Re: Cal Lab Magazine - International Journal of Metrology
One of the earliest schematics I crossed was the Howard W Sam's Photofact for a 1951 Westinghouse television.
It used the lower case letter 'u' for? mu, thus a 10 microfarad (microFarad) capacitor was marked? '10uf'? on the
schematic. Yes it was lower case? letter 'u' and lower case letter 'f'. Of course there were caps marked 'uuf'
for micromicrofarad, today referred to as picoFarad using the letter pair 'pF'.
It was not until encountering an IBM Selectric typewriter that the secretaries writing the typing the manuals
began using the actual ¦Ì symbol. Before that time, the used the lower lower case letter 'u' as that was the
closest thing on the manual Underwood manual typewriters of the period.
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Re: Cal Lab Magazine - International Journal of Metrology
Such as furlongs per fortnight.
Many years ago I worked in a computer department The manager, who I had very little respect for, asked me for the heat output of the computers. I emailed an answer in watt. I heard from someone else that he didn¡¯t want it in watt, although no unit was specified. I could have guessed he probably wanted BTU as it was for air-conditioning. But I decided to convert the watt to kilo joule per fortnight, and gave him that. I then received a response that watt was okay.?
Dave?
-- Dr. David Kirkby, Kirkby Microwave Ltd, drkirkby@...Telephone 01621-680100./ +44 1621 680100 Registered in England & Wales, company number 08914892. Registered office: Stokes Hall Lodge, Burnham Rd, Althorne, Chelmsford, Essex, CM3 6DT, United Kingdom
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Re: Cal Lab Magazine - International Journal of Metrology
On Wed, 31 Aug 2022 at 15:07, MAX < max@...> wrote: The confusion of Mw and mw is one of my pet peeves.?
Neither are correct, as it should be mW or MW - in the case of a small amplifier, the output power is certainly not going to be MW or even kW do?
Watts (RMS) is one of my pet hates, as RMS power is nonsense. But I see it written quite a bit.?
With electricity prices rising so much in the UK, I think I might buy one of those 800 W amplifiers on eBay, that take a 12 V 5 A power supply. ???
What is the general opinion about using a lower case u to substitute for the greek letter mu for a multiplier in circumstances where it is unhandy to generate a mu?
My personal opinion is that a lower case u is perfectly acceptable in emails and other documents where it¡¯s not easily possible to create a mu, and even if you could, there¡¯s a good chance someone else might not see it as you intended.?
?73 (Regards). Max K 4 O D S.
Dave, G8WRB? -- Dr. David Kirkby, Kirkby Microwave Ltd, drkirkby@...Telephone 01621-680100./ +44 1621 680100 Registered in England & Wales, company number 08914892. Registered office: Stokes Hall Lodge, Burnham Rd, Althorne, Chelmsford, Essex, CM3 6DT, United Kingdom
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Re: Another Q-meter info source
Thank you.
73 (Regards).
Max K 4 O D S.
I've Never Lost the Wonder.
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-----Original Message----- From: [email protected] [mailto: [email protected]] On Behalf Of Jim Strohm Sent: Wednesday, August 31, 2022 8:41 AM To: [email protected]Subject: Re: [Test Equipment Design & Construction] Another Q-meter info source OK, I misspoke a little yesterday about the full nature of the article in the August QCWA newsletter. The article with the Q meter info is the "Vacuum Valley" article, and the Q meter info is toward the end of the article. Nevertheless, sometimes it's good to see what other hams are up to, and the editorial this month urges us NOT to lose the history and knowledge we've accumulated over the years. So I've attached the whole newsletter for your enjoyment and educational purposes. To the best of my knowledge, you have to be a QCWA member to see the newsletter online, a lot like the ARRL requires membership to see their premium content. There may be more Q meter info in next month's newsletter. 73 Jim N6OTQ On Tue, Aug 30, 2022 at 5:02 PM Jim Strohm via groups.io <jim.strohm@...> wrote:
Hi all
The August 2022 QCWA newsletter has an article about Q-meter design.
I haven't vetted it for accuracy, but it looks like it tells the
truth.
Knowing that not everybody here is a QCWA member ... if you'd like, I
can share the article here, "for educational purposes only."
Ask and ye probably will receive.
73
Jim N6OTQ
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Re: Cal Lab Magazine - International Journal of Metrology
I was also corrected once on the time base side of things: ? ns = nano second ? nS = nano siemens ? apparently, some areas this is the unit of interest and is taken quite seriously. ? Eric ? ?
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From: [email protected] < [email protected]> On Behalf Of Dr. David Kirkby, Kirkby Microwave Ltd Sent: Wednesday, August 31, 2022 9:26 AM To: [email protected]Subject: Re: [Test Equipment Design & Construction] Cal Lab Magazine - International Journal of Metrology ? On Wed, 31 Aug 2022 at 01:43, Tom Lee <tomlee@...> wrote: The rule is that units named for people are not capitalized when spelled out. That assures that "two watts" is a measure of power, while "two Watts" refers refers to two family members.
I said earlier that I thought the s should not be there, and cited an BIPM brochure, which did not actually substantiate my statement.? However, this document from the BIPM does. "A concise summary of the International System of Units, SI" It gives a logical reason why "2 watt" is correct, and "2 watts" is not. "Unit symbols are written using roman (upright) type, regardless of the type used in the surrounding text. They are mathematical entities and not abbreviations; unit symbols are never followed by a full stop (except at the end of a sentence) nor by an ¡®s¡¯ for the plural. The use of the correct form for unit symbols is mandatory, and is illustrated by examples in the SI Brochure" Unfortunately, that SI Brochure is not totally consistent, with both "683 lumen per watt" and "683 lumens per watt" in the same document. Also, multiple references to newtons, but I think the newton is the only unit to suffer from this "error". You will not find any references to farads, amperes,
If the IEEE wants "2 watts", and not "2 watt", then it's their publication, so they can have it. But I don't think it is technically correct. But I am not impressed with the way the IEEE accepts both positive and negative numbers in dB for the return loss of passive components. In one issue of a journal you will see someone write that an antenna had a return loss of -15 dB, and in another article the return loss is quoted as 15 dB. Fortunately the context is usually obvious.
Dave
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Re: Cal Lab Magazine - International Journal of Metrology
The confusion of Mw and mw is one of my pet peeves.? I often laugh out loud when I read a catalog description of a small pc board amplifier that delivers 500 Mw.? LOL.? What is the general opinion about using a lower case u to substitute for the greek letter mu for a multiplier in circumstances where it is unhandy to generate a mu? ? 73 (Regards). ? Max K 4 O D S. ? I've Never Lost the Wonder. ?
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From: [email protected] [mailto:[email protected]] On Behalf Of Tom Gardner
Sent: Wednesday, August 31, 2022 4:04 AM
To: [email protected]
Subject: Re: [Test Equipment Design & Construction] Cal Lab Magazine - International Journal of Metrology ? ? On Wed, 31 Aug 2022 at 01:38, MAX <max@...> wrote: This matter of lower case for units has me wondering.? Ever since I started my website I have been using a lower case f to represent farads.? Recently I received an email from someone who was retired from HP and its successor names correcting me that a capitol F should be used for Farads.? In the pages I have created since I have been using a capitol F as in pF, nF, etc.? So who is right?
In that case, either would be understood. In other cases, not necessarily, e.g.: ¡¤?????? multipliers, especially m/M in conjunction with frequency, e.g. a 10MHz oscillator with 10mHz resolution ¡¤?????? a personal hate: people that measure time in units of conductance, i.e. s vs S, seconds vs Siemens ¡¤?????? samples/second for scopes. There's no unit for samples, so I tend to use 1GSa/s Using the wrong units looks ignorant, and hence detracts from the message. Having said all that, I write "5ns" rather than the correct "5 ns", mainly to avoid line breaks splitting them.
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Re: Cal Lab Magazine - International Journal of Metrology
Dave, A few decades ago, one of my tech writing managers remarked that style rules were actually guidelines, kind of like the pirate's code from "Pirates of the Caribbean." It was one of the very few smart things she ever said. Anyway, since then, the consensus in tech writing is: 1. Be consistent, and implement an in-house style guide if you need to. 2. Follow as many accepted industry style guides as you can. (The SI brochure would be a good starting point.) 3. MAKE SENSE and achieve near-universal understandability and reader comprehension. I would add -- I'm not sure if it's SI or IEEE, but the abbreviation k for 1000 is lower case for quantities of 1000 or fewer, and UPPER CASE for quantities greater than 1000 -- specifically, 1024. As in 1024 bits = 1024 Kb, 1024 bytes = 1024 KB, etc. Since I'm retired now, I won't get on the units editing warpath. I'll leave that to the rest of you ... although I can probably hit 99% accuracy on every SI unit abbreviation if you ask, without having to consult anything except my poor tired brain. 73 Jim N6OTQ On Wed, Aug 31, 2022 at 8:26 AM Dr. David Kirkby, Kirkby Microwave Ltd <drkirkby@...> wrote:
On Wed, 31 Aug 2022 at 01:43, Tom Lee <tomlee@...> wrote:
The rule is that units named for people are not capitalized when spelled out. That assures that "two watts" is a measure of power, while "two Watts" refers refers to two family members.
I said earlier that I thought the s should not be there, and cited an BIPM brochure, which did not actually substantiate my statement. However, this document from the BIPM does.
"A concise summary of the International System of Units, SI"
It gives a logical reason why "2 watt" is correct, and "2 watts" is not.
To quote
"Unit symbols are written using roman (upright) type, regardless of the type used in the surrounding text. They are mathematical entities and not abbreviations; unit symbols are never followed by a full stop (except at the end of a sentence) nor by an ¡®s¡¯ for the plural. The use of the correct form for unit symbols is mandatory, and is illustrated by examples in the SI Brochure"
Unfortunately, that SI Brochure is not totally consistent, with both "683 lumen per watt" and "683 lumens per watt" in the same document. Also, multiple references to newtons, but I think the newton is the only unit to suffer from this "error". You will not find any references to farads, amperes,
If the IEEE wants "2 watts", and not "2 watt", then it's their publication, so they can have it. But I don't think it is technically correct. But I am not impressed with the way the IEEE accepts both positive and negative numbers in dB for the return loss of passive components. In one issue of a journal you will see someone write that an antenna had a return loss of -15 dB, and in another article the return loss is quoted as 15 dB. Fortunately the context is usually obvious.
Dave
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Re: Cal Lab Magazine - International Journal of Metrology
Thank you.
73 (Regards).
Max K 4 O D S.
I've Never Lost the Wonder.
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-----Original Message----- From: [email protected][mailto: [email protected]] On Behalf Of Wilko Bulte Sent: Wednesday, August 31, 2022 2:12 AM To: [email protected]Subject: Re: [Test Equipment Design & Construction] Cal Lab Magazine - International Journal of Metrology F for Farad is correct. Wilko
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Re: Cal Lab Magazine - International Journal of Metrology
Such as furlongs per fortnight.
Leon Robinson ?? K5JLR
Political Correctness is a Political Disease.
Politicians and Diapers should be changed
often and for the same reasons.
On Wednesday, August 31, 2022, 07:42:53 AM CDT, Dr. David Kirkby, Kirkby Microwave Ltd <drkirkby@...> wrote:
On Wed, 31 Aug 2022 at 01:38, MAX < max@...> wrote: This matter of lower case for units has me wondering.? Ever since I started my website I have been using a lower case f to represent farads.? Recently I received an email from someone who was retired from HP and its successor names correcting me that a capitol F should be used for Farads.? In the pages I have created since I have been using a capitol F as in pF, nF, etc.? So who is right? ? 73 (Regards). ? Max K 4 O D S.
It should be uF, nF, F etc. The person who sent you the email is correct. Look at the SI brochure I sent earlier.
Of the 7 base units (page 16), the ampere and kelvin are capitalised, as they are named after Ampere and Kelvin. So
290 K 1.5 A
The other 5 base units are lower case, as they are not named after anyone.
60 s 5 m
10 kg 2 mol 5 cd
All the derived units (newton, watt, rad, farad etc) follow the same convention, of being capital if named after an individual, but otherwise lower case. So since the unit of capacitance, the farad, was named after Faraday, so it is a capital F.
The litre, which is not an SI unit, but is acceptable to be used with SI units, is a special case. In theory it would be lower case, as its not named after anyone. A lower case l was acceptable since it was defined in 1879.? But the BIPM realised that a lower case L can be confused with the number one, so since 1979, the litre can be either l or L. Both are acceptable.
There are probably other special cases too.
I've asked someone at NPL to clarify if it should be "2 watt" as I think, or "2 watts" as apparently the IEEE want.
The great thing about standards is that there are so many of them, you are bound to find one you like. ????
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Re: Another Q-meter info source
OK, I misspoke a little yesterday about the full nature of the article in the August QCWA newsletter. The article with the Q meter info is the "Vacuum Valley" article, and the Q meter info is toward the end of the article. Nevertheless, sometimes it's good to see what other hams are up to, and the editorial this month urges us NOT to lose the history and knowledge we've accumulated over the years. So I've attached the whole newsletter for your enjoyment and educational purposes. To the best of my knowledge, you have to be a QCWA member to see the newsletter online, a lot like the ARRL requires membership to see their premium content. There may be more Q meter info in next month's newsletter. 73 Jim N6OTQ On Tue, Aug 30, 2022 at 5:02 PM Jim Strohm via groups.io <jim.strohm@...> wrote:
Hi all
The August 2022 QCWA newsletter has an article about Q-meter design.
I haven't vetted it for accuracy, but it looks like it tells the
truth.
Knowing that not everybody here is a QCWA member ... if you'd like, I
can share the article here, "for educational purposes only."
Ask and ye probably will receive.
73
Jim N6OTQ
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Re: Cal Lab Magazine - International Journal of Metrology
And as previously stated mF and NF are not the same
Lester B Veenstra K1YCM M?YCM W8YCM 6Y6Y (Reformed CTM1)
lester@...
452 Stable Ln (HC84 RFD USPS Mail)
Keyser WV 26726
GPS: 39.336826 N 78.982287 W (Google)
GPS: 39.33682 N 78.9823741 W (GPSDO)
Telephones:
Home: +1-304-289-6057
US cell +1-304-790-9192
Jamaica cell: +1-876-456-8898
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-----Original Message----- From: [email protected] [mailto: [email protected]] On Behalf Of Tom Lee Sent: Wednesday, August 31, 2022 3:15 AM To: [email protected]Subject: Re: [Test Equipment Design & Construction] Cal Lab Magazine - International Journal of Metrology or, rather, F for farad, if we're going to stick with convention. :) -- Prof. Thomas H. Lee Allen Ctr., Rm. 205 350 Jane Stanford Way Stanford University Stanford, CA 94305-4070 On 8/31/2022 00:11, Wilko Bulte wrote: F for Farad is correct.
Wilko
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Re: Cal Lab Magazine - International Journal of Metrology
On Wed, 31 Aug 2022 at 01:43, Tom Lee < tomlee@...> wrote:
The rule is that units named for people are not capitalized when
spelled out. That assures that "two watts" is a measure of power,
while "two Watts" refers refers to two family members.
I said earlier that I thought the s should not be there, and cited an BIPM brochure, which did not actually substantiate my statement.? However, this document from the BIPM does.
"A concise summary of the International System of Units, SI"
It gives a logical reason why "2 watt" is correct, and "2 watts" is not.
To quote
"Unit symbols are written using roman (upright) type, regardless of the type used in the surrounding text. They are mathematical entities and not abbreviations; unit symbols are never followed by a full stop (except at the end of a sentence) nor by an ¡®s¡¯ for the plural. The use of the correct form for unit symbols is mandatory, and is illustrated by examples in the SI Brochure"
Unfortunately, that SI Brochure is not totally consistent, with both "683 lumen per watt" and "683 lumens per watt" in the same document. Also, multiple references to newtons, but I think the newton is the only unit to suffer from this "error". You will not find any references to farads, amperes,
If the IEEE wants "2 watts", and not "2 watt", then it's their publication, so they can have it. But I don't think it is technically correct. But I am not impressed with the way the IEEE accepts both positive and negative numbers in dB for the return loss of passive components. In one issue of a journal you will see someone write that an antenna had a return loss of -15 dB, and in another article the return loss is quoted as 15 dB. Fortunately the context is usually obvious. Dave
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Re: Cal Lab Magazine - International Journal of Metrology
On Wed, 31 Aug 2022 at 01:38, MAX < max@...> wrote: This matter of lower case for units has me wondering.? Ever since I started my website I have been using a lower case f to represent farads.? Recently I received an email from someone who was retired from HP and its successor names correcting me that a capitol F should be used for Farads.? In the pages I have created since I have been using a capitol F as in pF, nF, etc.? So who is right? ? 73 (Regards). ? Max K 4 O D S.
It should be uF, nF, F etc. The person who sent you the email is correct. Look at the SI brochure I sent earlier.
Of the 7 base units (page 16), the ampere and kelvin are capitalised, as they are named after Ampere and Kelvin. So
290 K 1.5 A
The other 5 base units are lower case, as they are not named after anyone.
60 s 5 m
10 kg 2 mol 5 cd
All the derived units (newton, watt, rad, farad etc) follow the same convention, of being capital if named after an individual, but otherwise lower case. So since the unit of capacitance, the farad, was named after Faraday, so it is a capital F.
The litre, which is not an SI unit, but is acceptable to be used with SI units, is a special case. In theory it would be lower case, as its not named after anyone. A lower case l was acceptable since it was defined in 1879.? But the BIPM realised that a lower case L can be confused with the number one, so since 1979, the litre can be either l or L. Both are acceptable.
There are probably other special cases too.
I've asked someone at NPL to clarify if it should be "2 watt" as I think, or "2 watts" as apparently the IEEE want.
The great thing about standards is that there are so many of them, you are bound to find one you like. ????
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Re: Cal Lab Magazine - International Journal of Metrology
On Wed, 31 Aug 2022 at 01:38, MAX < max@...> wrote: This matter of lower case for units has me wondering.? Ever since I started my website I have been using a lower case f to represent farads.? Recently I received an email from someone who was retired from HP and its successor names correcting me that a capitol F should be used for Farads.? In the pages I have created since I have been using a capitol F as in pF, nF, etc.? So who is right?
In that case, either would be understood. In other cases, not necessarily, e.g.: - multipliers, especially m/M in conjunction with frequency, e.g. a 10MHz oscillator with 10mHz resolution
- a personal hate: people that measure time in units of conductance, i.e. s vs S, seconds vs Siemens
- samples/second for scopes. There's no unit for samples, so I tend to use 1GSa/s
Using the wrong units looks ignorant, and hence detracts from the message.
Having said all that, I write "5ns" rather than the correct "5 ns", mainly to avoid line breaks splitting them.
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Re: Boonton Q Meter Thermocouple & Precision Resistor
In the model 260, the oscillator supplies 1 amp of RF current to produce 20 mV across the 20 milliOhm LC series resistor. This would be 20 milliWatts across the resistor, but 200-300 milliWatts in the thermocouple if it is 0.2-0.3 Ohms.
I determined the 1 Amp current from the calibration procedure where 4 Volts applied to the voltmeter section equals a Q of 200. Q = Vout / V in, thus Vin = 0.02V.
The model 160 has the same 4V = Q of 200, but a 40 milliOhm resistance so current is only 1/2A. The 160 thermocouple then MIGHT be less fragile than the 260.
John
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On 8/15/2022 6:33 AM, Chuck Moore via groups.io wrote: Dave
The general test for the heater element is to measure the DC Resistance.
It is reported to be around 0.2 to 0.3 Ohms. Since the typical failure mode
is burn out, a positive continuity reading is usually regarded as proof the
heater is intact and infinite resistance is considered the failure mode.
When I first encountered a Boonton 260 circa 1980, I was told to never
place an ohmmeter across the terminals of the thermocouple due to its
fragility. Rather I could use a power supply set to current limit at 500
milliAmps and measure the voltage output. If the thermocouple produced
a voltage then it was considered ok.
As far as the susceptibility of the thermocouple being blown, Peter (AI2V)
explained that the later units produced in the 260 line were changed and
the thermocouples were much less likely to fail. He did not elaborate on
what change/s was/were made but said that if a person found a unit working
today, it most likely would be a model with the later thermocouple design.
Apparently the designs made before the change to harden the sensor
were much more fragile than I realized.
I have a couple of the 160's in the shed and intend to pull them out to see
if I can (1) access the thermocouple assemblies without destroying the
glass covering used to seal the sensor heads and (2) to determine how
realistic it is to expect to be able to repair a unit.
I read Brookes notes about his attempt to repair the sensor. It was not
clear if his repair used the same gauges of wire for the thermocouple
and heater as the original design. He mentioned he had difficulty with the
tracking of the readout on the "Multiply by" meter which is what the
resistors in the leads of the Multiply by" resistor were supposed to adjust.
While there was some slight variance between sensor heads, the meter
movement used for the "Multiply by" values varied and the combination of
the sensor head and meter variances were addressed using the led to the
custom values of the two resistors in the thermocouple-meter path.
I never imagined that such a low power would heat even a small
length of fine wire to such high temperatures. The chart showing
the temperatures vs current? were an eye opener. It sure puts into
perspective what 20 milliWatts can do with the right conditions.
Regards
Chuck
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Re: Cal Lab Magazine - International Journal of Metrology
or, rather, F for farad, if we're going to stick with convention. :)
--
Prof. Thomas H. Lee
Allen Ctr., Rm. 205
350 Jane Stanford Way
Stanford University
Stanford, CA 94305-4070
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On 8/31/2022 00:11, Wilko Bulte wrote: F for Farad is correct.
Wilko
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Re: Cal Lab Magazine - International Journal of Metrology
F for Farad is correct.
Wilko
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Re: Cal Lab Magazine - International Journal of Metrology
Hmmm, f or F?
I'd defer to IEEE and whatever other standard is applicable and
appropriate. I've been a tech writer since the late 1980s and
nowadays I refuse to get into the editorial and grammar wars. What's
important is that your readers understand what you're saying
(writing).
I suggest that all research the standards for expressing units. For
my part, I am TOO OLD to do it for you. The key? Your readers
understand what you are saying, whether or not your units descriptions
comply with standards.
If you don't know what to use, at least use whatever you use
consistently in each post, whether or not it's the same in your next
post. Generally we'll get the drift of what you're saying.
Just keep in mind -- if you misplace lower-case and upper-case
multipliers and there could be an actual misunderstanding with units,
it's your bad.
73
Jim N6OTQ
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On Tue, Aug 30, 2022 at 7:38 PM MAX <max@...> wrote:
This matter of lower case for units has me wondering. Ever since I started my website I have been using a lower case f to represent farads. Recently I received an email from someone who was retired from HP and its successor names correcting me that a capitol F should be used for Farads. In the pages I have created since I have been using a capitol F as in pF, nF, etc. So who is right?
73 (Regards).
Max K 4 O D S.
I've Never Lost the Wonder.
From: [email protected] [mailto:[email protected]] On Behalf Of Pete Harrison
Sent: Tuesday, August 30, 2022 2:39 AM
To: [email protected]
Subject: Re: [Test Equipment Design & Construction] Cal Lab Magazine - International Journal of Metrology
Thanks Dave.
I was also unaware of this . ive subscribed and found a few interesting documents on the site.
regards Pete
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Re: Cal Lab Magazine - International Journal of Metrology
Thank you. ? 73 (Regards). ? Max K 4 O D S. ? I've Never Lost the Wonder. ?
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From: [email protected] [mailto:[email protected]] On Behalf Of Tom Lee
Sent: Tuesday, August 30, 2022 7:44 PM
To: [email protected]
Subject: Re: [Test Equipment Design & Construction] Cal Lab Magazine - International Journal of Metrology? The rule is that units named for people are not capitalized when spelled out. That assures that "two watts" is a measure of power, while "two Watts" refers refers to two family members.
A seeming exception is "degrees Celsius," but the unit name consists of both words, and one does not capitalize degrees.
Abbreviations for units named after people are capitalized, however. Thus, a capacitance may be reported as 10 nanofarads or 10 nF.
-- Tom
-- Prof. Thomas H. Lee Allen Ctr., Rm. 205 350 Jane Stanford Way Stanford University Stanford, CA 94305-4070 On 8/30/2022 17:38, MAX wrote: This matter of lower case for units has me wondering.? Ever since I started my website I have been using a lower case f to represent farads.? Recently I received an email from someone who was retired from HP and its successor names correcting me that a capitol F should be used for Farads.? In the pages I have created since I have been using a capitol F as in pF, nF, etc.? So who is right? ? 73 (Regards). ? Max K 4 O D S. ? I've Never Lost the Wonder. ? From: [email protected] [mailto:[email protected]] On Behalf Of Pete Harrison
Sent: Tuesday, August 30, 2022 2:39 AM
To: [email protected]
Subject: Re: [Test Equipment Design & Construction] Cal Lab Magazine - International Journal of Metrology ? Thanks Dave. I was also unaware of this . ive subscribed and found a few interesting documents on the site. ? regards Pete
?
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Re: Making a Q-meter / References etc
If you think of the input and output signals being represented in polar form the value of R is always positive regardless of the value of theta.? This way you can enter the two voltages as positive numbers with a clear conches.? ? 73 (Regards). ? Max K 4 O D S. ? I've Never Lost the Wonder. ?
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From: [email protected] [mailto:[email protected]] On Behalf Of Dr. David Kirkby, Kirkby Microwave Ltd
Sent: Tuesday, August 30, 2022 6:16 PM
To: [email protected]
Subject: Re: [Test Equipment Design & Construction] Making a Q-meter / References etc ? Further to the application of dB to inverting amplifiers. ? All of the calculators that I have checked this on, return an error message when the ratio (Vout/Vin) is negative.
I will show you a calculator that does not - see attached. But consider a VNA connected to a wide-band amplifier with a gain of 10 dB. The output power is always 10 dB higher than the input. The VNA will show |S21| as 10 dB, irrespective of the phase shift through the amplifier. An inverted output is just a phase shift of 180 degrees. I would say the phase angle is irrelevant to the calculation of gain. ? When using a logarithmic ratio, a + prefix denotes a ratio greater than unity. And a ¨C prefix a ratio of less than unity. By convention the prefix can be omitted if gain, or loss, is implied. I.E. the 100W amplifier had a power gain of 30dB, or the attenuator had a loss of 3.5dB. In both cases the prefix is implied in the description.
True, and in both cases, the phase of the output is irrelevant in computing the gain (or loss) in dB. However, I do think people should use their common sense, and would enter two positive numbers, despite the phase being shifted 180 degrees. ?
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Dr. David Kirkby, Kirkby Microwave Ltd
John Kolb