Topics

One question only...


ajparent1/KB1GMX <kb1gmx@...>
 

Kees,

I disagree.  Its not opinion its measurements many more than a few stock.   
The sample size I've had opportunity to test grows as where I am there
are a lot of hams that build or do kits.  A few I've tested remotely by listening for
the spurs and they are heard. 

Also the BITX and the uBitx are very different in one area.  The Bitx20/40 and 17
commercial kits and many of the scratch builds are good as they all have adequate
filtering for spurs.  They are generally monoband and the few multiband versions
use per band filters that work with switching. 

The ubitx has only two filter groups the 30mhz low pass after T2 which allows anything
below about 31-33mhz (filter cutoff) to the amp and the tail end low pass filters
(switched, 4 of them) and in the 20mhz to 30mhz range the tail end filter is 30mhz
cutoff so everything below 30 mhz make it to the antenna.  That is the problem
there is no filtering at all below 30mhz.

The base design has a few holes and for 80-17M its OK for harmonics and spurs.
OK, means it may be marginal but a resonant antenna or tuner will be fine.
After all we are only trying to hit -43dbc.

The 20 to 30mhz region the spur issue is a no easy solution and 100% have it. 
Push for any power out and it gets worse.  People with tech license that want
10M will push as 2W is really poor.  I would not blame them either.  There is
only low pass so any spurs that are lower than 30mhz make to the antenna. 
Again a resonant antenna and a matchbox can help hide or lower its impact
it but its a design omission (adequate filtering before the amp).

It is part of the larger set of issues with the transmit side.  Most fixable but
the board layout is a contributing factor or makes it difficult.

Its biggest feature is a open RX that does from whatever the lower limit
in software to 30mhz.

Trust but verify, applies.

Allison


Arv Evans
 

Doug

It is actually 21.0107562936529321 percent.   8-)

No, I don't believe that either, because it has not been verified and may not be
verifiable.

Arv
_._



On Sun, Aug 5, 2018 at 8:55 AM Doug W <dougwilner@...> wrote:
Since we're on the topic of FCC regulations, while I have never seen an official statistic, I would venture to guess well over 90% of US hams violate 97.313(a) every single time they transmit.


--
www.bitxmap.com


Arv Evans
 

Gordon

Several years ago Hans G0UPL started marketing his SI5351a based VFO kit.  With that as
a very stable LO and a balanced mixer to LPF to Audio voltmeter it is possible to make a simple
receiver for chasing spurs, harmonics, and gremlins.  Of course it was impossible to resist
adding oscilloscope display and rewriting the software to scan specific frequency ranges.  Now
I have a direct-conversion spectrum scanner that can be calibrated and used to track ghosts
and goblins emanating from my home-brew builds.  Calibration is done by use of a fixed-value
step attenuator for 1, 2, 4, 5, 10, 20, 40, and 50 db. 
This has been a work-in-progress for several years and just keeps getting better as I find ways
to modify and to use it. 

Arv
_._


On Sun, Aug 5, 2018 at 10:07 AM Gordon Gibby <ggibby@...> wrote:
How could we make measurements of signal level accurately? Compared to fundamental?   Note  I would probably be using a 2nd uBitx as the receiver.


Gordon



On Aug 5, 2018, at 11:53, ajparent1/KB1GMX <kb1gmx@...> wrote:

On Sun, Aug 5, 2018 at 07:55 AM, Doug W wrote:
97.313(a)
A KW is the minimum power according to some. ;)

Snark:  For me 100W is serious QRO for HF.  At VHF I'm just warming up the driver.

Allison


Jack, W8TEE
 

That would make a great article!

Jack, W8TEE

On Sunday, August 5, 2018, 1:46:23 PM EDT, Arv Evans <arvid.evans@...> wrote:


Gordon

Several years ago Hans G0UPL started marketing his SI5351a based VFO kit.  With that as
a very stable LO and a balanced mixer to LPF to Audio voltmeter it is possible to make a simple
receiver for chasing spurs, harmonics, and gremlins.  Of course it was impossible to resist
adding oscilloscope display and rewriting the software to scan specific frequency ranges.  Now
I have a direct-conversion spectrum scanner that can be calibrated and used to track ghosts
and goblins emanating from my home-brew builds.  Calibration is done by use of a fixed-value
step attenuator for 1, 2, 4, 5, 10, 20, 40, and 50 db. 
This has been a work-in-progress for several years and just keeps getting better as I find ways
to modify and to use it. 

Arv
_._

On Sun, Aug 5, 2018 at 10:07 AM Gordon Gibby <ggibby@...> wrote:
How could we make measurements of signal level accurately? Compared to fundamental?   Note  I would probably be using a 2nd uBitx as the receiver.


Gordon



On Aug 5, 2018, at 11:53, ajparent1/KB1GMX <kb1gmx@...> wrote:

On Sun, Aug 5, 2018 at 07:55 AM, Doug W wrote:
97.313(a)
A KW is the minimum power according to some. ;)

Snark:  For me 100W is serious QRO for HF.  At VHF I'm just warming up the driver.

Allison


Arv Evans
 

Jack

The design won't stay still long enough to write an article.    8-)

It is actually pretty simple.  I used a 50 ohm resistor as the input to the balanced mixer.
That lets me use the step-attenuator (also home-brewed) for input calibration.  Plug-in
filters can be added to the front-end but normally I just use a tunable series LC to suck
out unwanted frequencies (2nd or 3rd or other harmonics of the LO).  Output of the mixer
goes through a termination (stolen from the BITX BFO mixer design), followed by an
emitter follower 2N3904 to feed audio to a voltmeter, or oscilloscope, or fldigi on Linux.

A PCB would be nice if I could ever settle on not making any more modifications.  To do
that I would have to draw a schematic, which has not happened yet.  It is just one of those
things that sets on a shelf above the workbench and gets used whenever needed.

Arv
_._


On Sun, Aug 5, 2018 at 11:51 AM Jack Purdum via Groups.Io <jjpurdum=yahoo.com@groups.io> wrote:
That would make a great article!

Jack, W8TEE

On Sunday, August 5, 2018, 1:46:23 PM EDT, Arv Evans <arvid.evans@...> wrote:


Gordon

Several years ago Hans G0UPL started marketing his SI5351a based VFO kit.  With that as
a very stable LO and a balanced mixer to LPF to Audio voltmeter it is possible to make a simple
receiver for chasing spurs, harmonics, and gremlins.  Of course it was impossible to resist
adding oscilloscope display and rewriting the software to scan specific frequency ranges.  Now
I have a direct-conversion spectrum scanner that can be calibrated and used to track ghosts
and goblins emanating from my home-brew builds.  Calibration is done by use of a fixed-value
step attenuator for 1, 2, 4, 5, 10, 20, 40, and 50 db. 
This has been a work-in-progress for several years and just keeps getting better as I find ways
to modify and to use it. 

Arv
_._

On Sun, Aug 5, 2018 at 10:07 AM Gordon Gibby <ggibby@...> wrote:
How could we make measurements of signal level accurately? Compared to fundamental?   Note  I would probably be using a 2nd uBitx as the receiver.


Gordon



On Aug 5, 2018, at 11:53, ajparent1/KB1GMX <kb1gmx@...> wrote:

On Sun, Aug 5, 2018 at 07:55 AM, Doug W wrote:
97.313(a)
A KW is the minimum power according to some. ;)

Snark:  For me 100W is serious QRO for HF.  At VHF I'm just warming up the driver.

Allison


F1BFU - Fr - 79
 

Hi Arv

your experimentation interests me. I'm finishing building QRPLabs VFO / SigGen with Relay Card to switch LPFs. I also have a K5BCQ attenuator. I would like to understand your use of the QRP Labs Signal Generator.
Please can you give me a little diagram of your editing ?

Many thnaks Arv

Le dim. 5 août 2018 à 20:05, Arv Evans <arvid.evans@...> a écrit :
Jack

The design won't stay still long enough to write an article.    8-)

It is actually pretty simple.  I used a 50 ohm resistor as the input to the balanced mixer.
That lets me use the step-attenuator (also home-brewed) for input calibration.  Plug-in
filters can be added to the front-end but normally I just use a tunable series LC to suck
out unwanted frequencies (2nd or 3rd or other harmonics of the LO).  Output of the mixer
goes through a termination (stolen from the BITX BFO mixer design), followed by an
emitter follower 2N3904 to feed audio to a voltmeter, or oscilloscope, or fldigi on Linux.

A PCB would be nice if I could ever settle on not making any more modifications.  To do
that I would have to draw a schematic, which has not happened yet.  It is just one of those
things that sets on a shelf above the workbench and gets used whenever needed.

Arv
_._


On Sun, Aug 5, 2018 at 11:51 AM Jack Purdum via Groups.Io <jjpurdum=yahoo.com@groups.io> wrote:
That would make a great article!

Jack, W8TEE

On Sunday, August 5, 2018, 1:46:23 PM EDT, Arv Evans <arvid.evans@...> wrote:


Gordon

Several years ago Hans G0UPL started marketing his SI5351a based VFO kit.  With that as
a very stable LO and a balanced mixer to LPF to Audio voltmeter it is possible to make a simple
receiver for chasing spurs, harmonics, and gremlins.  Of course it was impossible to resist
adding oscilloscope display and rewriting the software to scan specific frequency ranges.  Now
I have a direct-conversion spectrum scanner that can be calibrated and used to track ghosts
and goblins emanating from my home-brew builds.  Calibration is done by use of a fixed-value
step attenuator for 1, 2, 4, 5, 10, 20, 40, and 50 db. 
This has been a work-in-progress for several years and just keeps getting better as I find ways
to modify and to use it. 

Arv
_._

On Sun, Aug 5, 2018 at 10:07 AM Gordon Gibby <ggibby@...> wrote:
How could we make measurements of signal level accurately? Compared to fundamental?   Note  I would probably be using a 2nd uBitx as the receiver.


Gordon



On Aug 5, 2018, at 11:53, ajparent1/KB1GMX <kb1gmx@...> wrote:

On Sun, Aug 5, 2018 at 07:55 AM, Doug W wrote:
97.313(a)
A KW is the minimum power according to some. ;)

Snark:  For me 100W is serious QRO for HF.  At VHF I'm just warming up the driver.

Allison


Gordon Gibby <ggibby@...>
 

Thanks very much, that is a fascinating idea for a poor man spectrum analyzer.  

Gordon



On Aug 5, 2018, at 14:13, Gilles Delpech <gilles.f1bfu@...> wrote:

Hi Arv

your experimentation interests me. I'm finishing building QRPLabs VFO / SigGen with Relay Card to switch LPFs. I also have a K5BCQ attenuator. I would like to understand your use of the QRP Labs Signal Generator.
Please can you give me a little diagram of your editing ?

Many thnaks Arv

Le dim. 5 août 2018 à 20:05, Arv Evans <arvid.evans@...> a écrit :
Jack

The design won't stay still long enough to write an article.    8-)

It is actually pretty simple.  I used a 50 ohm resistor as the input to the balanced mixer.
That lets me use the step-attenuator (also home-brewed) for input calibration.  Plug-in
filters can be added to the front-end but normally I just use a tunable series LC to suck
out unwanted frequencies (2nd or 3rd or other harmonics of the LO).  Output of the mixer
goes through a termination (stolen from the BITX BFO mixer design), followed by an
emitter follower 2N3904 to feed audio to a voltmeter, or oscilloscope, or fldigi on Linux.

A PCB would be nice if I could ever settle on not making any more modifications.  To do
that I would have to draw a schematic, which has not happened yet.  It is just one of those
things that sets on a shelf above the workbench and gets used whenever needed.

Arv
_._


On Sun, Aug 5, 2018 at 11:51 AM Jack Purdum via Groups.Io <jjpurdum=yahoo.com@groups.io> wrote:
That would make a great article!

Jack, W8TEE

On Sunday, August 5, 2018, 1:46:23 PM EDT, Arv Evans <arvid.evans@...> wrote:


Gordon

Several years ago Hans G0UPL started marketing his SI5351a based VFO kit.  With that as
a very stable LO and a balanced mixer to LPF to Audio voltmeter it is possible to make a simple
receiver for chasing spurs, harmonics, and gremlins.  Of course it was impossible to resist
adding oscilloscope display and rewriting the software to scan specific frequency ranges.  Now
I have a direct-conversion spectrum scanner that can be calibrated and used to track ghosts
and goblins emanating from my home-brew builds.  Calibration is done by use of a fixed-value
step attenuator for 1, 2, 4, 5, 10, 20, 40, and 50 db. 
This has been a work-in-progress for several years and just keeps getting better as I find ways
to modify and to use it. 

Arv
_._

On Sun, Aug 5, 2018 at 10:07 AM Gordon Gibby <ggibby@...> wrote:
How could we make measurements of signal level accurately? Compared to fundamental?   Note  I would probably be using a 2nd uBitx as the receiver.


Gordon



On Aug 5, 2018, at 11:53, ajparent1/KB1GMX <kb1gmx@...> wrote:

On Sun, Aug 5, 2018 at 07:55 AM, Doug W wrote:
97.313(a)
A KW is the minimum power according to some. ;)

Snark:  For me 100W is serious QRO for HF.  At VHF I'm just warming up the driver.

Allison


Gordon Gibby <ggibby@...>
 

I have a couple of mixers sitting around waiting on me, and I already made my own si5351 digital VFO, so if I had the time this would be a great project, get my hands on some step attenuators.


On Aug 5, 2018, at 14:28, Gordon Gibby <ggibby@...> wrote:

Thanks very much, that is a fascinating idea for a poor man spectrum analyzer.  

Gordon



On Aug 5, 2018, at 14:13, Gilles Delpech <gilles.f1bfu@...> wrote:

Hi Arv

your experimentation interests me. I'm finishing building QRPLabs VFO / SigGen with Relay Card to switch LPFs. I also have a K5BCQ attenuator. I would like to understand your use of the QRP Labs Signal Generator.
Please can you give me a little diagram of your editing ?

Many thnaks Arv

Le dim. 5 août 2018 à 20:05, Arv Evans <arvid.evans@...> a écrit :
Jack

The design won't stay still long enough to write an article.    8-)

It is actually pretty simple.  I used a 50 ohm resistor as the input to the balanced mixer.
That lets me use the step-attenuator (also home-brewed) for input calibration.  Plug-in
filters can be added to the front-end but normally I just use a tunable series LC to suck
out unwanted frequencies (2nd or 3rd or other harmonics of the LO).  Output of the mixer
goes through a termination (stolen from the BITX BFO mixer design), followed by an
emitter follower 2N3904 to feed audio to a voltmeter, or oscilloscope, or fldigi on Linux.

A PCB would be nice if I could ever settle on not making any more modifications.  To do
that I would have to draw a schematic, which has not happened yet.  It is just one of those
things that sets on a shelf above the workbench and gets used whenever needed.

Arv
_._


On Sun, Aug 5, 2018 at 11:51 AM Jack Purdum via Groups.Io <jjpurdum=yahoo.com@groups.io> wrote:
That would make a great article!

Jack, W8TEE

On Sunday, August 5, 2018, 1:46:23 PM EDT, Arv Evans <arvid.evans@...> wrote:


Gordon

Several years ago Hans G0UPL started marketing his SI5351a based VFO kit.  With that as
a very stable LO and a balanced mixer to LPF to Audio voltmeter it is possible to make a simple
receiver for chasing spurs, harmonics, and gremlins.  Of course it was impossible to resist
adding oscilloscope display and rewriting the software to scan specific frequency ranges.  Now
I have a direct-conversion spectrum scanner that can be calibrated and used to track ghosts
and goblins emanating from my home-brew builds.  Calibration is done by use of a fixed-value
step attenuator for 1, 2, 4, 5, 10, 20, 40, and 50 db. 
This has been a work-in-progress for several years and just keeps getting better as I find ways
to modify and to use it. 

Arv
_._

On Sun, Aug 5, 2018 at 10:07 AM Gordon Gibby <ggibby@...> wrote:
How could we make measurements of signal level accurately? Compared to fundamental?   Note  I would probably be using a 2nd uBitx as the receiver.


Gordon



On Aug 5, 2018, at 11:53, ajparent1/KB1GMX <kb1gmx@...> wrote:

On Sun, Aug 5, 2018 at 07:55 AM, Doug W wrote:
97.313(a)
A KW is the minimum power according to some. ;)

Snark:  For me 100W is serious QRO for HF.  At VHF I'm just warming up the driver.

Allison


Arv Evans
 

Giles  F1BFU

I am not close to my hamshack to check for accuracy. 
The attached drawing shows the general idea from what I can remember.
Sweepy.png
Looking at this reminded me that with very little change it could be made
into a CW or swept frequency signal generator (Si5351a out through mixer
and attenuator, with audio into mixer to modulate carrier).  Every time I look
at this it seem to suggest yet another modification. 

Arv
_._



On Sun, Aug 5, 2018 at 12:13 PM Gilles Delpech <gilles.f1bfu@...> wrote:
Hi Arv

your experimentation interests me. I'm finishing building QRPLabs VFO / SigGen with Relay Card to switch LPFs. I also have a K5BCQ attenuator. I would like to understand your use of the QRP Labs Signal Generator.
Please can you give me a little diagram of your editing ?

Many thnaks Arv

Le dim. 5 août 2018 à 20:05, Arv Evans <arvid.evans@...> a écrit :
Jack

The design won't stay still long enough to write an article.    8-)

It is actually pretty simple.  I used a 50 ohm resistor as the input to the balanced mixer.
That lets me use the step-attenuator (also home-brewed) for input calibration.  Plug-in
filters can be added to the front-end but normally I just use a tunable series LC to suck
out unwanted frequencies (2nd or 3rd or other harmonics of the LO).  Output of the mixer
goes through a termination (stolen from the BITX BFO mixer design), followed by an
emitter follower 2N3904 to feed audio to a voltmeter, or oscilloscope, or fldigi on Linux.

A PCB would be nice if I could ever settle on not making any more modifications.  To do
that I would have to draw a schematic, which has not happened yet.  It is just one of those
things that sets on a shelf above the workbench and gets used whenever needed.

Arv
_._


On Sun, Aug 5, 2018 at 11:51 AM Jack Purdum via Groups.Io <jjpurdum=yahoo.com@groups.io> wrote:
That would make a great article!

Jack, W8TEE

On Sunday, August 5, 2018, 1:46:23 PM EDT, Arv Evans <arvid.evans@...> wrote:


Gordon

Several years ago Hans G0UPL started marketing his SI5351a based VFO kit.  With that as
a very stable LO and a balanced mixer to LPF to Audio voltmeter it is possible to make a simple
receiver for chasing spurs, harmonics, and gremlins.  Of course it was impossible to resist
adding oscilloscope display and rewriting the software to scan specific frequency ranges.  Now
I have a direct-conversion spectrum scanner that can be calibrated and used to track ghosts
and goblins emanating from my home-brew builds.  Calibration is done by use of a fixed-value
step attenuator for 1, 2, 4, 5, 10, 20, 40, and 50 db. 
This has been a work-in-progress for several years and just keeps getting better as I find ways
to modify and to use it. 

Arv
_._

On Sun, Aug 5, 2018 at 10:07 AM Gordon Gibby <ggibby@...> wrote:
How could we make measurements of signal level accurately? Compared to fundamental?   Note  I would probably be using a 2nd uBitx as the receiver.


Gordon



On Aug 5, 2018, at 11:53, ajparent1/KB1GMX <kb1gmx@...> wrote:

On Sun, Aug 5, 2018 at 07:55 AM, Doug W wrote:
97.313(a)
A KW is the minimum power according to some. ;)

Snark:  For me 100W is serious QRO for HF.  At VHF I'm just warming up the driver.

Allison


Jerry Gaffke
 

Arv,

I like it, nice and simple.

I'd consider a 50mhz LPF up front, another mixer, mmic amp, and one of these 86.85mhz SAW filters:
    https://wireless.murata.com/RFM/data/px1002.pdf
Then no worries about those harmonics.

Fully analyzing the audio tones using an FFT on an ARM processor should give
sufficient resolution for stuff like evaluating phase noise.

The simple direct conversion mixer means you get both sidebands.
But that software on the ARM could figure out which audio tones go up and which go down
as your VFO moves, and thus separate out high from low sidebands.

I've been thinking of building something like this for a couple years,
have not yet tried.
 
Jerry, KE7ER


On Sun, Aug 5, 2018 at 12:54 PM, Arv Evans wrote:
The attached drawing shows the general idea from what I can remember.
 


Jerry Gaffke
 

Of course, my suggestions make it not so simple.
And somehow anything capable of phase noise measurements
must also deal with a very powerful carrier, not trivial.



On Sun, Aug 5, 2018 at 01:19 PM, Jerry Gaffke wrote:
Arv,

I like it, nice and simple.

I'd consider a 50mhz LPF up front, another mixer, mmic amp, and one of these 86.85mhz SAW filters:
    https://wireless.murata.com/RFM/data/px1002.pdf
Then no worries about those harmonics.

Fully analyzing the audio tones using an FFT on an ARM processor should give
sufficient resolution for stuff like evaluating phase noise.

The simple direct conversion mixer means you get both sidebands.
But that software on the ARM could figure out which audio tones go up and which go down
as your VFO moves, and thus separate out high from low sidebands.

I've been thinking of building something like this for a couple years,
have not yet tried.
 
Jerry, KE7ER


Arv Evans
 

Jerry

This thing started out as an attempt to see if a simple receiver could be made to work
without any tuned front-end.  It does work, but received a lot that I did not want to hear.
That experiment then morphed into a fixed-gain receiver for evaluating received signal
levels.  Eventually rampant modifications brought it to this stage of development.  There
is still much more that can be done with the idea.

Your idea of directionalizing frequency movement is good, and is already being used to
determine the N-value of harmonics (2nd moves at twice frequency changes, 3rd at
3-times, and so on). 

Method of operation at present is to note level of spurious signal, then add attenuation
until the primary signal is at the same level.  Reading on the attenuator is then assumed
to be the level difference between primary and spurious.

Arv
_._


On Sun, Aug 5, 2018 at 2:19 PM Jerry Gaffke via Groups.Io <jgaffke=yahoo.com@groups.io> wrote:
Arv,

I like it, nice and simple.

I'd consider a 50mhz LPF up front, another mixer, mmic amp, and one of these 86.85mhz SAW filters:
    https://wireless.murata.com/RFM/data/px1002.pdf
Then no worries about those harmonics.

Fully analyzing the audio tones using an FFT on an ARM processor should give
sufficient resolution for stuff like evaluating phase noise.

The simple direct conversion mixer means you get both sidebands.
But that software on the ARM could figure out which audio tones go up and which go down
as your VFO moves, and thus separate out high from low sidebands.

I've been thinking of building something like this for a couple years,
have not yet tried.
 
Jerry, KE7ER


On Sun, Aug 5, 2018 at 12:54 PM, Arv Evans wrote:
The attached drawing shows the general idea from what I can remember.
 


F1BFU - Fr - 79
 

Many thanks Arv.
I will try in this way and I will keep you informed.

Gilles F1BFU / FR

Le dim. 5 août 2018 à 21:54, Arv Evans <arvid.evans@...> a écrit :
Giles  F1BFU

I am not close to my hamshack to check for accuracy. 
The attached drawing shows the general idea from what I can remember.
Sweepy.png
Looking at this reminded me that with very little change it could be made
into a CW or swept frequency signal generator (Si5351a out through mixer
and attenuator, with audio into mixer to modulate carrier).  Every time I look
at this it seem to suggest yet another modification. 

Arv
_._



On Sun, Aug 5, 2018 at 12:13 PM Gilles Delpech <gilles.f1bfu@...> wrote:
Hi Arv

your experimentation interests me. I'm finishing building QRPLabs VFO / SigGen with Relay Card to switch LPFs. I also have a K5BCQ attenuator. I would like to understand your use of the QRP Labs Signal Generator.
Please can you give me a little diagram of your editing ?

Many thnaks Arv

Le dim. 5 août 2018 à 20:05, Arv Evans <arvid.evans@...> a écrit :
Jack

The design won't stay still long enough to write an article.    8-)

It is actually pretty simple.  I used a 50 ohm resistor as the input to the balanced mixer.
That lets me use the step-attenuator (also home-brewed) for input calibration.  Plug-in
filters can be added to the front-end but normally I just use a tunable series LC to suck
out unwanted frequencies (2nd or 3rd or other harmonics of the LO).  Output of the mixer
goes through a termination (stolen from the BITX BFO mixer design), followed by an
emitter follower 2N3904 to feed audio to a voltmeter, or oscilloscope, or fldigi on Linux.

A PCB would be nice if I could ever settle on not making any more modifications.  To do
that I would have to draw a schematic, which has not happened yet.  It is just one of those
things that sets on a shelf above the workbench and gets used whenever needed.

Arv
_._


On Sun, Aug 5, 2018 at 11:51 AM Jack Purdum via Groups.Io <jjpurdum=yahoo.com@groups.io> wrote:
That would make a great article!

Jack, W8TEE

On Sunday, August 5, 2018, 1:46:23 PM EDT, Arv Evans <arvid.evans@...> wrote:


Gordon

Several years ago Hans G0UPL started marketing his SI5351a based VFO kit.  With that as
a very stable LO and a balanced mixer to LPF to Audio voltmeter it is possible to make a simple
receiver for chasing spurs, harmonics, and gremlins.  Of course it was impossible to resist
adding oscilloscope display and rewriting the software to scan specific frequency ranges.  Now
I have a direct-conversion spectrum scanner that can be calibrated and used to track ghosts
and goblins emanating from my home-brew builds.  Calibration is done by use of a fixed-value
step attenuator for 1, 2, 4, 5, 10, 20, 40, and 50 db. 
This has been a work-in-progress for several years and just keeps getting better as I find ways
to modify and to use it. 

Arv
_._

On Sun, Aug 5, 2018 at 10:07 AM Gordon Gibby <ggibby@...> wrote:
How could we make measurements of signal level accurately? Compared to fundamental?   Note  I would probably be using a 2nd uBitx as the receiver.


Gordon



On Aug 5, 2018, at 11:53, ajparent1/KB1GMX <kb1gmx@...> wrote:

On Sun, Aug 5, 2018 at 07:55 AM, Doug W wrote:
97.313(a)
A KW is the minimum power according to some. ;)

Snark:  For me 100W is serious QRO for HF.  At VHF I'm just warming up the driver.

Allison


Jerry Gaffke
 

Hmm,  
Any tone from the second harmonic would move twice as fast as the fundamental.
And 3x for the third harmonic etc.
So distinguishing that stuff in software, we might get by without that 86.85mhz IF filter.
And no front end LC.

So same as your schematic, but a $2 Blue Pill ARM board for the processor?
Something with a 16 bit ADC to listen to the audio with?

Jerry


On Sun, Aug 5, 2018 at 01:29 PM, Jerry Gaffke wrote:
Of course, my suggestions make it not so simple.
And somehow anything capable of phase noise measurements
must also deal with a very powerful carrier, not trivial.

On Sun, Aug 5, 2018 at 01:19 PM, Jerry Gaffke wrote:
Arv,

I like it, nice and simple.

I'd consider a 50mhz LPF up front, another mixer, mmic amp, and one of these 86.85mhz SAW filters:
    https://wireless.murata.com/RFM/data/px1002.pdf
Then no worries about those harmonics.

Fully analyzing the audio tones using an FFT on an ARM processor should give
sufficient resolution for stuff like evaluating phase noise.

The simple direct conversion mixer means you get both sidebands.
But that software on the ARM could figure out which audio tones go up and which go down
as your VFO moves, and thus separate out high from low sidebands.

I've been thinking of building something like this for a couple years,
have not yet tried.
 
Jerry, KE7ER


Kees T
 

Yes, Allison, Trust But Verify.

I have not had the opportunity to test a number of STOCK uBITX Transceivers to see what the spurs look like. You have apparently had a chance to look at a number of them so I defer to your assessment.  It does surprise me a little.

Guess the only clean solution is to just add a switchable Low Pass Filter (LPF) to the 5-10W output for the "culprit" frequencies you are going to use, maybe just the higher frequencies ?.....can't hurt, unless you forget to switch it to the correct band. W8DIZ used to offer a kit and I'm sure there are others out there now.

What would you suggest ? Do you know of any switchable LPFs out there ? I was fiddling around with a LPF/BPF unit years ago.  The LPFs were based on a W3NQN article from Feb 1999 QST. They worked well when tested in a professional lab.

73 Kees K5BCQ

Here is an excerpt from my website........ schematics are on my website too

  • These boards all have a 2.5" x 0.6" form factor and come in two varieties, BPF or LPF. Redundant header pins are located at both ends (or you can solder directly), The designs are symetrical so the boards can be reversed or flipped without effect. The boards can be used standalone and plugged one at a time or used with a switcheable host board of your design or mine (available later). I have the bare boards only and header pins available for $2 per board plus postage in the USA. Toroids are listed below (the capacitors are all 630V or 1KV NPO 1206/1210 size SMT. You would use one of the free programs like Jim Tonne's, ELSIE, or other filter program (AADE, etc) for the appropriate values for your needs.



Jerry Gaffke
 

Ah, you beat me to it!
Jerry


On Sun, Aug 5, 2018 at 01:56 PM, Arv Evans wrote:
Your idea of directionalizing frequency movement is good, and is already being used to
determine the N-value of harmonics (2nd moves at twice frequency changes, 3rd at
3-times, and so on). 


Kees T
 

Jerry,

We probably need another thread for Spectrum Analyzers since this one is "Does the uBITX have spurs and how to get rid of them".

Relative to a SA, I would consider using a EU1KY VIA as a base, Jack probably has more info ?

73 Kees K5BCQ


ajparent1/KB1GMX <kb1gmx@...>
 

Kees,

It didn't surprise me.  I was part of the minima and followed along with bitx before that
before it became Groups.IO.  Call it history.

The other part is any DBM your put in two signals and get a truck load out.
The buld of them are of the F, 2F, nF, harmonics of both pairs and their
sums and differences...  The running joke is a DBM is three ports of
consternation and pain.  Then to take the output unfiltered and amp it up.
on the assumption of a low pass filter fixes everything except all the signals
the result from differences.

The case that hit the fan was the last stage at 28.0 lets say.  The mixer has 
45mhz (more exactly 15khz lower but round numbers) and 73mhz to get 28mhz
and 118 mhz out.  the filter grabs the 118 and it is gone.  We forget the 2f,
so 90mhz (2*IF) -73 is 17mhz and that makes it thought he filter with the 28mhz.
So someone smartly says but only when your talking... but the uBitx has carrier
leakage so there is always 45mhz going to the mixer we only can talk about
magnitude. and since the drive is square and later found to be low drive as well
diodes make good hash chopping everything up (making harmonics like mad).

The result is the output above 20 mhz is unfiltered for the most part as the only
two in the system have a cutoff above 30mhz.   There is an amplifier in between
making all of the undesirables bigger. for the SSB case...

So the question is not if but how bad.  Measured result was confirmed as
typically less than -43 Dbc and more like anywhere from -29 to -34 on samples
at 2W out on 10M.  Push up the audio to get 3-4W and it gets really bad.

Also the drive to the DBM is preceded by a 6db pad to improve the match
but the drive to that pad is about 3dbm or worse so the mixer has a 6db lower
overload threshold being about 17db lesss than the drive which is -3dbm
resulting in -20dbm.  The poor mixer is starving along with the other two.
Doesn't help the case as we have a lot of gain between them despite the
filter losses (uuder 4db each).  Overload is inevitable.

Warren noted that the output of the radio in CW mode is rich in harmonics and 
at best marginal against the -43dbc limit.  Why?  Transformer and mixer at T2
is used as a switch during CW TX and the SI5351 is set to deliver the output 
frequency and turn off osc 1 and 0.  So the output of T2 is a square wave
at 3.5mhz and the first filter is about 31-33mhz so it passes up to the 9th harmonic
as it should into the power amp and the 7 element filter at the output has 
to try and clean it up.  Well that a fail.  So another systemic problem due
to insufficient band pass filtering where it can do some good.  But we have
a wide open RX that tunes 3-30 with ease complete with its own birdies.

So as you can see analysis and experience had me saying 3 or 4 years ago a 
band pass system is required.

Allison


Kees T
 

Good "One Question Only..." question you asked,  Brian L. Davis.

73 Kees K5BCQ


Arv Evans
 

Jerry

A several months ago I purchased one of the Blue Pill boards but it is just sitting
here on the workbench waiting for a suitable project.  It does look nice though.

Arv
_._


On Sun, Aug 5, 2018 at 3:05 PM Jerry Gaffke via Groups.Io <jgaffke=yahoo.com@groups.io> wrote:
Hmm,  
Any tone from the second harmonic would move twice as fast as the fundamental.
And 3x for the third harmonic etc.
So distinguishing that stuff in software, we might get by without that 86.85mhz IF filter.
And no front end LC.

So same as your schematic, but a $2 Blue Pill ARM board for the processor?
Something with a 16 bit ADC to listen to the audio with?

Jerry


On Sun, Aug 5, 2018 at 01:29 PM, Jerry Gaffke wrote:
Of course, my suggestions make it not so simple.
And somehow anything capable of phase noise measurements
must also deal with a very powerful carrier, not trivial.

On Sun, Aug 5, 2018 at 01:19 PM, Jerry Gaffke wrote:
Arv,

I like it, nice and simple.

I'd consider a 50mhz LPF up front, another mixer, mmic amp, and one of these 86.85mhz SAW filters:
    https://wireless.murata.com/RFM/data/px1002.pdf
Then no worries about those harmonics.

Fully analyzing the audio tones using an FFT on an ARM processor should give
sufficient resolution for stuff like evaluating phase noise.

The simple direct conversion mixer means you get both sidebands.
But that software on the ARM could figure out which audio tones go up and which go down
as your VFO moves, and thus separate out high from low sidebands.

I've been thinking of building something like this for a couple years,
have not yet tried.
 
Jerry, KE7ER