AmateurRadio.com

For readers local to my home area you may be interested in this exciting and free event in Ottawa this weekend. Full details can be found on the Artengine website. The essential details are:

Dates and times: Nov. 6th and Nov 7th, 12pm to 6pm.

Location: Arts Court 2 Daly Ave. Ottawa, ON K1N 6E2

If you are not sure what makers do or what goes on at a Maker Faire take a look at this video of the 2010 Kansas City Mini Maker Faire

Having an interest in weak signal narrow band modes, not to mention APRS which requires you to park your receiver on a specific frequency, I have always wished that the frequency readout on my radios could be relied upon. The QRSS band, for example, is only 100Hz wide. If your dial reading is out by that much, you’ll miss it completely.

Many people try to calibrate their transceivers using WWV but that is not often a very good signal over here, and what with all the other carriers around 10MHz – many of them locally generated – you can never be sure that you have tuned to the right signal. I have wanted an accurate frequency reference for some time so a couple of weeks ago, following a comment by QRSS enthusiast Steve G0XAR, I ordered an Efratom LPRO-101 rubidium frequency standard on eBay. It arrived in about a week.

The unit I bought cost about £50 and came with a plug for the 10-pin connector and a 24V switched-mode power supply. These second hand units are widely available. New, they cost over $1,000 even in quantity. They are used in cellular base stations and are manufactured to have a maintenance-free life of ten years. To ensure reliable service the cellphone network providers take the equipment out of service before the ten years is up after which it is presumably shipped to China for reclamation. The used units should have several years of life in them, especially in occasional amateur use.

Rubidium frequency standards work by locking a crystal oscillator to the very precise frequency at which the amount of light from a rubidium lamp dips due to a phenomenon known as the hyperfine transition. A synthesizer locked to a reference oscillator is swept through this frequency until the dip is detected. The LPRO-101 includes an oven for the reference crystal, circuits to detect the dip and lock the oscillator, an output that tells you when the unit is locked, and the frequency reference output at 10MHz. The connector also provides signals that can tell you the state of health of the rubidium lamp. Once that fails you may as well scrap the unit because it can only be replaced by the manufacturer at a cost far in excess of what you paid for it.

To use the LPRO-101 you could simply attach a 24V supply and connect a cable to the 10MHz output. However, it’s useful to have a circuit that shows you when the unit is locked on frequency. I used one shown in an article by KA7OEI built up on a piece of Veroboard, which uses a dual-colour LED to light red when the reference oscillator is unlocked and green when it is locked. You can see the circuit board inside the partially assembled case.

The voltage regulator and crystal oven inside the LPRO-101 generate a lot of heat so the unit is intended to be mounted on a heat sink. I purchased a Hammond extruded aluminium case to use for the project, which should provide reasonable heat sinking for the module.

One thing I learned from researching on the internet is that the LPRO-101 will run cooler when operated from its minimum recommended supply of 19V. This just so happens to be the output voltage of the power supply for an old Toshiba laptop whose screen failed so I decided to use that instead of the 24V supply that was sent by the seller.

The other thing I learned is that the rubidium lamps wear out with time. When they are made, the manufacturer ensures that they contain sufficient rubidium to achieve the stated maintenance free life of ten years, so the expected life in continuous use would be ten years less the use it has already had.

If I ran the unit all the time my rig is on – for example as an external frequency reference for a transceiver – then it is going to fail sooner or later. If I only use it for frequency calibration purposes, switching it on only when needed, then it will probably outlast me. The TCXO in my K3 is pretty stable so I should be able to obtain adequate accuracy for my purposes by manually calibrating the master oscillator using the rubidium standard and repeating this as often as necessary. How often that turns out to be, we’ll see.

Here is the finished unit. Annoyingly, I messed up the front panel of the rather expensive Hammond case. Originally I had intended to use an SMA socket for the output but I didn’t get the holes for its two mounting screws in the right place and after filing to fit it looked unsightly. So I fitted a BNC socket instead which is what I should have done in the first place. Unfortunately you can see the two holes for the SMA mounting screws either side of the BNC socket. So my frequency standard doesn’t look quite as professional as this one built by DL2MDQ. Oh well, it’s only a piece of test equipment!

Over the last few days, I’ve been using the scan feature on the FT8900 a bit more from the car. I’m scanning particular channels, rather than the whole of the band, but it’s interesting to see what coverage I’m getting. I’ll probably add more channels to scan when I identify likely targets of semi-distant stations to listen for.

I thought it might be fun to try and put together a Google Map of what I heard this morning – I’ve colour coded the different bands.

View Heard by G4VXE this morning in a larger map

As you can see, GB3CF up in Leicestershire is probably the most distant station heard this morning. It fights it out on 145.600 with GB3WR. But I didn’t hear WR this morning and GB3CF was clearly audible just around Abingdon for a few hundred yards.

About a week or so, I got an e-mail from Matty, MD0MAN drawing my attention to some propagation forecasting websites. One that I hadn’t come across before, though somewhere at the back of my mind, I think I’ve heard it mentioned, is William Hepburn’s Tropospheric Ducting Forecast site.

The site allows you to select the area of the globe that you’re in – so in my case, I selected the North West Europe page but if you’re in North America, this is your map

But how well does it work? After Matty’s e-mail, I looked at the maps for the UK and NW Europe last weekend and could see that there would be a chance of some tropo to the South West towards the end of this week, from Thursday onwards.

Driving to the station this morning, with one VFO going on 145.650, there was another repeater just breaking the squelch – something not normally audible. Purely a guess, but I’ll bet it was the GB3TR repeater, to the South West of me, in Torbay.

An interesting site – I’m looking forward to keeping an eye on it. Thanks to William for some fascinating data and to Matty, MD0MAN for the tip-off.

Today I released a new version of my logging and data communications program for Elecraft transceivers, KComm, on my website. The program is developed in Lazarus / Free Pascal and is released under the GPL.

Apart from numerous bug fixes and small improvements I have made in the months since the last release, the new version 1.9 allows the receive and transmit sound devices to be selected separately. This is something that is becoming increasingly necessary, though users will have to play “guess the device number” as I don’t know how to find out the names of the sound devices in Free Pascal in order to display them in a list box. The program also supports the K3 “TB” command which allows it to get the text decoded by the K3 DSP in CW, PSK or RTTY modes and display it on the screen just the same as if you were using a sound card program.

Although I have given up developing ham radio programs in general, I am continuing to update and maintain KComm as it is the only one of my programs that I continue to use regularly. However this will be the last version for which I will be able to provide a compiled Linux binary. The screen of the old Linux laptop that I used to compile it has almost failed so I will not in future have a computer on which I can do this.

We Brits and our friends across the Atlantic may share a common language but sometimes it seems as if we live on different planets. One of the most obvious examples of this is that Americans sometimes seem to act as if Armageddon could happen at any minute, something that doesn’t seem to cause much lost sleep over here.

Perhaps I’m jumping to the wrong conclusion based on the higher emphasis given in the USA to the use of ham radio for emergency communications. Read some issues of QST these days and you might think that “emcomms” is what amateur radio is really all about. Many American hams maintain “go kits” – portable radio stations that they keep charged up and ready to go the moment they are needed. Over here we have something called Raynet, but I get the distinct impression that it is a bunch of people who would like to use ham radio to help in an emergency rather than a volunteer emergency service on the lines of, say, Mountain Rescue that has a clearly defined purpose and meets a genuine need.

In his latest blog “Smoke Curls” Jeff, KE9V recently posed the question of whether a portable QRP HF station was really useful in the context of emergency preparedness. Most of the replies seem to illustrate the extent to which the thought of a major disaster is never far away from the American consciousness. My comment that the only benefit I could see in having battery powered HF ready to use was so I could take advantage of the noise-free bands while the power is out – which in fact I did during the outage that occurred during the local floods a year ago – probably seemed rather flippant, though that wasn’t the intention.

My opinion is that emergency communications is a job for the experts and the last thing they need is a bunch of amateurs trying to help but more than likely getting in the way. The Cockermouth floods were the nearest I have ever come to being directly affected by a disaster and it never even entered my head that as a radio amateur I might be able to help. As for needing HF or any other kind of ham radio for personal emergency communications I still feel the likelihood of something happening in which my radio gear might end up being my only means of getting in contact with anyone I needed to is so remote that I’d cross that bridge if I ever came to it.

I would never assemble a “go kit”. And if I did, I know for sure that I would forget to charge the batteries or raid it for parts I needed for something else so it would never work in the unlikely event it was needed.

Is there a cultural difference between us and Americans in this regard, or is it just me?