|
That was before my time, but I do remember lots of HP and Varian and Tektronix gear in my dad's microwave spectroscopy lab back in the 1970s.? Gray rectangular waveguides, klystron signal generators, and Nixie tube frequency counters.? I don't think I've used any of that stuff since I graduated with a BSEE in 1988.? Maybe an HP 2.4 GHz klystron sig gen in the late 1980s.
Jim Ford
Sent from my T-Mobile 4G LTE Device
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-------- Original message -------- From: Lothar baier <Lothar@...> Date: 3/12/22 8:23 PM (GMT-08:00) Subject: Re: [HP-Agilent-Keysight-equipment] HP detector
I have dark memories of the era where we used slotted lines and HP SWR meters
? but I don’t remember the specific model of the detectors used ,? what I remember is that the detectors did not have a termination build in
?
?
I wonder if they were trying to protect the point-contact diode, and maybe wanted to deal with any possible VSWR it might be working with.
?
?
Yes, I agree that power would make more sense, as it doesn't vary along a mismatched line like voltage does.
Sent from my T-Mobile 4G LTE Device
-------- Original message --------
Date: 3/12/22 7:42 PM (GMT-08:00)
Subject: Re: [HP-Agilent-Keysight-equipment] HP detector
I find it a bit odd for them to specify a voltage rather than power , the only time I have seen this was for detectors that were used with slotted lines because slotted lines used
a probe which is not 50 ohm
?
?
Thank you, Lothar, thank you, n8zmTWH. Particularly the excerpt from the cut sheet;?what I was able to find out before was always catalog data (not a specific?datasheet), and the
Vp-p was not mentioned there. I've never seen both in relation to this unit.?
I may play it very safe - risk averse?here - and insert a 10dB or so attenuator before the detector.?
?
This is cut from an HP doc I found online, maybe the same one you have. Note that it says 3 V RMS, and (4.2 V pk).
Other items in that line were rated in mW, so ignore that here.
?
From: HP-Agilent-Keysiht-equipment@group
<[email protected]>
On Behalf Of Radu Bogdan Dicher
Sent: Saturday, March 12, 2022 9:19 PM
To: [email protected]
Subject: Re: [HP-Agilent-Keysight-equipment] HP detector
?
Back to this topic, as I've finally acquired an HP 8471A and want to make sure I'm not frying it during my first use.
The maximum levels allowed are specified at "3Vrms" "peak or average" - particularly the latter confuses me. How can this number, while being presented as "RMS," be both average and peak? Leaving aside for a moment different waveforms than sine. To me, those
numbers are never the "same." For instance, I am outputting signal from this Wavetek 1002 at +13dBm which, for better or worse, shows at the high impedance input of my HP54522A (@ 250MHz) as about 1.65Vrms/4.70Vp-p. Is this too much for the HP8471A?
I am intentionally not loading the signal with 50 ohm to artificially keep it as high as possible for a worst case scenario calculation. I assume the detector would "see" less volts as it's a 50ohm input device.?
I guess how this number would make sense to me would be something like - Vp-p should never exceed this many volts, regardless of the waveform input. But I am also not sure what is the exact burnout mechanism of failure for these.?
Thank you,
Radu.?
|
I have dark memories of the era where we used slotted lines and HP SWR meters
? but I don’t remember the specific model of the detectors used ,? what I remember is that the detectors did not have a termination build in
?
toggle quoted message
Show quoted text
From: [email protected] < [email protected]>
On Behalf Of n8zmTWH via groups.io
Sent: Saturday, March 12, 2022 10:11 PM
To: [email protected]
Subject: Re: [HP-Agilent-Keysight-equipment] HP detector
?
I wonder if they were trying to protect the point-contact diode, and maybe wanted to deal with any possible VSWR it might be working with.
?
?
Yes, I agree that power would make more sense, as it doesn't vary along a mismatched line like voltage does.
Sent from my T-Mobile 4G LTE Device
-------- Original message --------
Date: 3/12/22 7:42 PM (GMT-08:00)
Subject: Re: [HP-Agilent-Keysight-equipment] HP detector
I find it a bit odd for them to specify a voltage rather than power , the only time I have seen this was for detectors that were used with slotted lines because slotted lines used
a probe which is not 50 ohm
?
?
Thank you, Lothar, thank you, n8zmTWH. Particularly the excerpt from the cut sheet;?what I was able to find out before was always catalog data (not a specific?datasheet), and the
Vp-p was not mentioned there. I've never seen both in relation to this unit.?
I may play it very safe - risk averse?here - and insert a 10dB or so attenuator before the detector.?
?
This is cut from an HP doc I found online, maybe the same one you have. Note that it says 3 V RMS, and (4.2 V pk).
Other items in that line were rated in mW, so ignore that here.
?
From: HP-Agilent-Keysiht-equipment@group
<[email protected]>
On Behalf Of Radu Bogdan Dicher
Sent: Saturday, March 12, 2022 9:19 PM
To: [email protected]
Subject: Re: [HP-Agilent-Keysight-equipment] HP detector
?
Back to this topic, as I've finally acquired an HP 8471A and want to make sure I'm not frying it during my first use.
The maximum levels allowed are specified at "3Vrms" "peak or average" - particularly the latter confuses me. How can this number, while being presented as "RMS," be both average and peak? Leaving aside for a moment different waveforms than sine. To me, those
numbers are never the "same." For instance, I am outputting signal from this Wavetek 1002 at +13dBm which, for better or worse, shows at the high impedance input of my HP54522A (@ 250MHz) as about 1.65Vrms/4.70Vp-p. Is this too much for the HP8471A?
I am intentionally not loading the signal with 50 ohm to artificially keep it as high as possible for a worst case scenario calculation. I assume the detector would "see" less volts as it's a 50ohm input device.?
I guess how this number would make sense to me would be something like - Vp-p should never exceed this many volts, regardless of the waveform input. But I am also not sure what is the exact burnout mechanism of failure for these.?
Thank you,
Radu.?
|
I wonder if they were trying to protect the point-contact diode, and maybe wanted to deal with any possible VSWR it might be working with. ?
toggle quoted message
Show quoted text
From: [email protected] <[email protected]> On Behalf Of Jim Ford
Sent: Saturday, March 12, 2022 10:59 PM
To: [email protected]
Subject: Re: [HP-Agilent-Keysight-equipment] HP detector? Yes, I agree that power would make more sense, as it doesn't vary along a mismatched line like voltage does. Sent from my T-Mobile 4G LTE Device -------- Original message -------- Date: 3/12/22 7:42 PM (GMT-08:00) Subject: Re: [HP-Agilent-Keysight-equipment] HP detector I find it a bit odd for them to specify a voltage rather than power , the only time I have seen this was for detectors that were used with slotted lines because slotted lines used a probe which is not 50 ohm ? ? Thank you, Lothar, thank you, n8zmTWH. Particularly the excerpt from the cut sheet;?what I was able to find out before was always catalog data (not a specific?datasheet), and the Vp-p was not mentioned there. I've never seen both in relation to this unit.? I may play it very safe - risk averse?here - and insert a 10dB or so attenuator before the detector.? ? This is cut from an HP doc I found online, maybe the same one you have. Note that it says 3 V RMS, and (4.2 V pk). Other items in that line were rated in mW, so ignore that here. ? From: HP-Agilent-Keysiht-equipment@group <[email protected]> On Behalf Of Radu Bogdan Dicher
Sent: Saturday, March 12, 2022 9:19 PM
To: [email protected]
Subject: Re: [HP-Agilent-Keysight-equipment] HP detector ? Back to this topic, as I've finally acquired an HP 8471A and want to make sure I'm not frying it during my first use.
The maximum levels allowed are specified at "3Vrms" "peak or average" - particularly the latter confuses me. How can this number, while being presented as "RMS," be both average and peak? Leaving aside for a moment different waveforms than sine. To me, those numbers are never the "same." For instance, I am outputting signal from this Wavetek 1002 at +13dBm which, for better or worse, shows at the high impedance input of my HP54522A (@ 250MHz) as about 1.65Vrms/4.70Vp-p. Is this too much for the HP8471A?
I am intentionally not loading the signal with 50 ohm to artificially keep it as high as possible for a worst case scenario calculation. I assume the detector would "see" less volts as it's a 50ohm input device.?
I guess how this number would make sense to me would be something like - Vp-p should never exceed this many volts, regardless of the waveform input. But I am also not sure what is the exact burnout mechanism of failure for these.?
Thank you,
Radu.?
|
Yes, I agree that power would make more sense, as it doesn't vary along a mismatched line like voltage does.
Jim Ford?
Sent from my T-Mobile 4G LTE Device
toggle quoted message
Show quoted text
-------- Original message -------- From: Lothar baier <Lothar@...> Date: 3/12/22 7:42 PM (GMT-08:00) Subject: Re: [HP-Agilent-Keysight-equipment] HP detector
I find it a bit odd for them to specify a voltage rather than power , the only time I have seen this was for detectors that were used with slotted lines because slotted lines used a probe which is not 50 ohm
?
?
Thank you, Lothar, thank you, n8zmTWH. Particularly the excerpt from the cut sheet;?what I was able to find out before was always catalog data (not a specific?datasheet), and the Vp-p was not mentioned there. I've never seen both in relation
to this unit.?
I may play it very safe - risk averse?here - and insert a 10dB or so attenuator before the detector.?
?
This is cut from an HP doc I found online, maybe the same one you have. Note that it says 3 V RMS, and (4.2 V pk).
Other items in that line were rated in mW, so ignore that here.
?
From: HP-Agilent-Keysiht-equipment@group
<[email protected]>
On Behalf Of Radu Bogdan Dicher
Sent: Saturday, March 12, 2022 9:19 PM
To:
[email protected]
Subject: Re: [HP-Agilent-Keysight-equipment] HP detector
?
Back to this topic, as I've finally acquired an HP 8471A and want to make sure I'm not frying it during my first use.
The maximum levels allowed are specified at "3Vrms" "peak or average" - particularly the latter confuses me. How can this number, while being presented as "RMS," be both average and peak? Leaving aside for a moment different waveforms than sine. To me, those
numbers are never the "same." For instance, I am outputting signal from this Wavetek 1002 at +13dBm which, for better or worse, shows at the high impedance input of my HP54522A (@ 250MHz) as about 1.65Vrms/4.70Vp-p. Is this too much for the HP8471A?
I am intentionally not loading the signal with 50 ohm to artificially keep it as high as possible for a worst case scenario calculation. I assume the detector would "see" less volts as it's a 50ohm input device.?
I guess how this number would make sense to me would be something like - Vp-p should never exceed this many volts, regardless of the waveform input. But I am also not sure what is the exact burnout mechanism of failure for these.?
Thank you,
Radu.?
|
I find it a bit odd for them to specify a voltage rather than power , the only time I have seen this was for detectors that were used with slotted lines because slotted lines used a probe which is not 50 ohm
?
toggle quoted message
Show quoted text
From: [email protected] < [email protected]>
On Behalf Of Radu Bogdan Dicher via groups.io
Sent: Saturday, March 12, 2022 9:16 PM
To: [email protected]
Subject: Re: [HP-Agilent-Keysight-equipment] HP detector
?
Thank you, Lothar, thank you, n8zmTWH. Particularly the excerpt from the cut sheet;?what I was able to find out before was always catalog data (not a specific?datasheet), and the Vp-p was not mentioned there. I've never seen both in relation
to this unit.?
I may play it very safe - risk averse?here - and insert a 10dB or so attenuator before the detector.?
?
This is cut from an HP doc I found online, maybe the same one you have. Note that it says 3 V RMS, and (4.2 V pk).
Other items in that line were rated in mW, so ignore that here.
?
From: HP-Agilent-Keysiht-equipment@group
<[email protected]>
On Behalf Of Radu Bogdan Dicher
Sent: Saturday, March 12, 2022 9:19 PM
To:
[email protected]
Subject: Re: [HP-Agilent-Keysight-equipment] HP detector
?
Back to this topic, as I've finally acquired an HP 8471A and want to make sure I'm not frying it during my first use.
The maximum levels allowed are specified at "3Vrms" "peak or average" - particularly the latter confuses me. How can this number, while being presented as "RMS," be both average and peak? Leaving aside for a moment different waveforms than sine. To me, those
numbers are never the "same." For instance, I am outputting signal from this Wavetek 1002 at +13dBm which, for better or worse, shows at the high impedance input of my HP54522A (@ 250MHz) as about 1.65Vrms/4.70Vp-p. Is this too much for the HP8471A?
I am intentionally not loading the signal with 50 ohm to artificially keep it as high as possible for a worst case scenario calculation. I assume the detector would "see" less volts as it's a 50ohm input device.?
I guess how this number would make sense to me would be something like - Vp-p should never exceed this many volts, regardless of the waveform input. But I am also not sure what is the exact burnout mechanism of failure for these.?
Thank you,
Radu.?
|
搁补诲耻… ? Always a good idea. ? Tom H. ?
toggle quoted message
Show quoted text
From: [email protected] <[email protected]> On Behalf Of Radu Bogdan Dicher
Sent: Saturday, March 12, 2022 10:16 PM
To: [email protected]
Subject: Re: [HP-Agilent-Keysight-equipment] HP detector? Thank you, Lothar, thank you, n8zmTWH. Particularly the excerpt from the cut sheet;?what I was able to find out before was always catalog data (not a specific?datasheet), and the Vp-p was not mentioned there. I've never seen both in relation to this unit.? I may play it very safe - risk averse?here - and insert a 10dB or so attenuator before the detector.? ? This is cut from an HP doc I found online, maybe the same one you have. Note that it says 3 V RMS, and (4.2 V pk). Other items in that line were rated in mW, so ignore that here. ? From: HP-Agilent-Keysiht-equipment@group <[email protected]> On Behalf Of Radu Bogdan Dicher
Sent: Saturday, March 12, 2022 9:19 PM
To: [email protected]
Subject: Re: [HP-Agilent-Keysight-equipment] HP detector ? Back to this topic, as I've finally acquired an HP 8471A and want to make sure I'm not frying it during my first use.
The maximum levels allowed are specified at "3Vrms" "peak or average" - particularly the latter confuses me. How can this number, while being presented as "RMS," be both average and peak? Leaving aside for a moment different waveforms than sine. To me, those numbers are never the "same." For instance, I am outputting signal from this Wavetek 1002 at +13dBm which, for better or worse, shows at the high impedance input of my HP54522A (@ 250MHz) as about 1.65Vrms/4.70Vp-p. Is this too much for the HP8471A?
I am intentionally not loading the signal with 50 ohm to artificially keep it as high as possible for a worst case scenario calculation. I assume the detector would "see" less volts as it's a 50ohm input device.?
I guess how this number would make sense to me would be something like - Vp-p should never exceed this many volts, regardless of the waveform input. But I am also not sure what is the exact burnout mechanism of failure for these.?
Thank you,
Radu.?
|
Thank you, Lothar, thank you, n8zmTWH. Particularly the excerpt from the cut sheet;?what I was able to find out before was always catalog data (not a specific?datasheet), and the Vp-p was not mentioned there. I've never seen both in relation to this unit.? I may play it very safe - risk averse?here - and insert a 10dB or so attenuator before the detector.? Thanks again! Radu.?
This is cut from an HP doc I found online, maybe the same one you have. Note that it says 3 V RMS, and (4.2 V pk). Other items in that line were rated in mW, so ignore that here. ? From: HP-Agilent-Keysiht-equipment@group <[email protected]> On Behalf Of Radu Bogdan Dicher
Sent: Saturday, March 12, 2022 9:19 PM
To: [email protected]
Subject: Re: [HP-Agilent-Keysight-equipment] HP detector ? Back to this topic, as I've finally acquired an HP 8471A and want to make sure I'm not frying it during my first use.
The maximum levels allowed are specified at "3Vrms" "peak or average" - particularly the latter confuses me. How can this number, while being presented as "RMS," be both average and peak? Leaving aside for a moment different waveforms than sine. To me, those numbers are never the "same." For instance, I am outputting signal from this Wavetek 1002 at +13dBm which, for better or worse, shows at the high impedance input of my HP54522A (@ 250MHz) as about 1.65Vrms/4.70Vp-p. Is this too much for the HP8471A?
I am intentionally not loading the signal with 50 ohm to artificially keep it as high as possible for a worst case scenario calculation. I assume the detector would "see" less volts as it's a 50ohm input device.?
I guess how this number would make sense to me would be something like - Vp-p should never exceed this many volts, regardless of the waveform input. But I am also not sure what is the exact burnout mechanism of failure for these.?
Thank you,
Radu.?
|
This is cut from an HP doc I found online, maybe the same one you have. Note that it says 3 V RMS, and (4.2 V pk). Other items in that line were rated in mW, so ignore that here. ?
toggle quoted message
Show quoted text
From: HP-Agilent-Keysiht-equipment@group s.io <[email protected]> On Behalf Of Radu Bogdan Dicher
Sent: Saturday, March 12, 2022 9:19 PM
To: [email protected]
Subject: Re: [HP-Agilent-Keysight-equipment] HP detector? Back to this topic, as I've finally acquired an HP 8471A and want to make sure I'm not frying it during my first use.
The maximum levels allowed are specified at "3Vrms" "peak or average" - particularly the latter confuses me. How can this number, while being presented as "RMS," be both average and peak? Leaving aside for a moment different waveforms than sine. To me, those numbers are never the "same." For instance, I am outputting signal from this Wavetek 1002 at +13dBm which, for better or worse, shows at the high impedance input of my HP54522A (@ 250MHz) as about 1.65Vrms/4.70Vp-p. Is this too much for the HP8471A?
I am intentionally not loading the signal with 50 ohm to artificially keep it as high as possible for a worst case scenario calculation. I assume the detector would "see" less volts as it's a 50ohm input device.?
I guess how this number would make sense to me would be something like - Vp-p should never exceed this many volts, regardless of the waveform input. But I am also not sure what is the exact burnout mechanism of failure for these.?
Thank you,
Radu.?
|
So since this a RF detector I would imply that the 3V RMS is undrerstood to be in a 50ohm system ,? usually most wideband detectors are “force matched” either by using a internal 50ohm resistor or sometimes a 3dB pad !
For 3V RMS in a 50ohm system you would come out at about 20dBm which pretty much is in line with the specs of most diode detectors on the market
?
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Show quoted text
From: [email protected] < [email protected]>
On Behalf Of Radu Bogdan Dicher via groups.io
Sent: Saturday, March 12, 2022 8:19 PM
To: [email protected]
Subject: Re: [HP-Agilent-Keysight-equipment] HP detector
?
Back to this topic, as I've finally acquired an HP 8471A and want to make sure I'm not frying it during my first use.
The maximum levels allowed are specified at "3Vrms" "peak or average" - particularly the latter confuses me. How can this number, while being presented as "RMS," be both average and peak? Leaving aside for a moment different waveforms than sine. To me, those
numbers are never the "same." For instance, I am outputting signal from this Wavetek 1002 at +13dBm which, for better or worse, shows at the high impedance input of my HP54522A (@ 250MHz) as about 1.65Vrms/4.70Vp-p. Is this too much for the HP8471A?
I am intentionally not loading the signal with 50 ohm to artificially keep it as high as possible for a worst case scenario calculation. I assume the detector would "see" less volts as it's a 50ohm input device.?
I guess how this number would make sense to me would be something like - Vp-p should never exceed this many volts, regardless of the waveform input. But I am also not sure what is the exact burnout mechanism of failure for these.?
Thank you,
Radu.?
|
Back to this topic, as I've finally acquired an HP 8471A and want to make sure I'm not frying it during my first use.
The maximum levels allowed are specified at "3Vrms" "peak or average" - particularly the latter confuses me. How can this number, while being presented as "RMS," be both average and peak? Leaving aside for a moment different waveforms than sine. To me, those numbers are never the "same." For instance, I am outputting signal from this Wavetek 1002 at +13dBm which, for better or worse, shows at the high impedance input of my HP54522A (@ 250MHz) as about 1.65Vrms/4.70Vp-p. Is this too much for the HP8471A?
I am intentionally not loading the signal with 50 ohm to artificially keep it as high as possible for a worst case scenario calculation. I assume the detector would "see" less volts as it's a 50ohm input device.?
I guess how this number would make sense to me would be something like - Vp-p should never exceed this many volts, regardless of the waveform input. But I am also not sure what is the exact burnout mechanism of failure for these.?
Thank you,
Radu.?
|
Hi Bruce
You are probably correct from memory it was the first HP plug in I was repairing and it was in the trigger CCT? if the fault was there from manufacture
The scope would have had a bad history as not having a good sweep trigger it was? a Paine to find the fault and I couldn't find? a replacement so just turned the original around and all was OK
Regards Paul
?
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Show quoted text
-----Original Message-----
From: [email protected] [mailto:[email protected]] On Behalf Of Bruce
Sent: 20 February 2022 00:32
To: [email protected]
Subject: Re: [HP-Agilent-Keysight-equipment] HP detector
Another possibility is that the diode was mismarked, but correctly positioned in an auto-insertion pack.? Automation would ignore the mismarking, and final inspection could miss it.
Cheers!
Bruce
Quoting tmillermdems <tmiller11147@...>:
> /I have seen mismarked diodes as well as equipment that was never
> tested (or powered up). It's rare but it happens./
>
> /Regards/
>
> On 2/19/2022 5:14 PM, Paul Bicknell wrote:
>>
>> Hi just a line hear hopefully without stealing the thread when
>> repairing a HP 180 scope plug in one diode was reverse polarity to
>> its marking compared to others in the same plug in
>>
>> Reversing the diode fixed the problem
>>
>> My question is how did this change polarity as I assume it was
>> correct at manufacture of the plug in? otherwise the plugin should
>> have failed end of line testing
>>
>> Regards Paul
>>
>> *From:*[email protected]
>> [mailto:[email protected]] *On Behalf Of *Dave
>> Wright
>> *Sent:* 19 February 2022 15:13
>> *To:* [email protected]
>> *Subject:* Re: [HP-Agilent-Keysight-equipment] HP detector
>>
>> Tom,
>>
>> Thanks for the confirmation..!
>>
>> And, can you comment on if / how the whisker tip geometry might
>> affect characteristics..? I'm wondering if a 'blunt' tip at the
>> contact point might alter performance at high frequencies...
>>
>> _Dave KC6UPS
>>
>>
>
> --
> This email has been checked for viruses by Avast antivirus software.
>
>
>
>
|
Another possibility is that the diode was mismarked, but correctly positioned in an auto-insertion pack. Automation would ignore the mismarking, and final inspection could miss it.
Cheers!
Bruce
Quoting tmillermdems <tmiller11147@...>:
toggle quoted message
Show quoted text
/I have seen mismarked diodes as well as equipment that was never tested (or powered up). It's rare but it happens./
/Regards/
On 2/19/2022 5:14 PM, Paul Bicknell wrote:
Hi just a line hear hopefully without stealing the thread when repairing a HP 180 scope plug in one diode was reverse polarity to its marking compared to others in the same plug in
Reversing the diode fixed the problem
My question is how did this change polarity as I assume it was correct at manufacture of the plug in? otherwise the plugin should have failed end of line testing
Regards Paul
*From:*[email protected] [mailto:[email protected]] *On Behalf Of *Dave Wright
*Sent:* 19 February 2022 15:13
*To:* [email protected]
*Subject:* Re: [HP-Agilent-Keysight-equipment] HP detector
Tom,
Thanks for the confirmation..!
And, can you comment on if / how the whisker tip geometry might affect characteristics..? I'm wondering if a 'blunt' tip at the contact point might alter performance at high frequencies...
_Dave KC6UPS
--
This email has been checked for viruses by Avast antivirus software.
|
I have seen mismarked diodes as well as equipment that was
never tested (or powered up). It's rare but it happens.
Regards
On 2/19/2022 5:14 PM, Paul Bicknell
wrote:
Hi
just a line hear hopefully without stealing the thread when
repairing a HP 180 scope plug in one diode was reverse
polarity to its marking compared to others in the same plug
in
Reversing
the diode fixed the problem
My
question is how did this change polarity as I assume it was
correct at manufacture of the plug in? otherwise the plugin
should have failed end of line testing
Regards
Paul
?
From: [email protected]
[mailto:[email protected]] On
Behalf Of Dave Wright
Sent: 19 February 2022 15:13
To: [email protected]
Subject: Re: [HP-Agilent-Keysight-equipment] HP
detector
?
Tom,
Thanks for the confirmation..!
And, can you comment on if / how the whisker tip geometry
might affect characteristics..? I'm wondering if a 'blunt' tip
at the contact point might alter performance at high
frequencies...
_Dave KC6UPS
|
|
This email has been checked for viruses by Avast antivirus software.
|
|
Hi just a line hear hopefully without stealing the thread when repairing a HP 180 scope plug in one diode was reverse polarity to its marking compared to others in the same plug in Reversing the diode fixed the problem My question is how did this change polarity as I assume it was correct at manufacture of the plug in? otherwise the plugin should have failed end of line testing Regards Paul ?
toggle quoted message
Show quoted text
From: [email protected] [mailto:[email protected]] On Behalf Of Dave Wright
Sent: 19 February 2022 15:13
To: [email protected]
Subject: Re: [HP-Agilent-Keysight-equipment] HP detector ? Tom,
Thanks for the confirmation..!
And, can you comment on if / how the whisker tip geometry might affect characteristics..? I'm wondering if a 'blunt' tip at the contact point might alter performance at high frequencies...
_Dave KC6UPS
|
Tom,
Thanks for the confirmation..!
And, can you comment on if / how the whisker tip geometry might affect characteristics..? I'm wondering if a 'blunt' tip at the contact point might alter performance at high frequencies...
_Dave KC6UPS
|
Hi Dave,
Your belief is correct. GW Pickard’s patent 836531 shows an early version of what later became the standard diode symbol. The anode and cathode assignments happened later — initially, it was just “pointy thing means catswhisker, rectangle means rock”.
—颁丑别别谤蝉, Tom Sent from my iThing, so please forgive typos and brevity.
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Show quoted text
On Feb 13, 2022, at 3:30 PM, Dave Wright <davewrightsplace@...> wrote:
?OK, we have replaced the diode in our 8471A, and learned a few things along the way. In my preceding descriptions, I had Anode and Cathode reversed (for the standard Negative Output model). It is interesting, as in looking at the diode, you can clearly see the 'cat whisker' connection to the die, and that (I believe) is what begat the schematic symbol. _._,_._,_
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OK, we have replaced the diode in our 8471A, and learned a few things along the way. In my preceding descriptions, I had Anode and Cathode reversed (for the standard Negative Output model). It is interesting, as in looking at the diode, you can clearly see the 'cat whisker' connection to the die, and that (I believe) is what begat the schematic symbol. Later measurement of the forward voltage of the new diodes led to further confusion, until it was discovered that the DVM leads were reversed (never happened to any of you, right..?). In this particular diode, 1N831, the whisker is the cathode. So we have something on the order of 0.268 Vf, and a reverse breakdown around 2.9ish.... luckily the Fluke test current is 1mA. So yes, any RF or DC over +3V will toast your diode (well, depends on what is connected on the output end, but be careful). Also of note is the difference between the original diode, and the replacement. In the original, the 'whisker' is well formed into a very sharp point, and contacts the die in the center. The replacement looks like it was banged out by Thor's hammer. A very blunt contact point, nowhere near the center. I don't know how much difference this makes in performance, but I suspect it matters... Anyway, we made some measurements on the 8753D, more for our own edification than to offer any sort of performance spec. In the process, we discover our VNA needs some attention in the flatness department. The realm below 3MHz can't be trusted at present. What is noteworthy is looking at the performance of the input termination resistor in the BNC mount without the diode. Pretty much demonstrates that BNC is garbage at GHz. If any of you have a well calibrated VNA and an 8471A, I'd be curious to see how it looks on your machine...
As far as the replacement process, the photo captions should be enough, but if not I will elaborate.?
/g/HP-Agilent-Keysight-equipment/album?id=272489
Onward up the learning curve...
_Dave KC6UPS
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Hi!
Looking at the 1N831 data sheet, it appears that this is a fairly generic Silicon RF diode, and in fact looks like originally spec'ed as a mixer diode.. I am fairly sure that any HP leaded Schottky diode would work well here, like a 5082-2800 or 2817 type. Maybe even a BAT-85, which I have used on a crappy FR-4 board to over 1 GHz with pretty good flatness. The magic is the coaxial diode mount with the disk resistor & capacitor to give low parasitics in a ~50 ohm coaxial line circuit.
Jeff Kruth
In a message dated 2/9/2022 1:08:43 PM Eastern Standard Time, davewrightsplace@... writes:
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The HP 8471A OEM diode is 1N831, and there are some on eBay. I have two on the way now.
Left to right in the photo is the input termination resistor, 50 Ohms, some sort of film deposited on the disk between the BNC male center pin and a contact ring to the case. The diode anode lead is soldered directly into the input center pin at 'zero length'. ?The cathode lead passes through the center of a disk capacitor, measured as ~1500pf, and on to the center pin of the output BNC female.?
The assembly process will require care in soldering, I imagine it will go as: input R first, then output C, then screw gold plated center into the BNC male body, solder BNC female center pin to protruding cathode lead, and thread main body over all.
Intend to measure performance on 8753D VNA when completed.
More as it happens...
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OK - then ther should be no DC "roll off"
Cheers!
Bruce
Quoting Dave Wright <davewrightsplace@...>:
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The 8471A is DC coupled.
The input termination resistor is connected between the diode anode and case.
The output capacitor is connected between the diode cathode and the case.
_Dave
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The 8471A is DC coupled.
The input termination resistor is connected between the diode anode and case.
The output capacitor is connected between the diode cathode and the case.
_Dave
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Paul Bicknell