10 February 2018


Nikos in December 2017 (photo by SV3DVO)
A dear friend, Nikos SV3IC passed away on February 9th, 2018. I met Nikos for the first time in 1983, when he brought his new Yaesu FT-ONE to Zakynthos for the hams of the island to see it. I was a high school student then. When I moved to Patras to study Biology in 1984, I started working part time with Nikos - he built and maintained commercial radio networks. I learned a lot from him but most of all had the time of my life, laughing my head off with his jokes and pranks, involving everyone around him - myself not excluded, of course! He was very kindhearted and generous, a lively mind with a sharp wit and a mischievous, impish manner.
An expert CW operator, he could operate flawlessly at speeds which made me dizzy. Always defiant of  misfortunes, he never gave up on life - and his favorite pastime, smoking. Confined at home during his last years due to illness, he never lost his wit and to the last day remained active on ham radio talking to friends near and far. 

Thank you and farewell, Nikos.

28 November 2017

Bringing back the memories - restoring a Graetz tube radio

A heartbreaking sight...
Courage old chap! You'll make it!!
After a rather loooong hiatus, here I am back again! No semiconductor stuff this time, though! Let's go back in time (the late '50s) and resurrect a nice Graetz MW-SW tube radio! It was sent to me a couple of years ago to restore (along with a very interesting Marconiphone model which will appear in a future post) and this is the story of its coming back to life.
It was in rather heartbreaking conditions, all broken up, its nice bakelite casing in pieces (with some of them and the back cover missing) and everything covered up in years and years worth of grime and crud. (Click on the pictures for a larger version). One of the keys in front was missing, the power tranformer was burnt up, an IF can had a bad winding and - the worst - ALL of the RF coil pigtails at the underchassis were cut, probably by an industrious rodent which had left clear "marks" of its presence in several spots. Several other electrical problems became apparent during the restoration work, but they were not so serious.
RATS! Where are the coil pigtails?
Keeping detailed notes is a must.
Cleaning all that grimy mess of a chassis and case took a relatively long time and patience, but it was well worth it. When that task was complete, I started the electrical troubleshooting.
After ordering and installing a suitable new tranformer, I gradually checked and restored each stage. Surpisingly, most of the capacitors were OK! If memory serves, I found only a couple that had developed leakage. The reservoir electrolytic had more than its nominal capacitance and normal ESR.

Starting to look like a radio again...
It was during the testing of each component that I found that the IF can had a bad winding and opened it up to fix it. Fortunately, that proved easy. Finding where every RF coil should be connected on the bandswitch assembly was certainly the "funniest" part of the restoration! I also had to fit a new dial string, as the old one was badly frayed. After this was finally accomplished, the chassis was powered up and a voltage mesurement test showed some small remaining problems, which were quickly corrected. I found that the rectifier tube had gone bad and replaced it with silicon diodes in series with resistors, which were soldered on the tube socket lugs. That eased the burden on the transformer, too. It's very easy to remove them and fit a tube, if ever required. A loud hum could be heard when touching the grid of the audio amplifier tube, but no stations (of course) could yet be received.
To make a long story short, after restoring the function of every stage, I fully realigned the radio and it gradually came to life. First I aligned the IF, then the RF stages. Getting the dial indications to precisely correspond to the actual frequency is a very rewarding procedure. Stations started pouring in when I attached a wire antenna, and all of the wavebands became operational.
Putting the case back in one piece!
Alignment in progress...
Putting the broken bakelite case together was another challenge. I used epoxy glue and metal reinforcing clips to accomplish this. I formed, glued and painted a plexiglass sheet to put in place of a missing corner. Every brass part and insert of the front side was carefully cleaned, polished and protected with a thin acrylic coating. The speaker cloth was replaced with a new one. I was lucky to find a nice suitable replacement piece of cloth at a furniture shop. The case was finished up with gold paint because the original had faded with the years, and after several hours it was finally ready. I polished the bakelite with a silicone oil saturated cloth, which made it really shiny again and gave it a great colour and "depth". I made a complete back side cover out of thin plywood, as the original cover was lost (turns out I didn't take a photo of the cover).

The back side of the finished set.
Finished and singing!
Restoring an old tube radio is a very gratifying, educational and relaxing experience, especially when it's in the really bad shape the Graetz was delivered to me. It requires a lot of patience and  time, but in my opinion it's worth it. When you hear the first stations booming in after who knows how many years, it feels like you've given life back to a dear old friend. That particular smell emanating after the set warms up brings me back to my childhood, spending long night hours listening to my mother's Grundig 97WE (which still functions great!) to curious, noisy, wavering signals that arrived from the other side of the globe to my single wire antenna, strung out the window. Mysterious noises, warbles, twitters, whistles, strange music and serious, stentorean voices filled up my eager ears and made me wonder how it was ever possible for all those ethereal signals to travel so far and what each of them was. Listening to such signals coming from an old radio you've just restored to life is an indescribably joyful experience. Please don't throw those marvels of yesteryear away! If you don't want them, please try to find someone who appreciates them! They're a very important and beautiful piece of our technological history.
The Marconiphone radio restoration is another epic story, soon to be told!

26 April 2014

LDG AT-1000 autotuner acting strangely on some bands?

LDG autotuners are famous products worldwide, and for good reason: they are very well designed and built, providing a convenient solution when needed. There are very few complaints about them, as a quick Internet survey showed me. Why did I search, you say?
The other day a friend sent me an LDG AT-1000 that was acting up on some bands, failing to provide a match or even maximising SWR instead of minimising it, but working fairly well on other bands. He had been told it's the microcontroller's fault, and LDG even sent him a replacement chip (thumbs up for that kind of customer service), but the problem remained exactly the same with the new chip.
A quick check showed he was quite right: on 80, 40 and 30 meters the tuner was acting as a mismatcher, rather than a matcher. On 20 meters and higher bands, it worked rather well, although it seemed a bit "sluggish" (how's that for a scientific term?).
After examining the circuit in and out, I was sure that all of the relays, inductors and capacitors of the matching network were OK. I connected a dummy load at the output of the unit and saw that the autotuner indicated significant reflected power on 40 m, although there should have been none (I had it in the "bypass" position). "The SWR bridge circuit must be unbalanced", I thought - but why was it unbalanced on a specific frequency range? A Bruene circuit, if misadjusted,  behaves progressively worse as the frequency is raised - here, it was just the opposite! Nevertheless, I proceeded to balance the SWR bridge. For this, I cut the wire connecting the SWR circuit to the input of the tuner PCB, and connected a precision dummy load right after the bridge PCB with a very short piece of coax. I set an RF generator on 30 MHz and nulled the reflected power reading using the trimmer capacitor. Curiously, it was off by just a little. Hmmmmm...

Fig. 1. The bridge PCB in its original state.
After reconnecting everything back, I checked again on 40 meters with the dummy load at the output of the tuner, which was in the "bypass" position. There was a significant reflected power reading on the tuner's meter again - but NOT actual reflected power, as another SWR meter between the generator and the tuner showed me! Furthermore, on 20 meters there wasn't any reflected power indication on the tuner's meter with the same conditions! So something was clearly amiss with the bridge - but all of its components had checked out OK! Curiouser and curiouser!

Fig. 2. Look ma, no screws!
Fig. 3. The hi-tech insulators.
 After a considerable period of head-scratching, the light went on. The fact that the bridge was balanced on 30 MHz but not balanced on 7 MHz showed that at the lower frequency the RF currents must have been taking a detour. The only way I could visualise that happening, was through the grounding posts and grounding wire connected to the SWR meter PCB (Fig. 1 - click on the photos to enlarge). So I removed the two screws affixing the PCB to the posts, also disconnecting the wire this way. I checked again on 80 and 40 meters - and bingo! No reflected power indication any more! The bridge nulling remained excellent across 1.8 - 30 MHz. When I touched the PCB to the posts, the reflected power reading jumped up again. 
So, I modified the bridge structure by insulating the PCB from the grounding posts, as shown in Figs 2 and 3. I used a little square piece of thick paper at each post, hot-glued to the PCB and posts to accomplish my goal. I completely removed the grounding wire. After re-nulling the bridge (just to be sure), the tuner worked perfectly on all bands, with no abnormal readings at all. It even produced a 1:1 match feeding my 20 m quarter-wave ground plane at 80 m!
So, if your AT-1000 is horsing around on some bands, this trick may well work for you too. LDG might want to have a look into this matter and modify the design. For me it was yet another good reminder that RF currents, given half a chance, rarely pass from exactly where we would like them to!

Addendum: I just purchased a very nice LDG Z-817H tuner for my bicycle HF hamming during the summer! It has a different structure at our point of interest (the Bruene directional coupler is located on the main board) and a series of tests with various types of load conditions showed no tendencies for whimsical behavior. It successfully matched whatever I threw at it and had a nice time doing it. The directional coupler stays balanced throughout the operating range. Well done, LDG!

01 March 2014

Good news: YAESU has added the DC blocking capacitors at the IF filters of the FT-857D!

Fig. 1. The new FT-857D PCB.
Sometimes I think it's mothing short of a miracle that we can buy new technology products (like our transceivers) at VERY reasonable prices (not exactly so when I got into the hobby, 30 years ago - a handheld transceiver was a very expensive item in my country, it cost more than the monthly wages of a public employee).
In sharp (and delightful) contrast, recently I bought an Agilent E4406A Vector Signal Analyser,  an HP3586A Selective Level Meter and a Hagenuk Digiflex LAN Time Domain Reflectometer from the surplus market, at what must be a tiny fraction of their original cost! Mind you, the E4406A was about 45000 euros less than a decade ago! Long live companies like NOKIA (that's where my wonderful E4406A came from) and the ever-faster changing industry standards!
Fig. 2. The Serial Number.
But I digress... It seems that the nasty filter problem has caught the attention of the manufacturers! Tomi from Romania has sent me a photo of the PCB of the FT-857D he bought recently (Fig. 1 - click on the photos to enlarge), in which we can see that the DC blocking capacitors have been added! Thumbs up for Mama Yaesu! 
Maybe they do that for all their products now. I am sure other manufacturers have also taken steps to cure the nasty filter plague, but I haven't seen any concrete proof yet.
Tomi also sent me the serial number of his rig (Fig.2) - to save those that would like to add the capacitors in their recently-built rigs from the trouble! Thanks, Tomi!

05 November 2013

Great aerial video from the site of SV8S D-Star repeater in Zakynthos

Well, that's what they call a "bird's eye view", I guess! If you want to enjoy a great aerial view from the top of Skopos mountain in Zakynthos, a place that a lot of nice antennas call "home", use the link http://youtu.be/0Z1mXfpahfg (use "full screen"!). Mike, SV8KOM used his professional, high-tech, hex-rotor remotely controlled helicopter to record this video (and many others!). This is from where Stigma Radio 97.6 and Island FM 88.6  (in English) transmit their programs to the island and beyond! This is also the site of SV8S D-Star repeater (its antenna is located on the shorter mast, on the right of the one yours truly can be seen perched up on with his tools and stuff). It was a superb day to work on antennas! Oh, and I reeeeeally envy those birds!!

24 October 2013

Smoking is a no-no for your rig, too!

The photo (click to enlarge) shows the rather obvious effects of cigarette smoke on the keyboard membranes of a Kenwood TS-2000. The owner complained that the backlighting had gone very weak, so he suspected a circuit malfunction. Alas, his heavy smoking was the sole culprit.
The membrane soft plastic is normally semi-translucent whitish - not so after having been exposed to cigarette smoke for a while. It turned brown - and the worst part is, that this brown colouring is permanent! Obviously the stain gets into the plastic! This brown colouring acts as a filter for the green backlight, attenuating it greatly, to the point that it can be barely seen in complete darkness only. I have seen (and smelled!!) many rigs owned by smokers, it's definitely causing them serious cosmetic - and functional -  harm.
So, if you are a smoker, just imagine what kind of stuff the smoke is leaving behind in your poor lungs - perhaps quitting is the best option, both for you and your beloved rigs!

08 May 2013

Ants and aphids

You may have spotted a clue or two in this blog that I get most of my kicks from electronics and telecommunications. Nevertheless, having studied Biology at the University (fascinating science too), I frequently stop to admire the great work of Nature in all its diversity.
The other day I observed  what you can see in the photo (click on it to enlarge). The ants are seen "milking" the small dark-green aphids to get their honeydew (which they seem to greatly appreciate). The ants use their antennae to stimulate the aphids for this. They protect them from other insects that prey on them. This is called a "mutualistic relationship".

Now, you may wonder why I, being a radio amateur, like ants and other bugs. Easy: They use antennae, too!