|
Harvey,
Thank you again. My earlier comments to you and then Dave, W6OQ
would seem to applicable as a response.
I appreciate your thoughtfulness.
73,
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.
--
"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
--
"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
|
Everett,
Thank you. I have it.
Ray, W4BYG
On 8/10/2022 20:11, Everett N4CY via
groups.io wrote:
If you buy a SDRPlay, there is free SA software on SDRPlays
website.
Everett N4CY
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.
?
?
--
"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
|
Geoffrey,
Thank you for the suggestions. I have downloaded the software and
will try it out. I appreciate your assistance. I will keep your
email on my desktop and be sure to ask, if I need further help.
73, Ray, W4BYG
On 8/11/2022 09:33, Myosotis via
groups.io wrote:
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.
--
"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
|
Dave,
Thank you for the inputs and interesting information.
In my past I organized and lead a field test of various
commercial and a home brew 40 meter ground mounted vertical
antennas. This was basically focused on the improvements
experienced when starting with no radials laid on the ground to
4 radials and then doubling each increment of that, up to 32
radials. The signal improvements with the
additional radials was like or better than, adding a KW
amplifier.
We built a full sized 40 meter ground plane for the
reference antenna. It was matched at the base for a 50Ω
impedance and fed with about 10 watts from a transceiver.
The match was optimized for each antenna tested.
Related to your comment about using fiber
between the sites: Fiber was not feasible at this time for us,
so in order to remove the affects of any cables out to the
receive site some 7 or 8 wavelengths away, W4TNS built a battery
powered 40 meter to 3/4 meter (no AGC) upconverter. We tested it
to find it's best operating input levels for best linearity and
made sure to operate the tests within those limits.
We utilized a small 40 meter receiving loop on 40 meters and a 5
element transmit yagi on 3/4 meters to feed the resulting
signals back to a Tektronix 2710 SA ,via another 3/4 meter yagi.
Both yagis were stably mounted at about 10'. The accuuracies
were subject to +/ - 1db amplitude variations in the SA, but the
preparation, process and the excercize, provided an awesome and
informative time for the 15 or 16 participants.
The tests
also revealed there was very little difference in signal
strength between the full size vertical and? the
commercial multi-band antennas on 40 meters, even though
the loaded antennas were usually shorter and more
complex than the full sized simple ground plane.
We did not have time to check the higher bands.
We did check several 40 meter mobile antennas and found
them to be somewhat directional depending on the
mounting locations, but surprisingly effective.
We realized the setup was
subject to several other variations, but we felt the tests would
still be helpful and useful. It was a fun ham radio activity to
be a part of. All that were there related they learned a lot.
73, Ray, W4BYG
On 8/11/2022 10:00, Dr. David Kirkby,
Kirkby Microwave Ltd wrote:
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
--
"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
|
Zvone,
Thank you for your thoughtfulness. I don't speak or read German, but
if the article is posted online, I can use Google to translate it.
Regards,
Ray, W4BYG
On 8/11/2022 12:03, zvonimirmavracic
via groups.io wrote:
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
--
"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
|
Paul,
Good reason, I haven't tried it.
Ray, W4BYG
On 8/11/2022 12:34, Paul via groups.io
wrote:
That is why I
prefer to do my antenna work
after dark.
?
de Paul, W8AEF
?
?
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
--
"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
|
A Standard Antenna is described by EIA/TIA-329-B.? I have built a few for UHF & microwave frequencies.
The standard gain is 7.7 dB.
|
Unfortunately, in the world of EMC, where field strength measurements are our daily business, this antenna is not known for its accuracy. Indeed, its resonance frequency band is fuzzy and therefore wide inducing a very low accurate gain.?
See an excellent commercial realization of this antenna with the corresponding plots here :
http://schwarzbeck.de/Datenblatt/ksga2450.pdf
Therefore it is much more usual to use half-wave resonant dipoles as already indicated by Dr Kirkby. Of course any other calibrated antenna can also be used.
But field strength measurements have the distinction of having one of the highest inaccuracies recognized by the world of laboratory metrology since when we claim to have a measurement uncertainty of less than 3 dB, we are usually questioned by the auditors of accreditation bodies as to whether we are really being honest. In general, 4 dB of measurement uncertainty is accepted by all international standards.
?
|
Ray, W4BYG
