Sunday, December 13, 2015

New control and audio boards for the Trevo transceiver.

Decided to place the control board and the audio sub-system on new boards. This way will have a more standard fitting by means of header pins.
In the mean time I added a tone decoder (LM567), and sound card isolation on the audio board. On the control board I added the code for PTT and redesigned the input pins for the band and mode buttons.

I will for sure use almost, if not all, of the Arduino Uno imputs and outputs.

Here's the audio part (top) and the control board (bottom) with the PTT button for testing:

And the underside of the control board with the Uno:

The rotary encoder and the "IF" shit are in place on the board for troubleshooting, will be removed in the end. Still need to connect the output buffers for band-pass filters relay control

Have a nice week!

Sunday, November 15, 2015

Weather station with Arduino, DTH11 and MPL3115A2 Barometric pressure sensor

Nothing special here, I had the sensors laying around and a spare box and Arduino nano module so I just "glued" everything together. In the future I will proably put some remote sensors...if I have time and patience for it.

The finished product (with printed paper graphics glued on the plastic panel):

..This type of LCD is not the greatest of all, just used it because bought two out of curiosity, next time will stick with a classic one.

The internals:

..nothing special, there's a small hole near the humidity detector (blue module near the back panel) for faster response to temperature change.

View from the back, power is by USB directly on the Arduino nano module. The back of the Nokia LCD is visible on the back of the front panel:

Part of the code, just for future reference:
// Nokia 5110 libs
// alti/pressure sensor

 // DHT11 sensor
#define DHTPIN A1     // pin analog 1
#define DHTTYPE DHT11   // DHT 11

const int SENSORADDRESS = 0x60;

Adafruit_PCD8544 display = Adafruit_PCD8544(8, 9, 10, 11, 12); // arduino
Adafruit_MPL3115A2 baro = Adafruit_MPL3115A2();

  // readh dht11 variables
  float hum = dht.readHumidity();
  // Read temperature as Celsius
  float temp = dht.readTemperature();
  // read addfruit variables
  float pascals = baro.getPressure();
  float mb = pascals/100;
  // clear last data on display and display new data
  //display.print("--- Sensor ---");
  display.print("Humi. "); display.print(hum); display.println(" %");
  display.print("Temp. "); display.print(temp); display.println(" C"); // dth not so accurate
  display.print("mB. "); display.println(mb);

Have a nice week!

Monday, November 09, 2015

Airband receiver kit + Si5351

Got one airband receiver kit from a popular an auction site,

(kit's are cheaper now from what I've seen)

Kit includes everything and even some extra components (better more than less).
It worked first time after assembly. Already with that in mind (or as standalone in case of failure) decided to convert it to use the Si5351 clock generator IC, re-using the airband VFO box I made to convert the PAE receiver from single channel to VFO. The Park Air Electronics receiver conversion wasn't successful because of the low range of the internal VFO without manually retuning the coil so the box and the inner Arduino was kind of redundant:

The PAE airband receiver, single channel selection by dip switch's. for what the air band vfo box project was initial intended:
The airband VFO box was supposed to remotely change the DIP switch settings of the PLL, it worked as I programmed but the VFO tuning range was short so I only got 2Mhz excursion from the main frequency before the PLL unlocking... it was kid of bitter taste of a failure in the middle of a success.

So for the Airband kit I place the Si5351 (and the kit itself) inside the airband vfo box and changed the code from the DIP connections to the clock programming of the Si5351. The connection to the airband receiver kit mixer from the Si5351 is strait forward and worked first time:

For the in place kit connection on the PCB what needs to be changed is the connection to NE602 on pin 6 and pin 7, applying the VFO signal on pin 6 of the NE602, the oscillator part (in the kit) is removed by means of disconnecting pin 6 and 7 to the main board..

..using a simple adapter to be inserted inline without modifications on the PCB :

you see the two "missing" pins on the underside that will no connect pin 6 and 7 of the NE602 to the kit PCB
They are never the less connected on the top part of the adapter board and connected then to the VFO (si5351)

The kit without adapter

Final product with adapter in place and connected to the Si5351:
From left to right, back panel, airband kit, arduino and the si5351 module on top, and on the right the from panel with the LCD display and frequency selection buttons.

Still no external squelch and volume on the box (mid and right pot's) because I don't have a drill around....

The power will be provided from the Park Air electronics receiver, that will remain single channel, so when I power it on will get that channel and another one I can select on the new airband kit.

Have a nice week!

Sunday, November 01, 2015

Most import project so far - Night Light

....Yes, if you show LED's to a 5 year old they will never let you go... and if you show that they light up when connected to a will spend the rest of the day watching batteries getting drained.... If besides all this you have a spare project box in hand the litle ones will find a way of re purposing it!
That's what happened when I showed LED's (she discovered then in fact) to my little child, after playing a bit with the LED's she asked me for a night light, she never had one but she knewed what it was... here's the result:

Her design for the LED placement:

And switching bettwen the J of Joana:

And the heart:

Inside looks:

 ... she was also fun of the breadboard....and yellow wires!

I suggested blinking and doing circles using an Arduino but no, it was OK like Arduino was spared!

Have a nice week!

P.S. Now I have to connect to an external supply as requested/ordered!...

Monday, October 26, 2015

FT-707 repair (11) un-converting from CB to 10m

One of the FT-707's that I aquired recently had the CB conversion on band 10A to 10D, that is the allowed CB band in most countries and also the pirates low's and highs spread accross the 10A to 10D band switch.

The hardest part here was finding the right Crystals, the few that Yaesu dealers still have in stock are extremaly expensive.

I had sorted that a regular 14.318 computer crystal would work on the 10m B position (oscillating at 42 .954), very near the 42.987 as standard on the radio.

Here's the local oscillator table for 10m

Now I acquired some less expensive crystals very near the factory frequency and can get coverage from 27.9Mhz to 30Mhz (less 79Khz in the end) on the four segments covering all the 10m band plan.

Low part on the 10A position:

High part on the 10D:

Now it's a true amateur radio, not a CB one.

Since the pin's on the new crystals were larger than the existing ones I made some terminal adaptation, that's why they are higher than the one in the 10mB place, second from the left.

I needed to put new coils (new cores and rewound) for 10mA and B, due to previous expert that touched the radio, that was covered in a previous post.

Crystals used were these ones:

10m A - 42.444 Mhz
10m B - 14.318 Mhz (on the overtone)
10m C - 43.444 Mhz
10m D - 43.888 Mhz

Have a nice week!

Saturday, October 24, 2015

"New" equipment - Yaesu YR-901, YK-901 and Heathkit SB-610

..New as in new for me. Last August I bough this pieces of "furniture" for the shack, I know the post is a bit late, it's already October.
Only bough them because it was relatively inexpensive, so worst case scenario (they don't work) the box's will be used for some other project, I didn't tested yet, the decoder YR-901 looks ok, the SB-610 has some changes on the CRT tube connections so will be tested first with a bulb inline and after a small revision.
Here's some images for your viewing pleasure.

YR-901 CW/RTTY decoder:

With the matching keyboard, YK-901:

SB-610 Oscilloscope, transmitter monitor:

The YR-901 decoder will be a nice addition to the FT-102 Line:

...Have a nice weekend!

Sunday, October 04, 2015

More filters

Some time ago I bought 3 isolated filters, one LSB, one USB and the other for AM, the idea is to use them as secondary filter for the "Trevo"....or maybe for some other project.

This time I bought another set, including the board where they all seen to come from. It looks some sort or IF part of a radio, it has the MC1350, MC1496 for SSB/mixing/amplifying. Just can't find any reference about the board.

Anyhow, the idea is to remove the filters the IC's and parts for other projects.

It's cheaper to buy the 3 filters than a single one from a major brand, if they are good or not, that's another story.

Have a nice week!

ps: Updated here with more info

Thursday, October 01, 2015

Another kit

I always liked planes, when I was a kid my father was a plane maintenance mechanic, althoug I only went with him very few times to the hangars it was allways something that fascinated me.

Maybe one day I will try to fly one, I think planes and trains are the only transportation mean that I'm not certified to "drive"...

Passing trough the local supermarket there was some promotions on plane kit's, so why not!?
So far I've built two, one for each year that I've been in Ireland.


and 2014:

...this Year still didn't spotted the promotion...

PS: If you think it's easy to make, think again, you really need some patience to do it , tough that's no rocket science.

 Have a nice day!

Monday, July 20, 2015

Trevo bandpass filter - I

Slowly I'm getting the "Trevo" transceiver built.

I'm trying to get now the bandpass filter to some usefull state.

Here's the progress with the inclusion of relays for switching.

...decision that I already regretted after soldering all those small relays, each one is an inverter, so it takes two for each band, and I'm also grouping two separate sets (one for the low bands, the other high bands)...and still missing almost all the coax from the filters to the relays!

General schematic is this one:

...adapted from the "Speaky" transceiver without the diode switching part.

The filter includes a tuning voltage that is applied to C21, kind of pre-select with varicaps, input is applied on L2(3,4), output goes on L3(3,4) or vice-versa if you care....

The varicaps are going to be changed to diferent type from the ones in the "Speaky" because they are made of un-obtanium so I expect to do some changes in the filter componentes values.
The baseline is the following:

I never testes this configuration for the 160m band so I might have to change design for that band. Will probably include also one option for VLF bandpass or a filter bypass.

Still a lot to be done.

Have a nice week!

Sunday, June 28, 2015

FT-707 repair (10) Finding replacement coils

As stated on a previous post of the FT-707 repair series I had to remove two coils from the 10m A and B local premix oscillator, to use on the 40 and 30m band because there was a previous owner that really made a mess out of it.
Now I'm the the process of finding replacement ones, the coils are a non existing item and there is not much information on their specs so I got some coils from the junk bin and started to find which ones would work by winding them on a trial and error process.
For that I replicated the oscillator part from the technical manual on a small PCB:

..the assembly:

 ..this way it's easier to test multiple coils.

The output of the circuit looks similar to this when the coil is ressonant or near ressonance:

 After some testing I already have one coil finished and in place, it's not perfect but for now fits the bill:

I used some IC terminals to test in the board also and if needed replacing latter on: was easier this way to avoid do much soldering on the board.

 The coil is marked "3392" and comes from an unknown board that my guess was used on a wallkie-talkie (has cristal holders and a side switch), whatever that coil match's in terms of specs or inductance to is unknown to me, I have to build and inductance meter yet.
I run 2 turns for the secondary and 6 for the primary for 10m B band, the removal or increase in the coil number is done by testing with a crystal upper in frequency and also lower of the main one for test and see if the output increases or decreases, eg: if more amplitude on a 50Mhz than on a 35Mhz for a 42Mhz center frequency I assume the higher the amplitude the closer to the resonance frequency so has low inductance and more turns needed (keeping the same parallel cap, 39pf).

If you look closer still missing the first coil for the 10mA, top of the right column of coils, I already have one tested, just not in place, marked "3410 E 0" that works with a 14Mhz crystal (42Mhz overtone), just waiting to find a suitable crystal for 42.5Mhz, the one I previously placed there doesn't want to oscillate on overtone, was placed before proper testing and was removed.

Now it's like this:

 ... except that the band is already on the correct band soon as I have the 10m A in place I might leave 10m C and D with the CB frequencies :)

Have a nice week,

Saturday, June 20, 2015

Arduino digital out, 4 to 16 decoder/demultiplexer

.. .Using an 74HCT4514 ...

Controlling the VFO for the "Trevo" transceiver from the Arduino poses a small problem, the Arduino doesn't have enough output lines to control all the bandpass filters so I had to come up with a solution. There are some I2C IC's that would expand the digital output pins and do the job but I think that's like killing flies with a cannon so I went to a more "old school" approach.

The 4514 series IC used here, in high speed version (HCT not realy needed), is a 4 to 16 decoder with input latches, the latches are not needed on this case since there will be no signal change from the command lines.

Basically you input a 4 bit (parallel) binary and you have 16 digital outputs according to the truth table here:

This is the assembly (LED's were place on the first 3 outputs to check that is working correctly)

And the control schematic from the Arduino:

Sample code to output high (1) on Q1 of the 74HCT4514, pin 9:

// start sample
// setting the pins on the Arduino
pinMode(13, OUTPUT); pinMode(12, OUTPUT); pinMode(11, OUTPUT); pinMode(10, OUTPUT);
// send the data "1000"
digitalWrite(13, 1); digitalWrite(12, 0); digitalWrite(11, 0); digitalWrite(10, 0);
 // end sample I still have to code the rest so that a band change activates the correct output...

Have a nice weekend!

Sunday, June 14, 2015

Mixers tested

Here's some of the passive mixers I normaly use.

From top to bottom, ADE-1, TUF-1, SBL-1 all 7 dbm level.

I've been experiencing with the ADE-1 using the IF out as input for the VLF range and it works nicely, contrary to one could think. I'll post in the future the experiments.
I'm also favoring more this mixer since it's the cheapest of the 3.

The SBL-1 I use in HF range but also made a VHF transceiver using it for the reception part.

The TUF-1 only used it on the "Speaky" kit, might replace the ADE-1 in the "Trevo" transceiver design with it.

Have a nice week.

Sunday, June 07, 2015

FT-707 repair (9) No external VFO

Looking back, this is the 9th issue found between the two sets, hopefully will be the last!

The problem with the "blue" FT-707 was that the external VFO was not working with the set, it was working with the other set so the VFO is ok.

I started looking at the diagram, for sure the issue is in the connection to the external VFO, the VFO ligt's and controls the radio if you press the RX but no frequency, only the 91Mhz symptoms of no VFO:

Started by testing the switch inside the plug with a make shift adapter (the shield of a plug):

One of the poles in the plug swithc put's inline a 50 ohm resistor so it's easy to test from the RF board, pin 3 of J05 "memo out".

All the connections were tested and all with continuity....what is going one here? Something is not right!

Let's bring the heavy troubleshooting stuff.... the oscilloscope, before that,  just powered on the radio once more and the external VFO was working!... Hum!?, probably the contact creaner I aplied on the swithc changed things... good, let's close the lid before it breaks again.... then is when it stops again, ahhh, a broken cable for sure, some touches on the cables and voila the culpit (external vfo in):

The press of the lid against the cable would disconnect and that's why when I did the testing it was all ok. live and learn!

For now this will end the FT-707 repair series, they only need a god tuning and some cleanup, if something major "arrives" will post here.

Have a nice week!

Saturday, June 06, 2015

FT-707 repair (8) No output on 12, 17 and 30m band

This one was not obvious for me, still isn't completely understood, only fixed, one of the reasons for not "getting there" faster was I was also having low to none output on 20m, so was suspecting something on the bandpass filters or the associated switching circuit. The filter weren't making much sense because reception was had to be something else.
As soon as I figure out that low output on 20m was due to improper bandpass tune it become obvious which way to go for finding the actual issue.

This is the board in question and the problem is around there...(RF unit PB2093b) !:


So what I did was disconnecting the output to the PA and place the scope to check for the level before amplification, after "tuning" the 20m band filter only no power on 12 , 17 and 30m band... so what is common between the bands and only on the TX circuit if I excluded the filters?:

So it was starting to be obvious that the issue was with the associate circuit of Q04, started measuring on the anode of D20 and noticed the bias was smaller every time I selected 12, 17 or 30m band and keyed the transmitter, the bias is also dependent on TX 13.8 (pin 3) from J02 plug, so for each test transmitting must be done. The only cause of smaller bias can only be diodes  D21, D71 and D72, impossible for 3 diodes to be out of spec/broken at the same time and since the voltage droped they were for sure working (an open diode would keep the bias high and a short one very low, was not the case in either). So I lifted the diodes and voila', everything back to life. I'm sure the actual "fault" is somewere else, measured R06 and is spot on so could be any of the other parts. As soon as I have patience and more time will try to dig furter.
I think Yaesu might have placed the 3 diodes in the circuit after checking that probably some bands had excessive power and that as a way to limit a little on the output since the diodes will drop the bias lower and the series of D20 with the PN junction from base to emitter, at the moment I see no other reason for the use of the diodes there and only on these 3 bands, it should not be curing any instability since the band's are not even sequential....

Here the "offending" diodes lifted?

And already outputing some power into a dummy load with the watt-meter in the 15W scale and the carrier control fully counter-clockwise (low output).

..I will leave as it is for now, at least this unit I can consider as fully operational....

On to the next unit, the blue light one!

Have a nice weekend!