DH2VA's Pic-a-Star diary

This website was done to document my progress (and failures, hi)..

10.01.05

Finally, I have some spare time to start the Pic-a-Star project. As I am more familiar with SMD circuits, I launch a question into the forum about having some upgrades integrated into one new PCB artwork.. well, to summarize the result in short, I guess I am going to listen to the veterans of Star-building and start with the provided designs. So here we go.. two hours later, I had a etched and drilled DDS board and display board for the Pic-n-Mix thanks to John's artwork!

13.01.05

I asked in the forum for some help getting the crystals for the Codec and DSP boards.. Steve, G6ALU was so kind to help me out, thanks a lot! I am now building the DSP + Codec board as far as possible so I can do the LED+hum testing once the crystals are here. I don't have a good idea how to get this gmon.hex into the EPROM. I guess, I have to build one (www.batronix.de has complete EAGLE data and the software).

19.01.05

The mail had a nice surprise for me: the yesterday ordered parts are already here.. PCBs, here I come!

21.01.05

First Pics available. The first shows my quite messy workspace, but I still find things (and more important, tools!) quickly. Entropy increases quickly anyhow, so I rarely clean it up.. It is antistatic though. Most important is the stereo microscope (left pic) .. spotting soldering errors and trace breaks is SO much easier, I would never give it away anymore.

The right picture shows a closeup of the work of the last days.. DSP board fully assembled on the left, only lacking the crystals and the EPROM (programmer is missing, which has to be build in the next few days..).. The boards look a little bit empty because they are mostly lacking the big electrlytic caps, but as I had some 10uF ceramic caps at hand, these are mounted on the bottom side.

The display board is 99% assembled with the IC to be put into the sockets. The 74LS47 display decoder is problematic, as this part seems to be obsolete.. I have two other decoders at hand and will try to make a small adapter board to fit these into the DIL socket. The timer board is ready for the PIC, which will be programmed in the next days. The Pic-n-Mix DDS board is etched, but not yet drilled, the IF board is etched and drilled, but is waiting for the filter, so I can adjust the stack height, before soldering the end panels and start populating the board.

I also got some replies on my question about the specifications of the roofing filter. The proposed 10M4D seems to be the best choice (4 kHz BW, 80 dB stopband), so I will definetely try to go this way.

24.01.05

Work is progressing on the DDS board. First, I assembled the oscillator from part 14, Fig. 27. It does oscillate, however, by no means fixed to the crystal frequency but nicely tunable with the trim-cap. I'm going to ask the question in the forum, if there might be a problem with the crystal I have. In the meantime, I continue populating the DDS board.

After some reply in the forum and some search in older posts, I decided to investigate this problem later. Just putting all together and see what happens. One thing is different though: after using the proposed changes in the resistors of the crystal heater (errata document), I had to tune the trimmer to a voltage of about 0.5 V over the 18 Ohm resistor (suggested replacement for 2.7 Ohm). Sounds reasonable, as this creates a heat power of about 200 mW in th FET.

The Pic-n-Mix is finished including the DDS assembly, but lacking some crucial things:

The output transformer of the DDS board. The ferrites are expected to arrive next week.
The 74LS47 display decoder. Expected in the same shipment.
The Eprom. Ebay shipment awaited. The Eprom-Programmer has been etched, but is lacking components (same shipment..).

But some things DO work: two display dots are flashing (should be like that, without DSP?), the LED on the DSP board is lit, but not flashing (Eprom..).

Next things to do: assemble the status board and wire to the Pic-n-Mix. Make adapter to program 16F627.

25.01.05

The status board is now (again) almost assembled. I ran out of 1k resistors and LEDs, which are added to the next parts order. But the keypad is fitted to the status board, which gives a nice and handy unit. In addition, the two 16F627 for the S-meter and the timer board were programmed using IC-prog and the JDM programmer. You always need only MCLR, RB6, RB7, GND and +5V to program the flash PICs! For WinXP users: you have to run IC-Prog as administrator..

For tomorrow, some interesting things are on the list: program the EPROM with the programmer (see above), testing of the DSP unit, testing of the Pic-n-Mix including status board and starting the Magic Roundabout assembly. The IF board is almost untouched, as I am waiting for the crystal/filter pair to fit the stack height to. For the bandpass, I am thinking about using self-wound coils, as unwound kits ('Neosid Spulenbausätze') are available at www.qrpshop.de. I have an LCR meter and a network analyzer at hand so this is not an impossible task, but I have asked this question in the forum, perhaps somebody else tried this already.

26.01.05

The parts arrived and the programmer was finished.. unfortunately, the first try went wrong due to excessive cable length between the programmer and the parallel port.. but I don't have a UV-lamp to erase the EPROM! I tried it with the UV-lamps of the machine, which I use for transferring the layouts to the photoresist, but no luck. Luckily, our local electronic parts shop had one eraser and was willing to clear my EPROM at no cost (thanks a lot!!). Back to the lab and second try: this one went fine. EPROM plugged into the DSP board, power on .. and a flashing LED, great! Next was to load the test5 from the PC to the DSP, which initially failed until I increased the delay in pc.txt to '6' (machine here is 2.4 GHz, WinXP). Now LED toggleling is fine as well as the nice hum tone when checking the CODEC loop. What next? I am still lacking the filter/crystal pair for the IF board, so I will start with the Magic Roundabout..


An overview of all completed modules. Status board on the left, Pic-n-Mix and DSP and timer board at the front.		A close-up of the DSP board. I have put some Kapton tape under the crystal to avoid any shorts.		A detailed picture of the DDS board. The master oscillator is not yet shielded, but this will be one of the very last steps. Also, the output filter, ampllifier and transformer are not fitted yet.

28.01.05

I tackled today the construction of the Magic Roundabout. First fit all standard components I have in stock, which means no diplexer coils and J310 due to the lack of ferrite beads (this should be cured, once I am back from visiting my parents on the weekend, as my dad should have some in the junk box). Then a deep breath and read the T6 winding instructions.. read a second time.. and start. I made a small photo-story, which is shown here, to help anybody who is also not sure how to do it. Fitted T6, T3 and T2 (NOW, this latter two are really easy..). Looks quite nice! So off to the weekend and get the remaining parts :)

Addendum: while typing the T6 winding instuctions on the laptop in the train, I found my first serious error! I should have read the T6 instructions a third time.. what happened? I wound it the right way, but connected it wrongly and now the leads are too short.. GRR! I will cut it apart and re-wind it on Monday. So doing this winding manual was already beneficial.. for ME!

1.2.05

Today, I re-wound the T6 transformer to correct the error I did on Friday. I also finished T1, of which I have made some pics as well.. Now I understand the sentence '...so nobody can see how it was done.'.

The next shot shows the almost finished Magic Roundabout.. it was late today, and I couldn't find the trimmer rightaway, so this last component has to wait until tomorrow. The next big module is the IF board!

3.2.05

No pictures today, as I was running out of time. BUT: the IF board is almost finished.. The missing parts are now the filter with the matching and the crystal. I also started installing some of the screening, as I have some nice copper sheet available, which can be easily cut with scissors. To ensure this is nicely solderable, I clean the edges with a fibreglass pen (don't know the exact translation, but this pen is very effective to clean the copper). Also not installed yet are the AD603 and the two TL072.. due to stupidity, I had the TL052 in my order, which needs more supply voltage to work.. :(.

Another problem might be a missing part for the MixAdapter, which replaces the SBL-1 mixer. The needed part is a BN43-2402 ferrite core, which I have not ordered.. maybe this is replaceable with some other core.. I am waiting for some comments from the forum.

Hint for all builders: check ALL part lists... not only those in the main document.

Next things: finish IF board and start integration into case.. as I already said: I don't want to test flying boards, so I have collected parts for a case, which allows me to access all boards, while installed.. some pics will follow in the coming days.

10.2.05

Unfortunately, I am grounded by a flu in the moment, so no progress on the hardware and none on the diary. Only a status report how far I got and some comments:

The Pic-N-Mix part is now equipped with the rotary enconder I got at Ebay. 'Unfortunately', it has 400 pulese per revolution instead of the original 180, so every touch on the wheel first initiated the variable rate tuning (yes, both directions work) and then the flywheel function.. where the frequency is sent off into heavens. Actually, I would like to have the flywheel default programmable, so I could just turn it off by default rather than having it on by default.. But I guess this is an easy tweak in the PIC code.
The IF board is almost finished with some parts still missing (which are stuck at my parents house in Germany): the TL072s, some more 100 pF trimmers and few more items. I applied some first shielding walls from thin copper sheet, but none of those are restricting of any component for now. Just a sidenote: these 100 pF trimmers are VERY heat sensitive. The 10.710 MHz oscillator however is already working and maximized in output.
A first idea for the case is there: made up out of aluminum sheets with profiled edges. The front and back plates are screwed into the profiles and make up a frame. the left and right plates are screwed into this frame and form the mounting frame for all the electronics. The Pic-n-Mix and the status board are mounted to the front panel while the other modules are mounted to the inner shielding, which is itself fixed to the frame. The upper and lower cover have no connection to any module and can therefore applied the the very last moment. By doing so, top and bottom access is possible, even during installation.. which might be useful, as this stuff has to be commissioned.. :)

5.4.05

No entries for quite a while.. mainly due to QRL. But now things have cleared quite well and I can write down the little progress I actually did in the last 8 weeks:

The Pic-N-Mix is now fully working. I exchanged the 24 MHz crystal by a 123 MHz overtone crystal, as I failed to acquire lock. With the 123 MHz crystal, locking was a piece of cake.. Next thing to do here is the shielding of the LO and build the small LO filter.
The IF board is now finished and mated with the DSP board to form the DSP assembly. After some help from the forum, I finally found out that switching on the monitor is mandatory (!) to get some data on the PC monitor display. I misread the monitor function to be some audio monitor, which is clearly not the case.. my fault.
The main elements for the case are there and joined together. Next step here is to fix the two parts of the Pic-N-Mix to each other before mating the Pic-N-Mix as a whole to the front panel.. wait, I also need some VFO tuning knob. I need some mass here to increase the inertia.. let's see what our workshop has from 'junk' stainless steel.
The bandpass is 90 % complete. Good results were obtained for all bands with Neosid coil kits except for 60, 40 and 30 m, where the needed inductance is rather large. I therefore ordered the missing coils as TOKO-type from www.jabdog.com. This should do the job. A tiny copper short, which activated the 17/15 m section with RF power fooled me for almost two hours.. luckily, I have a network analyzer here which pointed me to the right BPF section, but the microscope was needed to spot this litttle etching leftover.. grr!

Most of the next tasks are mechanic stuff and honestly, I don't like it..

25.4.05

Here is the promised teaser (click on image to enlarge):

I am VERY proud to being able to get all millings correct at first try.. so now I have a nicely fitting frontpanel. Unfortunately, the case is empty, apart from the status board and the DDS assembly. But all the other things are there, so I need some time to start building the shielding..

5.5.05

Some advances in internal shielding! I have all compartments ready, less the small openings for connecting the different modules together.. Some serious wiring comes next!

17.5.2005

Some MAJOR progress: all modules of the basic Pic-a-STAR documentation are now assembled into the case and put into service. After finding some bugs (forgot to connect power to the 10.7 MHz LO oscillator, FST3126 used in IF board instead of FST3125), a STAR came to life and produced some very nice noise and an HI.. :). However, without an antenna, I turned up the AF gain way too much and thought to be annoyed by the 1.4 kHz pilot tone of the 3rd method receiver principle. Yes it is there, but with reasonable settings, you will never notice it or in other words: as soon as you connect some junk wire to the ANT jack, the external noise will easily mask the tone. I already listened to some DL, G, UA stations on 80m and two stations on 20m with a US accent, but as they had a quite convenient chat, they did not bother to give their callsigns. I dont think I can expect more with 5m of wire hanging across my balcony in downtown Zuerich (which is a city with a population of 340.000) with all the man-made noise around me. Still two things are clearly missing: complete the internal screenings, as on 40m and up, multiplex noise is really annoying. Second, a more decent antenna, probably with some very primitive wire tuner first. I had some problems with calibrating the digital S-meter aas with 2.2=102, it seemes that the S-meter response rapidly dropped below S6.. however, with 2.2=104, everything looks much nicer and after reprogramming the Status Board PIC, the digital S-meter is also working fine. ADDENDUM: just after finishing the S-meter tuning, my Star tumbled off the table to the ground, some 80cm lower.. the BANG was too loud to be comfortable and I was quite scared when I switched the unit back on again.. luckily everything seems to be fine, partly due to the fact that the units are internally not directly fixed to the case but via the screening walls made of 1.6mm FR4. This might have absorbed the larges shock spikes. Still, the araldite joint for fixing the Keypad came loose, which is right now curing again. See pictures below. I still want to get the box back to my home tonight and have another round with 2.2=104.

Front view of my Pic-a-STAR during curing of the keypad glue.	Top view of the opened Pic-a-STAR.

Close-up shot of the IF assembly and BFP module. The 30m filter coils are expected until end of the week.	A homebrew DDS signal generator 0-50 MHz with a lab switch attenuator.

23.5.05

The G6ALU PA was assembled and integrated over the weekend in the STAR box. Setting the bias currents worked just like in the instructions, all pot's are about 2/3 scale to achieve the required quiescent current of 750 mA.

Today for the first time, real power was applied via the BFP. I did no accurate power metering up to now and no proper tuning of the drive power while monitoring the output on a scope, but 20W (43dBm) should be in reach. For not overloading the scope, I have here a 20dB/50W attenuator, which is a 'leftover' from my last project, which was a 23cm 50W PA from G3WDG. Plus another 20dB Weinschel attenuator, just to be on the safe side.. Some pics for you:

Complete view of my Pic-a-STAR including the G6ALU PA.	Closer view of the installed PA.

Detailed picture of the PA. Still missing the T/R switching..	Sideview of the PCB mounting (M6 brass nuts as spacers) including the transistors and the heat sink.

30.05.05

On the last weekend, I took the Pic-a-Star to the annual fieldday of our local radio club in Germany. And here we go: after fixing the voltage divider on the T/R switching transistor (which refused to switch with a supply voltage lower than 12.4V) a STAR was born and I had nice contacts with W4ZCB, G3ZCU and an italian OM (non-STAR). Certinly a great moment for me, but only the first step with more to come! Still missing the LPF, the LO filter and some nice antenna tuner. Also I would like to style my front panel a little bit more and include a small speaker into the case for basic listening capability, even without using external speakers or headphones.

Following are some pictures from our fieldday, for a full overview, also of the antennas, go here (thanks to Wolf, DF1GW for the nice photots!). The used antenna was an inverted-V dipole configuration with 5 legs called V-Star (hi) due to the star-appearance when looking from above. By choosing either 2 legs one can change the beaming direction.

DH2VA (right) with another OM at the HF-'shack'.	Close-up view of the equipment: Pic-a-STAR, TS-430 and MFJ tuner.

Explaining Pic-a-STAR.. it's getting warm.. see the towel?	See my big grin? Finally on-the-air: DH2VA - STAR owner!

DH2VA working with the V-Star antenna.	Unfortunately, I can't put up something like this in Zuerich downtown..

A great day comes to an end..	It's time to enjoy the other side of the fieldday!