Posts Tagged ‘Kit Building’

OAFS failure

One of the things I had intended to do this year was install the external frequency reference module in my Elecraft K3 in order to get the best possible frequency accuracy for digital modes. To this end I had ordered an Off-Air Frequency Standard (OAFS) kit from Spectrum Communications so as to avoid wearing out my rubidium frequency standard. I had completed populating the OAFS board a couple of weeks before I ended up in hospital. So I thought I would try to see if it worked, as that would simply involve connecting up a speaker, ferrite rod antenna and power supply.

It began to look as if the predictions of the couple of people who commented or emailed when I first posted about the OAFS were going to be right. I could hear BBC Radio 4 long wave in the loudspeaker but it was very weak, presumably (as I had been advised) due to North Cumbria being a poor location to receive the transmission. When I checked the frequency of the phase locked loop it remained steadfastly on 216.4kHz regardless of the setting of the trimpot.

The instructions supplied with the kit suggested that it might be necessary to change a resistor value if the loop will not lock on to 198kHz so I wrote to Tony Nailer at Spectrum to see if he had a suggestion. Unfortunately his reply was that if the loop will not change frequency with the pot there must be a solder bridge or other assembly error. I checked my soldering as best I could and re-did any joints that looked suspect but the way my eyes are now any sort of cross checking between the schematic and the circuit board to look for errors is impossible.

I haven’t really figured out what is wrong with my eyes but it is as if they no longer have the ability to vary focus. I can only see clearly what is at the exact focal point of whatever spectacles I am wearing. When something is out of focus my head swims and I have to close my eyes for a few minutes to steady it again. So any sort of constructional work now is well-nigh impossible.

Tony offered to get the OAFS working for me for a fee if I sent it to him, but at this point I think it would be a waste of money. I can’t see myself installing the frequency reference boards in my K3 now even if I still had the same interest in doing so. So I think the OAFS is destined for the G4ILO junkbox.

Home-build D-Star radio

Years ago, after I built my Elecraft K2 I had the idea that I would only use home-built radio equipment. However I found that it was no longer possible to buy a kit to build a 2m FM radio. This afternoon I visited a site mentioned by Tim, G4VXE in his latest blog posting and was intrigued to find that a Dutch group is working on a design for a VHF/UHF transceiver kit. Not only that, it is apparently being developed in consultation with Elecraft and is built into an Elecraft EC-1 (K2) enclosure!

The basic kit will be for an analogue FM transceiver with modules for 2m, 70cm and 23cm (it isn’t clear to me whether you must choose one of these bands or whether you can fit all of the modules.) But with the addition of another module it can also become a D-Star transceiver!

Now I have never made any secret of my dislike of D-Star, mainly due to the fact that one manufacturer has a monopoly on the provision of radios. But a home-brew D-Star transceiver that doesn’t require you to buy anything from Icom and would sit neatly alongside my K2 in a matching enclosure could just be the thing that makes me swallow my objections. Yes, it will still have an AMBE chip containing the proprietary codec. But most of my radios contain chips with proprietary firmware so I don’t think that’s a good enough reason for continuing to avoid D-Star.

Home-build D-Star radio

Years ago, after I built my Elecraft K2 I had the idea that I would only use home-built radio equipment. However I found that it was no longer possible to buy a kit to build a 2m FM radio. This afternoon I visited a site mentioned by Tim, G4VXE in his latest blog posting and was intrigued to find that a Dutch group is working on a design for a VHF/UHF transceiver kit. Not only that, it is apparently being developed in consultation with Elecraft and is built into an Elecraft EC-1 (K2) enclosure!

The basic kit will be for an analogue FM transceiver with modules for 2m, 70cm and 23cm (it isn’t clear to me whether you must choose one of these bands or whether you can fit all of the modules.) But with the addition of another module it can also become a D-Star transceiver!

Now I have never made any secret of my dislike of D-Star, mainly due to the fact that one manufacturer has a monopoly on the provision of radios. But a home-brew D-Star transceiver that doesn’t require you to buy anything from Icom and would sit neatly alongside my K2 in a matching enclosure could just be the thing that makes me swallow my objections. Yes, it will still have an AMBE chip containing the proprietary codec. But most of my radios contain chips with proprietary firmware so I don’t think that’s a good enough reason for continuing to avoid D-Star.

QRSS beacon progress

Yesterday I finished building the QRSS beacon kit board. The keyer chip sends the wrong callsign but it that was no reason not to build the kit. It’s a very easy kit to build although there are no fewer than five toroids to wind which is a lot for such a simple project. Some people hate winding toroids though I find them easy to do and can’t see what all the fuss is about.

The only other slight difficulty with the  kit is that the potentiometer for setting the output power has leads that are too big for the holes in the PCB. This is mentioned in the instructions, where it is recommended to use component lead offcuts to extend the originals. My junk box was supplemented a few months ago with a Maplin bargain pack of assorted potentiometers and lo and behold it yielded a wirewound trimpot of exactly the right value that perfectly fitted the PCB holes. So I used that instead.

When the board was finished I powered it up using my bench power supply and PM20 QRP absorption wattmeter. In the photo I have breadboarded a regulator from 9V down to 5V as I was toying with the idea of running the beacon from a rechargeable PP3 battery (the board will fit into a case I have which has an integral PP3 battery holder) and wanted to see how much heat the regulator would dissipate.

I found that I could get a maximum of just under 100mW from the beacon with about 120mA current drawn. This is a little less than the specification. The instructions suggest that a bit more than 100mW should be possible, but the shortfall isn’t enough to worry about. For longer battery life I will run the beacon at 50mW which draws a current of around 65mA.

To get the transmitter on frequency and set up the mark/space frequency shift I used my K3 and QRSS VD software. The signal, even on the dummy load of the power meter, was very loud which was helpful getting it into the ball park. I had to disconnect the antenna, switch in the attenuator and back off the RF gain to reduce the signal to a level where I could fine-tune the frequency and see what the signal would look like on the air.

And here it is, sending G4LIO! It’s a bit frustrating not being able to connect it to an antenna and put it on the air because of the wrong callsign. I’ve been promised a new chip and I practically snatched the post out of the hands of the postwoman but it hasn’t come yet. In the meantime I can think about putting the beacon into a nice box. Forget winding toroids, for me that is the hardest and least enjoyable part of any constructional project!

QRSS Keyer

I have operated most of the reverse beacon and weak signal modes but one that I have never tried is QRSS. “QRS” is the Morse Q code for “send slowly” so QRSS means send very slowly indeed. QRSS beacons send your call using very, very slow Morse, which listeners receive using a “grabber”, which is a slow moving waterfall display. If you’re lucky, they will email you a reception report, but you can also look for your signal yourself on one of the various online grabbers.

One day I planned to build my own QRSS beacon. When I found out that Hans Summers G0UPL had produced a QRSS beacon kit I was disappointed to learn that all the kits had been sold at the US Dayton hamfest. However I recently discovered that he had made a new batch of kits and not wanting to wait and find out they were all sold at the G-QRP Convention I ordered one at the weekend. The order process was extremely professional (amateur components suppliers who expect you to email your order and credit card details please note) and the kit arrived this morning.

I opened the envelope and was very impressed to find that the package included a printed copy of the instructions as I had expected to have to print them myself from the website. The PCB is of very high quality. But as I tipped the parts on to the workbench my heart immediately sank.

Because the microcontroller chip which keys the transmitter and has been preprogrammed with my callsign was wrapped in a slip of paper on which was written G4LIO, a transposition of my call that often afflicts people on the air as well – I don’t know why. The incorrect call was also written on the jiffy bag the kit came in. I checked the emailed copy of the order and the mistake was not mine.

After an exchange of emails with Hans I installed the chip in its socket, applied power and connected an earpiece to pin 2 which produces an audio tone to verify whether the chip had been programmed incorrectly. It sent G4LIO. 🙁 Why is it always me that gets the kits with the missing or faulty parts?

No shame, no pride

A few weeks ago fellow blogger Dominic M1KTA wrote that he was selling off some unwanted projects from his shack, including some unbuilt or part-completed kits. A little while ago he wrote: “I have decided to stop selling off project builds now and I am keeping hold of everything until a rally when I can sell them in person as I have had a complete nightmare after selling one of the projects over the internet to someone I believed was capable of finishing it and has demanded I rebuild and re-align it after they hacked about with it themselves to the point where it no longer functions, they melted the pcb connectors and filed away part of the pcb and at least one track in the process to attempt to squeeze it into a box that was too small and demanded a paypal refund. I am never again selling a ‘built’ project over the internet it is too risky for me.”

I have bought things before, either at rallies (hamfests) or from ads in RadCom, that were found not to work and sometimes revealed some astonishingly ham-fisted handiwork inside. The purpose of some modifications defied understanding. I either fixed them myself or wrote it off to experience.

The idea that someone could buy an unfinished kit and then try to make the seller liable for their inability to complete it just beggars belief. It seems some members of this hobby have no shame and no pride.

I told Dom he should publish the callsign of this so-called amateur as a warning to other sellers to steer clear. I know I would.


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