The "Speaky" HF SSB transceiver and other homebrew projects

Ciencia an Mirandes - Al Centificu Eilustradu

2012-01-17T11:23:00.005Z

Or: "Science in Mirandês - The illustrated scientific"

This post is not only about ham radio or electronic design but about an interesting blog I found; not only for the subject in it but because it's written in a language I know very little.... "Mirandês".
This is the first blog I found about ham radio and science in this language, and I found it by mere chance during a web search.

You probably don't know (for the not Portuguese natives, and many natives for that matter) much about this language but Portugal has two official languages (since 1997), yes that's right, beside Portuguese there's also "Mirandês" language.
Mirandês is just spoken by a very small community in the North East part of the country and it's only learn at school in that area, for me and as a simple explanation it's a mix of Portuguese with Spanish adding the country North-East accent. For a language student that could not be the most accurate way of putting things....for English readers to understand I would say it could be a mix of ancient English with current English on a Scotish accent :)

Here's a litle sentence from the blog, in Mirandês and my translation to Portuguese, Spanish and English so you can see similaritires between languages.

In "Mirandês":
"De restu hai uns méźes atras la NASA dixu que punarie outra véç l purgrama an lliña... y ya sta"

In "Portuguese":
"De resto hà uns meses atras a NASA disse que punha outra vez o programa em linha...e já está"

In Spanish:
"Además hace unos meses, dijo la NASA volvió a poner el programa en línea ... y ya está"

In English:
"After all, some month's ago, NASA said that would put again the program back on line (track)... and it's done"

I point the fact that language knowledge is an valuable tool, normally my radio searches are in English because of the language wide spread but I do find many interesting pages on other languages like French, Dutch, German, Russian and Japanese, being, from my perspective, the last two the most outside the norm radio designs (specially in component references). So, next time, you, the reader, could try to search something translated to another language, you'll see some different results for sure!

The "ciencia an mirandes" (Science in Mirandês) blog is here

Even if you don't understand the language at least the images and videos are universal.

Have fun, in any language!

Handycam CCD-F370E mini crt - II

2012-01-13T16:26:00.004Z

I have a spot!

...but before this image, first I cut the vertical deflection coil... had 50% chances of finding it on the first try... I did!

Then cut the horizontal deflection coil (actually I removed the plug on the coils) and got the spot! I new beforehand that the timing/blanking circuit would work erroneous or would stop working since the coil is part of the circuit so I replaced the crt coil in the control circuit with a 33uH or 330uH choke coil (I think... orange, orange, some sort of grey, have to measure and try another), the spot got better and more focused but still not perfect.

..I could just had hook up some signal to the coils...but no! This way is more fun!

Now the problem will be the "Z" axis, I can build an video blanking circuit in tandem with a sawtooth generator (and feed the video in the original circuit) but that would be to much trouble, I will try to control directly the crt or add just a marginal circuit in the blanking part which is pin 11 in the following control circuit.

More search (use an translator if your Russian is like mine...zero, besides: Vodka, Polyakov, Piskunov and Dasvidania! Sorry for the spelling) and I found a similar design (from Samsung) on the one I have:
The red dots are the blanking circuit, I am thinking in "attack" directly "G1" on the tube or maybe the center part of the pot controlling the intensity, (not perfect but should work), I think it's better than removing the tube and make a new HV circuit.

have fun, I am having... a lot!

Handycam CCD-F370E mini crt

2012-01-12T18:42:00.006Z

Short story: I have a Sony videocam bough some years ago but I think I never recorded anything with it, it was bought second hand and for some years it worked, I mean, I could see the lens image on the viewfinder but it stopped working some months ago, the camera can't focus anymore and I have only what looks like out of sync in the viewfinder, probably some cap leaked and or out of specs.
Since I never used the camera and there are less bulkier and digital alternatives nowadays, why not open it up and remove some components; being the most interesting parts the microphone, the lens and the view finder. Specially the viewfinder looks interesting to make a tiny oscilloscope (while I don't fix my broken scope) or an ATV video monitor.

Now on to dis assembly:

The viewfinder part...

After searching I found some people in the same path but no detail on pin out for the minicrt, so, on to some reverse engineering.

It took me some 10 minutes to find the connection pinout, just to discover the crt would not give image although the record led (connected to the crt control board) indicated power. I increased the voltage to test on 9V (was using 6V and is correct). Nothing! Bloody hell! I hate reverse engineering!
Stopped and waited some time, then returned and had another look just to discover my fault, I was biasing the power the wrong side, I mean I thought the led was switched by the positive but instead is the negative (cathode, anode is always connected to +), it also helped tracing a big coupling cap connect to the only IC in the board (it had to have power directly connected so easy to trace to power line)..... "et voilá", the thing works but I still didn't connected any signal to the board.

The small component near the crt in the following image is an 1W zener.... it's really small the crt but with the lens it's easy to view.
Now the pinout:
After all this work.... if I had just looked bellow one cap I had noticed that there was an video IC bellow it.... if I looked on the IC datasheet I had easily found the pinout, live and learn! Now I have to trace deflection coils to the AN2512 ("Electronic View-finder driving IC") to make tests on deflection.

Now the lousy video:

Have fun!

The "Speaky" reborn

2012-01-09T19:32:00.005Z

The Speaky HF SSB/CW transceiver kit was the main reason for this blog to start, at that time I wanted to document the building process of the kit but after a while it became the virtual space for my radio electronics projects.
I did finished the build process of the kit but got some bug's on the first test so decided to stop for a while. Now I will rebuild the kit, mainly the cabling to the main board, I made it short the first time and got to the conclusion I need easy access to make further tests.

Today I started debugging the project, the first problem was the frequency counter, a swapped cable (signal and ground) was the reason for not counting the LO frequency, now it's ok but there are around 30 new cables to be done.... lot's of work for the upcoming times....

Only the 40m band module in place, still need to solder the 17m one and probably add another one, the main board allows for 5 band modules, only ordered 2 at that time.

It was also an opportunity to clean the mess in the bench :)

LASER AM modulator

2012-01-07T14:24:00.005Z

Here's the LASER pointer AM modulator, QRO version, as promised in last post!

The receiver used in tests is the same I've been using in previous tests except I changed the 2 green LED's for an IR diode.
If the LASER is pointed directly at short distance directly to the diode the receiver (LM386) get's overloaded, just point slight off-side.

I'll stop for now this light comunication tests, was just to test the concept. I also tested the AM modulator circuit against a small crystal oscillator buffer and it worked nice.

Have fun!

Health and a Happy new year

2011-12-31T18:01:00.002Z

Are all my wishes to this blog readers.... and maybe some Eur/USD/GBP/etc to spend on electronic components :)

Here's the light modulator in QRO version...and a better reception "antenna"!

Will post more details next year! It was made today.

Have fun!

6500K AM transceiver

2011-12-29T18:20:00.008Z

After the build of the 6500K AM modulator I had to do a compatible receiver. Following the tests with the green LED's I thought they were the right candidates to "antennas"...

before the receiver part build I made a small audio oscillator since it's easier to test with a steady source than a mic, this one oscillates around 1100 Hz.

The oscilator "out" after the pot and 0.22 cap connect's directly to the transmit driver input:

There is nothing simpler, not high performance of course...

Receiving part is just the 2 green LED's connect directly to the input of an LM386 amplifier with 200x gain. Standard from datasheet and no input level pot.

And here the prototype in test:

I got 1 inch range before signal get's to low, in fact signal is just near the noise floor of the LM386, an preamplifier would increase a little bit but using LED's as light receivers isn't the most efficient way of doing things, an LDR or a phototransistor will do a better job for sure. Anyhow it's just a proof of concept....

Have fun!

Powered by led's II

2011-12-28T21:03:00.003Z

Another test with LED's, last time I didn't tested all in the junk box... now I tested the green variety, 2 in series.

The light emitter in the video is my Christmas self present, one LASER pointer that doubles as a small lantern with 2 bright white LED's. Local electronic store doesn't store LASER led's so for 2.5 Eur I had one, just have to disassemble it for further tests in light transmission. The optics su!"# big time but it works for small scale tests.

I did test also a Ge diode with a glass envelop and it did respond to the LASER light giving 21mV, it was an OA90 type I think.

Trying to scale the led's for power harvesting isn't interesting, it's cheaper to buy a small solar panel (from my head calculation) and also other solutions, will try them one of this days.

Electronics - Zener

2011-12-26T23:53:00.007Z

I post some schematics, some are mine, mostly aren't.... I do understand some basics on electronics but as year's pass somethings are getting forgotten so here's an exercise to remember....

Zeners are tiny little funny devices.... they sit quiet in their room until someone drops them a voltage over their rated value, basically like diodes but on a bigger scale (voltage wise), and then they tend to conduct some electrons.... I never thought it was so difficult to explain what components do..... let's say a zener is the equivalent of a series connection of diodes but connected the other way around, polarity wise.

So let's see a tipical circuit with a zener:

There's a power supply, Vs a resistor R, a zener (that weird diode) and the famous (or not) NE602.

So let's see from an engineering point of view.... the potencial diferencial sum (basicaly the sum of voltages) in a circuit should be "0" (zero)... if not you are creating an energy monster :) but this doesn't matter for the zener subject...just for puting arrows in the circuit case some old teacher of mine sees this...

On we go...

Let's supose we need to stabilize the voltage in the NE602 at 6.2V (just because it eases some math and circuit simplicity). It's also nice to know that the NE602 needs about 2.5mA (0.0025A) of current to work and we have a power supply of
13.8V (most of the time) and our zener can witstand 41mA (normaly more but this is a tested current value from the datasheet and we whant things cool)

Now, we can do this in two ways....

The worst case scenario and the low power scenario...

* The worst case scenario:

Let's say we can have a problem in the power supply and voltage can raise to 24V

We would have to drop some 17.8V in the resistor to maintain 6.2V in the NE602 so our resistor should be (U/I) 17.8 / (Iz + Ine602) = 17.8 / (41mA + 2.5mA) = 409 Ohm...
Power dissipated in the resistor is: 0.77W
Power dissipated in the zener is: 0.25W

So what about when we are runing the nominal 13.8V:
We would have to drop 7.6V in the resistor (13.8V less the zener 6.2V), if our resistance is 409 Ohm then the current is: U/R = 7.6/409 = 18.5mA that is 2.5mA for the NE602 and 16mA in the zener diode.
Power dissipated in the resistor is: 0.14W
Power dissipated in the zener is: 0.099W

* The low power scenario:
Let's save the planet and make low CO2 emissions:
We have a good 13.8 power supply the NE602 consuption is still 2.5mA and we will give just 5mA for the zener (he must do something and still have some margin for power supply flutuation)
Our resistor is now: U/I = (13.8-6.2) / 7.5mA = 7.6 / 7.5mA = 1013 Ohm
Power dissipated in the resistor is: 0.057W
Power dissipated in the zener is: 0.031W
Much less power than on the worst case scenario...
...let's just see what max voltage the circuit can withstand...
We use the same 41mA max on the zener and 2.5mA on the NE602 so voltage on the resistor is R*I = 1013 * 43.5mA = 44V plus the 6.2 on the zener that's: 50.2V
And what if the voltage drops: let's acount only for the NE602 current so the voltage in the resistor is 1013*2.5mA = 2.53V plus the minimum for the NE602 that we consider is 6.2 then the voltage in the circuit should be no less than: 8.73V.

Conclusion:

The worst case scenario let's you drop more on the power supply voltage (409*2.5mA is less than 1013*2.5mA).
The low power scenario covers you more on over voltage and has less power consumption at normal operating points...you choose!

Have fun!

Mussels...

2011-12-16T16:53:00.005Z

The problem of being a home brewer/DIY/having the knack ,on electronics is that sooner or latter you end up thinking you can build/make anything...
One of the first things outside electronics I did was changing the car oil, the sparks and air and oil filter.... it went well...but now it's something different, after watching some Australian "Master Chef" episodes I convinced myself that cooking is easy....compared to harmonics/IP3/band filters, etc...

Here's a local recipe with Mussels (they were also "caught" by me).

You will need:

*Mussels
*Garlic
*Onion
*Olive oil

Just pour some olive oil, some chopped peaces of garlic and onion on a pan, take it to the stove in a slow cooking position.
As soon as the onions and garlic start to get a light yellow color (means they are starting to get cooked) pour the mussels inside, keep a low power on the stove, cover the pan and let them cook in the steam. Do not put water or salt, they have plenty of salted water inside. Let them cook until they have the shells fully open.

The mussels should be fresh an alive.

Here's the outcome:

It's more of an entry or "tapas" than a meal.

A circuit in the next post... or another recipe!

Mains filter, results

2011-12-09T13:10:00.004Z

I told you I would write about the mains filter performance after the little VDR issue (blast off).

Well... did it worked?.....did it?...... n....no! Can't win all the time!

I'm sure the mentioned filter would work in minor interferences from mains, so the filter will be put in line with the transceiver power line (it's 230V AC powered).

I am not the first one to have issues with switching power supplies since by their nature they are an RF source and this one is a beast, 4A at 20V, normal laptops are have half the rate in current, I guess this computer is not very economical in power consumption.

When removing interferences that you suspect are from a power line there is some simple stuff one can do:

*Put a power line filter: Didn't worked in my case. If the power is DC sometimes a simple capacitor in parallel or an inductor in series will do the trick (low pass filter), capacitors "don't like" voltage change so do the inductors with current.

*Invert the power plug terminals: This will work if the source problem is unbalanced (power line wise)

*Some ferrite cores around the power cables. I've used this method wen using the Si570 RF generator close to some testing boards and it works (Now when using the Si570 I power it up from a separate power supply).

*Build a Faraday cage: Will work as long as that any "air" space in the gaps is smaller than the interfering wavelength... but for my case I suspect the interference is getting in from the antenna cable since the FT-102 it's self is build in a metallic "Faraday cage". I discarded the hypotheses of the interference getting picked by the antenna since it's 10m away, never the less further tests will be conducted...like removing the antenna cable and the microphone.
I didn't tested yet was to put the laptop power supply inside the filter cage and earth blindage exiting the power cable or even moving to another plug (it's to far away for connecting the laptop to the screen monitor).

*Put and isolation transformer (230V/230V): That is expensive and I would prefer to put again the small computer previous used that I know causes no interference.

Well...the saga will continue....I will test more this weekend.

6500K AM modulator

2011-12-05T11:28:00.005Z

...Or a "spread spectrum" AM modulator, 390 to 750nm wavelenght, or 400 to 790 THz..... or a white LED AM modulator... now you get it?

Following some LED experiments I wanted to try some light comunication, so decided to do one of the basic forms of modulated light communications, AM, for good or for worst the idea was just to have some fun....

Here's the transmission part, when time permits (I still have a huge backlog on lower frequencies projects) will make some companion receiver and put a mic on this "transmitter".

As you can understand, first I did the schematic and then the final draw on paper...
Any NPN transistor should work but more led's (more power!) will require a more robust transistor, the speaker was just to ear the modulation noise (touching the LM386 input pin), I had no mic at hand.
The pot set's the bias point, and the led should be always on (a steady carrier!?), changing bright by modulation.
LM386 gain was set by an 10uF cap between pin 1 and 8 as standard design.

You can ear noise and see some modulated light in this lousy video:

Have fun!

Powered by led's

2011-12-03T18:08:00.004Z

I do like led's but aside the fact they are nice to show power on in circuits I only did some minor tests with them. One of the experiments some time ago was to use a led as a poor and small replacement for a solar cell, yes led's can generate small amounts of energy. Some can sense radiation and other types of PN junction can be nice for temperature sensing (like 1n4148 diode)... normaly components have more than one function you know?! The classic example is a resistor used as a camera flash :) One time action of course!

Next images you have an infrared led, (I think, since I don't remember the specs or even when it was bought) the outer case is light blue and emits no visible light when direct biased.

Here in reverse connection getting some direct sun light.
Two of them in series should give 1.4V althoug on a very small current, this multimeter has 10M of internal impedance but if you put some in parallel you end up with a very small power supply as long as the sun shines...

Here's the "power" from a white color paint!:

Incidently this gave me the idea of using one of this for a very crude Sun photometer.... maybe one of this days...

And in the dark:

This led was the best one I tested, other standard types gave worst results.

Have fun!

Mains filter

2011-11-22T10:40:00.005Z

A friend gave me one of those new computers....a tablet...:)

...never mind the missing screen (there's an vga plug), it works and it was cheap!

My idea was to put Linux in it and use at the weekend shack, it came with windows something installed and for now will stay that way (sure not for long since I'm a bit allergic to that OS).
After some psk and rtty decoding apps installed, decided to hook it up to the FT-102. I was a rainy day and I was getting a lot of interference, I thought it was the weather but after shutting down the computer I notice the interference had gone and the only (confirmed) source was the computer power supply! Rat's! Something had to be done....

So I came up with the idea of making a mains filter idea. The other option includes a Faraday cage for the power supply or getting another computer.

Here's the assembly of the interference filter for the mains power supply:

well....did it worked?.....no and not tested yet, after powering it up (I should had tested before closing the box) the VDR blew up, I guess that it was underrated or I didn't looked very well to the schematic of the donation computer power supply were I removed it and probably the VDR was not on the mains line and was not rated for over 230V.

Now that I removed the broken VDR I have to wait for the next weekend to conduct further tests.

Here's the schematic used:

..never mind the VDR (it's just for spike protection), it's not installed at the moment. If you duplicate this, get capacitors rated for at least 500Vrms, the ones I used are rated 1KV and came from a computer power supply.
The number of turns it's not critical as long as they don't create a lot of impedance on the mains 50Hz....I guess something bellow 1000 turns it's ok :) The idea is to create some high impedance on HF and VHF.

I also placed a ferrite core (the ones used in computer power cables) around the cables as a "won't hurt, probably will help" option.

The white output is the filtered one (it's an old household mains plug), the other two are input and a not filtered output, they came with the donated box (a broken computer power supply).

There's no reason for this schematic do not work at least reducing the level of interference. If it reduces all ,then it's a bonus.

New 10m radio

2011-11-12T23:08:00.005Z

I don't have much time to do QSO's, in fact time is short even for soldering.... but I have a new radio.... A "Dragon" delta force.... don't you just love the names some manufacteus give to radios? There's also the same radio under the "Magnum" brand. Probably one of this day's someone is going to build the "Kalash terminator" 10m mobile.... :)
Here's the lousy photo:

10m was hot today, I've heard a lot of QSO's and almost pushed the ptt to answear a CQ call from the USA...maybe tomorow!

My first impression on the rig is a positive one, it works and receives nice, vfo operation is not easy on 1khz step since it counts from 1 to 9 but then returns to 0 without increment the 10's Khz...! It's not build like Yaesu, Kenwood etc, in term's of knobs material and front panel (didn't looked inside yet) but enough for the intended function, a receiver for some dowconverter's I will build.

FM crystal radio

2011-10-08T13:11:00.005+01:00

I'm back!...Along with the lousy photos and the rusty English...

Having already build a lot of receivers with different approaches I have never tried FM with a "crystal" radio. Now is the time.

This is a simple circuit and honestly I wasn't expecting much performance but is fun and helps getting some momentum for future builds.

I can only get two very faint stations and with an external amp based on an LM386, my "crystal" earpiece I guess is not crystal....

My implementation

The schematic was "borrow" from here. Go on, see the original and nice implementations on that site.

Original schematic from the author site

L: 5 Turns of 1mm silver wire on an "Edding 3000" pen (around 12mm), diode connects to 2.5 turn (half the coil), spacing is around 2mm
D: OA90 or 1N34 (not sure, it wasn't marked) I tried several glass diodes and results were similar.
R: 150 K
C3: 18p
C1: 82p
C2: used one trimmer of 25p (80pf on the original schematic)
Antenna was around 25cm of wire and the 2 station's received are less than 8 km from the shack.

Have fun.

Summer...

2011-09-21T22:22:00.001+01:00

Sorry for not posting for the last few months but honestly I've been very busy.

Some 20 years ago I took the training in beach lifeguard, then I did some work on the beach in the following years as a summer job. At that time the training was valid for 5 years and I didn't renew it until this year.
This time, (20 years later) it was not easy from a physical point of view to make the training, most of my colleagues weren't even born when I did my first lifeguard summer on the beach.
I was the oldest in the class (but not the slowest swimming) although my time in the 400m is a little more than the double of the current olympic record :) anyhow I'm not thinking in going for an olympic medal

In June I was counting only to work some days replacing some colleagues on leave but I was offered full time in a near by beach so I end up doing all the summer season from 15 June to 15 September ence not having much time for this blog.

Partial view of the beach

The beach dog with the lifeguard hat and the yellow flag!
By the way in all the beach's were's a lifeguard there's a pole with a flag system for sea water conditions: green for good conditions, swiming is allowed; yellow for moderate conditions were swiming is not allowed but a bath is and red for dangerous conditions were beeing near the waterline is dangerous and is forbiden to go to the water (we have some tolerance during a red flag day).

My observation point and some rescue equipment.

During training! Why swim when you can go by "boat"? Guess who am I in the photo! :)

In the end all went smooth and I only had to do some small rescues.

Now I am slowly getting back to electronics and to this blog. Stay tuned!

What's this ? III

2011-05-12T14:33:00.000+01:00

While I don't get time to make a more useful and tangible electronic construction here it goes another "what's this" question....:
What type/model is this and what's the frequency range?

From the last post, here it goes the image on reference point GPS receiving antennas for error correction on GPS signal.

As usual in Peniche there's always a seagull on top of something...

What's this ? II

2011-04-30T12:28:00.005+01:00

Here's another question, this time I know the answer...

The location is "Cabo Carvoeiro" (Cape Carvoeiro) located near the city of Peniche and of course the building is a lighthouse so that doesn't count as an answer, the antenna is a T type being the top part made of 2 parallel cables (lenght is 92m height is 27m), so could be probably a simple T with more bandwidth or sort of a terminated loop. There's also the possibility of beeing 2 antenas in redundance! Sory but I don't have more exact technical details.
The question is: what's the purpose of the antenna?

Anyhow the late antenna is almost as good as the HF one I putted in my alternative shack.... made in 20 minutes...

can't get more simple than this...2 pieces of wire forming a dipole. Not perfect but much better than using the VHF antenna (it was for reception only!)...

Meanwhile I have been busy with other stuf so you have to wait for some more solderings... maybe next week.

World Amateur Radio Day

2011-04-18T11:55:00.003+01:00

It's today!

The IARU theme for the 2011 World Amateur Radio Day is:

"Amateur Radio: The first technology-based social network"


...some do take it to the extreme!

have fun!

What's this?

2011-04-12T23:03:00.003+01:00

I haven't had much time for soldering so here's just a litle radio related post to keep the blog updated.

One of this days I went to the city park with my daughter for some fun and in this public space there's a nice little plane, it's there for the time I remember, for some time neglected now it's on a more proper shape. Beeing an ham, couldn't help from spoting some radio related parts.... but there's one I don't know what is it maybe someone can tell me:

The white cap look's like an insulator for the HF antenna at least it's very similar to the ones used in boats but the bullet shaped big device on top I could only guess it's some sort of radar or direction finding antenna inside, honestly I don't know, maybe someone knows....

The plane it's a Beechcraft DS 18/C 45 under "FAP" registration number 2508

100 W on the cheap

2011-04-01T11:02:00.005+01:00

I spend some time yesterday thinking in today's build up.

Having read a post with schematics of compact fluorescent lamps I thought what could be done with those components.
Searching in components specs I noted that the MJE13001 transistors have an TF of 1000000000mHz so that's qualify them to be used in an HF amplifier, also their absolute voltage rating is in the order of 400V (collector to emitter).
I didn't planed to use the 400V but instead a more conservative 110V.
I also found that the toroid present in this lamps (first schematic on the site referred) it's similar to those used in broadband transformers (type 43 material) so will be used also.

Remember that voltages present could be lethal so take absolut care building this stuff.

Here's the schematic:

You should absolutly place a bandpass filter since transistors are working near saturation ence increasing harmonics.
Also place a a cover in the assembly before firing the power because they will get a little, just a little bit hot.... also usefull to remove hardware interferences :)
you can reuse the 1 Ohm resistor from the lamp and place them in the emitter of each transistor, reducing a little bit the output power to around 50W according to my readings.

So here you have from 5W to 100W with a light bulb and 2 power transformers!

Photos of the prototype will be placed tomorrow since I run out of cell phone battery. that allways hapens to me in April first.

Day at the beach

2011-03-27T22:28:00.003+01:00

Like most Sundays I go for a visit at my parents house.
The day usually begins with some sort of computer problem I must sort out...today it was no exception, the monitor of one of my father's computer didn't turned on, after the normal cable debug I fixed it really fast, exchanged the monitor and putted the old one in the things to fix later or for parts.... while I debugged the problem turned on the FT-102 on 20m band for some listening, and hell, even with the vhf dipole connected the contestants were putting 55, 57 on the southern Europe... who cares about QRP?! Anyhow, Im not a big fan of contests so headed to the beach.... much better, althoug the temperature was not that high, around 18ºC... :)
Here's something for the Eskimos:

Meanwhile the tube/valve direct conversion receiver already works but I am having some impedance mismatch at the rf mixer output so will have to fix it without hopefully putting a, rare around here, audio impedance transformer.

Have a nice week!

ECC82 Downconverter

2011-03-25T21:54:00.002Z

I bough a spare ECC82 valve when I built the ECC82 regen receiver, already tried a valve VFO (worked), now decided to tryout a valve down converter as a first test to a tube direct conversion receiver.

Basically one half of the ECC82 is running as vfo then there's a single balanced mixer and will be an audio amplifier using the other half of the ECC82.
Interesting thing is that this circuit worked first time, I even forget to count the turns in the mixer core, the rfc was the first coil I found from an old PSU and the mixer output termination was the first small cap I found...
Signal out is not much but hell what do you expect from a lousy mixer made from a binocular core and 2 diodes and 4m of cable laying in the floor working as antenna...

The oscillator was running at 6.7Mhz and I was listening on 365Khz so one of the received frequencies was 7.067Mhz... I promise a schematic soon.

Add: here is the schematic used:

Inside the sat-finder

2011-03-17T20:33:00.003Z

Being a curious "animal" decided to have a look inside the sat-finder, probably the only equipment I own that never had been opened for "evaluation".
Here's the outcome:

There's some common components an LM358 opamp and a "C1C" component I could not identify or find info about, probably a dual diode or some transistor but it's marked as U1... so it could be also an IC. It's for sure the first stage for measuring the signal from the line.

Found very few schematics about sat-finder but here are some links:

This one also used an LM358: http://www.khazama.com/project/satfinder/default-en.aspx
Homebrew but it could be very close to what's inside..

and this one: http://www.neazoi.com/echochanceller/Satellite_Finder.gif