Sunday, February 27, 2011

Tube/Valve receiver... building the box

I wanted for some time to build a valve receiver but I wanted also to make a nice little box for it. Now here's the box buildup process documented.

An old box part of a military direction finding equipment.

Now on a peace mission...
Unfortunately I broke part of the capacitor in another experiment. Electrically is ok.
The "tube" just for the photo.

All the wire come from scavenged parts, mostly from computer power supply's

The color choice was just because that was the only color I had at the moment in the "tool shop"!.. well I had a granite looking one but...not really nice for a receiver.

It will be called the "Red hot regen".... the red part I think it's obvious, the hot it's from the warm of the tube and the regen part...well it's a regenerative receiver... obvious hum?
The worst part is that I already made quick test in the box and now I have a very noticeable reception of 94 Mhz FM local broadcaster, probably I will need some filter in the antenna input.
Power supply and speaker amp will be outside due to space constraints.

Have a nice week!

Tuesday, February 22, 2011

Tube/Valve receiver

For some time that I wanted to do a simple valve receiver (or tube depending on which side of the Atlantic you are). So now was the time!
After some testing I finally started to get some signal:

Will put the schematic online as soon as I have all issues fixed... like having an easily to duplicate "tuning" coil.
Main design is a "regen" found in the internet with 12v "HT" power supply.

it's really nice to see the glow on the valve.... most similar thing with transistors is when they explode or when resistors get overloaded...

Saturday, February 19, 2011

ARAL ham radio fair 2011

This had all the conditions to be a perfect day! I went early in the morning with some components list to buy at the ARAL ham radio fair.

(not my car! :)

After arriving I gave a quick look and in one of the tables I spotted something that I really wanted and it was on my list... some MAR-6 devices! I though: well just will give another look and before leaving I will get them, after a wile I returned to the table and started to look for the devices plastic bag.... not found, asked the salesmen where were the devices....."Sold" he answered, immediately the day got grey..I should say: black! I am fuc"#$!#"....I am pis"#$!# of... completly... for the first time I take a list and spot something matching it's gone after beeing in my hands... not fair!

Anyhow this I think was the first year I found some components in good shape that matched what I wanted. Also spotted a lot more interesting stuf but money isn't elastic :)

In the end the other thing I found in my list was an ECC82 tube, bought 2 just in case.
The other stuf not found was mostly specific crystal frequencyes and 2 HSMS2800 diode for a 1.2Ghz swr metter.
I came up with 2 extra 21.415Mhz filters I have no imediate use.... if you have an MAR-6 and want to swap for one I would be glad to do so.

Tuesday, February 15, 2011

Resistor color code wheel

Found this nice color code wheel and decided to give it a try. The most you use your multimeter the most you start forgetting basic stuff like the resistor color code, it's like doing math by hand or by via a calculator...
This should also be nice for a kids project at school age.

Here's the outcome:

And assembled:

Original work and better photos at:

Have fun.

Monday, February 14, 2011

ATV... the station

Not having much time for soldering, decided to organize the ATV station. Here's the outcome:

From left to righ: The dummy load on top of the transmitter (the PC power supply box) and the video camera; bellow: the satellite receiver and the antenna rotator.
On top a cable tv splitter with the signal strength meter

Still no audio for 6Mhz sound carrier and no clue in what is the issue. 6.5Mhz carrier works nice.
Still need to put the antenna rotator in the roof and make 2 antennas and a preamp.

Small video of everything working:

And the antenna rotator, never placed to work after being bought (around 2003)...typical

Wednesday, February 09, 2011

ATV... transmitter box

Just "bought" a new box for the ATV transmitter! I had to swap some time ago one of the PC's power supply so the old one is recycled!

By the way, this mic didn't worked for this circuit, I had to use another one.

The plugs on the PCB were keep in place case I decided to remove-it from this box.

The switch above the microphone is for 6.5/6Mhz audio carrier switching but at the moment I only have audio on 6.5, must investigate if it's any problem in the module or in the switch, the sat receiver let's me tune the audio carrier from 5 to 9 MHz.

Now the front panel labeling will be for another day, so does the external antenna.
A fuse might be a good thing to add on to the circuit...right now is unprotected. The camera get's the power from the main switch (on the left).

Wednesday, February 02, 2011


I normally don't program in "perl" but sometimes it's the best tool for the job... I am also sure you are more used to my soldering than programing skills....or lack of them :)
I needed to get data from a serial port and place it on a MySQL database. Using almost the same code I changed it to get the sentences from my APRS TNC.

here it goes the "perl" part:

#!/usr/bin/perl -w
use Device::SerialPort qw( :PARAM :STAT 0.07 );
use Mysql;
my $host = "localhost";
my $database = "your_db";
my $tablename = "aprs_data";
my $user = "your_user_name";
my $pw = "keep_it_secret_the_pass";
my $status = "0";
# for the first serial port..
# my $PORT = "/dev/ttyS0";
# for the first usb/rs232 converter
my $PORT = "/dev/ttyUSB0";
# the software...
my $ob = Device::SerialPort->new($PORT);
$connect = Mysql->connect($host, $database, $user, $pw);
open(SERIAL, "+>$PORT");
while (my $line = ) {
$myquery = "INSERT INTO $tablename (id, sentence, date_created, status) VALUES (DEFAULT,'$line',DEFAULT,'$status')";
$execute = $connect->query($myquery);

You need to change the "VARIABLES" part... but that's should be logic for you... I hope!
The database has the following structure (for MySQL):

-- Table structure for table `aprs_data`

`id` int(16) NOT NULL auto_increment,
`sentence` varchar(256) NOT NULL,
`date_created` timestamp NOT NULL default CURRENT_TIMESTAMP on update CURRENT_TIMESTAMP,
`status` tinyint(4) NOT NULL default '0',

Since I am using it for other stuff I placed the extra fields of time stamp and status.
You need to parse from the database all the received sentences for a more human readable form...

This is the output from my "WB8WGA APRS TNC" (
in the form of (id sentence time stamp status) on boot:

289 WB8WGA MODEMLESS TNC V 1.08 2011-02-02 20:45:17 0
290 Type HELP for Info 2011-02-02 20:45:17 0
291 2011-02-02 20:45:17 0
292 cmd: � 2011-02-02 20:45:38 0

Don't forget to set it to monitor mode.
If I have a little spare time will write a parser and a Google maps display

That's it.

ATV...on air

After getting ready for ATV and a little blast, my first transmission! Worked first time, now with a new/old tv set for testing :)

In the back a really messy shack.

Audio also worked fine since the camera had a mic input.
Probably will take another 5 years to put an external antenna and make the first qso. Will see.