AmateurRadio.com

My home made USB digital modes interface “SignaLink clone” has been completed. It has been in use for several days and is currently in use with my K2 for 30m APRS.

USBlink interface with cables for FT-817

I have written up the project on the G4ILO’s Shack website. See home-brew USB digital modes interface.

My bureau-workshop

I have sometimes seen comments to this blog that are disparaging towards the idea of stealth operation. I don’t for a moment accept that stealth antennas are worse than the modest wire antennas many hams in the UK who don’t have deep pockets, large gardens and amazingly tolerant neighbours use. RF doesn’t care whether an antenna is visible or not, it’s what you do to make the antenna invisible that might compromise performance and with the small gardens without trees that so many of us in the UK have, most of us have to live with compromise.

But the real test of a ham radio station is whether it allows you to pursue enough activities to maintain interest in the hobby. And based on that criterion I think G4ILO does very well. One of the best additions to the shack was to make a dedicated work area for construction in a bureau unit whose door drops down to make a work surface and which can be closed when I have done enough without having to put everything away. I have a greater interest in building stuff now that I have somewhere to do it.

In fact there are more things I would like to do, radio-wise, than I have time to do. Last weekend, for example, I would like to have tried making some contacts in the worldwide RTTY contest but of all the radio things I did that weekend, giving away some contest points was something I didn’t get around to.

Today I was trying to finish up my homebrew SignaLink USB clone, but I made the mistake of turning the K3 on and leaving JT65-HF running and I kept on being distracted by seeing CQ calls from DX stations. In between work on the interface I made contacts with YV6BFE, N8ABY, AA1CZ and KD0AGX plus a couple of Europeans, all using 25W to the attic dipole. My signals were spotted in Japan and far eastern Russia, though I didn’t hear anyone that far east. DU1GM, whom I worked a few days ago, was calling for most of the afternoon with no takers.

The SignaLink USB clone is just about finished and does work. After I made up an interface cable between it and the FT-817ND I made one solid PSK31 contact with F5TTI on 30m with it on the test bench. So now it just has to be put into its case and it will be completed.

This morning a small package arrived from India. It is a FoxTrak-M APRS Tracker Module kit from Fox Delta.

Fox Delta has an interesting range of kits for anyone interested in APRS, packet radio, digital modes or EchoLink. They are all extremely good value – the website suggests that they are sold on a non-profit basis. A couple of weeks ago I asked about one of these kits in a forum somewhere and an American ham complained that the parts were of poor quality, the instructions were poor and it took a long time to come from India. I think that is just the biased nonsense one sometimes hears from US hams about anything from India or China. The PCB is screen printed and looks fine, all the components are standard components and have been packed into individual small polythene bags for each value, and it took a week to arrive which is a lot faster than anything coming from the US via the postal service. It’s true you don’t get Elecraft style step by step building instructions, but it really isn’t rocket science to work out which part goes where on the circuit board.

Hopefully this module will form a stand-alone GPS tracker that I can use with my other VHF radios. However, before I get started on it I have to finish my DIY SignaLink USB project.

I installed a four port RS-232 serial card in my shack PC today. When I bought the computer earlier in the year I purchased and installed a two port serial card, thinking that would be enough. But it wasn’t. You can never have enough serial ports if you want to interface with radios. With four, I can now have CAT control of both the K2 and the K3, the TNC connection to the Kenwood TM-D710 and one more which is currently controlling the PTT of the FT-817 for the EchoLink node but could be used for the control port of the Kenwood if I ever decided to use that for EchoLink. No more hassles with USB to serial adapters, and all my USB ports are free for things like sound cards. I don’t know why people use laptops for shack computers, they provide far fewer options.

Needless to say, things did not go as smoothly as they could have done. I thought I could have COM2 for the K2, COM3 for the K3 which would be easy to remember. But Windows gave the ports the designators COM3, 4, 10 and 11. There’s an option to reassign the port numbers but Windows claimed that everything from COM2 to COM9 was in use. By what, was my unanswered question.

In the end I decided to name the ports COM2 through COM5 as I wanted regardless of Windows’ protestations. They did work, but finding out which port was which was a matter of attaching a radio to one socket, loading a program and trying all possible COM port numbers until it worked, as there was no logical correspondence between the numbering and the sockets on the back of the computer. Who said it was meant to be easy anyway?

Despite all this I managed to make a few contacts using JT65A on 20m including DU1GM, N0OB and K1CF, using 25W to the dipole.

Although I now have computer control of the K2 I don’t have a sound card interface as I have cracked open the plastic case of the USB audio dongle and superglued the bottom half containing the PCB to the stripboard on which I will be building my homebrew SignaLink clone. Of course, now I have a serial cable connection between the computer and the K2 I don’t need a VOX controlled interface, never mind an isolated one because the serial cable will bypass the isolation anyway!

As regular readers will know, I’ve been playing about with APRS quite a lot in recent weeks and I’m starting to get the urge to build something APRS related. I’m planning to order one of the inexpensive FoxTrak kits, which lets you use a standard VHF FM radio to transmit position reports. To do that you also need a serial GPS and on searching eBay I became aware that serial GPSes seem to be rather more expensive than USB or even Bluetooth devices. This led me to wonder whether it would be possible to hack a USB GPS to use with a tracker like the FoxTrak. My investigations led me to this article by Primiano Tucci on GPS Hacking.

This post is basically an un-loseable bookmark to myself, since it will probably be a few weeks before I get around to working on this and by then I’ll have lost the article and never be able to find it again. But it might be of interest to someone else or provoke some interesting comments.

Although I’ll probably build the the FoxTrak as-is and test it with one of my 2m rigs I’m really interested in trying HF APRS on the move without having to buy an expensive TNC or lug a laptop around me so I can use AGWPE to generate the 300baud audio. So I’d also be interested to know whether anyone has modified the FoxTrak (or the TinyTrak which I believe is very similar) for the 300baud tones? I know the OpenTracker+ from Argent Data does 300baud “out of the box” but it’s quite a bit more expensive, enough more expensive to attract the punitive import fees that will almost double the price.

I did a quick lash-up of the UHF FM transmitter module I received a few days ago which I was planning to use in a low-power Echolink node, mainly just to see if it worked. It did, but I discovered a small snag. The audio output isn’t squelched.

The Echolink software requires either normal squelched FM audio or a carrier operated squelch signal on one of the serial port control lines. As neither of those is provided I guess I am going to need to generate a squelch signal derived from noise. But as I am not knowledgeable enough about electronics to design my own circuit I am going to have to find one first. This appears easier said than done, though there seem to be a surprising number of patents on the subject.

It isn’t an urgent problem as I’m not in any hurry to build this project. I’ll probably have more enthusiasm for it once the gloomy autumn weather starts.

Yesterday I was surprised to receive a package, by air mail, from Greece. It was the micro transceiver module I ordered at the beginning of April from Elcom Research. I was informed that it had been sent by registered air mail, but when it didn’t turn up and further emails went unanswered I opened a dispute with PayPal which was judged in my favour and the money was returned to my account on May 21st.

What I received was just what you see in the picture (less the PL259-BNC adapter which was included in the picture for scale). No documentation, no indication as to what the connections to the 10-pin connector are, nothing. It is completely unusable as sent. What’s more, the Elcom Research website I originally ordered it from now seems to be defunct. The only identification is the part number FC201SA on the circuit board. I typed that into Google and found that the module is an FC-201/SA Audio/Data RF Module manufactured by Friendcom in China. Google also turned up a PDF user manual on the Friendcom site, so I was able to download and print off that.

From the manual it appears that Friendcom would normally supply a cable for the 10-pin connector. I didn’t receive one. Without it I will have to solder directly to the pins, because although it looks like a standard 0.1in PCB header connector it isn’t. The pins have a spacing of about 1.8mm. I haven’t been able to find a mating connector, though I admit I haven’t looked at the professional parts suppliers as with minimum order quantities and so on it isn’t economic to order a single connector from them anyway.

My intention with this module had been to make a micro-power Echolink hotspot. As I no longer expected to receive it I had moved on from that idea, but now it’s here I guess I’ll have to pay for it. I don’t plan on doing anything with it until the autumn at least, as for me summer is not the time for constructional work.