The 13 MHz beacons are legal under Part 15. They only run a couple
milliwatts.
W1TAG has calculated that the beacons with a couple milliwatts meet the
regulations:
www.w1tag.com/Hifer2.pdf
The FCC has known about them for many years. Never - not once - have they
attempted to shut one down. I am always amazed that we can have propagation
that allows me to hear them in the Midwest!
A squarer is an FSK CW signal with typically a 4 or 5 Hz shift. Many are
QRSS, commonly with a 6-second "dit" and an 18-second "dah." They are
copyable by looking at your radio's audio with a computer sound card with a
program such as Spectrum Monitor, and a frequency range of maybe 20 to 50
Hz. You can visually copy the CW that way. The term "squarer" is in common
use by those of us who copy these beacons.
There are occasionally a couple QRSS squarers at the very bottom of the 40
meter band. The ones I've heard are on 7000.400 and 7000.700 kHz. With a
4-second FSK and a QRSS with the 6-second dit, bandwidth is so narrow that
there is no chance of them being out of the band. The ops only activate
them when they can be there as control operators, so operation is random
and unpredictable. They will QSL reception. I have their QSL's. To the
untrained ear, they sound like carriers. But to those who have been
listening to QRSS squarers, we recognize they aren't just carriers and set
up to decode them.
You learn something new every day, eh? I'm surprised that there aren't more
hams interested in what goes on outside the ham bands on shortwave.
Zack W9SZ
toggle quoted message
Show quoted text
On Tue, Feb 2, 2021 at 3:47 PM David Eckhardt <davearea51a@...> wrote: What the dickens are "Squarers"? I'll confess the ISM bands are a good
place to hide possibly illegal and unlicensed emissions. However, as a
licensed ham for some 61 years and worked professionally in the EMC
regulatory world for some 35 years, I can not condone the practice.
Dave - W?LEV
On Tue, Feb 2, 2021 at 9:19 PM Zack Widup <w9sz.zack@...> wrote:
Probably has nothing to do with his use, but 13.56 MHz and surrounding
frequencies on shortwave are the homes of many unlicensed CW beacons. Many
are "squarers."
Zack W9SZ
On Tue, Feb 2, 2021 at 8:52 AM Jim Lux <jim@...> wrote:
On 2/2/21 5:04 AM, brown.beard.2020@... wrote:
Hi All
Sorry if this is not the right place to ask. Feel free to point me to a
more suitable place for my questions.
I have an antenna connected to a 13.56MHz RF signal and would like to
add a ferrite core to the cable from the antenna to the device to
filter
out any noise coming from the environment.
How do i determine the appropriate specs for the ferrite core?
That's the ISM frequencies just below the amateur radio 20 meter band,
so anything that works for 14 MHz (20m) will probably work just fine
for
13.56 MHz.
In general, 31 mix is a good choice for HF - it's suitably lossy at
those frequencies. You might check out K9YC's choke cookbooks and
other
writeups..
You're presumably at low power for something like a badge reader, so
you
probably aren't as interested in low loss transmitter designs.
*RFI, Ferrites, and Common Mode Chokes For Hams
<>**Most recent update
April
2019.*This tutorial is directed specifically to RFI in ham radio
applications. It includes an extended discussion of the use of common
mode chokes in antenna systems and for suppression of RFI. A chapter on
audio and computer interconnections in ham stations shows how to make
bulletproof connections between a computer sound card and ham rigs for
SSB, RTTY, PSK31, and SO2R contesting without expensive interface
boxes,
using nothing more than simple cables with the right connectors on each
end. There's also a chapter on grounding and bonding.
This is a new applications note summarizing my work on *Chokes and
Transformers For Receiving Antennas.
<
**NEW!*October
2018
<
Virus-free.
www.avg.com
<
<#DAB4FAD8-2DD7-40BB-A1B8-4E2AA1F9FDF2>
--
*Dave - W?LEV*
*Just Let Darwin Work*
|
On Tue, Feb 2, 2021 at 01:10 PM, David Eckhardt wrote: There are 7 frequencies allocated by the FCC for that purpose in that specific
ISM band - in a NON_RADIATIVE MANNER. Not so: §18.305 Field strength limits. (a) ISM equipment operating on a frequency specified in §18.301 is permitted **unlimited radiated energy** in the band specified for that frequency. (Emphasis mine.) However: (b) The field strength levels of **emissions which lie outside the bands** specified in §18.301, unless otherwise indicated, shall not exceed the following: ... (Emphasis mine.)
|
Re: backyard antenna ranges
I'm having lots of trouble with my local area coverage. Neither my
multiband HF vertical (a CHA-250B with its base mounted about 14ft above
ground) nor my G5RV dipole in roughly NVIS mount with 100w can be heard on
10m or 40m by friends about 2-6 miles away. My main interest is about a
500-1000 mi radius around my QTH. Now trying a KISS-SSB counterpoise and
also my ATAS-120a autotune stick that goes with my FT-991a. VHF isn't a
problem. Any suggestions?
Chuck
K4TZO
toggle quoted message
Show quoted text
On Tue, Feb 2, 2021 at 5:40 PM Jim Lux <jim@...> wrote: I'd like to start a discussion about using the NanoVNA (or NanoVNA2) in
the context of a backyard antenna range. One of the tricky things about
doing antenna measurements has always been the whole "calibration"
thing, or the need to remote control a source (or receiver).
Hey, the NanoVNA does half that work for you! It's in the back yard, so
it's probably not going to be doing very much for your 160meter full
size yagi, but for VHF and UHF, or for "near field" systems with small
loop antennas, it should work quite nicely. If you wanted to evaluate
the antenna on a walkie talkie, it would be great.
The current crop of VNAs doesn't do WiFi bands, but I think it's useful
to think about it. (these days, running patterns of 2.45 GHz antennas
is a standard thing in undergrad antenna classes - but they get to use
the fancy Keysight box, provided at attractive prices to universities)
What I'm thinking is using a deliberately non-matched "probe", the
radiation pattern of which you can determine by modeling. Or build 3
and do a three cornered hat measurement. It could be as simple as a
(very) short dipole with a good choke.
|
Yes, RFID uses the 13.56 MHz ISM band (yes, I've worked professionally
there, as well....), but energy is closely coupled only inductively - NOT
in a radiative manner. Some 'uninitiated' engineers call the usually
pringed inductor an antenna, which it certainly is not.
Dave - W?LEV
toggle quoted message
Show quoted text
On Tue, Feb 2, 2021 at 9:28 PM Jim Lux <jim@...> wrote: On 2/2/21 1:10 PM, David Eckhardt wrote:
13.56 MHz is an ISM (Industrial, Scientific, and Medical) frequency. There
are 7 frequencies allocated by the FCC for that purpose in that specific
ISM band - in a NON_RADIATIVE MANNER. Why are you connecting an antenna to
a 13.56 MHz source? RFID uses 13.56 MHz with radiated fields (limited, it's true), but all
those "near field communications" things are also 13.56 (Subway cards,
cashless payments, etc.).
If you're making a "long range" reader (e.g. for a doorway portal
application) you wind up with directive arrays of some sort, but you
also run into problems with RFI.
Most of the MetCal soldering stations operate on 13.56 MHz.
Dave - W?LEV
On Tue, Feb 2, 2021 at 8:57 PM Jim Allyn - N7JA <
jim@...>
wrote:
On Tue, Feb 2, 2021 at 05:54 AM, <brown.beard.2020@...> wrote:
I have an antenna connected to a 13.56MHz RF signal and would like to add a
ferrite core to the cable from the antenna to the device to filter out any
noise coming from the environment. It isn't clear to me what the situation is here. Do you mean you have an
antenna connected to a 13.56 MHz signal coming from a signal generator
or
transmitter of some sort, and you wish to transmit that13.56 MHz signal?
Or, you have an antenna you are using to receive a 13.56 MHz signal, and
you would like to prevent interference picked up by the transmission
line
from being brought into the shack? Or you have something else (NOT
13.56
MHz) you are trying to receive and the 13.56 MHz signal is interfering
with
it? Please clarify.
--
*Dave - W?LEV*
*Just Let Darwin Work*
|
Re: backyard antenna ranges
Jim, I've usually used a capacitive probe for the purpose at home. That
means a very short probe above an image plane or a very short dipole as a
function of the wavelength of the highest frequency desired. It works well
as a pretty much frequency insensitive receiving antenna.
And, I believe the latest version of the NANO V2's end at 6 GHz.
You have hit a need directly on the head. If you don't, I will - given a
little time to decompress from my CMC ventures....
There are available PC printed LPDA's available with published antenna
factors that cover up to 3 GHz for less t6han $15. i have two. These are
about as good for the amateur as the expensive LPDAs used professionally in
accredited labs.
DO IT for the good of the NANO bunch!!!!
With encouragement:
Dave - W?LEV
Dave - W?LEV
toggle quoted message
Show quoted text
On Tue, Feb 2, 2021 at 10:40 PM Jim Lux <jim@...> wrote: I'd like to start a discussion about using the NanoVNA (or NanoVNA2) in
the context of a backyard antenna range. One of the tricky things about
doing antenna measurements has always been the whole "calibration"
thing, or the need to remote control a source (or receiver).
Hey, the NanoVNA does half that work for you! It's in the back yard, so
it's probably not going to be doing very much for your 160meter full
size yagi, but for VHF and UHF, or for "near field" systems with small
loop antennas, it should work quite nicely. If you wanted to evaluate
the antenna on a walkie talkie, it would be great.
The current crop of VNAs doesn't do WiFi bands, but I think it's useful
to think about it. (these days, running patterns of 2.45 GHz antennas
is a standard thing in undergrad antenna classes - but they get to use
the fancy Keysight box, provided at attractive prices to universities)
What I'm thinking is using a deliberately non-matched "probe", the
radiation pattern of which you can determine by modeling. Or build 3
and do a three cornered hat measurement. It could be as simple as a
(very) short dipole with a good choke.
--
*Dave - W?LEV*
*Just Let Darwin Work*
|
Re: USING THE NANOVNA AND SAVER TO MEASURE CM ATTENUATION THROUGH CMCs
On Tue, Feb 2, 2021 at 02:34 PM, Dragan Milivojevic wrote:
Hardware capability? What are you referring to?
In order to do the S21 series method of determine complex impedance you need the Port 1 (CH0) and Port 2 (CH1) impedance to be very close to 50 ohms. You also need to be able to do 10/12 point error correction which the nanoVNA cannot do. Both are necessary in order to get an accurate S21 phase measurement. VNA's like Agilent etc can do the measurement because they are bidirectional. Kurt Poulsen described the issue in this post... /g/nanovna-users/message/13075?p=,,,20,0,0,0::Created,,s21+series+method,20,2,0,73384240 I have tried using attenuators on CH0 and CH1 to overcome the 50 ohm issue but the phase was still off even though I carefully constructed test jigs to minimize parasitic capacitance. You can easily see the problem if you make a test jig that measures a 1000 ohm SMD resistor which has minimal reactance at HF frequencies. The S21 magnitude will be accurate but the S21 phase will not be 0 so when you do the calculations you get a reactance that is not there... Roger
|
I'd like to start a discussion about using the NanoVNA (or NanoVNA2) in the context of a backyard antenna range.? One of the tricky things about doing antenna measurements has always been the whole "calibration" thing, or the need to remote control a source (or receiver).
Hey, the NanoVNA does half that work for you!? It's in the back yard, so it's probably not going to be doing very much for your 160meter full size yagi, but for VHF and UHF, or for "near field" systems with small loop antennas, it should work quite nicely.? If you wanted to evaluate the antenna on a walkie talkie, it would be great.
The current crop of VNAs doesn't do WiFi bands, but I think it's useful to think about it.? (these days, running patterns of 2.45 GHz antennas is a standard thing in undergrad antenna classes - but they get to use the fancy Keysight box, provided at attractive prices to universities)
What I'm thinking is using a deliberately non-matched "probe", the radiation pattern of which you can determine? by modeling.? Or build 3 and do a three cornered hat measurement.? It could be as simple as a (very) short dipole with a good choke.
|
Re: USING THE NANOVNA AND SAVER TO MEASURE CM ATTENUATION THROUGH CMCs
Hardware capability? What are you referring to?
toggle quoted message
Show quoted text
The second issue is how to measure common mode impedance accurately. It
is relatively easy to determine the magnitude of the impedance |Z| using
S21 but even that requires careful jig construction especially if we want
to make measurements higher than HF. The complex impedance (R+/-jX) can be
determined by several methods: S11 or S21. The problem with the S21
measurement method is that it requires additional calculations to determine
R+/-jX and the NanoVNA does not have the hardware capability to do this
accurately. However S11 measurements can be made on the NanoVNA to
determine R+/-jX but the estimate gets poor if we go much beyond 1000 ohms.
Just like S21 measurements the test fixture should be built to minimize
parasitics and be calibrated with suitable loads.
Rather than repeat what the authors above have written on this subject I
suggest readers take a look at this post by K6JCA which has a lot of
theoretical background, measurements and an extensive reference list.
|
On 2/2/21 1:46 PM, David Eckhardt wrote: What the dickens are "Squarers"? I'll confess the ISM bands are a good
place to hide possibly illegal and unlicensed emissions. However, as a
licensed ham for some 61 years and worked professionally in the EMC
regulatory world for some 35 years, I can not condone the practice. It is legal to run an unlicensed transmitter on 13.56, as long as the power is low enough (i.e. meets Part 15). A few mW is typical, and as sunspots heat up, you could "work the world" with suitable modulation. And to keep it notionally nanoVNA centric, at that power level, every little bit helps when it comes to designing and match, although the goal isn't low DC power, it's to keep the radiated power below the FCC limit (some 10-20 mV/meter, as I recall). A NanoVNA might make a handy way to actually measure that radiated field. (or, at least, the antenna efficiency) by using a calibrated antenna on the other port and measuring S21.
|
What the dickens are "Squarers"? I'll confess the ISM bands are a good
place to hide possibly illegal and unlicensed emissions. However, as a
licensed ham for some 61 years and worked professionally in the EMC
regulatory world for some 35 years, I can not condone the practice.
Dave - W?LEV
toggle quoted message
Show quoted text
On Tue, Feb 2, 2021 at 9:19 PM Zack Widup <w9sz.zack@...> wrote: Probably has nothing to do with his use, but 13.56 MHz and surrounding
frequencies on shortwave are the homes of many unlicensed CW beacons. Many
are "squarers."
Zack W9SZ
On Tue, Feb 2, 2021 at 8:52 AM Jim Lux <jim@...> wrote:
On 2/2/21 5:04 AM, brown.beard.2020@... wrote:
Hi All
Sorry if this is not the right place to ask. Feel free to point me to a more suitable place for my questions.
I have an antenna connected to a 13.56MHz RF signal and would like to
add a ferrite core to the cable from the antenna to the device to filter
out any noise coming from the environment.
How do i determine the appropriate specs for the ferrite core?
That's the ISM frequencies just below the amateur radio 20 meter band,
so anything that works for 14 MHz (20m) will probably work just fine for
13.56 MHz.
In general, 31 mix is a good choice for HF - it's suitably lossy at
those frequencies. You might check out K9YC's choke cookbooks and other
writeups..
You're presumably at low power for something like a badge reader, so you
probably aren't as interested in low loss transmitter designs.
*RFI, Ferrites, and Common Mode Chokes For Hams
<>**Most recent update April
2019.*This tutorial is directed specifically to RFI in ham radio
applications. It includes an extended discussion of the use of common
mode chokes in antenna systems and for suppression of RFI. A chapter on
audio and computer interconnections in ham stations shows how to make
bulletproof connections between a computer sound card and ham rigs for
SSB, RTTY, PSK31, and SO2R contesting without expensive interface boxes,
using nothing more than simple cables with the right connectors on each
end. There's also a chapter on grounding and bonding.
This is a new applications note summarizing my work on *Chokes and
Transformers For Receiving Antennas.
<
**NEW!*October
2018
<
Virus-free.
www.avg.com
<
<#DAB4FAD8-2DD7-40BB-A1B8-4E2AA1F9FDF2>
--
*Dave - W?LEV*
*Just Let Darwin Work*
|
Re: [Ham-Antennas] USING THE NANOVNA AND SAVER TO MEASURE CM ATTENUATION THROUGH CMCs
Gary,
IF the alternative RF path is down a pair of antenna wires near a feed
point where the equivalent impedance is ~75 Ohms, then 3K ohms looks very
good. On the other hand if end-feeding and using the choke to hold back
the RF on the feedline, then RF impedance at the point of the choke might
be >2k Ohms and 3K ohms is hopeless.
This is why my original post of my results attempted to measure the
series impedance (mostly inductive) at various frequencies within the
amateur bands of my CMCs (using the HP-9753C
VNA). I use a 450-foot long doublet fed with (mostly) 400-ohm
parallel conductor transmission line (about 65-feet total of that Xline).
As such, the impedance presented here in the shack
is all over the Smith Chart. I could evaluate the effectiveness of my
chokes only by knowing the series Z they presented and the impedance of the
antenna/feedline presented in the
shack. Others wanted to see the attenuation of CM energy as measured
in a 50-ohm system. That's why I presented that measurement in the second
set of measurements I sent out
yesterday. Used as I do, every installation in the world will be
different.
The impedance of my antenna does not hit the real axis of the chart
anywhere in the amateur bands. The lowest frequency 1/2-wavelength
resonance (with a bit of capacitive end loading)
is roughly 950 kHz in the bottom third of the AM BCB. My w/c
impedance is on 40-meters: 1000 - j 1100 ohms. In my installations, I
believe a better metric with which to measure the
performance of my CMCs is the balance between current going up and
back on the parallel line transmission line. I have built a small piece of
equipemt to measure just that. I've also
taken each CMC and using an o'scope and a signal generator measured
the balance of amplitude and phase reversal from the two DM ports with CM
drive from the signal generator. That
has not appeared in my measurements as I'm trying to stick with the
NANOVNAs.
The antenna where I was trying to use this was in between those extremes,
but the NEC model run suggested that I was losing about 40% of my power
to/through the choke on 160.
The final test I put my CMCs through is in place between the output of
the matching network (L-network) and the parallel conductor transmission
line to the set of wires *at power*. I start
with around 400-watts. That caught one CMC wound with house wiring
insulated with PVC - bad heating of the insulation. It was eventually
unwound. Those wound with solid AWG #12
solid enamelled copper conductors exhibited bad coronal discharge
between winding pairs of the line on the cores. If you are, indeed, losing
40% of your power on 160-meters at 100-
watts, I'd expect some major amount of heating would be evident. If
not, something in the model is missing.
Several decades ago, I started with CMC wound on a large core of 43
material using RG-142 coax. That the 'high power' teflon insulated, silver
plated conductor 50-ohm coax. I finally
came to realize its only function was to present a large inductive
reactance to the CM energy on my transmission line. A choke wound in
bifilar manner accomplishes that in addition to
ensuring the currents cancel within the core which forces CM energy
passing unattenuated through the core - the DM energy. Therefore, all my
chokes of resent build have been bifilar
windings on the cores.
Dave - W?LEV
toggle quoted message
Show quoted text
On Tue, Feb 2, 2021 at 7:40 PM Gary Rondeau <grondeau@...> wrote: Dave,
I just went through the process of winding various number of turns and
various tightness of spacings of those turns for big coax and FT240-31
cores. this is a common way to generating a CMC, but what I discovered is
that the performance is all over the map depending on the band you are
trying to choke, and how you do the winding. Big coax (RG-11 in my case)
has a substantial bend radius so the coils are big and there is a lot of
capacitance. 8 turns through the core could generate anywhere from about
20 to 50 pF depending on how it was done. It is hard to get a maximum
equivalent parallel resistance larger than about 3k ohms, and inductance
around 130uH. More than one core is desirable.
IF the alternative RF path is down a pair of antenna wires near a feed
point where the equivalent impedance is ~75 Ohms, then 3K ohms looks very
good. On the other hand if end-feeding and using the choke to hold back
the RF on the feedline, then RF impedance at the point of the choke might
be >2k Ohms and 3K ohms is hopeless.
The antenna where I was trying to use this was in between those extremes,
but the NEC model run suggested that I was losing about 40% of my power
to/through the choke on 160.
Gary AF7NX
--
*Dave - W?LEV*
*Just Let Darwin Work*
|
On 2/2/21 1:10 PM, David Eckhardt wrote: 13.56 MHz is an ISM (Industrial, Scientific, and Medical) frequency. There
are 7 frequencies allocated by the FCC for that purpose in that specific
ISM band - in a NON_RADIATIVE MANNER. Why are you connecting an antenna to
a 13.56 MHz source? RFID uses 13.56 MHz with radiated fields (limited, it's true), but all those "near field communications" things are also 13.56 (Subway cards, cashless payments, etc.). If you're making a "long range" reader (e.g. for a doorway portal application) you wind up with directive arrays of some sort, but you also run into problems with RFI.
Most of the MetCal soldering stations operate on 13.56 MHz.
Dave - W?LEV
On Tue, Feb 2, 2021 at 8:57 PM Jim Allyn - N7JA <jim@...>
wrote:
On Tue, Feb 2, 2021 at 05:54 AM, <brown.beard.2020@...> wrote:
I have an antenna connected to a 13.56MHz RF signal and would like to add a
ferrite core to the cable from the antenna to the device to filter out any
noise coming from the environment. It isn't clear to me what the situation is here. Do you mean you have an
antenna connected to a 13.56 MHz signal coming from a signal generator or
transmitter of some sort, and you wish to transmit that13.56 MHz signal?
Or, you have an antenna you are using to receive a 13.56 MHz signal, and
you would like to prevent interference picked up by the transmission line
from being brought into the shack? Or you have something else (NOT 13.56
MHz) you are trying to receive and the 13.56 MHz signal is interfering with
it? Please clarify.
|
Re: USING THE NANOVNA AND SAVER TO MEASURE CM ATTENUATION THROUGH CMCs
On Mon, Feb 1, 2021 at 02:00 PM, David Eckhardt wrote: I promised this, so here it is. See the attachment for a procedure to
measure the CM attenuation through CMCs and other 4-terminal devices (as in
s-parameters). Comments and improvements are welcome before I post it to
the files section.
Dave, The measurement of common mode attenuation as it pertains to baluns and RF chokes has been discussed in this group several times and there is a lot of good info in those posts. Reading through these and other excellent references on the Internet one can see the two main areas of concern... - How to measure common mode impedance accurately - Does measuring common mode impedance reflect what happens to common mode current reduction in an antenna system? Let me start with the latter. Several well-known authors on this subject (Tom Roach (W8JI), Jim Brown (K9YC), Owen Duffy(VK1OD), Jeff Anderson (K6JCA) and Steve Hunt (G3TXQ -SK) all stress that knowing the magnitude of the impedance |Z| is not a useful indicator of how well a balun or RF choke will reduce common mode current. As a minimum we need to know the complex impedance R+/-jX and even this only gives a subjective answer. If the choking impedance is primarily reactive the common mode current could get worse depending on the feedpoint impedance of the antenna. What is effective is if the resistance is high and how high is a subject of debate. What is generally accepted is that if common mode impedance |Z| is less than 500 ohms it will be a poor solution. Also there is no direct relationship between the common mode impedance of the RF choke and balun and the reduction in common mode current that would be measured when installed in an antenna system. The second issue is how to measure common mode impedance accurately. It is relatively easy to determine the magnitude of the impedance |Z| using S21 but even that requires careful jig construction especially if we want to make measurements higher than HF. The complex impedance (R+/-jX) can be determined by several methods: S11 or S21. The problem with the S21 measurement method is that it requires additional calculations to determine R+/-jX and the NanoVNA does not have the hardware capability to do this accurately. However S11 measurements can be made on the NanoVNA to determine R+/-jX but the estimate gets poor if we go much beyond 1000 ohms. Just like S21 measurements the test fixture should be built to minimize parasitics and be calibrated with suitable loads. Rather than repeat what the authors above have written on this subject I suggest readers take a look at this post by K6JCA which has a lot of theoretical background, measurements and an extensive reference list. Roger
|
Probably has nothing to do with his use, but 13.56 MHz and surrounding frequencies on shortwave are the homes of many unlicensed CW beacons. Many are "squarers." Zack W9SZ On Tue, Feb 2, 2021 at 8:52 AM Jim Lux <jim@...> wrote: On 2/2/21 5:04 AM, brown.beard.2020@... wrote:
Hi All
Sorry if this is not the right place to ask. Feel free to point me to a more suitable place for my questions.
I have an antenna connected to a 13.56MHz RF signal and would like to
add a ferrite core to the cable from the antenna to the device to filter
out any noise coming from the environment.
How do i determine the appropriate specs for the ferrite core?
That's the ISM frequencies just below the amateur radio 20 meter band,
so anything that works for 14 MHz (20m) will probably work just fine for
13.56 MHz.
In general, 31 mix is a good choice for HF - it's suitably lossy at
those frequencies. You might check out K9YC's choke cookbooks and other
writeups..
You're presumably at low power for something like a badge reader, so you
probably aren't as interested in low loss transmitter designs.
*RFI, Ferrites, and Common Mode Chokes For Hams
<>**Most recent update April
2019.*This tutorial is directed specifically to RFI in ham radio
applications. It includes an extended discussion of the use of common
mode chokes in antenna systems and for suppression of RFI. A chapter on
audio and computer interconnections in ham stations shows how to make
bulletproof connections between a computer sound card and ham rigs for
SSB, RTTY, PSK31, and SO2R contesting without expensive interface boxes,
using nothing more than simple cables with the right connectors on each
end. There's also a chapter on grounding and bonding.
This is a new applications note summarizing my work on *Chokes and
Transformers For Receiving Antennas.
<>**NEW!*October
2018
<> Virus-free. www.avg.com <> <#DAB4FAD8-2DD7-40BB-A1B8-4E2AA1F9FDF2>
|
13.56 MHz is an ISM (Industrial, Scientific, and Medical) frequency. There are 7 frequencies allocated by the FCC for that purpose in that specific ISM band - in a NON_RADIATIVE MANNER. Why are you connecting an antenna to a 13.56 MHz source? Most of the MetCal soldering stations operate on 13.56 MHz. Dave - W?LEV On Tue, Feb 2, 2021 at 8:57 PM Jim Allyn - N7JA <jim@...> wrote: On Tue, Feb 2, 2021 at 05:54 AM, <brown.beard.2020@...> wrote:
I have an antenna connected to a 13.56MHz RF signal and would like to add a
ferrite core to the cable from the antenna to the device to filter out any
noise coming from the environment.
It isn't clear to me what the situation is here. Do you mean you have an
antenna connected to a 13.56 MHz signal coming from a signal generator or
transmitter of some sort, and you wish to transmit that13.56 MHz signal?
Or, you have an antenna you are using to receive a 13.56 MHz signal, and
you would like to prevent interference picked up by the transmission line
from being brought into the shack? Or you have something else (NOT 13.56
MHz) you are trying to receive and the 13.56 MHz signal is interfering with
it? Please clarify.
-- *Dave - W?LEV* *Just Let Darwin Work*
|
On Tue, Feb 2, 2021 at 05:54 AM, <brown.beard.2020@...> wrote: I have an antenna connected to a 13.56MHz RF signal and would like to add a
ferrite core to the cable from the antenna to the device to filter out any
noise coming from the environment. It isn't clear to me what the situation is here. Do you mean you have an antenna connected to a 13.56 MHz signal coming from a signal generator or transmitter of some sort, and you wish to transmit that13.56 MHz signal? Or, you have an antenna you are using to receive a 13.56 MHz signal, and you would like to prevent interference picked up by the transmission line from being brought into the shack? Or you have something else (NOT 13.56 MHz) you are trying to receive and the 13.56 MHz signal is interfering with it? Please clarify.
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Re: USING THE NANOVNA AND SAVER TO MEASURE CM ATTENUATION THROUGH CMCs
For those that may use Google, Google Docs will read and create DOCX files.
*Clyde K. Spencer*
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On Tue, Feb 2, 2021 at 3:18 PM Jim Lux <jim@...> wrote: On 2/2/21 10:17 AM, David Eckhardt wrote:
oooops. When I send them to the files section, I shall do so. Thanks
for the suggestion. I thought Apple could read .docx files. Are we back
to Apple vs. IBM? Humbug...... I suspect it's MS Word vs something else.
.docx works just fine on Mac OS, but you need MS Word.
Dave
On Tue, Feb 2, 2021 at 6:15 PM Joe St. Clair AF5MH <saintc@...
wrote:
I suggest that you convert the document to PDF format. The .docx format
seems to be problematic on non-Microsoft systems.
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Re: Antenna QUIZ (to help interpret NANO VNA graphs) de k3eui Barry
The simplest book which covers the proper subjects with as little calculus
as I've seen is:
Surprisingly enough, MFJ has an excellent resource. I picked up a copy at
HRO a couple of years ago, well before the COVID thing. It's a bit terse
in treatments, but its pretty good:
*ANTENNAS AND TRANSMISSION LINES* by John A. Kuecken, Published: MFJ,
First edition, 2nd printing ......... no ISBN number
While one can hardly treat the subject without a little calculus, he has
kept it to a minimum. However, a solid and working knowledge of algebra
and trigonometry is required.
If you ae looking for a reference with absolutely no calculus and still
treats the necessary subjects properly, your out of luck. The book
published by MFJ is about as close to that as I've come across and is still
responsible to engineering and physics. Even the J. D. Kraus *ANTENNAS*
requires calculus. Without that math tool, you're up a creek as E&M
requires calculus. Try the MJF book. I believe it's the best on the
present market with minimal math.
Or take the plunge and learn a bit of good solid math. Life-long learning
is golden, especially in retirement.
Dave - W?LEV
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On Tue, Feb 2, 2021 at 7:36 PM Dave Daniel <kc0wjn@...> wrote: Having not seen or read that book, I can’t say. Perhaps someone else on
the list can answer that.
DaveD
On Feb 2, 2021, at 14:15, Cierra <dubosec@...> wrote:
On Mon, Feb 1, 2021 at 10:21 AM, Dave Daniel wrote:
Does something like the Practical Antenna Handbook by Carr and Hippisley provide a good overview of antennas for a ham without a background in
calculus? I can't exactly undertake a graduate-level study of the topic at
the moment, haha.
There are many textbooks out there. Some are:
Any revision of John Kraus’ “Antennas” text (classic and probably the
best choice when starting out)
Any revision of Balanis’ “Antenna Theory” text
Weeks’ “Antenna Engineering” (another good entry-level text)
Collin “Antennas and Microwave Propagation”
Collin and Zucker “Antenna Theory” (2 volume set)
Elliot “Antenna Theory and Design”
Lee “Vertical Antenna Handbook”
RSGB “Antennas for all Locations”
Shelkunoff of early Bell Labs fame also wrote several texts on
antennas, at
least one of which is advanced.
Realize that most of the above are engineering textbooks and thus are
mathematically-based. Some are quite old. I would use bookfinder.com
and
search using the author’s name and “antenna” in the title field.
DaveD
On Feb 1, 2021, at 10:27, Cierra <dubosec@...> wrote:
Other than the ARRL Antenna Book, are there good resources to
investigate to
learn more about these topics?
--
*Dave - W?LEV*
*Just Let Darwin Work*
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Re: USING THE NANOVNA AND SAVER TO MEASURE CM ATTENUATION THROUGH CMCs
On 2/2/2021 3:18 PM, Jim Lux wrote: On 2/2/21 10:17 AM, David Eckhardt wrote:
oooops.? When I send them to the files section, I shall do so.??? Thanks
for the suggestion.? I thought Apple could read .docx files. Are we back
to Apple vs. IBM?? Humbug...... I suspect it's MS Word vs something else.
docx works just fine on Mac OS, but you need MS Word.
Open Office works good with docx files.? Gave up on Microsoft stuff when they went to a subscriber model. Eric WA3UYI -- This email has been checked for viruses by Avast antivirus software.
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Re: USING THE NANOVNA AND SAVER TO MEASURE CM ATTENUATION THROUGH CMCs
On 2/2/21 10:17 AM, David Eckhardt wrote: oooops. When I send them to the files section, I shall do so. Thanks
for the suggestion. I thought Apple could read .docx files. Are we back
to Apple vs. IBM? Humbug...... I suspect it's MS Word vs something else. .docx works just fine on Mac OS, but you need MS Word. Dave
On Tue, Feb 2, 2021 at 6:15 PM Joe St. Clair AF5MH <saintc@...>
wrote:
I suggest that you convert the document to PDF format. The .docx format
seems to be problematic on non-Microsoft systems.
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Jim Allyn - N7JA
Chuck Cole
Roger Need