Re: MORE CMC SINGLE CORE DATA
Mark, There are always those snakes who will seek
to take advantage of people's ignorance. If boosting their victims self esteem
by feeding them wive's tails and simple explanations that serve their purpose
they will readily do so. Are you maybe thinking about clever businessmen who sell $1000 copper-free, super-low-distortion power cables to HiFi fans? Or were you thinking about companies that sell $300 professional, ultra wide frequency response microphones to hams, to be used for SSB transmission? :-) There are many people who derive satisfaction from buying overpriced and overrated stuff. So even those sellers do serve a function. But I, and obviously you, prefer buying cost-effective stuff, that serves many purposes while costing little money. Best example to be cited here: The NanoVNA! I see my duty to educate my fellow hams with what
little I DO know, and hopefully learn in the process. Excellent. I try that too. Also, I hadn't considered that flux might vary inversely and linearly with mu
for a given voltage, all else being equal, You got it wrong again!!!!!! When everything else is constant: - The flux is independent from ?, at a given voltage. - The flux is proportional to ?, at a given current. - The current is inversely proportional to ?, for a given voltage. - The voltage is proportional to ?, for a given current. I shall review the equations on the
matter. I always have to perform a mathematical proof to retain these ideas. Have a look at my page about electromagnetism essentials. It's not in the style a university professor would like, but I think it explains the basics in an easier-to-use way than textbooks: Manfred
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It's common practise so yes:
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On Sat, 23 Jan 2021 at 20:48, Michael Foerster <mcfroston@...> wrote: I've been reading the comments recently on using CMC baluns on antenna
systems and I too am a firm believer in using them. I've seen my noise
level go down considerably in my semi-urban location.
My question has to do with using CMC balun over multiple antenna. I have
a series of dipoles, 160/80/60 and 40m (on the boom of my TH11DX), and the
TH11DX for 20/17/15/12/10 meters.
These are all fed to the rig via an automatic remote antenna switch at
the base of the tower.
I have a CMC on the output of the antenna switch that's wound with 17
turns of RG-400 on a #31 - 2.4" core (with a crossover).
The problem, as I understand it, when using a balun like this (close
windings) on the higher frequencies have capacitive leakage.
So, I was going to wind another CMC with fewer turns to cover the 14 -
29.7 MHz and build a remote relay switch (switching both the center and
shields) between the two baluns, located at the base of the tower.
HOWEVER, it occurred to me that rather than switching between them,
perhaps I could just put them in series. The series losses would be
minimal (probably less than the relays that would be inserted), and
hopefully, the inductive reactance between the two would add up, but also
keep the reactance at the higher frequency much higher because of the
addition of the CMC wound for the higher bands.
Does this make sense?
--
Mike, W0IH
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I've been reading the comments recently on using CMC baluns on antenna systems and I too am a firm believer in using them. I've seen my noise level go down considerably in my semi-urban location.
My question has to do with using CMC balun over multiple antenna. I have a series of dipoles, 160/80/60 and 40m (on the boom of my TH11DX), and the TH11DX for 20/17/15/12/10 meters.
These are all fed to the rig via an automatic remote antenna switch at the base of the tower.
I have a CMC on the output of the antenna switch that's wound with 17 turns of RG-400 on a #31 - 2.4" core (with a crossover).
The problem, as I understand it, when using a balun like this (close windings) on the higher frequencies have capacitive leakage.
So, I was going to wind another CMC with fewer turns to cover the 14 - 29.7 MHz and build a remote relay switch (switching both the center and shields) between the two baluns, located at the base of the tower.
HOWEVER, it occurred to me that rather than switching between them, perhaps I could just put them in series. The series losses would be minimal (probably less than the relays that would be inserted), and hopefully, the inductive reactance between the two would add up, but also keep the reactance at the higher frequency much higher because of the addition of the CMC wound for the higher bands.
Does this make sense?
--
Mike, W0IH
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Re: EFFECT OF CMCs and/or BALUNS on RECEIVED NOISE
OOOOOooops.......RIGHT MOST ENTRY in the table...... Dave On Sat, Jan 23, 2021 at 6:24 PM David Eckhardt <davearea51a@...> wrote: I'll include a few pictures of the choke I used for the on-the-air (S+N)/N
short experiment. I'll also attach the table of measurements in which this
choke is the left-most entry.
Again, the CMC is wound in bifilar manner with no twists or crossovers on
two stacked Material 31 cores of 2.4" OD. The windings consist of AWG #12
enamelled solid copper wire. See attachments.
Dave - W?LEV
On Sat, Jan 23, 2021 at 5:43 PM Floyd <fhh11@...> wrote:
Dave,
I very much appreciate your work on CMCs. I have a similar antenna to
yours (four half waves in phase called a Frankin Antenna fed from a
balanced tuner with 430 ohm ladder line. Like Joe, K7JOE, I would
appreciate the details of the CMC that you used and its location with
respect to the antenna's feed point. Again thank you for sharing.
Floyd K2DUV
--
*Dave - W?LEV*
*Just Let Darwin Work*
-- *Dave - W?LEV* *Just Let Darwin Work*
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Re: EFFECT OF CMCs and/or BALUNS on RECEIVED NOISE
I'll include a few pictures of the choke I used for the on-the-air (S+N)/N
short experiment. I'll also attach the table of measurements in which this
choke is the left-most entry.
Again, the CMC is wound in bifilar manner with no twists or crossovers on
two stacked Material 31 cores of 2.4" OD. The windings consist of AWG #12
enamelled solid copper wire. See attachments.
Dave - W?LEV
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On Sat, Jan 23, 2021 at 5:43 PM Floyd <fhh11@...> wrote: Dave,
I very much appreciate your work on CMCs. I have a similar antenna to
yours (four half waves in phase called a Frankin Antenna fed from a
balanced tuner with 430 ohm ladder line. Like Joe, K7JOE, I would
appreciate the details of the CMC that you used and its location with
respect to the antenna's feed point. Again thank you for sharing.
Floyd K2DUV
--
*Dave - W?LEV*
*Just Let Darwin Work*
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Re: MORE CMC SINGLE CORE DATA
Here is an excellent starter with nothing more than algebra required:
Dave - W?LEV
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On Sat, Jan 23, 2021 at 4:53 PM Mark KA2QFX <ka2qfx@...> wrote: Dave and Manfred,
Thanks for your comments. All points well taken. I'll forego additional
philosophical rant save for this: There are always those snakes who will
seek to take advantage of people's ignorance. If boosting their victims
self esteem by feeding them wive's tails and simple explanations that serve
their purpose they will readily do so. I see my duty to educate my fellow
hams with what little I DO know, and hopefully learn in the process.
Thank you for your efforts toward that end.
Also, I hadn't considered that flux might vary inversely and linearly with
mu for a given voltage, all else being equal, I shall review the equations
on the matter. I always have to perform a mathematical proof to retain
these ideas.
73,
Mark
--
*Dave - W?LEV*
*Just Let Darwin Work*
|
Re: EFFECT OF CMCs and/or BALUNS on RECEIVED NOISE
Dave,
I very much appreciate your work on CMCs. I have a similar antenna to yours (four half waves in phase called a Frankin Antenna fed from a balanced tuner with 430 ohm ladder line. Like Joe, K7JOE, I would appreciate the details of the CMC that you used and its location with respect to the antenna's feed point. Again thank you for sharing.
Floyd K2DUV
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Re: EFFECT OF CMCs and/or BALUNS on RECEIVED NOISE
In the example of the benefits of using a CMC or true balun, I used two stacked cores of 31 material with an OD of 2.4". I wound 18 turns of AWG #12 enamelled solid copper wire in bifilar manner with no twists or crossovers on the core. It was tight, but I got 18 turns on the stacked cores. Measurements of that CMC and others are included in the table I've previously put out on this group. The CMC is placed between the open wire feeders in the shack and the 'input' (as opposed to the 50-ohm matched port) of the L-Network matching network (a.k.a.: antenna "tuner"). I only strove to illustrate the need for and usefulness of a CMC or balun. It was a 'quickie' on my part. I could include additional bands, but I'll leave that as an exercise to the interested and motivated ham. If my putting out this information which might motivate others to do more testing on their own, so much the better! Dave - W?LEV On Sat, Jan 23, 2021 at 2:31 PM Joe K7JOE via groups.io <k7joe= [email protected]> wrote: Hi Dave. Consider to add some more info on your word document. Can you
highlight
A) WHAT was the construction of your common mode choke used in the
example-- mix ? donut size? number of turns? coaxial cable or enamel
wire? etc.
B) WHERE it was placed. eg. benefits in placing it immediately at the
feedpoint. 0.1 lambda below the feedpoint on the feedline, or at the
entry point to the shack (or, in my case, i have choke in all those
places)....
C)Also it would be good to make the photos and observation on multiple
bands. eg... 28 mhz... 14 mhz.... 7 mhz... 1.8 mhz. I find that
certain devices or noise sources impact certain bands more... for example,
big common mode problem impacts the 14 mhz here, but does not at all
impact 7 mhz.... etc. Adding mix 31 to my 160M antenna was NO HELP AT
ALL...but adding mix 75 at the feedpoint WAS AMAZING IMPROVEMENT .
Good info. I am believer in chokes and have pounds and pounds of ferrite
on my antenna feedlines. It DOES help .
Joe K7JOE
"no cheesy quote"
-- *Dave - W?LEV* *Just Let Darwin Work*
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Re: [nanovna-f] EFFECT OF CMCs and/or BALUNS on RECEIVED NOISE
If one reads the small amount of verbiage which I started with, you would
already know I turned on preamp 1 ONLY to raise the level of noise shown on
the waterfall. I have that adjusted for normal operation such that the
noise only tickles the waterfall on 40-meters during the daytime. I do NOT
use the preamps AT ALL below 20-meters.
Something hams need to embody in their bits of knowledge is the FACT that
turning on a preamp to see the S-Meter jump around more aggressively does
NOT generally increase readability of a weak signal. In reality, the
preamp when improperly applied can actually degrade the (S+N)/N by the
noise figure of the preamp. Both noise and signals are amplified by an
equal amount. On the lower bands, a preamp is NOT needed with any of our
modern transceivers. On 10-meters where local and atmospheric noise is
usually low, a preamp can and typically does offer an increase in (S+N)/N.
On 75-meters at night, a preamp is totally useless as band noise is well
above receiver noise. Of course, if a highly compromised antenna must be
used like a passive very short monopole or small loop, an appropriate
preamp is usually required. But,......that preamp is not of the design
found in our transceivers. My 450-foot long doublet fed with parallel
conductor transmission line certainly does not require a preamp on anything
below 20 meters!
*Kernel of knowledge*: Readability of a signal is all about (S+N)/N and
NOT.....N O T......about how much the S-meter jumps around.
*Statement of fact*: Readability of a signal is all about (S+N/)/N and
NOT.......N O T......about how much the S-meter jumps around.
Dave - W?LEV
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On Sat, Jan 23, 2021 at 5:02 PM Arie Kleingeld PA3A <pa3a@...> wrote: What I meant is that noise or signal level does not change. It is a
fieldstrength outside your transceiver.
Switching on a preamp makes signals more audible (sometimes) but still,
then EM fieldstrength is the same. So When the signal is captured with
your antenne and comes into the TRX, than you can read on the S-meter
whatever the manufacturers like ;-)
Besides that, the noiselevel on HF is usually pretty high in urban
areas, signal to noise ratio will not change if you add just that little
preamp noise. Band noise is dominant (mostly) except on higher freq
bands. Not going into detail too much.
73
Arie
Op 23-1-2021 om 10:37 schreef David Reichard:
Arie: All signals are amplified. So a 10 dB amp would increase the desired signal 10 dB and the noise level 10 dB too. Maybe the
signal-to-noise ratio (SNR) does not change--is that what you meant? In the
real world, an amp adds its own noise to the noise already in the signal,
so the SNR would be worse than without the amp. I'm not an engineer, so
correct me if I'm mistaken:)
-David Reichard KD6DWR
--
*Dave - W?LEV*
*Just Let Darwin Work*
|
Re: [nanovna-f] EFFECT OF CMCs and/or BALUNS on RECEIVED NOISE
What I meant is that noise or signal level does not change. It is a fieldstrength outside your transceiver.
Switching on a preamp makes signals more audible (sometimes) but still, then EM fieldstrength is the same. So When the signal is captured with your antenne and comes into the TRX, than you can read on the S-meter whatever the manufacturers like ;-)
Besides that, the noiselevel on HF is usually pretty high in urban areas, signal to noise ratio will not change if you add just that little preamp noise. Band noise is dominant (mostly) except on higher freq bands. Not going into detail too much.
73
Arie
Op 23-1-2021 om 10:37 schreef David Reichard:
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Arie: All signals are amplified. So a 10 dB amp would increase the desired signal 10 dB and the noise level 10 dB too. Maybe the signal-to-noise ratio (SNR) does not change--is that what you meant? In the real world, an amp adds its own noise to the noise already in the signal, so the SNR would be worse than without the amp. I'm not an engineer, so correct me if I'm mistaken:)
-David Reichard KD6DWR
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Re: MORE CMC SINGLE CORE DATA
Dave and Manfred,
Thanks for your comments. All points well taken. I'll forego additional philosophical rant save for this: There are always those snakes who will seek to take advantage of people's ignorance. If boosting their victims self esteem by feeding them wive's tails and simple explanations that serve their purpose they will readily do so. I see my duty to educate my fellow hams with what little I DO know, and hopefully learn in the process.
Thank you for your efforts toward that end.
Also, I hadn't considered that flux might vary inversely and linearly with mu for a given voltage, all else being equal, I shall review the equations on the matter. I always have to perform a mathematical proof to retain these ideas.
73,
Mark
|
Re: EFFECT OF CMCs and/or BALUNS on RECEIVED NOISE
Hi Dave. Consider to add some more info on your word document. Can you highlight
A) WHAT was the construction of your common mode choke used in the example-- mix ? donut size? number of turns? coaxial cable or enamel wire? etc.
B) WHERE it was placed. eg. benefits in placing it immediately at the feedpoint. 0.1 lambda below the feedpoint on the feedline, or at the entry point to the shack (or, in my case, i have choke in all those places)....
C)Also it would be good to make the photos and observation on multiple bands. eg... 28 mhz... 14 mhz.... 7 mhz... 1.8 mhz. I find that certain devices or noise sources impact certain bands more... for example, big common mode problem impacts the 14 mhz here, but does not at all impact 7 mhz.... etc. Adding mix 31 to my 160M antenna was NO HELP AT ALL...but adding mix 75 at the feedpoint WAS AMAZING IMPROVEMENT .
Good info. I am believer in chokes and have pounds and pounds of ferrite on my antenna feedlines. It DOES help .
Joe K7JOE
"no cheesy quote"
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Re: EFFECT OF CMCs and/or BALUNS on RECEIVED NOISE
this is very good information and indeed two of the big issues in today's typical ham environment are:
1. urban living with many more generators of wide band RF noise in that environment than in past decades. switching power supplies, cable modems, led lighting etc.
2. the increase in restrictions on antennas resulting in the use of compromise antennas for many hams.. If it is anything end fed or off center fed -- by design they are no longer balanced and thus are subject to the adverse effects of common mode currents. Those current impact both transmit and receive and common mode choking is extremely important. in fact, it's almost a crime IMO to sell these antennas without the necessary CMC chokes included (or to claim they are unnecessary) since most new hams have no idea about this topic. They get on the HF air, have RF issues, get discouraged, and leave HF for DMR....
Yes, Mix 31 ferrite donut should probably be the next TIME man of the year.... at least for hams.
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Re: [nanovna-f] EFFECT OF CMCs and/or BALUNS on RECEIVED NOISE
Arie: All signals are amplified. So a 10 dB amp would increase the desired signal 10 dB and the noise level 10 dB too. Maybe the signal-to-noise ratio (SNR) does not change--is that what you meant? In the real world, an amp adds its own noise to the noise already in the signal, so the SNR would be worse than without the amp. I'm not an engineer, so correct me if I'm mistaken :)
-David Reichard KD6DWR
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Noise levels do not change if you turn a pre-amp on or off. Nor do
signal levels.
S-meter readouts may change (depending on which TRX you're using).
Some S-meters go 6dB/S-point, others (like ICOM) 3dB/S-point and some
older TRXs it's variable :-)
So be careful.
73,
Arie PA3A
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The firmware updates so far have been designed to perform as many operations as possible from the built-in processor.
This was approached by two very active programmers and one of them developed the firmware (DiSlord) and the other the PC software (OneOfEleven) to a higher level.
No further development is likely to be expected, so I strongly recommend that anyone who can install the latest 1.0.45 firmware and use NanoVNA-App v1.1.205 (Windows) on their computer.
Many thanks to them for making the improvements in their spare time, all selflessly.
73, Gyula HA3HZ
--
*** If you are not part of the solution, then you are the problem. ( ) ***
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Hi Jim,
Based on the firmware, you received a previously assembled device. During manufacture, it was placed in either a burr or low-spacing housing, so this was a defect. If you place a plastic washer on the screw blocks, which raises the lid by approx. With 0.5mm, you won't have such a problem later. It is advisable to upgrade the firmware, the current latest is v1.0.45 made by DiSlord. You can also find it on my website or in the group wiki and Files folder. If you don¡¯t know how to do it, you¡¯ll also get an answer from the link above.
Successful use.
73, Gyula HA3HZ
--
*** If you are not part of the solution, then you are the problem. ( ) ***
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Re: [nanovna-f] EFFECT OF CMCs and/or BALUNS on RECEIVED NOISE
HI all,
Just to keep in mind.
Noise levels do not change if you turn a pre-amp on or off. Nor do signal levels.
S-meter readouts may change (depending on which TRX you're using).
Some S-meters go 6dB/S-point, others (like ICOM) 3dB/S-point and some older TRXs it's variable :-)
So be careful.
73,
Arie PA3A
Op 23-1-2021 om 01:26 schreef David Eckhardt:
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With no preamps turned on in the Icom 7300 (or 7610), my noise floor is S-0
(-100 dBm) or lower most of the time during the day. On 160 and 75 toward
evening, it comes up a bit, but that is just cosmic and atmospheric noise.
Dave - W?LEV
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Found the problem. The plastic screen protector was wadded up under the case cover. I removed the cover, cleaned off the protector , and reassembled. Works fine!
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Re: EFFECT OF CMCs and/or BALUNS on RECEIVED NOISE
thanks On Fri, Jan 22, 2021 at 10:31 PM David Eckhardt <davearea51a@...> wrote: The calibration of the 7300 S-Meter is published by Icom. I have also
tested it using an Agilent Signal Generator. Be rest assured, the 7300 and
7610 S-Meter is 3 dB per S-Unit.
Dave - W?LEV
On Sat, Jan 23, 2021 at 12:54 AM Paul W8SBH <proinwv@...> wrote:
I use CMCs on two antennas; a dipole and a 1/4wave 2 meter vertical with
counterpoises. But I have a third antenna, an off center fed dipole with a
balun. I have assumed that the balun will also function as a CMC. Do you
agree?
On a slight off subject. I was surprised to see you state that the 7300
Smeter was 3dB per division. How did you determine that.
Thanks for the good information
Paul W8SBH
--
*Dave - W?LEV*
*Just Let Darwin Work*
-- Paul W8SBH ?? ?? ???? (this too shall pass)
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Re: EFFECT OF CMCs and/or BALUNS on RECEIVED NOISE
The calibration of the 7300 S-Meter is published by Icom. I have also
tested it using an Agilent Signal Generator. Be rest assured, the 7300 and
7610 S-Meter is 3 dB per S-Unit.
Dave - W?LEV
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Show quoted text
On Sat, Jan 23, 2021 at 12:54 AM Paul W8SBH <proinwv@...> wrote: I use CMCs on two antennas; a dipole and a 1/4wave 2 meter vertical with
counterpoises. But I have a third antenna, an off center fed dipole with a
balun. I have assumed that the balun will also function as a CMC. Do you
agree?
On a slight off subject. I was surprised to see you state that the 7300
Smeter was 3dB per division. How did you determine that.
Thanks for the good information
Paul W8SBH
--
*Dave - W?LEV*
*Just Let Darwin Work*
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Arie Kleingeld PA3A
David Reichard
Gyula Molnar