Tuesday, November 26, 2013

Newsky TV28T RTL 2832U / R820T DVB-T DAB FM SDR

Sorry for not updating so often now the blog, I have time but have been without patience to write. While before coming to Ireland I wrote in English just for fun, now that I write and speak every hour of the day I get a little tired!

Back to radio...

Some time ago (in September) bought one of those new (at least for me) TV receiver dongles with the initial idea to make a simple spectrum analyzer or a standalone receiver using one of the small Linux computers boards.

What I got in the mail:

 And the cost was 19 Eur, so, excluding the computer you have a nice receiver for a small amount of money (that's always relative).

After installing in the laptot according to one of the guides (you have to use a diferent driver from the one that comes with the card) and to make the initial test, I placed on the airband for the Cork airport approach and connected around 50 cm of solder "wire" acting as antenna:

This is the screen on the Cork approach frequency

The plane was here:
 Then requested to change for tower frequency

 And prepare for landing (north wind most likely):


 There's a discrepancy in the plane reported altitude and the airpot one so I guess that someting is changed in the ADS-B system used in the plane spotter site.

It was fun! Placed the card together with the other electronic components and when I get one of those small computer boards will place it on a standalone box....

Have a nice week!

Tuesday, September 24, 2013


I had to build something while I don't have everything set around so decided to buy a small kit and build an AM receiver. The kit looked well built and affordable, using a classic design approach, eg somewhere in the 70's with two 455Khz IF and a diode detector.

So, 2 weeks after paypal payment it arrived at the front door (it come from Malaysia, but I think there's resellers in Europe).

The the built process took about an hour done in small bits, I first tested the audio amplifier part and then proceeded without further "delays". Didn't worked (got any station) at first time because I had no power supply (still don't) and was running it from a Nokia mobile phone charger which infected a lot of noise in the power line. Now I'm running it from a 9v battery and a LM7806.
I works, sensitivity is, well, low, but enough for during the nigth get one or 2 stations from Europe.
I might try to add an extra coil, parallel to the coil in the ferrite and connect an long wire aerial for reception improvement.

Here's the marketing photo:
What you see is what you get in the kit.

Mine when arrived:
 I bough from the same seller two small 300pF variable capacitors... their allways handie...

...as always in my assemblies the box is something for "one of these days"...

Have a nice week!

Sunday, September 15, 2013

North Cork Radio Rally

I'm getting international in therms of radio rallies, after the Moscavide (PT ARVM) one, Leiria (PT ARLA) and Friedrichshafen (DE), now I went to Cork (IR NCRG).

 ...next is Dayton?
It was easy to find the spot since I had already explored a little bit of that area in town, arrived at 11H00, the starting time of the event, and everything was already set. Weather was the classical Irish for this time of the year; you guessed, rain in the morning and then some sun.... and then a little more rain, but was mild rain.
There were the usual sellers and the normal boxes full of odds and ends.

Got home this:

 I never learn....why did I asked the price of the rack airband receiver?...oh well, if it works I will probably leave it like this, if it doesn't I got a really nice quality box and a bunch of components.

I met Ed, EI2HEB who is one of the organizers of the event and we ha a little chat. From what I understood there was another foreign visitor from the Netherlands, so, that made this one a truly international event.

Unfortunately I did not took pictures because run out of memory on the phone and could not delete existing images.

Overall was a nice morning and I got some more stuff to play.

Have a nice week!

Sunday, September 01, 2013

New method for PCB making...

...At least for me.

I normally don't do much PCB, using the standard method or standard methods, but this time since there was a need to solder an SMD amplifier device it seemed that could be a good idea to do so. Just because I'm out of my normal shack I started to look for alternatives for the normal Iron perchlorate liquid and came up with a new product to dissolve the cooper. The method is explained elsewhere in the net by it's creator.

 Basically it's 50% of Hidrogen Peroxide (oxygenated water sold in pharmacies used as an disinfectant for small cuts on skin,, at least I used wen I was a kid) and 50% of vinegar with some salt to taste! Without the salt it would not work and you must be adding some so the process continues.

Here's the board before being cuted. The device to solder (PGA103+) is near the 1n5711 diode, big hum?

Had to buy an hacksaw for the job:

And now the mix, from time to time the board must be shaken and some salt added.
 The rest of the cooper part was protected with clear tape.

The final result:
 Does it pays of? No, except if you are in an island and really need to make a pcb....
and if you want to know I used normal white wine vinegar. Took me around 45 minutes from start to finish.
Now I still have to solder!

Have a lot of fun!

Sunday, August 04, 2013


 After almost two month after arriving to this Island (Ireland) I decided it's time to restart my soldering activities.
Since I didn't had space to bring my shack with me, when I flew in, I opted to bring just a small container of hard to find components, what I didn't knew is that all electronic component are hard to find here.
After some search I found only one company selling electronics around and for getting things worst is one that nowadays is more focused in ready made stuff, oh well..., they still sell you a resistor, if its on their catalog....but you will pay premium price! I will never complain again on the prices back home!

Anyhow, after the initial shock I managed to buy some stuff need, other will have to be sourced in the Internet and back home.

here's my shack "equipment" so far:

Top row was bough yesterday, a soldering "station", cheap and according to a fellow ham, durable. Got also a spare sponge since the one in the kit is very small. Two pcb's for rapid prototyping and one for more definitive setup, also sourced a cheap knife on a pound shop for making traces on the pcb and to remove insulation from wires.
 Bottom row: On the left, the box of components that come with me on the plane and on the right two minicircuits rf amp in static protection on top of the letter that bring them. An ofter from a nice fellow ham living on the north side of  the island East of this one. By the way, there's no island to West, just a big pond...

I still need a multimeter, probably I'll ask for shipping me from home one of mine's since I have too many multimeter's, well I have too many soldering irons also but they are almost all junk...

Now the idea is to start building a new receiver, first the audio amplifier and rf preamp and then all the circuits in the middle! Easy!

Stay tuned and have a nice week!

Saturday, June 29, 2013


Well, after 2 weeks in Ireland i'm starting to think if it's not better to ask for a local ham license.
For now it's not of much of a use since I still don't have a soldering iron to build a radio and the "Speaky" was to big to bring with me.

While I don't share some solder work here's some images from Cork and Ballincollig (were I am).

As the Irish say: Thanks a million!

Wednesday, June 19, 2013

New adventure

A new adventure...

Flight went well, sleep almost all of it and was wake up by the cabin voice stating the approach...

Now have to find a soldering iron but still on limited bandwidth to update the blog.

Have fun!

Sunday, June 16, 2013

End block for a spectrum analyzer add on.

Is it preferable to have an spectrum analyzer for ocasional rf work or a nice scope and then make a spectrum analyzer add on module?

Well for me, and for now I'm going the path of the spectrum analyzer module add on, since a stand alone spectrum analyzer is far more expensive than any of my radios....you get the point. Some past experiments on a similar module were already made some blog posts ago
 by using the RSI from a AM detector chip, now I'm using another approach with the AD8307 logarithmic amplifier.

On to the schematic:

It's basicaly a "Bitx" 10 Mhz filter terminated in 50 Ohm (I hope, not measured yet)
connected to an AD8307 with about 45 Ohm input (from Analog datasheet)

On the right of the schematic there's an option for a common 10.7 Mhz filter from Murata (did not test this option).

Here's some signal "injection" for a preliminary test:

With the output from the "signal generator" (dip meter) 1 Mhz from the filter center frequency:

Without signal:
 And at filter ressonance:

The AD8307 is the SOIC version and after all was not that hard to solder, I removed some cooper from the board and lay'd there the IC, then soldered some wires to the necessary pins:

Will continue this experiments as soon as possible....that may take some time...

Until then, solder what you can... and have a nice week!

Thursday, June 13, 2013

20m band module

20m band module:

Done, but the switching (pin) diodes are standard rectifier 1n4007, it works and for now enough.
I tried to replaced the original schematic varicaps by BB909 type I bought in bulk and.....works nice, although specs are a little different in terms of ratio, but not capacity.
The paint job on this BB909 is not their best feature and after scraping the paint a little bit I can see a diode similar to 1n914 and 4148. I suspect it's some re-branding by the manufacturer which is specialized in hard to find components.

30m band is in prep, oscillator crystal already in place but I suspect will take some time to finish this one....

The Speaky with 5 band modules (2 unfinished):

Also finished the antenna tuner with coil connections for the present "Speaky" bands: 40, 20 and 17m. It also tunes 80m if needed on my piece of wire antenna (something that resembles an dipole :).

Have a nice weekend!

Tuesday, June 04, 2013

In the mail

Arrived this:

For another generic power meter. This time I bought in SOIC form instead of standard DIP, it's a fourth of the price.

Meanwhile changed the the VFO coil on the 20m band module, still need to replace the 18.118 MHz crystal for the 18 Mhz one so I can use the lower part of the band. Now starts here:

Stay tuned!

Tuesday, May 28, 2013

Continuing the Speaky new band modules.

Got this today:


So it's just a matter of time (I haven't) to build new modules!

Monday, May 27, 2013

New antenna tuner box

Finally a new box for the antenna tuner, I really hope it's final, it's already the second incarnation of this tuner....

 A good friend offered his carpenter services to build a really nice box without screws to hold the front and back panel.
And I could not say no, I could never had build something like this, it's out of my patience limits, not to mention carpenter skills...

Inside is also the swr meter circuit board:

 The tuner it self it's not connected yet since I needed to calibrate the swr meter part first.

Will be using 2 scales selected by the switch bellow the crossed needle meter. One 0-30W and the other 0-300W, just hope the rectifier diodes can withstand the power.

Matching the "Speaky" line?

Maybe I can get some more time this week to connect the tuner parts, coil and variable caps for a live test.

Have a nice week.

Saturday, May 25, 2013

Today's work

Today's work was this:
 Placed connector pins on the two new "Speaky" band module boards and also the VXO's adjustable cap (very small inside the red square), still waiting for the toroid's and crystals to continue building. Top board is a standard "Speaky" module.

And this:

top board is going to be a noise bridge with switched bypass (unfinished), bottom board is a swr meter circuit for the new antenna tuner (reworked, finished but not calibrated yet).

Another work for today was to fix the car brand badge, some time ago it fallen of but a good friend gave me a spare one and this time I bonded it with two compound glue instead of the standard 2 pin press fit, I'm sure it will not fall anytime soon.
Yesterday I went by to Lisbon and although always bellow the speed limit looks like I smashed a small bug...

...that's called dead bug style building...

Have a great weekend!

Wednesday, May 22, 2013

FM loop

Not much time for shack work but today was a local holiday so decided to build something.

Well, continuing, the circuit bellow is not exactly a loop but an FM tx and FM rx connected without antenna....

I had to test true FM modulation (without multiplication and on "low" frequencies) using an crystal or coil and test FM detection using an NE602, so latched up two simple circuits and connected them back to back.

Took me some time to find in the "junk yard" a suitable 10.7Mhz IF transformer/coil. Most I found were for 455Khz but luckily in an old car radio there were two (the green and the orange in the picture). I could use the green coil also for FM tx but in this first test I used a 10.7 crystal for the FM carrier, I wanted a more stable source.

Transmit part is from SM0VPO: http://www.sm0vpo.com/tx/fm-tx1.htm
I just used the modulation part until the first BC547 (I used an 2n2222) and then a simple buffer before injecting the signal on the NE602 part.
The receiving end is from KF5OBS: http://jaunty-electronics.com/blog/2012/08/no-tune-ne602-ne612-fm-demodulator/
I scaled the circuit (more or less) to 10.7, removed the input amp and placed a simple trim-pot attenuator, input from the bufer output on the tx part.
Audio amp is one general purpose class AB with discrete components. A simple LM386 would to the same job, just had this one at hand.

Audio is still not perfect on both TX and RX but quit understandable. More tweaking is needed specially in the TX part. Anyhow this is just a concept, I will test other simple circuits that could be handy for adding FM to the "Speaky".

Meanwhile I "prepared" 2 more band modules for the "Speaky" but still have to wait for some T37-2 toroids to arrive for the bandpass and oscillator parts... see bellow on the assembled module the wood toroid for the VFO part.

Have a nice day!

Wednesday, May 08, 2013

Thermal paste

What to do on a Sunday afternoon and your computer gets a little on the hot side?....and you just find out that the thermal past between cpu and dissipator is worn out..?

First you test with aluminum foil:

...and fails miserably...

..then you remember something about chemistry and "Fluor" supposedly is a nice conductor but toothpaste has a tendency to dry out...no problem: just add some silicon based gel or a petroleum derivative like the following product to remove cloth stains...

Mix on a 50/50 proportion, or 70/30 or...whatever......put on the CPU (careful for not to spill on the sides) then assemble everything again:

first the dissipator

then the fan

Now test it!:

 ..before the toothpast and supergel mix it was 2600RPM and around 70ÂșC

I'v been running over a week on this mix but eventualy one of this days will place a proper thermal past.... next experiment is to find a catalytic converter for the car to run on water! :)

Have a nice week!

Sunday, April 28, 2013

New coil for the antenna tuner

It was a "profitable" Saturday yesterday, build the new coil for the (re)new antenna tuner:

I had this form with some kind of steel wire wrapped around and since it was not solder-able I removed the old one and now placed normal 1.5mm2 section household wire. Unfortunately I had no more wire around so it was not till the end of the form, anyhow I suspect the inductance will be more than enough for the intended purpose. Don't "trust" the MFJ reading at the measure frequency frequency since there's lot of inter winding capacitance. My rough calculation for the coil will be around 50uH.

Here's the donator coil wire (the old one):

Had to strip the insulator which is always a pain...
...and still had time to make an oscillator just for fun...

And to place the AM demod part for the Speaky in a new board, pictures and schematic later on the blog.

Have a nice Sunday!

Thursday, April 18, 2013

Happy Birthday IARU


IARU Birthday: (18 April 1925)

Happy birthday!

Filter shape

Just the filter shape from an ongoing project...

Scale is not linear and I don't like the re-trace so probably will change schematics a little. Will post more when happy with design.