be a subscriber to post to the list. > Subscriber Info (Addr. Change, sub, unsub etc.): > http://mailman.qth.net/mailman/listinfo/elecraft > Help: http://mailman.qth.net/subscribers.htm > Elecraft web page: http://www.elecraft.com -Jack Brindle, W6FB ======================================================================= _______________________________________________ Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
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In reply to this post by Mike Scott-7
As you make the RF probe better able to handle high RF voltages you will
also cause it to be less accurate at lower RF voltages. The common RF probe diodes have a turn-on voltage of about 0.2 volts. Below that, they are almost open circuits and have no output. Higher PRV diodes have turn-on voltages of closer to 0.6 volts - three times that of the more sensitive diodes. So it takes three times the RF voltage to even begin to show a DC output and you'll need to be well above the turn on voltage to show an output that accurately indicates the RF applied. Put two or three diodes in series and you'll need 1.2 to nearly 2 volts to just start showing some indication of an output. Bottom line, don't try to use such a probe for low RF levels. Ron AC7AC _______________________________________________ Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
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Thanks, Ron, and everyone. I am trying to measure the RF voltage at
the dummyload, and calibrate the K2 RF meter. The probe is fine at 20watts, what everyone has recommended I check it at. I was just trying to read it at 100watts to verify that the K2 meter tracked with the output. That's when I took out the diode. Tom and Don both warned me about this, but I just had to push the envelope. I'll just set it at 20watts and let it go at that. I'll see if I can find some 1N34A diodes locally. The voltages range from 25v to 70v. 71 volts equals 100.8 watts, if I remember my calculations. Stan Rife W5EWA Houston, TX K2 S/N 4216 -----Original Message----- From: [hidden email] [mailto:[hidden email]] On Behalf Of Ron D'Eau Claire Sent: Monday, May 22, 2006 9:20 PM To: [hidden email] Subject: RE: [Elecraft] Elecraft RF Probe As you make the RF probe better able to handle high RF voltages you will also cause it to be less accurate at lower RF voltages. The common RF probe diodes have a turn-on voltage of about 0.2 volts. Below that, they are almost open circuits and have no output. Higher PRV diodes have turn-on voltages of closer to 0.6 volts - three times that of the more sensitive diodes. So it takes three times the RF voltage to even begin to show a DC output and you'll need to be well above the turn on voltage to show an output that accurately indicates the RF applied. Put two or three diodes in series and you'll need 1.2 to nearly 2 volts to just start showing some indication of an output. Bottom line, don't try to use such a probe for low RF levels. Ron AC7AC _______________________________________________ Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com _______________________________________________ Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
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The diode probe measures peak voltage if it's a standard diode/cap detector... and it needs to handle the peak inverse voltage, which would be 100V ( 70.7v RMS) across a 50 ohm load at 100W. A series pair of 1N5711 Schottky diodes should give you 140V PIV, which should be safe. The drop will still be quite low... lower than a single silicon diode, but obviously twice as high as a single Schottky. If you go that route, you should put a 1 meg resistor across each diode to balance the voltage across them. Larry N8LP Stan Rife wrote: > Thanks, Ron, and everyone. I am trying to measure the RF voltage at > the dummyload, and calibrate the K2 RF meter. The probe is fine at 20watts, > what everyone has recommended I check it at. I was just trying to read it at > 100watts to verify that the K2 meter tracked with the output. That's when I > took out the diode. > > Tom and Don both warned me about this, but I just had to push the > envelope. I'll just set it at 20watts and let it go at that. I'll see if I > can find some 1N34A diodes locally. > > The voltages range from 25v to 70v. 71 volts equals 100.8 watts, if > I remember my calculations. > > > > Stan Rife > W5EWA > Houston, TX > K2 S/N 4216 > > > -----Original Message----- > From: [hidden email] > [mailto:[hidden email]] On Behalf Of Ron D'Eau Claire > Sent: Monday, May 22, 2006 9:20 PM > To: [hidden email] > Subject: RE: [Elecraft] Elecraft RF Probe > > > As you make the RF probe better able to handle high RF voltages you will > also cause it to be less accurate at lower RF voltages. > > The common RF probe diodes have a turn-on voltage of about 0.2 volts. Below > that, they are almost open circuits and have no output. Higher PRV diodes > have turn-on voltages of closer to 0.6 volts - three times that of the more > sensitive diodes. So it takes three times the RF voltage to even begin to > show a DC output and you'll need to be well above the turn on voltage to > show an output that accurately indicates the RF applied. Put two or three > diodes in series and you'll need 1.2 to nearly 2 volts to just start > showing some indication of an output. > > Bottom line, don't try to use such a probe for low RF levels. > > Ron AC7AC > > _______________________________________________ > Elecraft mailing list > Post to: [hidden email] > You must be a subscriber to post to the list. > Subscriber Info (Addr. Change, sub, unsub etc.): > http://mailman.qth.net/mailman/listinfo/elecraft > > Help: http://mailman.qth.net/subscribers.htm > Elecraft web page: http://www.elecraft.com > > _______________________________________________ > Elecraft mailing list > Post to: [hidden email] > You must be a subscriber to post to the list. > Subscriber Info (Addr. Change, sub, unsub etc.): > http://mailman.qth.net/mailman/listinfo/elecraft > > Help: http://mailman.qth.net/subscribers.htm > Elecraft web page: http://www.elecraft.com > > > > Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
Re: Elecraft RF Probe
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In reply to this post by Ron D'Eau Claire-2
Ron, AC7AC, wrote:
As you make the RF probe better able to handle high RF voltages you will also cause it to be less accurate at lower RF voltages. The common RF probe diodes have a turn-on voltage of about 0.2 volts. Below that, they are almost open circuits and have no output. Higher PRV diodes have turn-on voltages of closer to 0.6 volts - three times that of the more sensitive diodes. So it takes three times the RF voltage to even begin to show a DC output and you'll need to be well above the turn on voltage to show an output that accurately indicates the RF applied. Put two or three diodes in series and you'll need 1.2 to nearly 2 volts to just start showing some indication of an output. Bottom line, don't try to use such a probe for low RF levels. --------------------------------------------------------------------- Quite right, but there is a way to overcome this problem which is to apply an offset DC bias to the diode(s) which cancels the diode's natural 'bias'. The diode(s) will then conduct with low applied 'signal' voltage. Requires a stable and 'quiet' DC source e.g. a battery, and stable resistors in the DC 'level adjust' circuit, plus care when setting up. Perhaps it is not worth doing this unless there is a REAL need for a probe that can measure low RF levels. 73, Geoff GM4ESD _______________________________________________ Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
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Geoff, GM4ESD, wrote:
Quite right, but there is a way to overcome this problem which is to apply an offset DC bias to the diode(s) which cancels the diode's natural 'bias'. The diode(s) will then conduct with low applied 'signal' voltage. Requires a stable and 'quiet' DC source e.g. a battery, and stable resistors in the DC 'level adjust' circuit, plus care when setting up. Perhaps it is not worth doing this unless there is a REAL need for a probe that can measure low RF levels. ------------------- Some years ago Wes Hayward, W7ZOI, published a nice design for such a low-level detector in "Solid State Design for the Radio Amateur". It uses a simple op-amp and a second diode to set up the proper bias for the detector diode so that ordinary small-signal silicon diodes (e.g. 1N914) could be used to measure very small RF voltages. I used the circuit myself for a number of years. Ron AC7AC _______________________________________________ Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
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Hi...
some told that we can plug all the time the Elecraft K2 probe .. and some no cause of harmonics !?.. what's about pse ? Tks and 73 from french riviera Jean louis K2 #5371 _______________________________________________ Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
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In reply to this post by srife
Bonjour Jean Louis et tout le monde,
I've read recently that it is better to remove the K2 probe and store it out of the radio. Leaving it in can cause some minor issues. How is your WX. Wait, don't tell me, I'll only be jealous! I'm in Vermont. It is about 50f (10c?) and cloudy - again! 73 - Keith KD1E - - K2 5411 - -----Original Message----- From: [hidden email] [mailto:[hidden email]] On Behalf Of f5nhj Sent: Tuesday, May 23, 2006 1:23 PM To: Ron D'Eau Claire; 'Elecraft Discussion List' Subject: Re: [Elecraft] Elecraft RF Probe Hi... some told that we can plug all the time the Elecraft K2 probe .. and some no cause of harmonics !?.. what's about pse ? Tks and 73 from french riviera Jean louis K2 #5371 _______________________________________________ Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com _______________________________________________ Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
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