SMD soldering success

I have used the tools and materials described in my posting on 20th August to solder successfully in place the frequency synthesiser chip, ( encircled in the picture ); an amazing result, considering it was the first SMT component I had ever attempted to solder, ( since being properly equipped ), and I had only 'perfected' my technique on a scrap piece of circuit board a few moments earlier !
The chip is Analog Devices Inc. 50MHz CMOS complete direct digital synthesiser type AD9835 which measures 5.1mm x 4.5mm and has 8 connection pins on each of the two longer sides to be soldered.
The mixture of 'through hole mounted' components and SMD on the same board is convenient and acceptable for prototyping. With this first SMD soldering success behind me I shall, in time, convert the circuit board completely to SMT in a future version.
Now let me see if the code I have written, ( see 17th May ), to control the chip will actually get it to do what I want.

Matchbox

During the summer I don't operate my amateur radio station on the low frequency bands, ( 80m, 160m and 2190m wavelengths ); the atmospheric noise, mostly from thunderstorms within a radius of about 4000kms from me, just doesn't give a pleasant listening experience, as well as blotting out the weak signals which I need to hear. Conditions in winter for radio communication on these bands are much better, particularly for making very long distance contacts. My favourite time for concentrating on these bands is around the time of the autumn and spring equinoxes. I am starting to get excited as such conditions will soon be arriving again.
I use the same antenna on each band, namely a vertical, aluminium pole which rests on an insulator at its base. Over the years I have collected many useful insulators of this type, both ceramic and glass, by looking on the ground at the bottom of telephone poles.
I have just cleaned the insulator, ( a white, ceramic one ), checked and weather-proofed the connections to the antenna, confirmed that it is resonant on my preferred frequencies and impedance-matched to the 50 Ohm coaxial feeder cable from the transmitters.
The matching networks, ( a tapped coil for the 80m band, a L-C 'L' network for the 160m band ), are located inside the storage container with lid, otherwise known as the "Matchbox", at the foot of the antenna, with the exception of the loading coil for the 2190m band which is too large to fit inside.
Perhaps this year I will reach my target of making contact with 160 different countries on the 160m band.

ESD and SMD

Many modern electronic components are vulnerable to electrostatic discharge, ESD, and may also be miniscule surface mount devices, SMD, ( typically with dimensions of only a few hundredths of an inch ), for circuit boards using surface mount technology, SMT. The synthesiser chip, which I referred to on 17th May, is both. Since then I have assembled the necessary tools, materials and aids to work successfully with such components.
On the heat-resistant anti-static work mat I've placed some other ESD accessories; wrist-strap, anti-static brush and earth plug.
For soldering and handling I have a 48 watt temperature controlled soldering iron, tips with sub-millimetre pointed ends, 0.38, 0.56 and 0.70mm diameter solder, solder-wick ( size AB ), liquid flux, solder paste, iso-propyle alcohol for cleaning off flux residue, tweezers and a swivel mounted vice. Regarding the vice, mine has a groove along the length of the jaws, making it ideal for holding circuit boards.
Obviously it is fundamental to be able to see the SMT components properly. So to help me in this regard, and also for inspecting my work, I've collected various types of optical aids, handheld and hands-free, with magnifications from x1.5 to x20. The adjustable 2.5 watt LED light will illuminate the work surface without too much glare or shadow.
All that is now left to chance is a steady hand !

ISS and I-Gate

The International Space Station, ISS, has been very easy to see just after dusk for the last few evenings. The first module, called Unity, was placed in orbit in 1998.
About September 2005 I became registered as an authorised Internet Gateway, ( I-Gate ), for traffic relayed by the ISS, and seeing the ISS recently rekindled my interest. With my laptop connected simultaneously to a radio transceiver and the internet I can receive and pass on to an internet server messages, beacons, locations, and weather reports from ground-stations, sent via the ISS.
The first couple of lines of text show that I sent traffic to an address APRS via ARISS, ( the ISS ); the content is my ground-station location and a text string stating that it is an internet gateway, digital repeater and weather station. The next two lines show that 2 seconds later my transmission was relayed by the ISS, which inserted its callsign RS0ISS-4, and was received by me and any other ground-stations in range of the ISS at that time.
In lines 5 and 6, I sent a kind of greetings message to everyone, and again, 2 seconds later, receive it back. I have in the past sent personal messages to specific stations and weather, ( 'WX' ), reports; but on this occasion I didn't leave myself with enough time to download weather data from my weather station to the laptop, before the ISS was above the horizon.
It is not possible to 'I-Gate' ones own transmissions; another 'I-Gate' has to do that. My first transmission contained coordinates; so when an I-Gate in the Netherlands received it, I could then be plotted on the map. Look for the green star with 'D', meaning digital repeater. The station UT1HZM in the Ukraine appears on the map only thanks to me; I received and 'I-Gated' his transmission. A station in Belgium, using my email address, subsequently emailed me.
Quite a few stations were active during that particular ISS pass over Europe yesterday between 2139 and 2154 CET. Some of them, ( white 'WX' in a blue circle ), were transmitting weather reports.
All up and down link transmissions to and from the ISS took place on a frequency of 145.825MHz, +/- Doppler shift, with a data rate of 1200 bps, AX25 packet unprotocol information, ( UI ), frames. I used a 50 watt transmitter, TNC-2 terminal node controller with the TNC-laptop interface running at 9800bps, and 'white stick ' antenna; the software packages are AGW Packet Engine, UISS and UI-View.
Perhaps this evening I will send a weather report for all the world to see !
Click on the post title link for more information, the latest maps and traffic from the last two hours or so.

Noise factors

Having achieved over the years considerable success with radio communication on the VHF bands using terrestrial modes of radio-signal propagation and reflecting my signals from the ionised trails formed by meteorites as they burn up in the earth's atmosphere, I am considering a new, formidable, challenge; reflecting my signals from the moon, to be able to contact amateur stations on the other side of the world on VHF. Signals received via the moon will be very weak, however, and at present noise may be a limiting factor. All radio signals are received in the presence of noise, from external atmospheric, man-made and galactic sources as well as that added by the receive equipment itself. Even an electronic component, such as a resistor, lying unconnected on the work-bench generates noise at the sub-atomic level, unless kept at a temperature of -273C ! Powered-up equipment at room-temperature is much noisier. I had been wondering if my equipment would be sensitive enough to receive signals reflected from the moon from other stations, as well as my own, or would they be buried under the noise and be undetectable.So I carried out an assessment of the noise performance of my VHF receive set-ups, for 50, 70 and 144MHz frequencies, and found it to be poor in each case. The noise is excessive for consistently successful 'moonbounce', though there is always the possibility of the occasional 'freak' contact. My assessment method, using my 144MHz set-up as the example, is shown in the upper picture.
I can't control external noise, but fortunately there is still a remedy; fit a low noise receive signal pre-amplifier as close to the antenna as possible. I set about designing one, first for 144MHz, based on a low noise n-channel dual gate mosfet transistor, type BF991, which is specified to 200MHz, ( circuit shown ). With a noise figure of 1.28dB and sufficient gain, this little amplifier should do nicely and allow a signal power of 1.306x10e-4 picowatts from the antenna to be detected with a signal / noise ratio of 10dB in a 2400Hz receiver bandwidth ! I will need to modify the circuit for the other two frequency bands mentioned, just by changing the attenuation of the 50 Ohm pad and the values of the frequency dependent components.
So three preamplifiers in all - my list of circuits to build during next winter just keeps growing !

The 500 watt amplifier under cover

This is the same amplifier that I posted here on 25th January, and used to such good effect during my radio contacts with the Balkans mentioned yesterday. It occurred to me that if I am going to use it frequently, perhaps even every day, over the next few weeks, then I had better carry out some maintenance on it.
So today I disconnected it, removed its covers, cleaned the airways and checked that all the mechanical connections were secure. These can work loose in time owing to thermal cycling, and several needed further tightening.
With the bottom cover temporarily removed there was a rare opportunity, not to be missed, to take a picture. Pictures of the equipment I build are actually very useful to refer to if I want to make any changes, and are not just for blogging purposes of course.
To give an idea of the amplifier's size, it measures 50cm x 25cm x 25cm ( w x d x h ). Regarding it's weight; suffice to say that it's almost too heavy for me to carry !

The metre wavebands - playtime on VHF

My VHF antennas have passed a visual inspection. They survived the ice and snow of winter remarkably well and are still intact. This is very fortunate because in spring and summer I devote more time to listening on the VHF bands in order not to miss the favourable atmospheric conditions, more frequent at this time of year, which allow greatly extended communication ranges on these wavelengths.
Such conditions occurred earlier today in a SSE direction, when I contacted numerous amateur radio stations on the 6 metre band, ( 50MHz ), upto 1840 kms away in southern Bulgaria and Greece.

Iceland's volcanic plume

The plume of volcanic ash belching from the Eyjafjallajoekull volcano, ( 1666m ), in the Katla range is visible from space. It can just be seen on an image I received yesterday, 19th April at 1215gmt, from the NOAA 19 weather satellite on 137.10MHz.
At first I had almost overlooked it, believing, because of the enormous publicity the eruption had attracted, that from the satellite's viewpoint most of western Europe would be hidden from view under the ash cloud. A further series of images captured today from NOAA 15, 18 & 19 confirm the continued presence of the plume, but show it to be diminishing.
I shall be following the progress of the ash plume/cloud from space and post additional pictures if they are more distinctive.
Iceland is at the limit of my range from here for clear satellite reception; the satellite being only just above my horizon as Iceland comes into view !

Full earth disc

Previously posted weather satellite imagery has been from satellites in low earth orbit as they pass over above my horizon for upto 15mins every 100mins or so. For full earth disc pictures I had to receive the signals from satellites much further away in the geostationary orbit; in particular satellite Meteosat 7 at 0 deg. E. Using an 80cm satellite tv dish pointing in that direction, I had no problem receiving the analogue WEFAX imagery on 1691MHz. The last time was in 2002; it doesn't seem so, but I checked. That's a long time ago. How time flies !
Recently, I have been occasionally listening for Meteosat 7's transmissions again; but heard nothing. Has the satellite re-entered, or been parked into a graveyard orbit, I wondered. No, instead it has been moved to above the Indian Ocean.
More importantly, the analogue service ceased anyway probably early in 2004. I can't receive the new higher resolution digital service from Meteosat 9, Meteosat 7's replacement at 0 deg. E, without spending some money on equipment. I might not bother.
So, if in the future I don't receive any more full earth disc pics, I have posted one from my archive from 2002, and we just have to imagine the quality and resolution of the digital pics nowadays; or use the web, but that would be too easy.

Sat pic gallery

Today's images in the visible light band which I received "off-air" from the US National Oceanographic and Atmospheric Administration, ( NOAA ), low earth orbiting weather satellites, NOAA18 & NOAA19, automatic picture transmission, ( APT ), weather facsimilie, ( WEFAX ), service.

From top to bottom:-
NOAA19, 1104gmt, downlink 137.10MHz
NOAA18, 1141gmt, downlink 137.9125MHz
NOAA19, 1246gmt, downlink 137.10MHz
NOAA18, 1323gmt, downlink 137.9125MHz

There is still some sea-ice to be seen at the northern end of the Gulf of Bothnia.
If you look carefully you may see a red cross which gives away the position of my ground station.

The changing seasons

It is interesting to follow the seasonal changes on earth from the images which I receive directly from weather satellites. The last time on 26th January, ( see post ), showed Europe from Germany eastwards under ice and snow. The images which I captured today tell a very different story.
The infra-red image I have chosen to post here was derived from the heat detected by the infra-red sensor onboard satellite NOAA18, and transmitted on 137.9125MHz at 1151gmt. Darker shades, ( black, brown, green ), represent warmer areas than lighter shades, ( blue, white ). Many Baltic countries had a fine, warm day today. I was outdoors making the most of it !

Loopy thoughts

I've been sorting through my stock of coax cables. If I join together several lengths of the same thickness of 6mm, I could make one length of 70 metres. Perhaps it will be enough to construct a reasonably effective rectangular loop antenna for transmission on the longwave 2190m band.
So let's see.
I could support it vertically from two trees in the garden 20 metres apart, with the vertical plane running N-S. The area enclosed by the loop would be 300 square metres.
After doing some quick calculations, I predict Rrad = 121 micro Ohms, and efficiency = 0.0076%, assuming rf losses = 1.6 Ohms.
In terms of efficiency it will be nearly 4dB worse than my existing longwave Marconi antenna. Another limitation is the loop's bi-directionality, ( Marconi omni-directional ); so radiation broadside ( E-W ) could be 30dB down on end-fire direction ( N-S ).
I wonder if making it will be worth the effort.
Has anyone made a longwave loop antenna of a similar size ?
If so I would be pleased to hear of your experiences with it.
I won't be buying a single 70m length of new coax just yet !

Antenna traps using coaxial cable

Traps are tuned circuits used in various types of antennas to allow multiband operation. They can be bought from commercial sources, or home-made with the advantage of low cost, ( almost nil ), and your choice of design frequency rather than the manufacturer's. Ever since I burnt out a bought trap, I have always made my own.
My preferred method is to use coaxial cable formed into a coil round plastic drain-pipe, and avoids using a high voltage capacitor as the self-capacitance of the cable tunes the coil to resonance. I have made lots in the past, several of which are currently incorporated into some of my antennas. For lowest loss traps, coax cable having the thickest inner conductor practicable should be chosen, unless the weight causes the antenna element to sag excessively.
The one I have just made is for a modification to improve my longwave antenna. It consists of 6mm diameter RG58C/U type coax cable round a 90mm diameter pipe. I easily tuned it to the precise frequency I wanted using a 'dip' oscillator, frequency meter and adjusting the spacing between the end turns of the coil. Then the turns were held in place by applying hot melt glue into the gaps.

Spring cleaning

Every year at around this time I like to clean the inside of my fan-cooled amplifiers; suck out the dust, remove dead insects and spiders, and also clean the fans themselves. Over the course of a year's use a lot of dirt gets drawn in and accumulates. Cleaning should ensure reliable operation over the next 12 months.
My 150 watt VHF amplifier for 144MHz has its top cover removed prior to undergoing this treatment. It uses the American, Eimac type 4CX250B, ceramic, external anode, tetrode tube; also shown with its ceramic chimney alongside.

Compliments always welcome

I have just received an unexpected email from Michal, a Polish radio amateur, callsign SQ7JZI, who has been monitoring my longwave transmissions recently. He wrote, " Incredible VLF signal to 137KHz, congratulations. What equipment do you use ?"
Of course I had to tell him, and encourage him to radiate his own signal. Then there will be 3 from Poland on the 2190m band.
Signals on this band are rare; still none at all from many of Poland's neighbouring countries. I hope someone from there will one day be able to change that. It would certainly add interest.

Circuits

This evening I have been transmitting on longwave, waiting for a contact partner, but none appeared, although I know that my signal was being received in Nuernberg, Germany, 745 kms away.
While waiting, I realised that until now I had never placed on my blog a circuit diagram for any of my construction projects; and yet there might be some visitors who would like to copy some of my designs.
Although the picture can be enlarged by clicking on it, whether I do this again still depends on the clarity.
Anyway, I try it at least once, with the circuit schematic of my GS31B 50MHz amplifier from 4 years ago. ( see also 25th January 2010 ).

My Russian toys

Though not dolls, there is nevertheless a progressive increase in size.
They are Russian made high power triode tubes, ( thermionic vacuum tubes, valves ), ideal for use in VHF/UHF transmitter power amplifiers, and significantly cheaper than western alternatives.
So, from L - R, the ones I have are type GI46B, GS31B and GS35B; in each case the suffix 'B' denotes tube variant suitable for forced air cooling, with or without the finned anode cooler. ( An 'A' here would mean water-cooled ).
The GS31B is a spare in case the one in my 50MHz amplifier, ( see post of 25th Jan, 7.23pm ), fails one day.
I am currently building an amplifier for 144MHz using the GS35B.
I haven't decided what to use the GI46B for yet. If I can obtain a second one, then making an amplifier for 432MHz using both tubes with their outputs combined would be an interesting construction project.

International Space Station

I was sitting in my radio room while wondering what to do next when I saw a radio contact confirmation card on the wall. Perhaps because it has been there a long time, I rarely notice it. As it may be of interest to the many visitors to my blog, I have put it here. The card shows the International Space Station, ISS, of course, and was sent to me as a memento of a conversation I had with Bill McArthur, the Mission 11 (?) commander, as the ISS passed over on 27th November 2005 at 11.00am.
I guess the ISS has grown in size since then !

Frequency synthesiser

Having decided on all the additional functions I want, ( band change, tuning step selection, PTT and output filter ), and the switches and connections that will be needed, during the last few days I have progressed further with the frequency synthesiser project from the experimental and development stage, ( see 25th January ), to the first, ( boxed ), prototype. The green, back-lit, dot-matrix liquid crystal display gives a particularly pleasing appearance. The source code still needs some refining. The inset shows new code being uploaded via the 'in-circuit serial programming' interface, ICSP.

Weather bad, longwave good

Tonight it is snowing again. The large coil is outside and connected to my antenna, but has little protection from precipitation. Although the weather is poor, radio propagation conditions on longwave tonight have been good. I have just completed a contact with Gerhard in Austria. The screen shot shows him calling me at the start. The other horizontal lines are sidebands from the LORAN-C navigational system on 100KHz. There are LORAN-C sites in coastal regions of northern Europe. We have to put up with its interference until the system is supersceded by GPS. The sound it makes is like a steam locomotive travelling at 100mph. To our advantage, however, these 'lines' give a useful indication of propagation conditions on 136KHz, and were strong and clear tonight; hence the possibility for my contact with Gerhard.
My signal was also picked up 745 kms away in Nuernberg, Germany !