Date   
Re: reverse polarity protection (ubitx.net)

Mike Woods
 

MVS Sarma

It is the drawing of the jack that people are referring to, not the positioning of the fuse!
The vertical bar would normally represent the sleeve - and you have this connected to the fuse and on to +12v?   Shouldn't the sleeve and the tip be reversed in the diagram?  Or do you normally have the sleeve positive and the tip negative (some people do - but most don't) in which case the diode is shown incorrectly!

73
Mike

On 8/08/18 12:34 AM, Mvs Sarma wrote:
Sarma surely responds.
 The reverse protection diode has been shown in the ubitx sch , both v3 and v4 perhaps.
 I would only suggest that let us have a fuse in series to dc of say 5 amps. the reverse diode would sit after the fuse to ground.
 Any accidental reverse connection , the fuse would blow and reverse voltage would not continue to the actual circuit, once fuse blows.


Regards
MVS Sarma
 

On Tue, Aug 7, 2018 at 1:56 PM, Mike Woods <mhwoods@...> wrote:
Jonathan

I will add PH2LB's reverse voltage protection solution to that page at your suggestion.  I hadn't noticed that idea previously, but did recognise the distinctive build so I guess it is on ubitx.net somewhere.

I am not sure about the diagram from MVS Sarma.  Let's wait and see whether he responds?   He may care to redraw the diagram if he agrees!  Everybody seems to draw those sockets differently ...

73

Mike ZL1AXG ubitx.net


On 7/08/18 2:58 AM, Jonathan Washington wrote:
Hi there,

In wiring my µBITX based on the guides and notes available at hfsignals.com, ubitx.net, this group's wiki, and the like, I noticed a discrepancy related to reverse polarity protection.

I believe the diagram with included fuse by MVS Sarma at https://ubitx.net/ubitx-fix-reverse-polarity-protection/ has the jack wired in reverse (- tip, + sleeve) of the standard (+ tip, - sleeve).  I suppose wiring it this way could be a good way to test if the fuse will do its job!

I should note that this solution seems preferable to the solution(s) provided in W4RJP's wire-up diagram (v1.9) posted at https://groups.io/g/BITX20/wiki/UBITX-Assembly , where it looks like the fuse and the diode would both blow in the case of reverse voltage, and the reverse voltage would still flow through the µBITX.  In MVS Sarma's solution, my understanding is that only the fuse would blow, and the µBITX wouldn't be exposed to any reverse voltage.

Also, I wonder if Mike might consider adding to the reverse polarity page PH2LB's reverse polarity protection solution from here:

I haven't tried it yet, but it seems ridiculously simple, and reasonably effective.  I'd probably still want to add a fuse with that solution, though, to protect against accidental shorts.


Jonathan, KD5CFX


--
Mike Woods
mhwoods@...


--
Mike Woods
mhwoods@...

Re: BITX40 LPF mod

Henning Weddig
 

Arv,

please re-simulate with real inductances i.e. with a reasonable Q  of 100.  This limited Q will already introduce a series resistance ( remember : Q = R /XL). Similar the caps also have a limited Q but "normally" larger, although I doubt if this is true for chap SMD caps.

Henning Weddig

DK5LV 


Am 07.08.2018 um 17:46 schrieb Arv Evans:

Re.  BITX-40 LPF Mod
When I added the parallel capacitance to notch out the 3rd harmonic the simulator showed
a very narrow notch.  Today I tried adding a resistance in series with that parallel capacitor.
The result is a much broader notch at approximately 21 MHz, but still with 63 db of attenuation.
LTspice IV -
BITX_40__output_filter_with_parallel_resonance_and_Series_Resistance.asc_032.png
The upper trace is frequency response and the lower trace shows phase shift.  Adding the resistor seems to have
tamed the phase shift so it does not show a dramatic transition at resonance of L7 and C3.

Next possibly illogical step is to notch out any 2nd harmonic energy at 14 MHz.  This was done with a series trap
(R3, C1, L4).  With R3 at 1.5 ohms this looks promising.
LTspice IV -
BITX_40__output_filter_with_21MHz_parallel_resonance_and_14_MHz_Trap_with_Resistance.asc_035.png
Upper trace shows frequency response and lower trace is phase shift.   
Results look like (1) no additional insertion loss, (2) Reasonably broad notch at 14 MHz, and
The notch at 21 MHz is still there, and (4) overall LPF roll off still starts at 10 MHz.

Will this actually work in a real-world circuit?  It will be interesting to find out.  If it does work it
could insure that 2nd and 3rd harmonics can be reduced to way below FCC requirement for the
BITX-40 transceiver.  The trap idea is interesting because more traps could possibly be added
to take care of any 12 MHz IF leak-through, or any other spurious signal that looks like it might
be a problem. 

Could this approach be applied to the uBITX filter problem...maybe, but I will leave that to people
who are much smarter than myself.

Arv
_._



On Mon, Aug 6, 2018 at 10:22 PM Arv Evans <arvid.evans@...> wrote:
Glen VK3PE

That is something that can be tested.  It doesn't show in the simulator, but real-world
may be different.  When I get to actually wiring this it will be easy to test.
Thanks for the info.

Arv
_._

On Mon, Aug 6, 2018 at 10:18 PM Glenn <glennp@...> wrote:
Arv,
I read somewhere that its a good idea to drop the inductor value by 25% or so, (cant recall exact %) then calculate the parallel Cap value for the required notch.  Otherwise i think the RL is compromised.
Or my memory is suspect, quite possible........
vk3pe

Re: One question only...

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

Re: need a new pc ??

Doug W
 

On Tue, Aug 7, 2018 at 10:44 PM, Doug W wrote:
I am not saying you couldn't run WSPR from an Arduino, but I think you'd be hard pressed to get the same functionality for $10.
Just to clarify I am comparing the Pi for $10 with an Arduino, you still need to add the cost of the shield but even without the shield you'd need at least an LPF either way and the shield gives you a LPF, BPF, and a buffer amp.
 
--
www.bitxmap.com

Re: Low Receive Audio

Jerry Gaffke
 

OK, so transmit works well on both CW and SSB.
I assume that's transmitting into a dummy load.

What kind of antenna do you have?
These are made to work with a good efficient and resonant antenna system, suitable for transmitting.
Ten feet of wire hanging out the window is not going to cut it.
The typical shortwave broadcast receiver has a lot more RF gain so it can deal with crummy antennas,
if the uBitx had that much gain it would overload when used with a decent ham antenna.

You might try touching your antenna coax center conductor to T2 pin 1, coax braid to the groundplane
on the bottom of the rig.   This goes around the relays at K1 and K3,
also around the 30mhz lowpass filter at L1,2,3.  Does it get louder?

Also short across the relay contacts labeled M1 and M2.
Those are there just to reduce the kerchunk sound when you hit the PTT switch to transmit.
A bad relay contact would seriously reduce receive audio (probably to nothing at all).

Otherwise it's down to the RF amps at Q10 and Q30, also the audio pre-amp at Q70.
Those are all auto-stuffed surface mount parts, and we seldom hear of trouble with any of that.
But it's possible.
Get some good light and a magnifier of some sort, look for bad solder joints.

What kind of test equipment do you have?

Jerry



On Tue, Aug 7, 2018 at 08:23 PM, Terence Taylor wrote:
Both CW and SSB are making rated power.

Re: need a new pc ??

Doug W
 

On Tue, Aug 7, 2018 at 07:49 PM, Howard Fidel wrote:
If you have an interesting project for it that can't be done with an Arduino, I'd like to hear about it.
I missed responding to that part of your post.  I am currently running it as a WSPR beacon in my detached garage.  I am using the shield from TAPR.  I can remote into the ZeroW with my phone via VNC and maintain control.  The RF used to knock out the wifi but I separated the shield with jumper wires and it works fine.  I am not saying you couldn't run WSPR from an Arduino, but I think you'd be hard pressed to get the same functionality for $10.
 
--
www.bitxmap.com

Re: S-Meter on Ubitx, trying to get to work..

Kevin Rea
 

Yes I did, but I don't know what to put in the various squares after that for values.

Kevin

Re: Low Receive Audio

Terence Taylor
 

Both CW and SSB are making rated power.

Re: Low Receive Audio

Jerry Gaffke
 

I assume you are checking for power out in CW mode.
Does the transmitter work in SSB mode?
That would prove out the modulator/demodulator, the 12mhz crystal fllter, and the 45mhz crystal filter.
None of those are involved when transmitting CW.



On Tue, Aug 7, 2018 at 07:57 PM, Terence Taylor wrote:
Just finished wiring up my V.4 kit from Farhan. I have the EXTREMELY low receive issue. I have rated power output on transmit and very loud CW sidetone audio. What RX audio that I can hear (from a local broadcast station) is quite clear and understandable. Anyone have any thoughts/guidance?

I have tried the calibration and BFO setting and neither one seems to do any good. I have loaded the CEC firmware, but this was present before that.

Low Receive Audio

Terence Taylor
 

Just finished wiring up my V.4 kit from Farhan. I have the EXTREMELY low receive issue. I have rated power output on transmit and very loud CW sidetone audio. What RX audio that I can hear (from a local broadcast station) is quite clear and understandable. Anyone have any thoughts/guidance?

I have tried the calibration and BFO setting and neither one seems to do any good. I have loaded the CEC firmware, but this was present before that.

Re: S-Meter on Ubitx, trying to get to work..

M Garza <mgarza896@...>
 

Have you enabled the S meter in the Ubitx Memory Manager?


On Tue, Aug 7, 2018, 8:06 PM Kevin Rea <reakevinscott@...> wrote:
Hi guys, 
I built the little s-meter circuit at this page:
http://www.hamskey.com/2018/06/creating-simple-s-meter-sensor-for.html
I have checked my wiring 3 times, and it all looks like it is correct.
I have a 3.2" nextion display.
everything works nicely, but I do not see any S-Meter indication.

any ideas ?
is there something I have to activate ?
kevin rea
lancaster, calif.
k6rea

Re: need a new pc ??

Tom, wb6b
 

Here is an interesting library that lets you control the Raspberry Pi GPIO pins with much the same simplicity as the Arduino I/O library.

http://wiringpi.com

Tom, wb6b

Re: Harmonic performance - SSB vs CW

Jack, W8TEE
 

It also has considerably more memory resources and external interrupts. The Mega 2560 Pro Mini also has a smaller footprint than the standard Mega, which could save a few nano acres.

Jack, W8TEE

On Tuesday, August 7, 2018, 9:17:11 PM EDT, Arv Evans <arvid.evans@...> wrote:


John  KC9OJV

Very possible, and possibly an interesting project.  The Arduino has I2C data interface
which could be used as master and slave to allow one to send control signals to the other. 
There are several other communication possibilities between a pair of Arduino that might
be employed to do the same thing. 
Alternatively we could use an Arduino 2560 with its 54 digital I/O pins and 16 analog ports.
This is probably a preferred method because it requires only one Arduino

https://www.arduino.cc/en/Main/ArduinoBoardMega2560?setlang=en

http://tinyurl.com/ya6bmsux

Arv
_._

On Tue, Aug 7, 2018 at 6:14 PM John KC9OJV <greusel@...> wrote:
Would it be useful to piggyback a second Arduino simply to provide another bank of I/O ports?

John
KC9OJV

Re: No email

Arv Evans
 

Its up.


On Tue, Aug 7, 2018 at 6:55 PM RICHARD <k6kwq@...> wrote:
Is the list down?

Re: Harmonic performance - SSB vs CW

Arv Evans
 

John  KC9OJV

Very possible, and possibly an interesting project.  The Arduino has I2C data interface
which could be used as master and slave to allow one to send control signals to the other. 
There are several other communication possibilities between a pair of Arduino that might
be employed to do the same thing. 
Alternatively we could use an Arduino 2560 with its 54 digital I/O pins and 16 analog ports.
This is probably a preferred method because it requires only one Arduino

https://www.arduino.cc/en/Main/ArduinoBoardMega2560?setlang=en

http://tinyurl.com/ya6bmsux

Arv
_._

On Tue, Aug 7, 2018 at 6:14 PM John KC9OJV <greusel@...> wrote:
Would it be useful to piggyback a second Arduino simply to provide another bank of I/O ports?

John
KC9OJV

Re: need a new pc ??

Doug W
 

On Tue, Aug 7, 2018 at 07:49 PM, Howard Fidel wrote:
I picked it up for $5. Not sure what to do with it, and it needs special mating cables to use it.
That's why I paid $10 and got it with onboard wifi. I run it headless via PuTTY or VNC.  
 
--
www.bitxmap.com

S-Meter on Ubitx, trying to get to work..

Kevin Rea
 

Hi guys, 
I built the little s-meter circuit at this page:
http://www.hamskey.com/2018/06/creating-simple-s-meter-sensor-for.html
I have checked my wiring 3 times, and it all looks like it is correct.
I have a 3.2" nextion display.
everything works nicely, but I do not see any S-Meter indication.

any ideas ?
is there something I have to activate ?
kevin rea
lancaster, calif.
k6rea

Re: BITX40 LPF mod

Jerry Gaffke
 

It is possible to use a square wave as the signal source in a VNA.

I looked hard at the N2PK VNA a few years ago, that is a sine wave source
into the DUT, and the signal out of the DUT is inspected by two mixers with a LO
at the same freq as the DUT source but in quadrature, outputs at DC.  (Now that's baseband!)


The W5BIG AIM430 VIA creates 2 sine waves from DDS chips for DUT source and an LO to the mixers,
the two mixers effectively measure current and voltage from the DUT into a load resistor.
The mixers get sampled with ADC's and that data is passed on to a PC for an FFT to 
find the amplitude and phase of the two 1khz audio signals (which represent RF voltage and current)
He's got it pretty well described here:  http://w5big.com/QST_Article.pdf

The DG8SAQ VNWA is similar, but he's got that thing wound up to work well at some
very high frequencies, far higher than any of the data sheets for the parts being used
would suggest possible.  Well regarded, and very accurate.  Not cheap.
Mixer outputs are at a few khz, as I recall.
He's sellng lots of these, does not provide complete instructions on how to go into competition.
 
The AQRP VIA that Kees sells is is similar to the AIM430.  The big difference here is it
gets by using all square waves.  An FFT is carried out by an on-board ARM processor,
and by ignoring all but the 4khz difference frequency between DUT source and the LO to the mixers,
it can ignore the harmonics in the square wave.  It has recently been extended for use
as a two port VNA.  A nice self contained unit with touch screen at a good price.
    http://www.qsl.net/k5bcq/Kits/Kits.html




From post 56160:
>  I'm seriously considering putting together a signal analyzer along the lines of your earlier post.
>      Step_Attenuator -- 50mhz_LPF -- diode mixer -- MMIC_Amp -- PX1002_SAW -- ad8307 -- Nano_ADC
>  In parallel with the AD8307, add an SA612A plus audio amp so I can hear it.
>  There's lots of information in that audio if you know what to expect.

If instead of one SA612A we have two mixers driven with quadrature LO's, we could use SDR
techniques to separate upper and lower sidebands in an ARM processor.
But then we have pretty much all we need for an AQRP style VIA.
Hence the creeping featurism that prevents me from ever getting out the soldering iron.

Of course, it would take me a year to figure out the DSP software involved.
Just listening to an AD8307 with an ADC makes the software trivial.
And gives us a spectrum analyzer perfectly suitable for poking at a uBitx with.

Jerry,  KE7ER



On Tue, Aug 7, 2018 at 04:30 PM, ajparent1/KB1GMX wrote:
The basic theory is phase of source and phase of returned signal, S11 Rx,Jx is the result
or reflected (referenced to 50 ohms) voltage and phase.  To do that you need to do
phase comparison and mixers like DBM can do that.

There are two systems in use to do that one uses a current measurement and voltage 
and compared those to reference (source signal) the other uses directional couplers
and refernce their output to the source.  The source has to be clean sine.  Once you
have phase and amplitude data (basically S11) you can calculate the result and
plot it as smith, polar, or as desired.  Not trivial but not rocket science (logs trig and
a little vector math).

Both require a clean sine source as harmonics will render teh results useless.  Simple
example is MFJ259B.  FYI if the source has issues in the 259B the readings are bad
and part of calibrating it is verifying the output has minimum (-40dbc) harmonics. 
I've replaced the diodes in mine and recalibrated it.  

Re: Harmonic performance - SSB vs CW

Tom, wb6b
 

What is interesting about the spectrum analyzer screenshots is the harmonics do not get progressively weaker with increasing frequency. 

There is a lot of current flowing across the board to the finals. It could be the harmonics are coupled common mode into the grounds, at the capacitors, of the filters.

Providing a more reliable ground across the uBITX board, via low resistance connections, through metal standoffs, to the four corners of the board might help.  That was the thought, anyway.

Tom, wb6b

Re: Harmonic performance - SSB vs CW

ajparent1/kb1gmx
 

You could, send commands to it via serial (2 pins clock and data).
 
Using  2 pins and a 74166 would get you 8 outputs and potentially 8 inputs too
if you add a 74165.
Or the same two could go into a 74138 to get a 2:4 decode or 3:8 decode.

You can also multiplex the 4 pins for the LCD as they cause no display
changes without R and E signals so those 4 with a single pin could be
latched to add pins.

Allison