AmateurRadio.com

The success of my project to make an FM version of G3XBM’s Fredbox was always going to depend on the receiver. The Fredbox receiver is a simple three transistor super-regenerative design. This is the only practical way to make a receiver small enough to fit in a hand-held case. It is also the only cost-effective way to do it, because making a conventional double-conversion receiver with crystal control just wouldn’t be worth it for such a project.

What I didn’t know were a) would the super-regenerative receiver work with FM signals (the original Fredbox was designed for AM) and b) would it be sufficiently stable to stay on frequency without the benefit of crystal control? However, what I didn’t give too much thought to was the possibility that I wouldn’t be able to get it to work at all.

Because this is a VHF circuit I didn’t think I could try it out on the breadboard so I made it up directly on to Veroboard. The layout is pretty similar to Roger’s original layout from what I can tell from the pictures on his website, although I think he made an etched circuit board, something I’m not able to do.
I drew up the layout using a bitmap editor. This shows the components from the top view. The large outline components are the Toko S18 inductors, and the red lines are wire links below the board connecting the ground traces. The schematic for the receiver part of the Fredbox is shown below. As with the Nano-40 I used an MPS13 in the audio stage in the hope of getting a bit more audio gain.

I applied power and expected to hear a hissing sound in the earpiece which stops when a signal is tuned in. However I heard nothing at all. The audio stage appears to be working, as I can hear a faint buzz if I touch something metal to the input.

Alan, VK2ZAY had a lot of trouble getting the receiver to work as well, and he is an experienced constructor who knows what he is doing. I suppose this should have warned me off trying this project. Alan replaced the axial choke for L3 with half a dozen turns of wire on a ferrite bead, and I did the same, but to no avail. I also substituted a variable trimpot for R2 which in many other super-regenerative receiver designs is a variable regeneration control. But no matter what the setting of the pot I could not get any regeneration to occur at all.

I think my FM Fredbox is about to become yet another abandoned project. 🙁

The Digital Voice Access Point (DVAP) Dongle is a small device now available in the US that plugs into a computer and lets you create your own low power (10mW) RF gateway to the D-Star network.

Leaving aside my dislike of D-Star (it is incompatible with existing radios and requires you to purchase an Icom radio to participate, which in my book makes it effectively a proprietary system) for a moment, as someone living in an area where you hardly ever hear any 2m FM activity I can see the attraction of something like this. It would allow one to make some internet-linked ham radio contacts from around the house using a hand-held.

A couple of years ago I started looking into the idea of setting up a low-powered personal EchoLink node, for similar reasons. I prefer EchoLink to D-Star for the simple reason that almost any existing FM radio can use it (as long as it has a DTMF keypad). EchoLink has been going for years and already has a critical mass of users, which is surely more important from the point of view of finding people to talk to than using some new and more state of the art system?

Unfortunately it appeared that in order to set up an EchoLink node I would need to apply for special permission, providing details of three people who could turn the equipment off on instructions from Ofcom, wait months for permission to be granted, etc., etc., which is way too much hassle. I don’t think you are exempted from this procedure simply because the RF output power of the node is very low. Because of this restriction doubt if many people in the UK will be using the DVAP Dongle either.

As someone who likes a walk in the great outdoors I enjoy reading accounts of people who take their radios out into the countryside for a bit of QRP fun. Today I thought I would try to emulate them. However although I did make a few contacts the attempt was a bit of a disappointment on several counts. Even the photos I took with my camera self-timer were disappointing as the operator completely obscured the radio and a picture of myself sitting on the ground at the foot of a tree apparently talking to my hand is not something I feel should be preserved for posterity on the internet.

As the CQ WW WPX SSB contest was on I thought this would be a good opportunity to make some QRP SSB contacts. The batteries in the FT-817ND seemed to be less than fully charged, and the battery endurance of that radio is poor enough already thanks to its power-hungry receiver. I decided to take my K2 instead, which would give me the benefit of 10W output and really punchy audio. So the local dog walkers witnessed the odd sight of someone setting off up the forestry track into the woods near Watch Hill wearing boots and rucksack and carrying a small Pelican case.

Fifteen minutes later they would have witnessed the even odder sight of the same person trying to throw a stick with a bit of wire attached over a tree branch. Now I know why the MP-1 was invented! After about ten minutes of persevering I managed to get the wire over a branch about 12ft high. The stick hung down the other side tantalizingly out of reach and I spent the next five minutes trying to hook it with the end of my walking stick so that I could pull the wire taut and secure the end of it.

I had previously prepared two lengths of wire for my portable antenna. One is about 22ft long, and has a few feet of nylon cord attached to the end for tying to sticks or rocks to hurl over branches and then secure in position as the radiating element. The other is about 16ft long and is laid out along the ground as a counterpoise. They are fixed to the red and black terminals respectively of a BNC to binding post adapter which is plugged in to one of the antenna sockets of the K2. The reason for the selection of these particular lengths is that I seem to recall them being suggested by Elecraft as good lengths to use with the T1 portable auto-tuner.

There are no picnic benches or tables in the forest so I just sat down on the ground and used the Pelican case as a table. The K2 sat on that, and the antenna ran off directly behind it at about a 45 degree angle, over the tree branch and down a few feet at the other side. The counterpoise ran off at right angles.

I switched on the K2 which was still on 15m from my last mobile outing and immediately heard many strong signals. However signals didn’t seem as loud or as plentiful as I would have expected during a major contest. I pressed the Tune button and the K2 ATU whirred away and finally delivered its verdict: 9.9:1! It couldn’t match it!

I didn’t hear anything on 10m so that wasn’t worth trying. I got a usable SWR on 17m but there was hardly any activity on that band. On 20m the best SWR was between 2:1 and 2.5:1, and on 40m I managed to get 1.5:1. Unfortunately the K2 is a bit SWR-sensitive – something I never noticed during the years I used it as my main home station when I could always get a 1.2:1 or better – and it flashed up Hi Cur (high current) when I tried to use 10W on 40m. So I had to back my power down to use that band, which didn’t help matters.

I made nine contacts in less than an hour’s operating, which included a break to eat my sandwiches:

1130   7.113  ON5SY   59  609  59  001
1131   7.123  PI4Q    59  801  59  002
1133   7.167  PA6Z    59 1022  59  003
1138   7.123  SP4TKR  59 1130  59  004
1143  14.286  YL6W    59 2416  59  005
1212  14.292  HG1S    59 1821  59  006
1215  14.315  OG6N    59 1450  59  007
1217  14.321  SN2B    59 2772  59  008
1218  14.335  SP9LJD  59 1876  59  009

But these were not nice easy contacts like I made using the same radio and the same power from the car using the MP-1 antenna. My thanks, as well as my apologies to the stations that wasted valuable minutes trying to pull my call and serial number out of the ether.

It was getting a bit cold and I felt a few spots of drizzle so I decided to call it a day. I think I’ll stick to taking VHF on hikes in future.

This isn’t original, though I’ve edited it a bit. It was sent to me as one of those chain emails, so my apologies if you have already seen it. But I thought it was so true, I just had to share it. I think everyone should read it.

To all who were born in the 1930s, ’40s, ’50s and 60s!

We were born to mothers who smoked or drank while they carried us and lived in houses full of asbestos. They took aspirin, ate blue cheese, raw egg products, bacon and processed meat, tuna from a can, and didn’t get tested for diabetes or cervical cancer.

Our baby cots were covered with bright coloured lead-based paints. We had no childproof lids on medicine bottles, doors or cabinets. We rode in cars with no seat belts or air bags. We rode our bikes without helmets or shoes.

The shops closed at 5pm and didn’t open on Sundays, but we didn’t starve! Our only take away food was fish and chips – no pizza shops, Burger King or McDonald’s. We ate crisps with salt in them, white bread with real butter, drank full cream milk and soft drinks with sugar in them, but we weren’t overweight because we were always outside playing!

We rode bikes or walked to school and didn’t get abducted. Our teachers would hit us with canes and gym shoes and bullies ruled the playground. It didn’t harm us.

When we wanted our friends we would just walk or ride round there and yell for them. No one was able to reach us all day. We would leave home in the morning and play all day, as long as we were back when the streetlights came on.

We collected old drink bottles and cashed them in at the corner store to buy toffees, gobstoppers, bubblegum and bangers to blow up frogs with. We would spend hours building go-karts out of old prams and then ride down the hill, only to find out we had no brakes. We built tree houses and dens and played in river beds with matchbox cars. We were given air guns and catapults for our birthdays. We fell out of trees, got cut and dirty, broke bones and teeth and there were no lawsuits from these accidents.

We did not have Playstations, Nintendo Wii, X-boxes, no video games at all, no 999 channels on satellite TV, no video/dvd movies, no mobile phones, no personal computers, no Internet, no Internet chat rooms. When we wanted to make friends we went outside and found them!

We had freedom, failure, success and responsibility and we learned how to deal with it. And you are one of them. Congratulations for surviving despite so many difficulties!

One of the things I have long wanted to do in this hobby is build a hand-held transceiver. I tried once back in the 1970s but the receiver didn’t work and the project eventually ended up in the garbage. Many months ago while browsing Roger G3XBM’s website I came across an old project of his called the Fredbox, a small, low-power hand-held 2m transceiver. This rekindled my desire to try to make my own VHF handy transceiver so I started the process of accumulating the parts that would be needed to make my own Fredbox.

However there were two problems. Roger designed the Fredbox as an AM (amplitude modulation) transceiver, a mode that was probably still in common use back in the 1970s when he first made it. Here, the only chance of making a contact with such a radio is if it transmits on 145.500 in FM mode, so I would have to modify the transmitter to produce FM instead of AM.

The other problem is that the Fredbox transmitter is crystal controlled. The days when suppliers advertised crystals for popular FM frequencies in RadCom at reasonable cost have gone, along with the crystal controlled transceivers that used them. I didn’t know where to obtain the crystal I would need but hoped that someone might have crystals from an old 2m radio that they wanted to get rid of.

My luck seemed to be in when, a couple of months ago, someone started selling batches of 2m crystals from old Japanese radios on eBay. I bid for and obtained three batches containing crystals for 145.450, 145.500 and 145.550MHz. I don’t know what radios these crystals were originally for or what oscillator circuit they were used in but by using the XBM80 as a test oscillator it appeared that most of the transmit crystals oscillated at around 12.1MHz.

I tried breadboarding the first oscillator stage of Roger’s Fredbox circuit in order to experiment with ways of FM-ing the signal but the crystal did not seem to be oscillating. I did some searching for other 2m FM transmitter circuits in the hope of getting some inspiration and came across one using an MC2833P IC – a complete FM transmitter on a chip. This seemed like the ideal solution, especially as the crystal used to get 144MHz output was 12MHz just like the crystals I had. Unfortunately I couldn’t find a supplier of this chip until on a whim I typed the part number into eBay. There was someone selling one chip! I ordered it and it arrived in the post this morning.

I built up the circuit from the application note on my breadboard (as you can see in the photo) but to my dismay I could not detect any signal when using any of my 2m TX crystals. It was very disheartening. I didn’t know if the chip was dead, whether I’d blown it by accidentally shorting together wires from components on the breadboard, or whether it was just a very fussy circuit. I experimented with different components and coils and got nowhere. I was just going for lunch when I had the idea to try one of my QRP CW frequency crystals. I had one for 10.106MHz and another for 14.060MHz. With both of those crystals I could detect not just a strong carrier on the fundamental frequency but also plenty of output in the 140MHz region. The chip is working, the problem is my eBay crystals!

The question is, what to do now? I guess the crystals I bought, being probably 35 years old, have deteriorated with age and are reluctant to oscillate. It appears that the only way to proceed with the project is to get a brand new 12.125MHz crystal custom made, if possible.

Due to having been banned from using the software I have not been keeping up with what is going on in the development of the ROS digital mode. However there have been a few interesting postings about it. In the digitalradio Yahoo group Skip KH6TY has posted the results of some tests conducted with ROS on 432MHz which appear to show that it suffers badly from the effect of doppler shift and flutter experienced at those frequencies, failing to decode over paths where Olivia was successful and even SSB was readable.

This has prompted a rebuttal from the ROS author, which however seems to overlook the problem of doppler distortion encountered by Skip. He has posted a series of comparisons between ROS 2250/8 and Olivia 32/1000 which purport to show that ROS holds up while Olivia prints garbage. He concludes: “The difference between both systems is about 5dbs (3.16 in natural units). This means that ROS8 need 3.16 times less power than OLIVIA 32/1000 to establish a QSO to 150 characters/minute.”

Assuming that this is true, I nevertheless feel that a tradeoff of bandwidth for power or speed is inappropriate in the context of the narrow HF band allocations for digital modes. Most amateur QSOs do not need to go at 150 characters/minute (most people can’t type that fast). On the other hand the 2250Hz wide ROS transmission blocks three channels that could be used for Olivia 32/1000, and even more channels that could be used for a narrower mode. The use of 2250Hz ROS effectively limits the number of people who can simultaneously hold a digital QSO.

Even if it is true that Olivia needs 3 times the power than ROS to get through, Olivia is still a better choice of mode in the real world, because it is easier to increase the power 3 times or to switch to a slower mode than to find extra space within the HF allocations to accommodate the use of such a wide mode.

ROS would be less of a problem if people used it only in circumstances where it would not be possible to communicate using a narrower mode. Unfortunately that discipline does not exist among today’s radio amateurs. People are using ROS to make contacts with others whose signals are strong enough that 30Hz wide PSK31 could be used. This is just selfish, and it is the reason why I feel that such a wide digital mode should not be permitted on HF at all.

Back in December I wrote that the RSGB had set up a Spectrum Defence Fund to enable radio amateurs to contribute towards the cost of a legal challenge to the UK spectrum management authority’s failure to take action over the interference caused by power line networking devices. Pleased to see some positive action being taken I made a donation and also posted links on my blog and website to encourage others to do the same.

Today I noticed, at the end of the RSGB Annual Report, the statement that “following advice from the Society’s solicitors … it was decided not to proceed at this time with any legal action.” So the RSGB has given up the fight and I have removed the links to the Spectrum Defence Fund from my website so that no-one else wastes any money on it.

Although PLT devices are a killer for any radio amateur unfortunate enough to live next door to one, it is clear from the noise at my own station and the comments I received from others with a similar problem that PLT is just the thick end of the wedge. A far greater number of short wave enthusiasts are having their enjoyment of HF ruined because of rising noise levels from a multiplicity of devices that individually would not be particularly intrusive. Whilst it is possible to track down and do something about a PLT installation, eliminating the noise that most of us in urban areas now experience from all directions would require the willingness of all neighbours to co-operate with finding the interference-generating devices and agreeing to replace them. This isn’t likely to happen. I fear the battle to keep the short wave bands free of interference is over and ham radio is a lost cause.

The only place to enjoy HF radio nowadays is out in the country, which unless you happen to live there means operating portable or mobile. The question is whether only being able to operate portable or mobile is enough to maintain most people’s enthusiasm? Although I recently enjoyed operating from my car on a couple of fine afternoons, it is no substitute for being able to go into the shack on a wet day or a winter evening and have a tune around and make a few contacts. I find I am turning on my K3 less and less often these days and when I do I often turn it off again soon afterwards without making any QSOs.

Will ham radio will still exist in ten years’ time? Many former short wave and FM radio stations now broadcast over the internet rather than the airwaves and I suspect that an increasing number of ham radio operators will end up doing the same. They will get worn down by the losing battle against electrical noise and antenna restrictions and be forced to swallow their objections and switch to online “virtual ionospheres” like QSONet and HamSphere (shown above) where there is no QRN. You only need to visit the HamSphere site to see the number of amateur license holders that have taken this step already.

The RSGB’s apparent acceptance that it can’t fight even a clear case of interference to short waves is clear evidence that this is a war we can’t win. Final surrender is just a matter of time.