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 70ºC

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!