Tuesday, August 26, 2014

Scope bandscope adapter

...Just some modules glued togetter:

 Signal on display is from a QRSS Kit at 14.200Mhz...

 placed very close to input since there's no positive gain in the circuit and the mixer was homebuilt.
 Lower channel is the trigger. Log detector is an AD8307 and IF filter (10Mhz) is incorrectly terminated....

...plenty of room to improve....

And... have a nice week!

Thursday, August 21, 2014

New oscilloscpe - Rigol DS1052E

...Yes, my third oscilloscope. First one, the "Kiotto" brand (nice crap of tech support) died some time ago. Then I bough a second hand "Hameg" HM307:

 (in need of some maintenance but still functional as long as I let it warm) which is on main shack.

This new "Rigol", I'v been thinking in getting it for almost a year, now was the time.
Here it is in all it's glory:

I am more productive building without an oscilloscope, only for some circuits that the wave form is important it will help me a lot, like the one in the picture.

Yes, if you want to know, the fan is noisy (I've seen server's less noisy) and yes you need to read the manual for more complex functions, for the default one just press the auto button. No, I will not try the 100Mhz hack for it....for now.
The scope comes with two test probes good to 6 Mhz.
The trace it's not as responsive as a crt scope but crt's can't do fft transformations or math on the input signals either.

I am almost sure the old Hameg will live longer since it can be repaired, the new modern equipments as soon as they have a problem, it's just a matter of sending to the bin.

Have a nice weekend!

Thursday, August 07, 2014

Front panel method

Decided for the first time to make a nice front panel, well, at least was the first time I succeed doing so.
Interesting enough is I made the front panel and a box before actually the equipment beeing fully operational and tested, so, now I have to make it work!

 The way as I made this was: made all the holes to the components, LCD and buttons, then printed the front panel as an overlay (trust me, it's better to print first and cut last, so you don't have to print many tests).
Before applying the paper I spayed prime on the aluminum panel, after dried used paper glue to fix and set the paper on top. Finally some varnish was spayed to give a more glossy look.

Because the prime was grey and the paper very thin (normal print paper) it got a slightly grey tone.
Another issue was on turnng the nuts of the buttons, with a plier, some small scratches were made.

The project it self is an arduino to select the frequency of the airband receiver I bough in 2013 in the Cork Ham radio rally, this one:

This receiver frequency is set inside by means of dip switchs on a MC145151 PLL and the idea of the project is to have an external box controlling the PLL so it can rapidly change frequency without opening the box.
Right now the code to select the frequency is working, only missing the output part and cabling to the PLL circuit. When finish will be posted here.

Have a nice weekend!

Wednesday, June 11, 2014

QRG - Trevo

Yup, it's possible to build a complete radio using only an multimeter as test tool but to know the exact frequency it's more practical to use a frequency counter.

Got myself a frequency counter kit, it will help me "debug" the VFO:

Now i'm on the 80 and 20m band (9 +/- 5.212)

Have a nice day!

Thursday, June 05, 2014

The "Trevo" works

Ok, I don't know in what frequency it his receiving, only I got my first copy of Morse signals from the ether!

The reason I don't know the frequency is simple, the only test equipment used so far is a multimeter.
After trying to figure it out the frequency of the VFO (I was suspecting that I could be receiving in the 40M or 80M band) I fired the qrss transmitter kit and set it for 3.580 Mhz, after tuning the VFO got my own test transmission (I was receiving some amateur Morse before).

The VFO (lower right on the image) is not the final design, just a quick lashed up design without great stability. Tuning is made by a varicap and a trimer cap, the two blue trimmers are for fine an coarse frequency set.

The only problems so far were:

* Incorrect publication, on the original article, of a component value on the bias of the BFO oscillator transistor which I discovered quick; the measured voltage was two low for bias and had reception for a second or so (after power on) before loosing it (was testing the BFO/product detector at 4Mhz since there's powerful AM stations around, now the BFO is back on 9Mhz)

* Thermal shutdown of the LM7912 (I'm using it so in the future I can add a 2n3055 with collector to ground) occurred on the makeshift power supply after some time of power on, now with more modules have to set another design to power the transceiver.

* Incorrect bias of microphone on the connection to the balanced modulator (still have to find out how a elect mic element does not needs power to give signal)

Work to be done:

* Decide on the VFO design
* Finish the transmit section
* Finish the band pass and low pass filters
* Adjust everything

That should be more one or two years at this rate!

Have a nice weekend.

Monday, May 26, 2014

FT-102 full line on desk

I finally had some time to assemble and test the new bought accessories to the FT-102.

Here's the result:

Now only some "minor" issues:

1- The HF antenna is broken (nothing to do with the radio tough)
2 -The accessories bough came with extended feet, the FT-102 didn't
3 - There are 2 birdies generated by the external VFO at 100Khz and 200Khz mark
4 - There's an offset of around 500Hz between the external VFO and the FT-102 counter (assuming one of them is correct, could not beat against WWV to confirm since the antenna is broken, see point 1)

How to address the issues:

1 - When I have time will fix it (not using this shack at the moment)
2 - Asked for the price of a pair of extended feet (got the reply while writing this; 5 GBP)
3 - Will investigate cable routing (signal is picked up on the antenna port)
4 - When I have plenty of time will adjust the thing

Another view of the setup:

Didn't tested the antenna tuner, assuming it's working.

Have a nice week!

Tuesday, May 13, 2014

New transceiver - Trevo

No, it's not the latest from the "East", it's not the latest from the brand that makes cooking ware.... it's simple the "Trevo", a new transceiver I'm building.

It's made in Ireland, were the water is free, (not anymore), by a Portuguese using mostly schematics from the rest of the world.... it can't go wrong....

The idea will be to have a medium performance transceiver for the everyday use, using some classic blocks without big fancy stuff. I'm building in blocks that at anytime can be changesd or replaced, also trying to use common components without compromising too much the performance. Most of the signal switching is done using relays (I might regret this in the future).

So far I made the following parts/modules:

*The BFO oscillator on the left, on the midle the mixer (ADE-1) and on the right the audio pre-amp chain. Isolated below, and still in the making is the AM detector

 *The IF amplifier chain on top, below on the left, the IF filters, one AM one SSB one LSB and one USB at 9.00 Mhz. On the right the first RF pre-amp and the attenuator.

*Bellow the audio amp on the left and on the righ just a makshift power supply, on top left an experimental mixer.
* The bandpass filtering section

* The mic amplifier on the right (741), SSB and AM modulator (by unbalancing) midle and left (MC1496).

Regarding the schematics, when I'm happy with the performance I will post them...just wait.

Since all transceivers have names/model, decided to cal this one "Trevo"; it could be the acronimouns for "Transmiter Receiver Evolution".... no, it's the Portuguese word for Shamrock which is one of the symbols of Ireland. I hope it makes sense....

Have a nice week and good luck!