Topics

One question only...


Christopher Miller
 

I wonder what the spurious emissions were like on this! The ARRL owns a spark gap transmitter that is housed in W1AW for what it is worth. They dont use it, though I think the time I was there they said they did once a year but whatever. I bet it is way worse than your uBitx. Enjoy!


On Mon, Aug 6, 2018 at 11:04 PM Timothy Fidler <engstr@...> wrote:
Belay all that .. Japanese LPF cct sent to the VK who is designing a replacement board.  It gets 5 bands out of three signals ie 00 is also interpreted as a command. as usual old Timmo Fidler went off half cocked but at least the archives kicked in.


Bill Cromwell
 

Hi Walt,

I still believe the problems can and will be overcome. There should be a flurry of activity while all the Bitx machines get updated with the fixes. I am sure it won't be as simple as a patch made of old chewing gum and a rubber band but it won't be like giving up an arm and a leg, either. I could be wrong. I was wrong once. I thought I had made a mistake but I hadn't <evil grin>.

There ARE some things to say about people who 'buy a Rigol' and concluding their findings must be accurate. Some can use them and some can't. This is really not the place to be parading credentials. There are people who can get the results with or without a 'Rigol' and others who can't even if they are shown a screen print. Spending time on that won't really resolve anything and will just create hard feelings. We need everybody aboard to get this radio on course. We can be sure there are issues. Debates about who said what and when they said it will not correct the problems. Only create more problems and maybe doom the radio to the landfill.

I won't be putting mine on the air until I have some sturdy filters on the output muzzling the spew. I am expecting an eventual, practical resolution to the problems:) This how 'open source' works :)

73,

Bill KU8H

On 08/07/2018 12:29 AM, WaltR wrote:
Hello Bill,

Its very unfortunate that a well intended kit that was assembled with
questionable quality parts, circuit and several other anomalies beyond
my comprehension, is in its present quandary. The principals it appears,
had good intentions and are to be commended for that. However, they have
no authority in North America. In fact the Border agencies of both our
countries are probably raising their eyebrows over the entire fiasco,
If not they soon will be. As I said earlier in my position As XO on
board ship I can’t afford to run afoul of the authorities so my bitx 40
and ubitx have been destroyed. Sad really, I will be looking at the kits
from QRP LABS. Or maybe I should purchase a good used FT817.
As an aside I had SIGINT techs look at the harmonic signature on the
Harris, Wolfsburg and Bendix King gear and found them to exceed
requirements by 30%, but of course again I’m comparing caviar to
peanuts. My wife chastises me for my attitude ergo I’m at sea for 6
months of the year. I’m trying to do better hi hi. It’s no wonder I’m
not allowed in the house before dark.

The sheer number of builders, the responses in this group, would suggest
that there is a strong need for a simple affordable all band QRP rig,
that is a fact, It will be interesting to see what happens in the next
while.

In the research I have done there are some kits available from China,
Russia and also Malaysia , they may be more in cost but perhaps ???


On a final observation you can buy all kinds of brands of test gear but
there are only certain brands that are deemed to be certification
instruments when operated by a certified knowledgeable technician, just
because you go out and buy a Rigol
doesnt mean that now you are instantly an industry expert.

Early day tomorrow, anchors aweigh at 0400

cheers and 73
WRS
--
bark less - wag more


ajparent1/KB1GMX <kb1gmx@...>
 

Rigol is a satisfactory machine if used properly.  Its big advanatage is price, for what it is and can do its a deal
you can't even get the attention of Keysight (Hp ne Agilent now...) refurbished equipment for that kind of money.

That said..

I've seen people using HP do stupid things and claim but the machine said such and so.  I've done it the hard
way for decades and every time I get a piece of gear life gets easier and I had to learn to use it correctly.  Most
if not all of the measurements discussed are not hard to do and do not require exotic gear but will require patience
and knowing how to perform the measurement.

To that end a copy of EMRFD the section on tests and measurements is well worth it.

Allison


m5fra2@...
 

The thing with any test equipment, apart from knowing how to use it,  is regular calibration.

 

Colin – M5FRA

 

From: BITX20@groups.io <BITX20@groups.io> On Behalf Of ajparent1/KB1GMX
Sent: 07 August 2018 15:13
To: BITX20@groups.io
Subject: Re: [BITX20] One question only...

 

Rigol is a satisfactory machine if used properly.  Its big advanatage is price, for what it is and can do its a deal
you can't even get the attention of Keysight (Hp ne Agilent now...) refurbished equipment for that kind of money.

That said..

I've seen people using HP do stupid things and claim but the machine said such and so.  I've done it the hard
way for decades and every time I get a piece of gear life gets easier and I had to learn to use it correctly.  Most
if not all of the measurements discussed are not hard to do and do not require exotic gear but will require patience
and knowing how to perform the measurement.

To that end a copy of EMRFD the section on tests and measurements is well worth it.

Allison


ajparent1/KB1GMX <kb1gmx@...>
 

Colin,

Two parts to that.  Local calibration standards commercial or home made work.
They are the day to day reference or needed in some gear to cal out cables and 
such.   I also have a set of precision mismatches that I've made, measured 
and recorded for testing if the gear is in question.  It also helpful for others as 
with known fixtures and standards I can help them get to a nominal cal.

The other is a budget.  Around here we budget a bit for ESSCO to cal the gear
as its then official to paying clients where traceability may be important. For 
the average ham though if the unit was in cal and the standards still read the 
same save your currency for other things.

To bring this down to earth.  A bunch of known value capacitors, resistors,
and an crystal oscillator of known stability checked against WWV or other
reliable frequency sources are easy to build and use tools to calibrate 
home made instruments with.   Even radio stations are handy as they
can be a reference and calibration point.  

However expensive and precision calibration is not required to get answers
good to more than 3 significant digits.  Often that's more than enough.

Allison


K5ESS
 

Probably has an exception per the great-great-great grandfather clause.

Mike

K5ESS

 

From: BITX20@groups.io [mailto:BITX20@groups.io] On Behalf Of Christopher Miller
Sent: Tuesday, August 7, 2018 1:13 AM
To: BITX20@groups.io
Subject: Re: [BITX20] One question only...

 

I wonder what the spurious emissions were like on this! The ARRL owns a spark gap transmitter that is housed in W1AW for what it is worth. They dont use it, though I think the time I was there they said they did once a year but whatever. I bet it is way worse than your uBitx. Enjoy!

 

On Mon, Aug 6, 2018 at 11:04 PM Timothy Fidler <engstr@...> wrote:

Belay all that .. Japanese LPF cct sent to the VK who is designing a replacement board.  It gets 5 bands out of three signals ie 00 is also interpreted as a command. as usual old Timmo Fidler went off half cocked but at least the archives kicked in.


Jerry Gaffke
 

Not all that great.
In he early 1970s one of my dad's acquaintances was an elderly ham, and was shedding his junkbox.
Gave it to me.
In addition to a couple dozen 810 transmitting triodes (late 1930's), there were four Ford ignition coils.

Here's a link about the W1AW spark gap transmitter:
    http://www.arrl.org/news/hpm-s-old-betsy-is-made-new-to-wow-the-crowds

Spark gap transmitters continued to be used on lifeboats (in at least a few places) till maybe 50 years ago.
Proven reliable technology for short distances, the sailors had long known to use and repair it.
And was something you could repair with a pocket knife and pair of pliers.

From    http://home.freeuk.net/dunckx/wireless/sparksnarcs/sparksnarcs.html

".... In the right foreground, labelled K, are four of the eight condensers. The zinc plate and glass condensers were immersed in oil and each was kept in a metal tank - hence the origin of the name "tank circuit" to describe the power output tuned circuit of a transmitter. .....
.....  spark generation of r.f. power proved amazingly durable, surviving until well after the Second World War. According to the British General Post Office "Handbook for Wireless Operators" published by Her Majesty's Stationery Office in 1954, spark transmission was still permitted on 500kc/s as emergency signalling reserve for ships, lifeboats etc ...."



An operating 10kW spark gap transmitter would make quite an impression.
Cool stuff.

Jerry, KE7ER
 


On Tue, Aug 7, 2018 at 01:47 PM, K5ESS wrote:

Probably has an exception per the great-great-great grandfather clause.

Mike

K5ESS

 

. . .

 

From: BITX20@groups.io [mailto:BITX20@groups.io] On Behalf Of Christopher Miller
Sent: Tuesday, August 7, 2018 1:13 AM
To: BITX20@groups.io
Subject: Re: [BITX20] One question only...

 

I wonder what the spurious emissions were like on this! The ARRL owns a spark gap transmitter that is housed in W1AW for what it is worth. They dont use it, though I think the time I was there they said they did once a year but whatever. I bet it is way worse than your uBitx. Enjoy!

 

On Mon, Aug 6, 2018 at 11:04 PM Timothy Fidler <engstr@...> wrote:

Belay all that .. Japanese LPF cct sent to the VK who is designing a replacement board.  It gets 5 bands out of three signals ie 00 is also interpreted as a command. as usual old Timmo Fidler went off half cocked but at least the archives kicked in.


m5fra2@...
 

Alison,

 

I should explain, it used to be my job, the repair and re-cal of scopes and spectrum analysers. It is different in a commercial/safety critical environment but without decent calibration you are working blind. Agreed, for amateur use there is a need to know where you are, roughly, and it all goes with knowing how to use the gear. Not saying that any of the tests done on the LPFs are wrong or that people do not know what they are doing but I think all users should be aware of the issues when using such gear.

 

Colin – M5FRA

 

From: BITX20@groups.io <BITX20@groups.io> On Behalf Of ajparent1/KB1GMX
Sent: 07 August 2018 18:32
To: BITX20@groups.io
Subject: Re: [BITX20] One question only...

 

Colin,

Two parts to that.  Local calibration standards commercial or home made work.
They are the day to day reference or needed in some gear to cal out cables and 
such.   I also have a set of precision mismatches that I've made, measured 
and recorded for testing if the gear is in question.  It also helpful for others as 
with known fixtures and standards I can help them get to a nominal cal.

The other is a budget.  Around here we budget a bit for ESSCO to cal the gear
as its then official to paying clients where traceability may be important. For 
the average ham though if the unit was in cal and the standards still read the 
same save your currency for other things.

To bring this down to earth.  A bunch of known value capacitors, resistors,
and an crystal oscillator of known stability checked against WWV or other
reliable frequency sources are easy to build and use tools to calibrate 
home made instruments with.   Even radio stations are handy as they
can be a reference and calibration point.  

However expensive and precision calibration is not required to get answers
good to more than 3 significant digits.  Often that's more than enough.

Allison


Ralph Mowery
 

When I was working part of my job was the calibration of instruments for a company that made polyester material. We had equipment that was sent off on a schedule to check it met standards.  Our on line instruments were verified by those.

You have to know the limitations of the equipment.  I had a good discussion with a production engineer on this.  He cold not understand why the computer readout that was showing 3 decimal places of temperature at about 300 deg C was off by 2 whole numbers.  All this was coming from a probe that had 2 RTDs and 2 thermocouples  in the same 1/2 inch tube.  He wanted to know which one was correct.  I told him to take his choice as they all were.  The TC and rtd were only rated at 2 deg C at that temperature by the makers.  Then each went through a sending unit  that was calibrated to 1/2 of a percent or less, then to the computer unit that had about the same error.  When all the errors were added together we were lucky to get with in 1 % , mostly 2 %.  However we could read to 3 decimal places.

The whole point is that with most parts used in the uBITX and other ham grade equipment is only 5 % or maybe even less, it is pointless to measure a filter cutoff at 12 MHz to within a couple of cycles or a db down.  You may be able to build one that way, but not mass produce them.

I found the filter in my uBITX was too sharp for me and the audio quality on transmit was not what I wanted.  I Changed the capacitors in the filter area  with some standard components.  I can, but did not measure to 10 hz or less, but did get a general overall curve that met my standards, and my friends I talk to all the time said it sounded very good to them.

de ku4pt


On Wed, Aug 8, 2018 at 1:34 AM, m5fra2 via Groups.Io <m5fra2@...> wrote:

Alison,

 

I should explain, it used to be my job, the repair and re-cal of scopes and spectrum analysers. It is different in a commercial/safety critical environment but without decent calibration you are working blind. Agreed, for amateur use there is a need to know where you are, roughly, and it all goes with knowing how to use the gear. Not saying that any of the tests done on the LPFs are wrong or that people do not know what they are doing but I think all users should be aware of the issues when using such gear.

 

Colin – M5FRA

 


ajparent1/KB1GMX <kb1gmx@...>
 

Colin,

My comments were more global, not in disagreement. 

I do work as a antenna and RF development engineer. mostly research and prototype
development.  So I think after a lot of decades I have a handle on equipment and cals. 
Most calibration is so you can prove the equipment works and for those rare precise
measurements required by spec to be traceable to a known standard even if production
has to tune every one to get it and the application doesn't really need it.

Answer to more than a few significant digits are sometime required 
but when you using reasistors, inductors, and capacitors typically only spec'ed to three
places any more precision is silly and base accuracy of a a few percent is adequate.

Practical knowledge, experience and application says who cares if the filter cutoff
is 5, 897,765.4hz if the real meaningful measure is less than needed attenuation at
third harmonic regardless of the measured value.

Allison


Jerry Gaffke
 

Even in the workplace, sending gear out for calibration is often a CYA maneuver.
If a customer sues due to a failure it's a way to demonstrate due diligence.
There certainly are cases where calibration is warranted from a technical standpoint,
but in my experience they are the exception.

For hobby use, getting most of us to spend money for a calibration service would be
a very hard sell.  Someone who has designed and built their own spectrum analyzer
from scratch will be in a much better position to evaluate results than someone
twisting knobs on a "calibrated" $20k system. 

Jerry, KE7ER


m5fra2@...
 

Alison,

 

And of course any calibration is to manufacturers specs so being precise is always within those boundaries.

 

Colin

 

From: BITX20@groups.io <BITX20@groups.io> On Behalf Of ajparent1/KB1GMX
Sent: 08 August 2018 16:56
To: BITX20@groups.io
Subject: Re: [BITX20] One question only...

 

Colin,

My comments were more global, not in disagreement. 

I do work as a antenna and RF development engineer. mostly research and prototype
development.  So I think after a lot of decades I have a handle on equipment and cals. 
Most calibration is so you can prove the equipment works and for those rare precise
measurements required by spec to be traceable to a known standard even if production
has to tune every one to get it and the application doesn't really need it.

Answer to more than a few significant digits are sometime required 
but when you using reasistors, inductors, and capacitors typically only spec'ed to three
places any more precision is silly and base accuracy of a a few percent is adequate.

Practical knowledge, experience and application says who cares if the filter cutoff
is 5, 897,765.4hz if the real meaningful measure is less than needed attenuation at
third harmonic regardless of the measured value.

Allison


Jerry Gaffke
 

I'm liking the looks of Arv's minimalist spectrum analyzer more and more.
Simple, sufficient for evaluating all the uBitx spurs (including any harmonics).
Perhaps somebody could kit it up such that it mates to a $3 Nano,
reports to a PC via the serial monitor.  Or to an LCD display.
Might take as little as $10 in raw parts cost?

The series tuned trap at the input could be left out.
If I'm measuring the 2'd harmonic and happen to also get some of the 4'th and/or 6'th, 
that's just going to add a dB or so to the measurement.   We're worried about
the sum of all those harmonics anyway.

Calibrate it first. 
The uBitx transmitting in CW mode feeding a 50 ohm dummy load is a good signal source.
Measure across the dummy load using a diode RF probe, set RV1 for about 1W using the RF probe before each measurement.
At one Watt of RF, that's sqrt(1Watt*50ohms) = 7.07 Volts RMS, or 10 volts peak, or 20 volts peak-to-peak into the RF probe.
Shield the rig and dummy load well, and maybe the first 20dB of attenuation after the dummy load too.
Set Arv's step attenuator to give the same reading out of his 2n3904 at each frequency you are calibrating for,
and record that attenuator setting. 

When looking at some dirt, set the step attenuator to give the same reading from the 2n3904 as you calibrated for.
The difference between that attenuator setting and the attenuator setting you recorded during calibration
is how many dB down from 1 Watt the offending dirt is.

Could watch the audio AC output of that 2n3904 using a diode rectifier feeding your Harbor Freight voltmeter.
Slowly sweep the frequency of the si5351 around the vicinity of the spur for maximum reading.

If everything proves linear enough, could slowly sweep the si5351 from 3 to 30mhz
and read the diode rectifier using a Nano ADC pin.
The Nano's program report any spurs found to a host PC through the Nano's serial monitor.  
The Nano's 10bit ADC has a maximum range of around 60dB, should easily cover a 40dB range accurately.
More than sufficient for evaluating our spurs, assuming the step attenuator gets set up correctly
before kicking off the sweep.
 
Jerry, KE7ER



On Sun, Aug 5, 2018 at 12:54 PM, Arv Evans wrote:
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 Evans
 

Jerry

Maybe add a python program on the attached PC to log level outputs and convert
that data into a conventional spectrum analysis diagram.  The possible mods just
Arv
_._


On Thu, Aug 9, 2018 at 12:42 PM Jerry Gaffke via Groups.Io <jgaffke=yahoo.com@groups.io> wrote:
I'm liking the looks of Arv's minimalist spectrum analyzer more and more.
Simple, sufficient for evaluating all the uBitx spurs (including any harmonics).
Perhaps somebody could kit it up such that it mates to a $3 Nano,
reports to a PC via the serial monitor.  Or to an LCD display.
Might take as little as $10 in raw parts cost?

The series tuned trap at the input could be left out.
If I'm measuring the 2'd harmonic and happen to also get some of the 4'th and/or 6'th, 
that's just going to add a dB or so to the measurement.   We're worried about
the sum of all those harmonics anyway.

Calibrate it first. 
The uBitx transmitting in CW mode feeding a 50 ohm dummy load is a good signal source.
Measure across the dummy load using a diode RF probe, set RV1 for about 1W using the RF probe before each measurement.
At one Watt of RF, that's sqrt(1Watt*50ohms) = 7.07 Volts RMS, or 10 volts peak, or 20 volts peak-to-peak into the RF probe.
Shield the rig and dummy load well, and maybe the first 20dB of attenuation after the dummy load too.
Set Arv's step attenuator to give the same reading out of his 2n3904 at each frequency you are calibrating for,
and record that attenuator setting. 

When looking at some dirt, set the step attenuator to give the same reading from the 2n3904 as you calibrated for.
The difference between that attenuator setting and the attenuator setting you recorded during calibration
is how many dB down from 1 Watt the offending dirt is.

Could watch the audio AC output of that 2n3904 using a diode rectifier feeding your Harbor Freight voltmeter.
Slowly sweep the frequency of the si5351 around the vicinity of the spur for maximum reading.

If everything proves linear enough, could slowly sweep the si5351 from 3 to 30mhz
and read the diode rectifier using a Nano ADC pin.
The Nano's program report any spurs found to a host PC through the Nano's serial monitor.  
The Nano's 10bit ADC has a maximum range of around 60dB, should easily cover a 40dB range accurately.
More than sufficient for evaluating our spurs, assuming the step attenuator gets set up correctly
before kicking off the sweep.
 
Jerry, KE7ER



On Sun, Aug 5, 2018 at 12:54 PM, Arv Evans wrote:
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. 

 


Arvo W0VRA
 

On Thu, Aug 9, 2018 at 01:55 PM, Arv Evans wrote:
Maybe add a python program on the attached PC to log level outputs and convert
that data into a conventional spectrum analysis diagram.
Has anyone looked into using SDRplay's new spectrum analysis software?


ajparent1/KB1GMX <kb1gmx@...>
 

Easy way for the less technical builder...

DVB-T dongle, Upconverter, PC or Andriod tablet with software pick one. Done.

Likely the PC or tablet is already around.  I got a cheap 4core android for 35$(in 2016) at Walmart.
The DVB-T about 20$.
The upconverter about 40$ Nooelec.  Or make it its a crystal source, DBM 
and two filters.  Schematics on the net.
Just a fast look at Amazon no doubt both can be found much cheaper.

The software.  I paid $4 for the android version because it was no ads and
worked well as the free version.  The Linux PC, Rpi, and windows versions are free.
 
There you have it a system that goes from MW through L band (1750mhz some higher).
It can serves well as a useful SA, wide tuning radio receiver and more.  FYI the
1750mhz  beats Rigol and HP (both top at 1500mhz) and there are a few sticks that
go past 2500mhz.

I will likely hear those DVB-t stick have limited dynamic range.. not a problem!
Use that with the substitution procedure and you will get any accuracy you want
if you take the time and effort.  With a really good attenuator and care you can
even beat lab grade!  Your not testing the stick, its a tuned detector.

We now have a working, portable SA for cheap.  With a RF source and patience
you can measure  SWR, return loss, filters, coils and caps at working frequency,
cable length, Panaramic adaptor for uBitx, receiver for the FM receiver for
SSB/CW EasySats, and test ones  imagination.  Likely need more  DVB-T sticks.

Allison


Doug W
 

I already had a rt-sdr and upconverter and thought I could figure out how to make it work.  Your post is perfectly timed.  Just yesterday I ordered the connectors I was missing to cobble it all together.

I was just reading about https://github.com/pavels/spektrum anyone ever use it?
--
www.bitxmap.com


Jerry Gaffke
 

Arv's mixer+si5351 would be easier to understand and hack,
no download of some bloated SDR software package required. 

The DVB-T route can be good, especially if interested in VHF and beyond.
Perhaps Arv's circuit could also serve as an up-converter so a DVB-T could be used at HF?

To be "easy" for anybody who hasn't done it already
there needs to be a couple pages of really explicit instructions.
Be it for Arv's mixer+si5351  or the DVB-T thing.

Jerry



On Thu, Aug 9, 2018 at 12:15 PM, ajparent1/KB1GMX wrote:
Easy way for the less technical builder...

DVB-T dongle, Upconverter, PC or Andriod tablet with software pick one. Done.

Likely the PC or tablet is already around.  I got a cheap 4core android for 35$(in 2016) at Walmart.
The DVB-T about 20$.
The upconverter about 40$ Nooelec.  Or make it its a crystal source, DBM 
and two filters.  Schematics on the net.
Just a fast look at Amazon no doubt both can be found much cheaper.


Arv Evans
 

Jerry, and others...

My little system is just a direct conversion receiver with Si5351a LO for wide frequency
coverage.  There are lots of potential ways to improve on the idea.

Arv
_._


On Thu, Aug 9, 2018 at 2:12 PM Jerry Gaffke via Groups.Io <jgaffke=yahoo.com@groups.io> wrote:
Arv's mixer+si5351 would be easier to understand and hack,
no download of some bloated SDR software package required. 

The DVB-T route can be good, especially if interested in VHF and beyond.
Perhaps Arv's circuit could also serve as an up-converter so a DVB-T could be used at HF?

To be "easy" for anybody who hasn't done it already
there needs to be a couple pages of really explicit instructions.
Be it for Arv's mixer+si5351  or the DVB-T thing.

Jerry



On Thu, Aug 9, 2018 at 12:15 PM, ajparent1/KB1GMX wrote:
Easy way for the less technical builder...

DVB-T dongle, Upconverter, PC or Andriod tablet with software pick one. Done.

Likely the PC or tablet is already around.  I got a cheap 4core android for 35$(in 2016) at Walmart.
The DVB-T about 20$.
The upconverter about 40$ Nooelec.  Or make it its a crystal source, DBM 
and two filters.  Schematics on the net.
Just a fast look at Amazon no doubt both can be found much cheaper.


Jerry Gaffke
 

Correction:  down-converter.
Unless you somehow got a DVB-T USB dongle that can transmit.


On Thu, Aug 9, 2018 at 01:11 PM, Jerry Gaffke wrote:
Perhaps Arv's circuit could also serve as an up-converter so a DVB-T could be used at HF?