Why Do We Still Have “AM” As A Mode on Rigs? June 30th, 2013
Having been involved in ham radio for well over fifty years, it is inevitable that times occur when you look back. This happened a few days ago when the subject of AM came up. In fact the customer was buying a new transceiver and enquired why manufacturers stuill included AM as a mode?
Today it is a mode that is still widely used in broadcasting but for communications purposes it is only widely used now by the aviation service. I believe that the reason it has been retained for aviation is that if two aaircraft call at the same time, it will immediately be apparent whereas with FM the strongest station wins. In addition, AM has proved to be better for weak signals and of course changing mode would be a nightmar At least that is what I was told on good authority many yeast ago when a changeover was underncinsideration.
Today AM is all but dead for ham radio. Yes I know there are pockets of activity, but it is very much a minority mode of operation. That is no bad thing on crowded bands, but when and where there is space it can provide some pleasant sounding signals. However, today’s AM is generated at low level and amplified in a linear manner to produce the final signal. That is so different to what it was in the days when AM was the “only” mode for the transmission of speech. In fact, many recently licensed hanms often think that sideband has always been around. Not so!
Up until the early 1960s AM was the primary voice mode and SSB was very much in its infancy with very few stations using it, The most universal form of AM was known as plate modulation. The basic RF carrier was produced from a simple VFO that often ran on the final frequency and so only needed a buffer amplifier and PA to produce a reasonable amount of power output. The RF amplification was normally class C which meant it was non-linear and quote efficient. However, to modulate the carrier to produce AM it was necessary to build an audio power amplifier that fed into a modulation transformer whose secondary was placed in series with the HT anode feed to the final RF amplifier. Modulation transformers were often surplus items and as i remember not always that easy to come by. They also had to be capable of handling the required power and high power surplus ones were even more difficult to find.
The principle was quite simple and adjustment was equally simple. You just increased the mic gain to the point just below that at which audio distortion could be heard! Some operators had the luxury of an ‘scope pt see the wavform and xheck for distortion. However, there was a need for a hefty power supply as both RF and audio power were being generated at high levels. VFO drift was often a problem particularly as to add a band we often simply tuned the buffer amplifier to the second harmonic of the VFO. Thus 3.5MHz became 7MHz and the drift likewise doubled! But it was an easy way to add a band. And as for 14MHz – – well you worked on the 4th harmonic. The results were somewhat unstable on many occasions, but it worked. There were other methods of modulation that needed less audio power such as screen grid modulation.
I have always believed that AM plate modulation sounded really good and much better than low level modulation going through a series of class A amplifiers. That of course may or may not be true as I am going back over fifty years.
In my office I have a reel to reel tape that, if the label is correct, carries several recordings of some local hams that lived nearby and would have been transmitting AM. It dates back to 1959. Unfortunately I don’t have access to a tape recorder so cannot play it. Indeed I do not even know if the label on the tape canister is correct, though I have no reason to doubt that it is. Another job to tackle when I retire! Peter G3OJV.
Digital Voice Modes June 29th, 2013
At a recent meeting I was asked what I thought of digital modes and how it was fairing in the ham radio market. I should explain that we were talking about digital speech and not data transmissions.
I well remember the launch of D-Star and the tremendous backing that Icom gave to the mode. Of course they had a commercial interest in this new mode and, judging by our dales, and sales reported around the world, they did very well out of it. Yaesu did have a foot in the door during the early discussions and development, but failed to follow it through into production. I never understood why this was, but with all the excitement and hype, Icom had the market all to themselves.
We have had a D-Star repeater here at Hockley for several years, and although our village is not on the top of a hill, the antenna is well sited for signals to the north and reasonable to the south. I well remember using an Icom handheld from home and working quite a few stations through it. But today the picture seems to have changed quite a bit.
Our repeater gets far less traffic and the demand for D-Star, whilst still there, is far less than it was. I don’’t currently operate D-Star myself, but the feedback I get from customers suggests, that in our area at least, the activity has dropped noticeably. The question of course is why has this happened? Is it not offering what it promised? Is it because only those who own Icom can use it. Certainly the more modes that are introduced, the more widely spread operation becomes, diluting the interest in each mode. In addition there is the novelty factor. This always produces an initial steep upward curve, followed by a variable gradient downwards. And a follow on question must be, is there much of a demand for any speech digital mode anyway?
Ham radio is different from the commercial market. We frequently operate in conditions where signal levels are low and interference is ever present. Is there currently a digital mode that can offer improved speech intelligibility under these conditions compared with SSB going through a narrow filter supplemented with DSP? I guess that one of the limitations is that unlike digital data, speech currently does not have any error correction capabilities or sampling ability. Maybe that will come. Maybe it won;t, and we will have to rely on the printed words on a screen! Only time will tell. Peter G3OJV
Flying High June 28th, 2013
It is my task to prepare our daily blog and this often means that I have to base it on events that I have been involved in. Yesterday I found myself in Oxfordshire where I was booked in for a couple of gliding flights, a gift from my daughters to celebrate my 70th birthday earlier this year. I have had some limited flying experience in the past and did a few hours of solo flying until an eye problem stopped me and has been with me ever since. So yesterday was my first flight in a private aircraft for a few years.
Putting on parachute is not the thing that gives you the most confident feeling, but it is essential in any case from a practical point of view because it acts as part of the seat. As I used to drive a Caterham 7car I was familiar with the full harness and so I was soon strapped in and ready to go. My instructor, who had served in the RAF explained that we would go form 0-60mph in 2 seconds. He was right! It didn’t take very long at all before we were released at 1000ft and free as a bird.
I looked above is at the cloud formation and wondered what kind of range I could achieve with a 2m handheld radio. Oxfordshire countryside is quite flat and this is no more apparent than when you have a 360 degree view of the landscape. We quickly found ourselves at 700ft but found a thermal and spent the next 10 mins in a tight circle centered over a thermal we found and topped out at 2000ft. My flying skills were rusty but I coped OK once I sussed out that the rudder needed a bit more movement than in a powered aircraft.
Well the flight lasted for around 30 mins before we ran out of lift. During that time it occurred to me that a glider could en a perfect platform for VHF operation. The noise level is so low that you don’t need a headset and there is no engine or electrical equipment to cause any interference. I have no idea whether this has ever been tried before, but it is an interesting concept.
Kenwood Japan Visit Waters & Stanton June 27th, 2013
There can be little doubt as to the popularity and the success of the Kenwood new TS-990s transceiver. They have managed to put into this package, just about everything that the modern ham operator could wish for, including an extra 3dab in the shape of a 200W power amplifier. And because of this increased power it means that you also get built-in power supply for your money.
Kenwood, like the majority of Japanese manufacturers take a very keen interest in how their products are received and what features they should consider for future developments. And for this reason, they visited Wares & Stanton yesterday to talk about the TS-990S and future products. In the photo above are Peter Waters, Jeff Stanton and the head designer of Kenwood Ham Radio division.
It was an interesting meeting and was particularly reassuring that Kenwood continue to regard ham radio as an important part of their business.
Rig Runner – Tidying Up The Shack June 26th, 2013
It’s good to tidy up the radio rom every so often, even though most of us know that it will not remain like that for very long. The main centre of attention in my station always seems to be the many leads that build up over a relatively short period and develop a mind of their own. And DC leads are a particular problem because with the larger power supplies now in wide use it is not uncommon to power a number of bits of gear from a single common power supply. The quick way is to twist the leads round the terminals of the supply unit, but this untidy and you cannot get more than Acapulco of leads onto one pair to terminals. fitting each set of leads with banana plugs makes for a better and tidier connection but the limit of how many leads that can be connected in this way is directly related to how many remittals there are in the power supply. Another factor that always concerns me is that many power supplies have variable output voltage features. if you opt to tuck the supply unit under the desk out of sight, there is always the risk that somehow the control knob may get nudged and the voltage will rise above the standard 13.8v figure. well now there is an answer.
West Mountain Radio in the USA produce something known as the rig runner. This is a multi terminal output box that connects to you main power supply and offers multi outputs. It employs the standard PowerPole connectors which are easily connected and take up very little room which means that they can be grouped together on a small space. West Mountain produce a range of these connector boxes catering for different numbers of output sockets and different total DC currents. Each pair of sockets are individually fused. A novel feature on some of the units is a set of three LEDs that indicate whether the output voltage is normal, high,or low. These units also feature an audible warning that sounds if the voltage rises behaviour the normal value. However, in the case of using the RigRunner in conjunction with a battery, where the voltage drop is the important factor, the user can open up the unit and and change the audible warning from high voltage to low voltage.
Each unit has a 2m lead and is provided with adequate PowerPole connectors to fit on the individual DC equipment leads. So I now have a tidier station and can instantly unplug any lead from the distribution unit, and safe in the knowledge that if the voltage rises or falls I can have an immediate audio warning.
Today we are expecting a visit from Kenwood. They will be bringing the designer of the TS-990 with them. This radio has proved to be a great seller for those who demand the best.
Verticals – The Answer For The Small Garden? June 25th, 2013
The other day a customer asked me about installing a ground mounted vertical antenna in his garden. It was a small garden and he was not sure if using a vertical would work for him. This is not an unusual question, and in reality there are few alternatives. A modest vertical is self supporting and takes up little space.
I have used a number of verticals and always seem to come back to the Hustler 4BTV. It is a classic and has been around for years. It covers 10, 15, 20 and 40m. There is a 5BTV which adds 80m and one that adds 30m. The reason I like it is because it is rugged and easy to install. But there are many others around that also have proved popular over the years.
A vertical needs a ground to work against, it is the missing half of the “dipole.” The better the earth, the better the efficiency and it is the earth that often causes the greatest headache. You can get away with a single stake in the ground. I know it works because I operated like this for a year or so at a previous QTH. But really you need to try and lay out some kind if radial system. One radial is better than none and more are even better. Contrary to common belief, ground radials don’t have to be a precise length. After all, lay a resonant antenna on the ground and see what happens to the tuning! Even quite short radials help, and the best advice I can give is put down what you can.
Theory, and experience, shows that verticals are quite good on 20m and above. On 40m where most contacts are around 200 – 500 miles during the day, the signal strength will be down, but will improve at night. That effect is even more noticeable on 80m. The other thing that is often commented on is the vertical antenna’s tendency to pick up more noise. This is partly true, but at my QTH my dipole picks up more noise than my vertical because of the dipole’ proximity. Strange but true.
So if you have a small garden and want an antenna that is not too noticeable, I would certainly recommend a vertical. It has served me well over the years.
Elecraft P3 June 24th, 2013
I have only ever used a spectrum display briefly, but decided that I would try out the Elecraft P3 in conjunction with the K3. It’s a nice arrangement, particularly as the P3 can be directly powered from the K3 DC socket. There are three connections needed between K3 and the P3.. These are, RS-232 data control. BNC IF feed and the DC supply cable. There are no initial settings to be made; the unit works straight out of the box.
The P3 can actually be used with any transceiver that has an IF between 455kHz and 21.5MHz. If you are using it with the K3 you must have the IF auxiliary board fitted to the K3. If you have not got one, they are easy to retrofit, The P3 provides a live display and can be adjusted to any bandwidth up to 200kHz. So this is the chunk of band that you can visually monitor without having to touch the tuning control. The vertical display is also adjustable and the scale can be switched between S-units and dB, which makes it very valuable when comparing signal strengths and is far more accurate than an S-meter. There is also an adjustable average facility available that causes less movement on the screen and is useful for accurately measuring peak levels.
In action I found the P3 to be particularly useful on quiet bands where it was possible to spot signs of activity. In this respect it is far better than a scanner because you can instantly see the whole band segment and not have to wait for the radio to tune through lots of channels or worry about having the right mode selected. It was also very useful for monitoring beacons. A good example is on 50MHz watching for sporadic E activity.
Another useful feature is that you can move the cursor via the front panel control and click on any display signal for instantly QSY of the K3 to that signal. In many respects it is rather like having an SDR transceiver without the need for a PC. I found it more useful than I had first imagined it to be. One interesting observation I was able to make was how the noise floor of each band in use was displayed. I could instantly see small changes as I turned various electrical items in my home on and off. These small changes could not be observed on the S-meter. For those who already own a K3 this is a very worthwhile addition which will prove very useful I am sure And if you want the ultimate display, there is the SVGA board that permits the use of a large monitor.
I intend to come back to the P3 as it seems to offer a lot of potential, not the least of which is the waterfall display. This should prove useful for beacon monitoring, PSK31 and RTTY.
Which Direction? June 23rd, 2013
One of the great things about ham radio is the very wide range of interests across the spectrum. And it is equally amazing how we all manage to choose an area that is special for us and gives us most pleasure. But not only do we have our areas of interest, we also have particular bands that interest us. It is more difficult to determine why some bands attract some and other bands attract others.
My first band of operation was 160m. I chose this band because it was the band most hams in the 50s and 60s cut there teeth on. It provided good local contacts and was very easy to build equipment for. A tube designed for audio power amplification purposes would usually work fine as an RF amplifier on 160m. And in those days, gardens tended to be bigger, so it was usually no problem to be able to put up a quarter wave length or more of wire,
And then we have those who are HF only or VHF only operatots. Some even are UHF only. There is indeed a very wides spread of possible bands to operate on. Few are able or have the time to operate on all the different bands and so a choice is inevitable. But what does seem to happen is that we view bands almost as if they have a character
of there own, which I suppose is true.. And that is probably why many of us have favorite bands. Some will struggle to work DX on 160m whereas it would be so much easier to use 40m or 20m. Others will sit and wait for 10m to open.The WARC bands seem to be the favorite of those who detest contests.
Much of this is all about challenge, and not always choosing the best band for the job. But whichever way that you look at, ham radio has an awful lot to offer and there are so many choices to make, it is sometimes difficult to know which choice is the best for you. But that is the charm of rhe hobby!
Learning The Code June 22nd, 2013
Every so often the subject of Morse code crops up. It is ususlly from a newcomer to the hobby and the enquiry almost always concerns the beast way to learning the cod and is there an easy way. Well there are no short cuts as such but there is what I regard as the sensible way and a method that not only worked for me, but also I know has worked for many others as well.
Firstly, don’t fall into the trap of practicing by kisten to the code at too slowe a speed. It is much better to listen at a faster speed and leave bigger gaps in between the letters. And the second point I would make which is very important, is to try to listen for the rhythm in the letters rather than trying to count dots and dashes. This is most important because if you want to increase your speed you must hear the code as a rhythm.
Try to always remember that CW should be heard as a language and that language is transmitted as a series of rhythms. If you keep this in the forefront of your mind, then you will be thinking along the right lines when carrying out your practice sessions. And remember tha you should also strive to not only be able to decode in your head,but also build up the words in your head. That really is the ultimate.
But there is no short cut to learning the code. It is a matter of regular practice. Once learnt, you will never forget it. Its a very worth while skill aand onvr that you should be proud of.
Seein Red on 2 Metres June 21st, 2013
The day before yesterday at lunch time, I put out several CQs on 144.300MHz without getting a reply. Listening around at the few beacons I normally receive it was obvious to me that the band was flat. That evening I had to go to London and whilst in a restaurant in the City I looked on my phone and saw red. Yes a mass of red – on DXmaps. I got home late that night by which time the band was dead again.
Yesterday at lunch time I listened on 2m briefly and the band was dead. Just as I was about to return to work I had a text from G0KSC telling me that he had been working into Italy on 2m the evening I was in London, and that I should keep an eye on 2m. So just before returning to work for the afternoon I doubled checked 2m. No, it was definitely dead. Dead as the proverbial Dodo! And as I write this at 5.30pm, afew hours later, at work I see that 2m is wide open and G0KSC tells me that he has just worked Greece and Bulgaria. Once again I see red!