Re: "Electric field strength" measurements?
Dave,
Thank you for your inputs.
I have a TinyVNA and I find the super small letters on the 2.8"
screen are very difficult to read, when testing outside. Using
it or the PC computer software inside works fine, but by itself
outside, not so much. If they ever come out with a 4" version of
the SA, maybe that would suffice. They certainly are in the
right price range for HR and hobbyist use.
I don't have the 4" TinyVNA so I don't yet know if that is any
better outside.
Someone on the list may have one and be able to comment on it.
Ray, W4BYG
On 8/10/2022 18:12, Dave W6OQ via
groups.io wrote:
Ray:
The TinySA spectrum analyzer may meet your needs. Pocket portable,
inexpensive, covers HF thru UHF and beyond. Can detect unmodulated
signals. And the linearity may be good enough that you won't have
to deal with calibrated attenuators, though of course you can.
There is a group.io group at?/g/tinysa?that
is owned by the developer. Check in there for the recommendations
of where to buy it so you get an original and not a worthless
clone.
Do you have any ideas for Standard antennas? I think that there
might be enough info on the internet to build your own for some
frequencies. Never quite got that far myself yet.
--
"If you want to build a strong house, I'll give you my engineer's number.
If you want to build a strong life, I'll introduce you to my carpenter."
Lebron and Heather Lackey
|
Re: "Electric field strength" measurements?
Paul,
Thank you for the suggestions. I'll look into it.
Ray, W4BYG
On 8/10/2022 16:50, PAUL KOBY wrote:
Have you considered used
field intensity meters such as the Eaton 17/27 or 37/57 or an
HP 3586A/B/C selective level meter?
Paul Koby
ka5obi
On Wednesday, August 10, 2022 at 03:16:41 PM CDT, Ray,
W4BYG <w4byg@...> wrote:
On the thread "...Making a Q meter":
On 8/10/2022 15:42, Dr. David Kirkby, Kirkby Microwave Ltd
wrote:
> if you look at the description of the group
>
> /g/Test-Equipment-Design-Construction
In reviewing the listed subjects, I would like to query
the group on
relatively simple "Electric field strength" measurements.
I have successfully made measurements in the past
utilizing Tektronix
2700 series spectrum analyzers, but I would be interested
in less costly
ways to compare HF and VHF antennas to a dipole standard.
In my retirement years, I no longer have such available to
me.
I am aware of the need for 5 to 10 wavelengths separation
between the
tested and sampling antennas, as well as ground
reflections, for
electric field tests. Also simple diode detectors with DC
amplifiers,
are seldom linear, nor are the input impedances, reliable
for accurate
comparisons, utilizing a calibrated attenuator for "A" and
"B" comparisons.
Anyone have something to offer on the subject?
Ray, W4BYG
--
This email has been checked for viruses by AVG.
--
"If you want to build a strong house, I'll give you my engineer's number.
If you want to build a strong life, I'll introduce you to my carpenter."
Lebron and Heather Lackey
|
Re: "Electric field strength" measurements?
Hello!
In July 2022 edition of German magazine Funk amateur, there is an article on how to measure/calculate antenna gain
using? Two-antennas-method and VNA.
My knowledge on the subject is poor, so describing? the article here? is not an good idea.?
But, if you want me to, I can scan the article and send it in individual email.
Warning, as I said, article is in German.
73, Zvone, 9a5b
|
Re: "Electric field strength" measurements?
On Thu, 11 Aug 2022 at 16:05, Adrian Godwin < artgodwin@...> wrote: I have a biconical antenna intended for EMC measurements, with a generic sensitivity chart that goes to 1GHz. It was originally supplied by Seaward, a UK company better known for electrician's test tools who briefly offered an EMC test kit. They have sold that part of the business and long forgotten about it.
Unfortunately, although I also have the associated analyser and a much more modern spectrum analyser, I don't have the original cable. This shouldn't be too much of a problem except that it means the sensitivity chart probably assumes an unknown cable loss.?
What I'd like is a calibrated transmitter to provide a reference point (perhaps more than one, for various frequencies). Perhaps just a dipole and a signal generator, if that can provide a known field strength. Such a device might also help Ray.
Can such a thing be made simply and provide a reference from first principles ?
Yes - if you are in the far field of an antenna and know
* Antenna gain (G - absolute number, not in dB. This is 1.64 for? a half-wave dipole)
* Distance (m)
* Power accepted by the antenna (so subtract reflected power)
Consider the antenna at the centre of a sphere. The sphere has a radius r. The surface area of the sphere is 4 Pi r^2. So the power density (watt per metre squared) is
Pd = P G / (4 Pi r^2)
The electric field E (V/m), magnetic field H (A/m), and power density W/m^2 are given by
Pd = E H
But E/H is the impedance of free space (around 377 ohm). So yes, you can work it all out from fundamental principles.
Dave
|
Re: "Electric field strength" measurements?
I have a biconical antenna intended for EMC measurements, with a generic sensitivity chart that goes to 1GHz. It was originally supplied by Seaward, a UK company better known for electrician's test tools who briefly offered an EMC test kit. They have sold that part of the business and long forgotten about it.
Unfortunately, although I also have the associated analyser and a much more modern spectrum analyser, I don't have the original cable. This shouldn't be too much of a problem except that it means the sensitivity chart probably assumes an unknown cable loss.?
What I'd like is a calibrated transmitter to provide a reference point (perhaps more than one, for various frequencies). Perhaps just a dipole and a signal generator, if that can provide a known field strength. Such a device might also help Ray.
Can such a thing be made simply and provide a reference from first principles ?
|
Re: "Electric field strength" measurements?
Hi Group,
When I was working for the local TV station as a transmitter tech for our network. We used a German made TV field strength meter, I can't recall the brand or model. It had a B/W crt on the left and it used a green fluorescent readout of frequency. It was in a brown case, about 15mm high by 300mm wide and ran off a 7Ah battery. We used it with a telescopic element dipole (one for VHF and one for UHF). This came with a calibration chart for antenna efficiency/frequency and a short length of flexible tape measure for setting the elements to the correct length for the frequency of the signal.
If you are only a few wavelength away, then you could probably manage with a simple diode detector. And an antenna similar to one mentioned above (suitably matched to the detector). Calibration would be an issue, but your relative measurements should be consistent. However, if like me, you have several high power transmitters in your vicinity, you may wish to add a passive tuner (or bandpass filter) in front of the diode. (I have five AM stations, 1 - 20KW ERP within 5Km, plus twelve FM stations, of 20KW ERP, two DAB transmitters and five 50KW ERP DTV transmitters within 7Km). I think that an adjustable length dipole would be easier (and cheaper) than a wideband antenna.
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-----Original Message----- From: [email protected] < [email protected]> On Behalf Of Ray, W4BYG Sent: Thursday, 11 August 2022 06:16 To: [email protected]Subject: [Test Equipment Design & Construction] "Electric field strength" measurements? On the thread "...Making a Q meter": On 8/10/2022 15:42, Dr. David Kirkby, Kirkby Microwave Ltd wrote: if you look at the description of the group
/g/Test-Equipment-Design-Construction In reviewing the listed subjects, I would like to query the group on relatively simple "Electric field strength" measurements. I have successfully made measurements in the past utilizing Tektronix 2700 series spectrum analyzers, but I would be interested in less costly ways to compare HF and VHF antennas to a dipole standard. In my retirement years, I no longer have such available to me. I am aware of the need for 5 to 10 wavelengths separation between the tested and sampling antennas, as well as ground reflections, for electric field tests. Also simple diode detectors with DC amplifiers, are seldom linear, nor are the input impedances, reliable for accurate comparisons, utilizing a calibrated attenuator for "A" and "B" comparisons. Anyone have something to offer on the subject? Ray, W4BYG -- This email has been checked for viruses by AVG.
|
Re: "Electric field strength" measurements?
Dear Ray,
I would run some tests on your RSP Duo to check it's accuracy and repeatability.? The Spectrum Analyser software for it can be downloaded from:??
Using a low-cost SDR for logging accurate RF power and SNR measurements can be found here:?
The SDR Console software has an on on screen signal strength logging graph the data from which can be exported to Excel etc.? The Air Spy software also has a logging function.
I check the calibration of mine using a -55 dBm output oscillator and check the settings for RF and IF gain.? If have found it to be accurate and repeatable.
There was an interesting page on the SDRC website about the S meter readings but I cannot find it, this is the nearest:
I use it for Medium Wave measurements, any questions please ask.
Sorry about the bold sections, BOLD stopped working after I copied the RS link.
73, Geoffrey.
|
Re: "Electric field strength" measurements?
On Wed, 10 Aug 2022 at 21:15, Ray, W4BYG < w4byg@...> wrote: On the thread "...Making a Q meter":
On 8/10/2022 15:42, Dr. David Kirkby, Kirkby Microwave Ltd wrote:
> if you look at the description of the group
>
> /g/Test-Equipment-Design-Construction
In reviewing the listed subjects, I would like to query the group on
relatively simple "Electric field strength" measurements.
If it can be measured it's on topic. I just updated the list to exclude things like ghost detectors, but otherwise, any measurement is on topic.?
Anyone have something to offer on the subject?
Ray, W4BYG
?
I did in a former job make field strength measurements where the whole of a passenger plane was considered the antenna - this was an expensive measurement to perform, as the plane had to fly around a mountain for a few hours. We used many tonnes of fuel as jet engines are inefficient at low altitudes. ??????
Not wishing to discourage measurements, but the truth is that modelling tools will be more accurate than measurements in many cases.
Spectrum analyzers are not particularly accurate measuring power. If you look at the calibration instructions for a professional spectrum analyzer, you will see that power meters are used. A measuring receiver is a professional tool for making power measurements at specific frequencies. They are very expensive on the used market. I have never looked, but I doubt that a spectrum analyzer would be used when calibrating a measuring receiver.?
A few random thoughts, on areas that others have not discussed.
One of the things that has always concerned me about antenna measurements is the influence of the cable and support structure. This has got me wondering if the detector should be a small battery powered device on the antenna, which transmits the signal level by optical fibre. The linearity of the detector is irrelevant, as that can be measured separately on a bench. Optical fibre is much lighter than any coax, so for small antennas, which the mass of the antenna is a lot less than the coax, this should allow smaller support structures.
A transmit antenna could have a small battery powered oscillator.?
I recently set up two large metal plates and applied AC from a signal generator to provide a known E field from?
E = V / spacing
I only did this to prove a cheap Chinese meter, which claimed to measure E and H from 20 Hz to 3.5 GHz was a piece of crap. I got a full refund via eBay, as the seller would not pay the return carriage to China.? ? 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
|
Re: "Electric field strength" measurements?
The HP 3586A/B/C selective level meter is by far the best instrument measuring data automatically (via HPIB). ? Lester B Veenstra? K1YCM? M?YCM? W8YCM?? 6Y6Y 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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From: [email protected] [mailto:[email protected]] On Behalf Of PAUL KOBY
Sent: Wednesday, August 10, 2022 4:50 PM
To: [email protected]
Subject: Re: [Test Equipment Design & Construction] "Electric field strength" measurements?? Have you considered used field intensity meters such as the Eaton 17/27 or 37/57 or an HP 3586A/B/C selective level meter? On Wednesday, August 10, 2022 at 03:16:41 PM CDT, Ray, W4BYG <w4byg@...> wrote: On the thread "...Making a Q meter":
On 8/10/2022 15:42, Dr. David Kirkby, Kirkby Microwave Ltd wrote:
> if you look at the description of the group
>
> /g/Test-Equipment-Design-Construction
In reviewing the listed subjects, I would like to query the group on
relatively simple "Electric field strength" measurements.
I have successfully made measurements in the past utilizing Tektronix
2700 series spectrum analyzers, but I would be interested in less costly
ways to compare HF and VHF antennas to a dipole standard.
In my retirement years, I no longer have such available to me.
I am aware of the need for 5 to 10 wavelengths separation between the
tested and sampling antennas, as well as ground reflections, for
electric field tests. Also simple diode detectors with DC amplifiers,
are seldom linear, nor are the input impedances, reliable for accurate
comparisons, utilizing a calibrated attenuator for "A" and "B" comparisons.
Anyone have something to offer on the subject?
Ray, W4BYG
--
This email has been checked for viruses by AVG.
|
Re: AC Voltage Calibrator, home built
At mains power frequencies (45 – 60Hz), an audio oscillator, audio power amplifier and a selection of mains transformers would work. This would easily provide voltages up to 110-120 and 220-240. I have successfully tested a Sangamo-Weston, S68 DC-AC dynamometer voltmeter. This 1953 laboratory instrument’s accuracy is specified as 0.5% and the instructions include the correction formula for temperature and frequency. This class of meter is very power hungry, requiring 151.286mA for full scale deflection, it has built in 10V, 20V and 50V ranges. I have constructed an external multiplier that gives 100V, 200V and 250V ranges. So it draws just under 38W at 250V. ? I used a 50W per channel stereo amplifier, driving a 50VA, 240V to 20v + 20V transformer. The two 20V windings were paralleled and connected to one channel. I used an oscilloscope to monitor the amplifier’s output, as I had previously damaged two other amplifiers. (I was checking for clipping, spurious oscillation and ringing). To get higher AC voltages, you could use two identical transformers, parallel the secondaries and series the 240V primaries, which should get you up to 500V. Note, that this is only a partial solution, as you still need to verify the output voltage with a known accurate meter. ? A Wien Bridge oscillator could easily provide you with frequencies in the range 10Hz to 1MHz. If you wish to build one, It is becoming difficult to get a suitable light globe for amplitude stabilisation. And the STC thermistors that were used in commercial oscillators, such as (here in Australia) the AWA G231 or the BWD 112B, are no longer manufactured. The G231 covers 10Hz to 30KHz and has nine switched output ranges from -60dBm to +20dBm. The output level is metered at the input to the 10Db switched attenuator and has an accuracy of ?±0.1dB (±1.14%). The BWD 112A has a sine wave out put (unloaded) of up to 25V and a square wave output of up to 20V, but has no output meter. ? For extended frequencies, Tektronix made the type 191, constant output signal generator, which covered from 350KHz to 100MHz in 7 ranges. It had a built in diode detector which could maintain the output level to within ±3%. The TV station that I worked at had one of these that was used in the calibration checks of oscilloscope vertical amplifiers and TV waveform monitors. ? The most accurate piece of test equipment that I have used (and own) is a Michael Cox Electronics type 139-2 response calibrator. These were made for the (analogue) television, broadcast industry. It provides a 15KHz square wave of 1V volt p-p into 75Ω and a 4.43MHz sine wave of 1V p-p, also into 75Ω. The calibration procedure for the ?15KHz was to force the output into the high, then the low state, and measure the difference between the two. They were to be adjusted to within ±0.1% of 1V. The 4.43MHz signal was to be checked with an RF power meter having an accuracy of ±0.23%. The 139-2 calibrator’s 4.43MHz signal was from a quartz oscillator derived square wave, which was then passed through a three section low pass filter. ? ? ? ? ? ? ?
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From: [email protected] <[email protected]> On Behalf Of tgerbic
Sent: Monday, 8 August 2022 19:16
To: [email protected]
Subject: [Test Equipment Design & Construction] AC Voltage Calibrator, home built? I have lots of equipment to do what I would call hobby level (non-NIST) equipment calibration. Perhaps quite a few of us can say the same but I think the one area of weakness for most of us is a variable frequency, variable AC voltage source.? I have, for example, a bunch of Fluke bench multimeters I thought I would test/calibrate last year. Everything was easy till I hit the AC cal sections. An AC calibrator would be very useful to me as I have a lot of meters, many have high frequency ranges up to or beyond 1Mhz, that call for different frequencies and a wide range of voltages.
What I would expect would be a low distortion sinewave with calibrated voltages from millivolts to over 300V. Frequency might range from perhaps 10hz to 1Mhz. Not necessarily continuous frequency but a range of frequencies required by most test equipment for calibration. It would be convenient to have output voltages that were calibrated/selectable for RMS, average, peak and peak to peak to align with calibration procedures across a large variety of test equipment. This would just be selections to vary the sinewave amplitude and perhaps a peak selector. Ideally it would have a low source impedance such that on at least some ranges you could have a calibrated AC current source.?
I can think of several designs that would provide the functionality but really need to think this through and limit the features to a more targeted amount. I have done some preliminary investigations to determine what ranges and frequencies I need for most of my HP, Fluke, Heath, Instek, Simpson, and other brand multimeters.
I think this would solve a big hole in hobbyist metrology. DC voltage, DC current and resistance are pretty easy to setup on the average workbench and get pretty accurate results. Frequency is pretty easy as well with GPS disciplined oscillators. AC is harder to deal with. While equipment exists to purchase/repair, it is generally pretty expensive and may have a limited range of voltage or frequency, unless it is really expensive.? I suspect most of us end up kludging up a test setup to at least get some of the required voltages and frequencies, unfortunately skipping many combinations.
I would like to get some thoughts from others about how they do AC calibration outside of a rheostat/isolation transformer on a 50/60Hz power line, or a sinewave generator for low voltages.
|
Re: "Electric field strength" measurements?
Have you considered used field intensity meters such as the Eaton 17/27 or 37/57 or an HP 3586A/B/C selective level meter? Paul Koby ka5obi
On Wednesday, August 10, 2022 at 03:16:41 PM CDT, Ray, W4BYG <w4byg@...> wrote:
On the thread "...Making a Q meter":
On 8/10/2022 15:42, Dr. David Kirkby, Kirkby Microwave Ltd wrote: > if you look at the description of the group > > /g/Test-Equipment-Design-ConstructionIn reviewing the listed subjects, I would like to query the group on relatively simple "Electric field strength" measurements. I have successfully made measurements in the past utilizing Tektronix 2700 series spectrum analyzers, but I would be interested in less costly ways to compare HF and VHF antennas to a dipole standard. In my retirement years, I no longer have such available to me. I am aware of the need for 5 to 10 wavelengths separation between the tested and sampling antennas, as well as ground reflections, for electric field tests. Also simple diode detectors with DC amplifiers, are seldom linear, nor are the input impedances, reliable for accurate comparisons, utilizing a calibrated attenuator for "A" and "B" comparisons. Anyone have something to offer on the subject? Ray, W4BYG -- This email has been checked for viruses by AVG.
|
Re: "Electric field strength" measurements?
Ray: The TinySA spectrum analyzer may meet your needs. Pocket portable, inexpensive, covers HF thru UHF and beyond. Can detect unmodulated signals. And the linearity may be good enough that you won't have to deal with calibrated attenuators, though of course you can. There is a group.io group at? /g/tinysa?that is owned by the developer. Check in there for the recommendations of where to buy it so you get an original and not a worthless clone. Do you have any ideas for Standard antennas? I think that there might be enough info on the internet to build your own for some frequencies. Never quite got that far myself yet.
|
Re: "Electric field strength" measurements?
If you buy a SDRPlay, there is free SA software on SDRPlays website.
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On Aug 10, 2022, at 6:59 PM, Paul via groups.io <w8aef@...> wrote:
?
Take a look at the RTLSDR dongle.? Cheap
and lots of software available.
?
Paul, W8AEF
?
?
Harvey,
Thanks for your inputs. I have an RspDuo and an Airspy+ . I've not tried them
for a application such as this. I tend to think one would not be able to
resolve enough detail accuracy with an SDR, but I have not tried it.
As for less costly commercial SA's, (all but the TinySA ($100 or so, with
2.8" screen)), costs near $1,000, as best I can see.? Also the specs
on what I have seen reveal questionable + and - amplitude accuracy. Absolute
accuracy is not necessary to reveal any differences between antenna signal
levels, but repeatability is important.
While I have much retirement time on my hands and a some dollars to play with
for parts, the commercial alternative is still a bit more than I want to spend.
I love building and experimenting.
Ray, W4BYG
On 8/10/2022 19:26, Harvey White wrote:
If you
had a software defined Radio, could you dig the data out of it?? No idea
about bandwidth or sensitivity, but it might be sufficiently sensitive
depending on the frequency you're interested in.? As an alternate thought,
aren't there some very inexpensive SA's out there?? Would they be
sufficient?
Harvey
?
On 8/10/2022 6:46 PM, Ray, W4BYG wrote:
Brooke,
Thank you for your comment. I agree using a SA is probably the best way to measure
EMF's. Been there done that.
But it seems that with some of the new chips today. a reasonable arbitrary log
characterization could be established (in dbm or dbV) with a reference dipole
and then switch the feed to the antenna with supposed gain (or loss) and use a
calibrated attenuator to match the level of the reference antenna, then read
the delta between them on the attenuator as gain or loss.
I suspect this has already been done by those that are much smarter than I.
Just trying to find out if it's so...
Ray, W4BYG
On 8/10/2022 17:24, Brooke Clarke via groups.io wrote:
Hi Ray:
I looked into Measuring EMFs and the best result was based on using a spectrum
analyzer that has calibrated amplitudes based on a 50 Ohm input.
?
?
|
Re: "Electric field strength" measurements?
Take a look at the RTLSDR dongle.? Cheap
and lots of software available.
?
Paul, W8AEF
?
?
Harvey,
Thanks for your inputs. I have an RspDuo and an Airspy+ . I've not tried them
for a application such as this. I tend to think one would not be able to
resolve enough detail accuracy with an SDR, but I have not tried it.
As for less costly commercial SA's, (all but the TinySA ($100 or so, with
2.8" screen)), costs near $1,000, as best I can see.? Also the specs
on what I have seen reveal questionable + and - amplitude accuracy. Absolute
accuracy is not necessary to reveal any differences between antenna signal
levels, but repeatability is important.
While I have much retirement time on my hands and a some dollars to play with
for parts, the commercial alternative is still a bit more than I want to spend.
I love building and experimenting.
Ray, W4BYG
toggle quoted message
Show quoted text
On 8/10/2022 19:26, Harvey White wrote:
If you
had a software defined Radio, could you dig the data out of it?? No idea
about bandwidth or sensitivity, but it might be sufficiently sensitive
depending on the frequency you're interested in.? As an alternate thought,
aren't there some very inexpensive SA's out there?? Would they be
sufficient?
Harvey
?
On 8/10/2022 6:46 PM, Ray, W4BYG wrote:
Brooke,
Thank you for your comment. I agree using a SA is probably the best way to measure
EMF's. Been there done that.
But it seems that with some of the new chips today. a reasonable arbitrary log
characterization could be established (in dbm or dbV) with a reference dipole
and then switch the feed to the antenna with supposed gain (or loss) and use a
calibrated attenuator to match the level of the reference antenna, then read
the delta between them on the attenuator as gain or loss.
I suspect this has already been done by those that are much smarter than I.
Just trying to find out if it's so...
Ray, W4BYG
On 8/10/2022 17:24, Brooke Clarke via groups.io wrote:
Hi Ray:
I looked into Measuring EMFs and the best result was based on using a spectrum
analyzer that has calibrated amplitudes based on a 50 Ohm input.
?
?
|
Re: "Electric field strength" measurements?
Harvey,
Thanks for your inputs. I have an RspDuo and an Airspy+ . I've
not tried them for a application such as this. I tend to think
one would not be able to resolve enough detail accuracy with an
SDR, but I have not tried it.
As for less costly commercial SA's, (all but the TinySA ($100 or
so, with 2.8" screen)), costs near $1,000, as best I can see.?
Also the specs on what I have seen reveal questionable + and -
amplitude accuracy. Absolute accuracy is not necessary to reveal
any differences between antenna signal levels, but repeatability
is important.
While I have much retirement time on my hands and a some dollars
to play with for parts, the commercial alternative is still a
bit more than I want to spend. I love building and
experimenting.
Ray, W4BYG
On 8/10/2022 19:26, Harvey White wrote:
toggle quoted message
Show quoted text
If you had a software defined Radio, could you dig the data out
of it?? No idea about bandwidth or sensitivity, but it might be
sufficiently sensitive depending on the frequency you're
interested in.? As an alternate thought, aren't there some very
inexpensive SA's out there?? Would they be sufficient?
Harvey
On 8/10/2022 6:46 PM, Ray, W4BYG
wrote:
Brooke,
Thank you for your comment. I agree using a SA is probably
the best way to measure EMF's. Been there done that.
But it seems that with some of the new chips today. a
reasonable arbitrary log characterization could be
established (in dbm or dbV) with a reference dipole and then
switch the feed to
the antenna with supposed gain (or loss)
and use a calibrated attenuator to match the level of the
reference antenna, then read the delta between them on the
attenuator as gain or loss.
I suspect this has already been done by those that are much
smarter than I. Just trying to find out if it's so...
Ray, W4BYG
On 8/10/2022 17:24, Brooke Clarke
via groups.io wrote:
Hi
Ray:
I looked into Measuring EMFs and the best result was based on
using a spectrum analyzer that has calibrated amplitudes based
on a 50 Ohm input.
|
Re: "Electric field strength" measurements?
If you had a software defined Radio, could you dig the data out
of it?? No idea about bandwidth or sensitivity, but it might be
sufficiently sensitive depending on the frequency you're
interested in.? As an alternate thought, aren't there some very
inexpensive SA's out there?? Would they be sufficient?
Harvey
On 8/10/2022 6:46 PM, Ray, W4BYG wrote:
toggle quoted message
Show quoted text
Brooke,
Thank you for your comment. I agree using a SA is probably the
best way to measure EMF's. Been there done that.
But it seems that with some of the new chips today. a
reasonable arbitrary log characterization could be established
(in dbm or dbV) with a reference dipole and then switch the feed to the antenna with
supposed gain (or loss) and use a calibrated attenuator to
match the level of the reference antenna, then read the delta
between them on the attenuator as gain or loss.
I suspect this has already been done by those that are much
smarter than I. Just trying to find out if it's so...
Ray, W4BYG
On 8/10/2022 17:24, Brooke Clarke via
groups.io wrote:
Hi
Ray:
I looked into Measuring EMFs and the best result was based on
using a spectrum analyzer that has calibrated amplitudes based
on a 50 Ohm input.
--
"If you want to build a strong house, I'll give you my engineer's number.
If you want to build a strong life, I'll introduce you to my carpenter."
Lebron and Heather Lackey
|
Re: "Electric field strength" measurements?
Brooke,
Thank you for your comment. I agree using a SA is probably the
best way to measure EMF's. Been there done that. Looking for a
less costly (think cheap), way to do it.
But it seems that with some of the new chips today. a reasonable
arbitrary log characterization could be established (in dbm or
dbV) with a reference dipole and then switch the feed
to the antenna with supposed gain (or loss)
and use a calibrated attenuator to match the level of the
reference antenna, then read the delta between them on the
attenuator as gain or loss.
I suspect this has already been done by those that are much
smarter than I. Just trying to find out if it's so...
Ray, W4BYG
On 8/10/2022 17:24, Brooke Clarke via
groups.io wrote:
Hi
Ray:
I looked into Measuring EMFs and the best result was based on
using a spectrum analyzer that has calibrated amplitudes based on
a 50 Ohm input.
--
"If you want to build a strong house, I'll give you my engineer's number.
If you want to build a strong life, I'll introduce you to my carpenter."
Lebron and Heather Lackey
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Re: "Electric field strength" measurements?
Brooke,
Thank you for your comment. I agree using a SA is probably the
best way to measure EMF's. Been there done that.
But it seems that with some of the new chips today. a reasonable
arbitrary log characterization could be established (in dbm or
dbV) with a reference dipole and then switch the feed
to the antenna with supposed gain (or loss)
and use a calibrated attenuator to match the level of the
reference antenna, then read the delta between them on the
attenuator as gain or loss.
I suspect this has already been done by those that are much
smarter than I. Just trying to find out if it's so...
Ray, W4BYG
On 8/10/2022 17:24, Brooke Clarke via
groups.io wrote:
Hi
Ray:
I looked into Measuring EMFs and the best result was based on
using a spectrum analyzer that has calibrated amplitudes based on
a 50 Ohm input.
--
"If you want to build a strong house, I'll give you my engineer's number.
If you want to build a strong life, I'll introduce you to my carpenter."
Lebron and Heather Lackey
|
Re: "Electric field strength" measurements?
Hi Ray:
I looked into Measuring EMFs and the best result was based on using a spectrum analyzer that has calibrated amplitudes based on a 50 Ohm input.
--
Have Fun,
Brooke Clarke
axioms:
1. The extent to which you can fix or improve something will be limited by how well you understand how it works.
2. Everybody, with no exceptions, holds false beliefs.
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Show quoted text
-------- Original Message -------- On the thread "...Making a Q meter":
On 8/10/2022 15:42, Dr. David Kirkby, Kirkby Microwave Ltd wrote:
if you look at the description of the group
/g/Test-Equipment-Design-Construction In reviewing the listed subjects, I would like to query the group on relatively simple "Electric field strength" measurements.
I have successfully made measurements in the past utilizing Tektronix 2700 series spectrum analyzers, but I would be interested in less costly ways to compare HF and VHF antennas to a dipole standard.
In my retirement years, I no longer have such available to me.
I am aware of the need for 5 to 10 wavelengths separation between the tested and sampling antennas, as well as ground reflections, for electric field tests. Also simple diode detectors with DC amplifiers, are seldom linear, nor are the input impedances, reliable for accurate comparisons, utilizing a calibrated attenuator for "A" and "B" comparisons.
Anyone have something to offer on the subject?
Ray, W4BYG
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"Electric field strength" measurements?
On the thread "...Making a Q meter": On 8/10/2022 15:42, Dr. David Kirkby, Kirkby Microwave Ltd wrote: if you look at the description of the group
/g/Test-Equipment-Design-Construction In reviewing the listed subjects, I would like to query the group on relatively simple "Electric field strength" measurements. I have successfully made measurements in the past utilizing Tektronix 2700 series spectrum analyzers, but I would be interested in less costly ways to compare HF and VHF antennas to a dipole standard. In my retirement years, I no longer have such available to me. I am aware of the need for 5 to 10 wavelengths separation between the tested and sampling antennas, as well as ground reflections, for electric field tests. Also simple diode detectors with DC amplifiers, are seldom linear, nor are the input impedances, reliable for accurate comparisons, utilizing a calibrated attenuator for "A" and "B" comparisons. Anyone have something to offer on the subject? Ray, W4BYG -- This email has been checked for viruses by AVG.
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Ray, W4BYG
Dr. David Kirkby, Kirkby Microwave Ltd