Re: Impedance 50 ohm Spectral analyzer HP8558B
Yeah.? Physics was my favorite subject back when I first attended college, followed by Chemistry.? Too bad that they didn't use the rope analogy more when the subject was electronics, although I understood what they were talking about (a bit) and did well in those two classes.? It's a real-world wording for a bit more difficult subject (the rope analogy was only applied to wave theory and resonance... connecting characteristic impedance and so on to it really does work)!
The analogy should be used more in basic Ham radio books, and even would be good for beginning electronics books.
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Show quoted text
On 6/10/21 1:03 PM, John Putnum, AC9UV wrote: Bob,
Glad that analogy found a home. Physics is a wonderful template that can be applied over many seemingly disparate situations. Jargon can get in the way of understanding, but at the same time is a good shorthand if you understand the fundamental meaning behind the words.
---John AC9UCV
On 06/10/2021 10:20 AM Robert D. Bowers <n4fbz@...> wrote:
That is an EXCELLENT analogy.? I'd never thought of it that way, but it
brings everything in... including things like phase angle.? (I'd never
heard or read that one before... )
Where it gets interesting is when you have a thin cord, a thick rope,
and then another thin cord (or some combination thereof)... SWR, line
losses, you name it also are well illustrated by that analogy!? (GRIN!)
Bob
N4FBZ
On 6/9/21 6:54 PM, John Putnum, AC9UV wrote:
CDT,
Well a simple answer is that there are two parts to Impedance. One
part is the resistance that can be measured by your ohm meter. That is
DC resistance. When you apply an ac signal to the device, then if
there is some magnetic materials that would create magnetic fields an
Inductive component along with the static electric fields (an
Inductive component) then you get some components that impede the flow
of electricity, hence impedance. The reason that is important is that
if impedances are matched then the signal flows through the circuit
without much loss (loss due to the dc resistance).? They call that
impedance matching.? You can see some of those effects with waves on
the water. If the waves hit a barrier then the waves are reflected
back. If they don't hit a barrier they just keep going.
fIf you have a rope tied to wall and shake the rope, the wave goes to
the wall and is reflected back. But if you have a thin rope tied to a
much thicker rope that is then connected to the wall then when you
shake the rope, when the wave hits the junction of the thin and the
thick rope, some physics magic happens, some of the wave moves into
the thick rope but some of the wave is reflected back to the thin rope
(as though it kind of hit a wall) this is what is called an Impedance
Missmatch.? The original wave will continue on the thick rope until it
hits the wall on the thick rope and the wave will reflect back along
the thick rope (Impedance mismatch between the thick rope and the wall).
So what we see now is a wave traveling back along the thin rope (first
reflection from the impedance mismatch between the thick and thin
ropes) and we see the original wave starting to travel back from the
wall along the thick rope.
When that reflected wave of the original signal on the thick rope that
is traveling back from the wall hits the junction with the thin rope,
some of that wave will move onto the thin rope and some of that wave
will reflect back towards the wall (because of the Impedance mismatch
between the two ropes).
So what we see now (depending on the length of the thin rope compared
to the thick rope) is a reflection of the original wave from the
junction of the two ropes traveling back at you, and a smaller
reflection of the original wave traveling back to you that bounced off
the wall and crossed the rope junction, and a reflection of that from
the rope junction traveling back towards the wall on the thick rope.
The space between the two impedance matches will have reflections
sloshing back and forth diminishing over time.
Lets say you gave the original signal one sine wave, (one up down back
to center flip), and you listened to the rope, you would first see a
small reflection back from the rope junction, then a larger (depending
on all the impedance mismatches) from the signal that reflected back
from the wall, then you would continue to see smaller and smaller
signals coming from the ringing in the thick rope that escaped over
the rope junction.
There is more technical detail with phase changes and such but that
can get in the way of understanding the fundamental effects of
Impedance mismatches.
So Impedance matches are important to limit reflections which is
another way of saying resistance to your signal getting to the antenna
or back from the antenna. The SWR? Standing Wave Ratio is a measure of
the transmitted energy to the reflected energy and is a measure of how
much of your signal makes it through to the antenna. So devices that
have an impedance rating like 50 ohms are geared to connect to other
50 ohm devices and not reflect much energy. So readings should be more
accurate because nothing is lost in the connection between devices.
Hope this narrative helps you understand some of those issues on a
very coarse level. But good and important information esp. for low
power operations like the ubitx and other QRP rigs.
? ?---John AC9UV
On 06/09/2021 2:20 PM Gerard <kabupos@...> wrote:
Hello,
I am sorry to ask the question here, but I have not yet received a
specific answer on the subject on the agilent group.
My question is simple: When we say that an analyzer has a input RF of
50 ohms, what does that mean? I don¡¯t think it¡¯s so simple.....
I take an ohmeter on the input RF N, what i have to get?? 50 ohms,
infinity, or something other? you may see my topic here:
[email protected] | Hp8558b spectral analyzer
(2/2)
</g/HP-Agilent-Keysight-equipment/topic/hp8558b_spectral_analyzer/83405508?p=,,,20,0,0,0::recentpostdate%2Fsticky,,,20,2,0,83405508>
I¡¯m stuck on my diagnosis
cdt
|
Larry G4GZG
What makes you suspect a lack of QC during assembly?? We need more? definitive?information in order to address any possible assembly problem.??
What version of uBITX do you have? What are your symptoms? What band were you using to test on? What voltage was being fed to the uBITX? What test equipment?were you using to determine the problem?
Each BITX board is powered and tested for proper operation prior?to? it being shipped to a customer.? Possibly something was missed or too? subtle to be found during factory testing, but 7000+ field tested units? would indicate that it was probably not a manufacturing?defect.
Arv? K7HKL _._
On Thu, Jun 10, 2021 at 7:32 AM Lawrence Stringer via <g4gzg= [email protected]> wrote: My Ubitx? ( From India) has this problem.? Basically its joined the queue? in the corner of the shack of stuff needing attention. I'll get round to it some day but in the meantime my old K1 is doing the QRP job.
I suspect lack of QC at the assembly point .
Larry G4GZG.
|
On 2021-06-10 09:52, Evan Hand wrote: Any "0" values for components are not installed. C261 & C262 have 0
value on the schematic. Makes sense. The sort of thing that you adjust as a design matures. I was going from the snippet of schematic in the Theory of Operation document. A bit out of date - as elaborate documentation often is. - Jerry
|
Re: Impedance 50 ohm Spectral analyzer HP8558B
On 2021-06-10 10:03, John Putnum, AC9UV wrote: ...Physics is a wonderful template that ---John AC9UCV All, I'd like to paraphrase a physics thing that came across my desk on Quora: What is electrical current? I always thought that current was movement of electrons. You sit at a point, watch the electrons go by, that's current. As opposed to voltage, which is what's pushing the electrons. The electrons race through the wires at the speed of light. This physicist on Quora said that the above is totally bogus & false. He was quite passionate about it. What current actually is, he said, is movement of *charge*. What is charge? Charge is ( I guess ) the energy state of an electron. This electron transfers its charge ( higher energy state ) to the next electron, the *charge* propagates from electron to electron at the speed of light. More or less. Can depend on the insulation. Why? Darned if I know, but it's important when you're trying to cut an antenna or a transmission line transformer. I'm thinking it's something like that desk toy with the hanging balls in a row. Aka "Newton's Cradle". - Jerry KF6VB
|
If it is self oscillation you should be able to shift the frequency by? touching the feedback part of that with a screwdriver or a test lead.
Arv _._
I am looking a the schematic of the transmit chain.? I possibly need to
check all the bypass caps.? C86, C92 etc.? Also the
negative feedback caps, C261 & C262.? And the values of the
negative feedback resistors.? Bypass caps can be checked by scoping the
hot end for RF.
? ?I used to do this stuff for a living, but that was 40 years ago.
Hopefully it's like riding a bicycle :).? If it is an oscillation,
those are hard to find because everything oscillates at once...
? ? ? ? ? ? ? ? ? ? ? ? - Jerry KF6VB
On 2021-06-10 06:01, jerry@... wrote:
> Rafael,
>
>? ? I was thinking exactly this last night.? Self oscillation of the
> final stage around 2MHz?? Mixing with the outgoing CW?
>
>? ? If so, maybe it would oscillate also on SSB mode?? I'll try that
> today.
>
>? ? ? ? ? ? ?- Jerry KF6VB
>
>
>
> On 2021-06-10 05:30, Rafael Pinto [PU1OWL] wrote:
>> Jerry,
>>
>> Can this be some form of self-oscillation? It is so bad, this looks
>> like single-tone FM!!
>>
>> Rafael Pinto
>>
>>
>> Links:
>> ------
>> [1] /g/BITX20/message/89084
>> [2] /mt/83413015/243852
>> [3] /g/BITX20/post
>> [4] /g/BITX20/editsub/243852
>> [5] /g/BITX20/leave/10189903/243852/952924773/xyzzy
>
>
>
|
Jerry,
Those used to be 100nF in v3, but since v4 they are not fitted, if I remember it correctly, to improve the gain in the top bands.?
Rafael
|
Re: Impedance 50 ohm Spectral analyzer HP8558B
Bob,
Glad that analogy found a home. Physics is a wonderful template that can be applied over many seemingly disparate situations. Jargon can get in the way of understanding, but at the same time is a good shorthand if you understand the fundamental meaning behind the words.
---John AC9UCV
toggle quoted message
Show quoted text
On 06/10/2021 10:20 AM Robert D. Bowers <n4fbz@...> wrote:
That is an EXCELLENT analogy.? I'd never thought of it that way, but it
brings everything in... including things like phase angle.? (I'd never
heard or read that one before... )
Where it gets interesting is when you have a thin cord, a thick rope,
and then another thin cord (or some combination thereof)... SWR, line
losses, you name it also are well illustrated by that analogy!? (GRIN!)
Bob
N4FBZ
On 6/9/21 6:54 PM, John Putnum, AC9UV wrote:
CDT,
Well a simple answer is that there are two parts to Impedance. One
part is the resistance that can be measured by your ohm meter. That is
DC resistance. When you apply an ac signal to the device, then if
there is some magnetic materials that would create magnetic fields an
Inductive component along with the static electric fields (an
Inductive component) then you get some components that impede the flow
of electricity, hence impedance. The reason that is important is that
if impedances are matched then the signal flows through the circuit
without much loss (loss due to the dc resistance).? They call that
impedance matching.? You can see some of those effects with waves on
the water. If the waves hit a barrier then the waves are reflected
back. If they don't hit a barrier they just keep going.
fIf you have a rope tied to wall and shake the rope, the wave goes to
the wall and is reflected back. But if you have a thin rope tied to a
much thicker rope that is then connected to the wall then when you
shake the rope, when the wave hits the junction of the thin and the
thick rope, some physics magic happens, some of the wave moves into
the thick rope but some of the wave is reflected back to the thin rope
(as though it kind of hit a wall) this is what is called an Impedance
Missmatch.? The original wave will continue on the thick rope until it
hits the wall on the thick rope and the wave will reflect back along
the thick rope (Impedance mismatch between the thick rope and the wall).
So what we see now is a wave traveling back along the thin rope (first
reflection from the impedance mismatch between the thick and thin
ropes) and we see the original wave starting to travel back from the
wall along the thick rope.
When that reflected wave of the original signal on the thick rope that
is traveling back from the wall hits the junction with the thin rope,
some of that wave will move onto the thin rope and some of that wave
will reflect back towards the wall (because of the Impedance mismatch
between the two ropes).
So what we see now (depending on the length of the thin rope compared
to the thick rope) is a reflection of the original wave from the
junction of the two ropes traveling back at you, and a smaller
reflection of the original wave traveling back to you that bounced off
the wall and crossed the rope junction, and a reflection of that from
the rope junction traveling back towards the wall on the thick rope.
The space between the two impedance matches will have reflections
sloshing back and forth diminishing over time.
Lets say you gave the original signal one sine wave, (one up down back
to center flip), and you listened to the rope, you would first see a
small reflection back from the rope junction, then a larger (depending
on all the impedance mismatches) from the signal that reflected back
from the wall, then you would continue to see smaller and smaller
signals coming from the ringing in the thick rope that escaped over
the rope junction.
There is more technical detail with phase changes and such but that
can get in the way of understanding the fundamental effects of
Impedance mismatches.
So Impedance matches are important to limit reflections which is
another way of saying resistance to your signal getting to the antenna
or back from the antenna. The SWR? Standing Wave Ratio is a measure of
the transmitted energy to the reflected energy and is a measure of how
much of your signal makes it through to the antenna. So devices that
have an impedance rating like 50 ohms are geared to connect to other
50 ohm devices and not reflect much energy. So readings should be more
accurate because nothing is lost in the connection between devices.
Hope this narrative helps you understand some of those issues on a
very coarse level. But good and important information esp. for low
power operations like the ubitx and other QRP rigs.
? ?---John AC9UV
On 06/09/2021 2:20 PM Gerard <kabupos@...> wrote:
Hello,
I am sorry to ask the question here, but I have not yet received a
specific answer on the subject on the agilent group.
My question is simple: When we say that an analyzer has a input RF of
50 ohms, what does that mean? I don¡¯t think it¡¯s so simple.....
I take an ohmeter on the input RF N, what i have to get?? 50 ohms,
infinity, or something other? you may see my topic here:
[email protected] | Hp8558b spectral analyzer
(2/2)
</g/HP-Agilent-Keysight-equipment/topic/hp8558b_spectral_analyzer/83405508?p=,,,20,0,0,0::recentpostdate%2Fsticky,,,20,2,0,83405508>
I¡¯m stuck on my diagnosis
cdt
|
Jerry,
Any "0" values for components are not installed.? C261 & C262 have 0 value on the schematic.? They are not installed.
73
Evan
AC9TU
|
A quick inspection of the v6 motherboard...
C261 & C262....
....Seem to be missing.
These are the negative feedback caps for the final transistors,
Q94 & Q95. There are surface mount lands for them, but no parts
installed.
Their associated resistors, R261 & R262, *are* installed.
Exact spec for these capacitors? Voltage rating, SMD size etc?
Not going to be easy to install these - they're almost right under the final transistors. Tweezers and smd rework air gun...
- Jerry KF6VB
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Show quoted text
On 2021-06-10 07:32, jerry@... wrote: Here's a tinySA of the output on 40M. Much nicer than 20, but still
not good. 3rd harmonic is only 23dB below the fundamental. Other
bands ( besides 20 ) are similar.
- Jerry KF6VB
|
Re: Impedance 50 ohm Spectral analyzer HP8558B
hello,
News from the internal attenuator of this 8558B HP
As this is a mechanical attenuator (Action of a rotary button only), I did this little test.
Disconnect in and out attenuator.?it is autonomous now
Sending a sinusoidal signal 10 MHZ with a generator via a resistor of 50 ohm
Oscilloscope measurement input and output.
As I turn the button, the signal drops out (constant input).
The method is not very academic and I am not amused to convert to DB. I am allergic to all measures in DB (LOL)
I think it works, because it¡¯s a constant decay, even if you only see a few millivolts 3 notches before the end of the rotation. (For only 0.3v input)
I did not want to force too much the signal to the enter?
I think it¡¯s not burned, so I¡¯m gonna look at something else
cdt
|
Re: Impedance 50 ohm Spectral analyzer HP8558B
That is an EXCELLENT analogy.? I'd never thought of it that way, but it brings everything in... including things like phase angle.? (I'd never heard or read that one before... )
Where it gets interesting is when you have a thin cord, a thick rope, and then another thin cord (or some combination thereof)... SWR, line losses, you name it also are well illustrated by that analogy!? (GRIN!)
Bob
N4FBZ
toggle quoted message
Show quoted text
On 6/9/21 6:54 PM, John Putnum, AC9UV wrote: CDT,
Well a simple answer is that there are two parts to Impedance. One part is the resistance that can be measured by your ohm meter. That is DC resistance. When you apply an ac signal to the device, then if there is some magnetic materials that would create magnetic fields an Inductive component along with the static electric fields (an Inductive component) then you get some components that impede the flow of electricity, hence impedance. The reason that is important is that if impedances are matched then the signal flows through the circuit without much loss (loss due to the dc resistance).? They call that impedance matching.? You can see some of those effects with waves on the water. If the waves hit a barrier then the waves are reflected back. If they don't hit a barrier they just keep going.
fIf you have a rope tied to wall and shake the rope, the wave goes to the wall and is reflected back. But if you have a thin rope tied to a much thicker rope that is then connected to the wall then when you shake the rope, when the wave hits the junction of the thin and the thick rope, some physics magic happens, some of the wave moves into the thick rope but some of the wave is reflected back to the thin rope (as though it kind of hit a wall) this is what is called an Impedance Missmatch.? The original wave will continue on the thick rope until it hits the wall on the thick rope and the wave will reflect back along the thick rope (Impedance mismatch between the thick rope and the wall).
So what we see now is a wave traveling back along the thin rope (first reflection from the impedance mismatch between the thick and thin ropes) and we see the original wave starting to travel back from the wall along the thick rope.
When that reflected wave of the original signal on the thick rope that is traveling back from the wall hits the junction with the thin rope, some of that wave will move onto the thin rope and some of that wave will reflect back towards the wall (because of the Impedance mismatch between the two ropes).
So what we see now (depending on the length of the thin rope compared to the thick rope) is a reflection of the original wave from the junction of the two ropes traveling back at you, and a smaller reflection of the original wave traveling back to you that bounced off the wall and crossed the rope junction, and a reflection of that from the rope junction traveling back towards the wall on the thick rope.
The space between the two impedance matches will have reflections sloshing back and forth diminishing over time.
Lets say you gave the original signal one sine wave, (one up down back to center flip), and you listened to the rope, you would first see a small reflection back from the rope junction, then a larger (depending on all the impedance mismatches) from the signal that reflected back from the wall, then you would continue to see smaller and smaller signals coming from the ringing in the thick rope that escaped over the rope junction.
There is more technical detail with phase changes and such but that can get in the way of understanding the fundamental effects of Impedance mismatches.
So Impedance matches are important to limit reflections which is another way of saying resistance to your signal getting to the antenna or back from the antenna. The SWR? Standing Wave Ratio is a measure of the transmitted energy to the reflected energy and is a measure of how much of your signal makes it through to the antenna. So devices that have an impedance rating like 50 ohms are geared to connect to other 50 ohm devices and not reflect much energy. So readings should be more accurate because nothing is lost in the connection between devices.
Hope this narrative helps you understand some of those issues on a very coarse level. But good and important information esp. for low power operations like the ubitx and other QRP rigs.
? ?---John AC9UV
On 06/09/2021 2:20 PM Gerard <kabupos@...> wrote:
Hello,
I am sorry to ask the question here, but I have not yet received a specific answer on the subject on the agilent group.
My question is simple: When we say that an analyzer has a input RF of 50 ohms, what does that mean? I don¡¯t think it¡¯s so simple.....
I take an ohmeter on the input RF N, what i have to get?? 50 ohms, infinity, or something other? you may see my topic here:
[email protected] | Hp8558b spectral analyzer (2/2) </g/HP-Agilent-Keysight-equipment/topic/hp8558b_spectral_analyzer/83405508?p=,,,20,0,0,0::recentpostdate%2Fsticky,,,20,2,0,83405508>
I¡¯m stuck on my diagnosis
cdt
|
Here's a tinySA of the output on 40M. Much nicer than 20, but still not good. 3rd harmonic is only 23dB below the fundamental. Other bands ( besides 20 ) are similar.
- Jerry KF6VB
|
Re: Chinese Linear R.I.P.
PU1OWL,
I would suggest going the attenuator route as some of the Chinese amps have a high SWR mismatch on the input.? The attenuator would reduce that to some extent.
I would also suggest that you start with the SWR meter between the rig and the amp with RV1 turned down (maximum clockwise, the control is reversed) for less than a watt and slowly increase noting the SWR.
For the one that I have been working on, I found it to be very sensitive to both bias and input levels.? ?I went through 3 sets of IRF520s until I got it to work.? The kit that I received could not set the bias to the correct value.? I had to modify the bias circuit.? I also put a 16ohm resistor across the secondary of the input transformer to get the SWR under control.
The amp is on the shelf right now as I need to verify that 20meters is in compliance.? At the time I built it I did not have a good way to measure the third harmonic on the upper frequencies.? It was more of a how it works sort of project, as I have my Icom 7300 if I want to go QRO.
You defiantly need proper test equipment to verify that the amp meets compliance requirements and the skill to use them.? It was a real learning experience for me.
73
Evan
AC9TU
|
Jerry,
Maybe a signal comparison with an oscilloscope starting with TP3 to TP7.? Other than the half-wave aspect of TP5 and TP7 it should be just an amplified signal.
Just a thought.
73
Evan
AC9TU
|
I have the following for sale. I had bought the kit hoping to
put together and find
I don't have the time to finish this project and other obligations
at the same time.
Asking less for what I paid.
I have the following;
- uBitX kit with v5 board
?
- 5" Nextion Display flashed and working with the Raduino
- Universal Case Black For uBitx Nextion Display Fitting 5 Inch
?
- Black 3D printed bezel for the case and Nextion Display
I had hooked up the encoder and is correctly working with the Raduino
everything originally sent with the
Universal Case, 5" Nexton Display and uBitx kit will be
included!
If
you want any particular picture of the contents let me know.
The Kit will be nicely packed for shipping!
With in the Continental USA shipping only, $250+ Shipping and
accept PayPal.
73,
Marty KD4HLV
|
My Ubitx? ( From India) has this problem.? Basically its joined the queue? in the corner of the shack of stuff needing attention. I'll get round to it some day but in the meantime my old K1 is doing the QRP job.
I suspect lack of QC at the assembly point .
Larry G4GZG.
|
I am looking a the schematic of the transmit chain. I possibly need to check all the bypass caps. C86, C92 etc. Also the
negative feedback caps, C261 & C262. And the values of the
negative feedback resistors. Bypass caps can be checked by scoping the hot end for RF.
I used to do this stuff for a living, but that was 40 years ago.
Hopefully it's like riding a bicycle :). If it is an oscillation,
those are hard to find because everything oscillates at once...
- Jerry KF6VB
toggle quoted message
Show quoted text
|
I've ordered some BFR106.? Looking forward to building a post-mixer amp.
The suggestion of the Si5351 is interesting too.? In my Specan, I packaged the Si570 in the first mixer module thinking to minimize the distance between oscillator and mixer.? But I forgot about the temperature rise generated by the MAV/GALI buffer amps in a small enclosed box.? I'm thinking about switching to the Si5351, locating it near the Nano/display, and using it to generate the two oscillator clocks similar to the uBITX architecture.? I'm also hoping that this will generate stronger drive to the mixers.
--
David KV4FP
|
Rafael,
I was thinking exactly this last night. Self oscillation of the final stage around 2MHz? Mixing with the outgoing CW?
If so, maybe it would oscillate also on SSB mode? I'll try that
today.
- Jerry KF6VB
toggle quoted message
Show quoted text
|
Hi Evan,
Yes, CW. Using the mic button to key, with the speed set to 1WPM. Have not modified the V6. The test setup:
v6 -> Narda 30dB attenuator -> tinySA.
- Jerry
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|
Rafael Pinto [PU1OWL]
Gerard
