Tuesday, September 19, 2017

XR2206 frequency generator

...Looks like I have to build all the projects that I didn't managed during my youth.... back then my preferences were power supplies, audio circuits and transmitters.
In the audio department something useful was an audio frequency generator , unfortunately an interesting project back then used a XR2206 IC which cost'd the equivalent to 6 Eur by today's money, that's not much, it was 30 years ago.
So back then the best I could manage was the finger test and check for audio output...

Recently come across one of those chips and decided to give it a go.

Here's the final outcome

It would be cheaper to buy one ready made... half the fun.
Also added an Arduino frequency counter with bubble display.

Inside plenty of space:

...but not everything fitted on the front panel:

And some outputs from it:

..I didn't used the full potential of the chip, it can do also some modulation but left that as a possibility for the future, it also only outputs AC component on the triangle and sinusoidal output.

Schematic was similar this one with small adaptations:

 In the initial testing of the counter code...

In all fairness, do I need it? No. Did I used it already, No... but less one project in my "youth" list.... If I remember still have a multimeter with the ICL7106 and an STK audio amp to do :)

Have a nice week!

Saturday, September 16, 2017

MAX7219 8 Digit Display Module Interference

While building the 50 Mhz receiver I notice after boxing it that there was a lot of noise, whistle type, in the audio overriding any possible reception.

Interference most of the time comes from supply line and I was pretty sure that was the source since the Arduino and the display module were previous connected to separate usb power without it being noticed. I knew the problem was in the display because the original one got "toasted" and interference was over when removed.

This week a new display module arrived and the interference started again after assembly.

...pesky little things, next time will go back to the usual LCD type.

First action was to kind of "shielding" cable from Arduino nodule to display, that made no difference, the cabling carries control signals plus power and I roled thin foil over it.

Second action was to add a small filter in-line with power supply. That placed the interference at a much lower level (not noticeable in operation). I also added a filtering capacitor of 220uF at the Bitx board vcc input. In terms of power I have the main line in the box to the Bitx board then Arduino, display and VFO are regulated downstream, one regulator for the Arduino and display module (module power is supplied by the Arduino) and the other regulator for the VFO.

Filter for the MAX7219 module that cured the interference is this one:

..worked fine first time, components values were eye balled, I have used similar ones to audio amp's (specially the LM386).
after installing and probing, looked like this:

The initial interference was like this at the speaker terminals:
and like this at the MAX7219 display module vcc input:
...this is AC coupled at the oscilloscope, on a perfect system should be a flat line, that is; no AC component on the DC line.
From the Arduino side at the supply line for the module,

looked like this:

...the VFO signal is all over the "shop".

Now with the filter and even more audio output the signal looks more of an proper audio one:

I like when it works first time! Now I can continue with testing and validating the receiver design (it's already fully boxed), when done I will post more details.

Bellow the current state in terms for from panel an inside:

Have a great weekend!


Thursday, September 14, 2017

Metal sponge for soldering iron tip cleanup

I think i'm melting solder for over 30 years... the first Iron used was one built by my father with a large tip, even so, I managed to work some stuff with it.
In my teen years I bough the cheapest I could find (no other choice), basically crap and still manage to so some work.

Only in 2005 or so I bough a decent one, still no soldering station and all that good stuff, the support for the iron and the cleaning sponge was still in the low end of the quality scale...

That good soldering iron "died" in 2013...

...back to crap equipment and to miracle making (on the left). That was in Portugal, in Ireland I have the cheapest one I found along with a "control" station that is always in the max temperature.... it works!

The iron is not the original because I broke it when replacing the tip. The tip shakes a bit but still OK.

Today, 2017, I have something completely different and new, as you can see I got the latest and greatest of the cleaning devices.... a metal sponge!!! (anyhow was the cheapest)

Need get used to clean the tip with this new this method but now I feel a professional.... still no proper soldering station, the things have "pornographic" prices!

Previously, the methods I used to clean soldering iron tips are, in no particular order:

1 - Slam the iron against the bench
2 - Pass rapidly the tip of the finger on the tip of the iron, it will not burn if your fast enough (took me some time and burn skin to master this one)
3 - Use the wet sponge

Have a nice week!

Sunday, August 13, 2017

ADSB + ACARS with SDR dongle on Linux

In 2013 I got one of those SDR dongles, Idea was for RF spectrum view and a standalone SDR receiver.
Well I tested it for some reception and it works ok for the price of it. Haven't used to much recently but in any case leaving here some details how to get ADSB and ACARS decoding if you use Linux, i've run it on two different Linux Mint distributions although the guide is more geared to Ubuntu.

The dongle with the test antenna (the classic piece of wire):

The complete instruction for ADSB I got from this site:
 ( http://landoflinux.com/linux_sdr_adsb_gqrx_radio.html)
There is also a version with MySQL support for historical logging at: 

After compile you can run the webserver with the display of planes using the following command:

# ./dump1090 --enable-agc --aggressive --net --net-http-port 8080

Point your browser to http://localhost:8080 and you should have a similar view to this:

and another along side with terminal for monitoring:

If you need to check if listening on port 8080 execute the following:

# netstat -ln | grep 8080

... output should be similar to this: 

tcp        0      0  *               LISTEN

If nothing returns then it's not listening....take in account that some proxy's software generally use port 8080, so look for another free if that's your case.

Running the command without options you just get the scrolling output of the frames received:

 For ACARS reception, follow this guide.

And run the following command (you can include just your area ACARS frequencies):

#./acarsdec -p 0 -r 0 131.525 131.550 131.725 131.825

If you look on the guide (on the link) there's a way of including frequency correction, I considered 0 just for testing and still got some outputs with the piece of wire antenna inside house:

...I'm positive I've flew in the the EI-DES from AerLingus before.

Have a nice week!

Sunday, July 02, 2017

50 Mhz receiver with Bitx IF

As referenced on last post, I'm building a 50Mhz receiver, for now will leave the transmission capability out, in any case provision his there.

Basically this is a Bitx used as 28Mhz IF for a 50/28Mhz transverter kit.

I found it more convenient to buy the board from India instead of making it dead bug, still changed the first mixer to an SBL-1 and the crystal filter to the one available.
The IF is 9 MHz and the IF filter is one of the KVG type as on the Telrad board, look's like that my previous reference to 560 Ohm termination of the filter was incorrect, Pete N6QW, on his blog post has a reference of 1000 Ohm.
I made an impedance match transformer with 6 turns in, from the amplifier side, to 12 turns on the filter side, assuming 150 to 560 Ohm inpedance conversion (150 Ohm is the expected "normal" Bitx filter impedance), it works fine so not even will test with different impedance match.

Here's, first iteration of the audio output without BFO adjust:

VFO will be provided by an Si5351 controlled by and Arduino and custom code.
Initial tests of the Bitx board were made on 14Mhz, so the input filter is left in place:

..the final input filter for 28Mhz is the one on the green pcb

another detail of the 14Mhz inboard original filter

A note for the front end amplifier, I didn't had the recommended 2sc2570 so placed an 2N3904 temporarily and it still works acceptable.

This will be prey much the final result as soon as I place the power and antenna connections...

...and upside down:

Maybe latter will add the S-meter:

Have a nice week!

Sunday, June 04, 2017

50 Mhz transverter kit

50 Mhz had been one of those bands that I never tried, till now.

Instead of making a receive converter I went the lazy route and bought a transverter in completed kit form.

The idea for now is just to add it to a Bitx converted to 28Mhz and be used only as receiver.

This week I wired the transverter to check if working correctly, connected to the FT-707 and got some faint signals (I'm using just a bit of wire as antenna).
Today the band is more open and got one big signal from EI9FVB, after checking the call and the locator, guess what, is in the same locator as me, no wonder. Previous test, during week, I managed to receive IS0BSR/P so reception part of the kit is working.

Here's some pictures for the future box while not everything is finished, will update when complete and if using the Bitx is a viable possibility for a 50Mhz receiver/transverter.

 Transverter on top of Bitx board and the VFO on the right. I decided to buy a Bitx PCB instead o making on bare copper one since it will be faster to build.

Transverter on final location inside the box, blue wire is the temporary antenna, the black one is the IF (28Mhz) output.
For initial testing the FT-707 was used, you need to add 22Mhz, so, the receive frequency is 50.178Mhz

The 10m filter (on the right) for the Bitx input: (will also try without it and rely on the transverter filtering)
..I also made testing with the "standard" Bitx coils ( soldered on the board) for 14m, 30m and 40m case the board be reconverted (that will probably be another post). 
The 10m filter values were from here, and it's similar to many others.

...and the matching curve, no calibration on the "analyser" values, but seems to work I connected to the Yaesu input for in air 10m testing and got signals... like if that was a valid test :)

The box/front panel will be this one: still need to change VFO code

...it's a reuse of VFO for the Telrad board from previous posts.

Have a nice week!

Sunday, May 21, 2017

Screen capture, on Linux, from Rigol DS1052E oscilloscope

Nothing fancy, just followed the code and description from here, deployed the needed libs on another Linux laptop I have, and voilà:

...a nice picture with zoom capabilities.

Had some initial problems with code in the article, had I followed the thread in the same and could had it fixed sooner. Basically the scope returns a little more data, 610 instead of 600, than expected by the Python plot function, so the following needs a change in the code:

#time = numpy.arange(-305.0/50*timescale, 305.0/50*timescale, timescale/50.0)
#time = time[0:610:1]

Where is 300 on the original is now 305 and where in the original code is 600, should be 610.

The image on the scope screen is the following:

The scope being detected as USB device:

This is running on Linux Mint with the following kernel: 4.4.0-53-generic #74-Ubuntu SMP Fri Dec 2 15:58:04 UTC 2016 i686 i686 i686 GNU/Linux

Have a nice week!