The "Speaky" HF SSB transceiver and other homebrew projects

New adventure

2013-06-19T01:15:00.000+01:00

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!

End block for a spectrum analyzer add on.

2013-06-16T21:31:00.001+01:00

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!

20m band module

2013-06-13T22:52:00.002+01:00

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!

In the mail

2013-06-04T23:32:00.000+01:00

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!

Continuing the Speaky new band modules.

2013-05-28T20:43:00.002+01:00

Got this today:

(T37-6*25)

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

New antenna tuner box

2013-05-27T22:19:00.001+01:00

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.

Today's work

2013-05-25T22:40:00.000+01:00

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!

FM loop

2013-05-22T20:50:00.002+01:00

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!

Thermal paste

2013-05-08T19:45:00.002+01:00

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!

New coil for the antenna tuner

2013-04-28T11:17:00.001+01:00

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!

Happy Birthday IARU

2013-04-18T23:03:00.002+01:00

WORLD AMATEUR RADIO DAY

IARU Birthday: (18 April 1925)

Happy birthday!

Filter shape

2013-04-18T12:45:00.000+01:00

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.

SAW generator

2013-04-15T19:11:00.000+01:00

Not much RF here, except it's part of a project involving RF.

A simple SAWtooth wave generator:

Schematic is from VK2ZAY and the current source my contribution. Incidentally I didn't tested the original design so don't know which is better...probably not mine!

(VK2ZAY schematic edited by me)

Now the output of the schematic:

Wave form with an 10uF capacitor:

...there goes the linearity... oh well...

here with 4.7uF capacitor and final configuration for now:

DC out is 2 to 7V approx (Vcc 9V).

The last wave feeding the oscilloscope horizontal circuit

Here the assembly:

Alan has other designs using discrete components I might test.

Have a nice week!

Speaky AM

2013-04-11T22:40:00.000+01:00

Not rocket science here. Just "grabbed" the 8Mhz pre-filtered and buffered output add-on of the Speaky and made a simple 8Mhz AM "receiver" with an IF of 455Khz. Mixer VFO runs at 8.455 since at 7.545 would put if receiving on the 40m (7.090Mhz) band also.

It's just a simple tuned input for an NE602 mixed with 8.455Mhz going thru an 455Khz filter feeding the AM demodulator part of an TCA440, then audio goes to the famous LM386.
Since it's a ongoing experiment will not place schematic for now, but works nice on this simple setup....I can still copy clearly some SSB transmissions, so I'm sure there's little carrier suppression on some rigs...

The main PCB and the TCA440 part were a re-use of one of my VHF air band receivers...another project that had a short live before donating parts...

Have a nice week and weekend!

New bands

2013-04-01T20:25:00.002+01:00

While some people over here were applying for access on the 5Mhz band, our telecoms regulator "ANACOM" on a bold move just gave us access to another 8 bands in the HF spectrum.

I think this is a shift from the classic deny first, allow latter paradigm that is so classic across all sectors of society.

The new bands in Portugal are as follow:

455 Khz
600 Khz
4 Mhz
8.865 Mhz
9 Mhz
10.245Mhz
10.7 Mhz
21.4 Mhz

All modes are allowed. This is of course on a non interference basis, hams are primary users.
Beacons are welcome using low bandwidth modes.

Frequency shift is allowed to a maximum of 15Khz deviation

Output power is not regulated yet but probably will be around a maximum of 17dbm to keep things even with the other allowed bands.

Let's hope this new bands get adopted all over the world!

Backlog...

2013-03-31T20:47:00.000+01:00

When you try to multitask on a single tread then for sure something gets behind...

Here some projects tested but lacking a proper finish touch:

Light TX and RX pair:

Work's but didn't tried yet with a magnifier glass to increase range.

A BITX 20:

Needs the front panel drilling and now the front end transistor that was needed for another project.

An 6m downconverter:

then used as a test board for VHF receiver using some BITX 20 modules.

An SWR meter board:

..and the "display":

...Still unboxed.

A full HF transceiver:

Working but never QSO'd. Will change audio path and need to put the low pass filters.

..many other projects still waiting conclusion most of them just need a box...

Think I have "work" for the next decade!

Have a nice week!

Got this...

2013-03-28T16:20:00.000Z

...in the mail yesterday:

...thanks to my PayPal account!

Those are 100 units of BB909B from DSI and about 50 (not exactly counted) BB909A from Philips.

The idea is to place them to work on the Speaky band modules replacing original BB409 varicaps that I can't find at reasonable prices.
I don't know if these "replacements" they will work but they were relatively cheap and can always be used for something else.

Here's capacitance versus reverse voltage on the "Speaky" BB409 units :

And here for the BB909 :

They almost match...

I measure some units received (both BB909A and BB909B) and seem to match the datasheet values, the Philips ones have a little higher capacity than DSI make.

Still in need of the toroids...

Speaky band module expander - issues

2013-03-22T22:47:00.000Z

....ah... the smell of success.... followed by disappointment... nothing beats the thrill of trying to find the problem without success guaranties!

I was building an expansion band module (for the band module expander...confusing hum?),

basically a blank band module that will allow me access from outside the radio bandpass and VFO signals

Then I was injecting an external VFO signal and noticed some instability in frequency using the 40m band.
(On the left using the Si570 as external VFO)

After debugging a little bit I discovered the culprit...

..the cable linking the two boards, the VFO part, so, for now the solution is simple, if I remove the cable, loosing the extra 5 band expansion I have no problem but I want to know the cause. The next few days I will experiment with cable length and some blindage, strange is that on the 17m band the problem doesn't show, so, I guess is more a capacitive issue than an inductive one given the wavelength difference. Funny is I tried to make the distance between the 2 boards the smallest possible just to avoid this possible issues.... yeah this time I thought before soldering...useless!

Have a nice weekend!

Speaky band module expander - rebuilt

2013-03-20T22:02:00.001Z

Just rebuilt the band module expander boards. Rebuilding allowed me to save some "veroboard" and correct inter-board wiring mistakes I made first time.

Here's the support for the five extra modules, the first five stay in the radio main-board.

For supporting to the chassis, used a 90º wood support transformed in double 90º with my special angle maker tool....the hammer!

Some varicaps are on the way to the shack so I can start building the modules still missing:

I also included, inside, another board for a second audio amp, main amp will be only for headphones and the computer audio interface:

..still unbuilt..

And here: 2 of my 3 transceivers....none is complete...

...but will be some day....

It's a long road...

Standard diodes for RF switching

2013-03-16T17:05:00.000Z

This idea of pressing ordinary diodes for RF work is not new, many LED's are working as varicap's, some diodes are protecting antenna front ends, other are working as zener's for transistor biasing and the list can go on...can you imagine that some diodes are even working as rectifiers?!!!...

Now, this idea come because I have some (8) band modules to build for the Speaky and each module uses 4 PIN diodes, so, that's 32 diodes more than the ones I have... or for the mater, the local electronic shop.

(PIN diode is BA479 on the schematic)

Using ordinary diodes for RF switching is nothing new, many circuits use them.... but are they good? Or just reasonable? I had to test for myself!

Built a small circuit: the diode being tested in series with an 82pF capacitor and connected to an C meter. By placing in series I avoid any possible influence on the meter measuring method by DC blocking with the series cap, anyhow I think the measuring method of the multimeter is by impedance, injecting an alternate signal, and not by capacitor charge.

Here's the measured and computed results from the series association:

Light blue/grey is capacitor impedance above 500 Ohm, less than that and gets to close to the usual 50 Ohm influencing circuit performance. That's the importance of having a very low diode capacitance for RF switching. If signal is of high value it's also needed a diode with high forward current to keep things linear.

So, from this simple test results, and if you go bellow 28 Mhz, the 1n4148 is probably a safe alternative for RF switching. Interesting is also the yellow LED result by would not use it in circuit due to voltage drop.
I don't know what was the issue with the Germanium diodes, didn't investigated further since I was more interested in Si type.

In the 14Mhz band module I built for the Speaky I used 1n4007 and 1n4148 without noticeable issues, let's see if it doesn't mess things with more modules in parallel.

Just a side note:
BA479 diodes have an capacity of 0.5pF at 100Mhz (from datasheet), 1n4148 have 4pF at 1Mhz (also from datasheet), so, if you go the VHF side I think the only way is to use real PIN diodes for RF switching.

...now I have to find alternative varicap's and ferrite cores...

Have a nice weekend!

Reader alternatives

2013-03-14T21:26:00.000Z

I use google reader service to keep up with blogs and sites I normally follow.
It suits the porpoise and it's easy to work with, plus it's web based so I can keep up with followed blogs/sites as long as I have network access and a browser.

Here's a screenshot when all the news for the day are read:

(no special order in the blogs list, except mine first :))

Now the problem is: Google will decommission this nice web app in July first.

I wonder what software fellow readers use to read blogs/feeds/site feeds.

Of course I could get an XML/RSS parser lib and make a small hosted app for the purpose but time is already short for soldering and I put soldering first in my free time...

I'm open to ideas, preferably web based, but I'm considering also Linux based ones also. So let me know your opinions!

Have a nice day!

New antenna tuner

2013-03-10T22:03:00.000Z

Ok, I have enough projects to finish, inclusive my "old" antenna tuner,...

...anyhow decided to rebuild it and re-use the nice box for other projects.
The "new" tuner will get a wooden box, it's cheaper and adds less inductance for the coil. So my only weekend project was to make new L shaped aluminum brackets to support the variable caps.

There's also a new coil made that I need to test.

Maybe during the week I can have more time for other projects in mind.

Have a nice week!

Speaky band module expander

2013-03-02T23:09:00.003Z

The "Speaky" comes standard with 5 band module slots, I wanted a little more.

Here's the idea, five original modules in the right and five more on the left.
At this point (on the next photo) I only had soldered the support for one additional module on the left (with my crude 20m module just for testing).

First live tests when I realized I had incorrectly wired the jumper cables between the two boards:

Still have to rewire the expansion (for the bandpass filter) cable (lower left on the "veroboard").
Also realized I don't need to duplicate all five original support mounts, just need to parallel one of them to the expansion board, sparing some "veroboard" for other projects. Again I went to fast from idea to solder...

Have a nice weekend!

Panadapter/bandscope/spectrum analyzer/decoder idea

2013-02-24T10:07:00.000Z

OZ9AEC had the nice idea of connecting one of those USB TV dongles to a "Beaglebone" board:

With that he got an "Spectrum analyzer", for about 140 Eur (more or less depending on supplier), and a computer running Linux.

Now...imagine...connect the same Beagle board (or any other small board running Linux) to a USB sound card, a USB to serial converter and a USB SDR receiver. The SDR input connected to your radio unfiltered IF, the serial interface to the radio control port and the sound card to the radio audio output and you end up with a box similar to this:

..except it will be a little bit cheaper and with more options... the P3 costs about 699.95 USD (530 Eur) and won't give you all mode decoding, only rig control and a bandscope.
But what's the point? A small laptot can do the same, yes it can but you can not do something similar to this with a laptop:

....ah... so many ideas, so little money :)

Have a nice week!

Mensagem

2013-02-23T14:41:00.001Z

"Mensagem" (Message in english) is a book by Fernando Pessoa, and one of the book's most famous quote is: "...o homem sonha, a obra nasce..." that translates to: "...man dreams, the work is born...".

...all homebrew, including the wood desk!
I built in a piece of pcb the 20m band module for the "Speaky" (working in the photo) but just the VFO part, bandpass for 20m is direct, anyhow receives nice. Still, more 7 band modules to build!

Have a nice weekend