Monday, October 04, 2010

One thing leads to another

Yesterday I began assembling the Foxtrak-M APRS tracker kit. After installing all the resistors I began adding the capacitors and found that I only been given 4 0.1uF capacitors instead of the 5 needed. I noticed that this was actually a mistake in the packing list, which stated 4 of these parts, so I turned to the computer to send an email to Dinesh so he could correct the mistake in future kits.

Whilst I was logged in to my Google account I checked the blogs I am following and read an interesting entry from PE4BAS about trying PSKMail. I noticed he had a gadget in the right hand column that said he was on the air around 18.100MHz (that's cool, I must try to set up something like that in KComm.) From the frequency I guessed Bas was on PSK31 so I switched on the K3 to see if I could spot him. I couldn't, but I did see some DX including a Japanese station.

This was on my 80/40/20/15/10/6m dipole, which my K3 ATU managed to tune to a 1.0:1 match. I decided to see how well I could hear the DX on the magnetic loop so I shut down the K2 which was running HF APRS and groped around the back to disconnect the loop, plug it into the K3 and tune it up on 17m. What a difference resonance makes! The DX signals were noticeably stronger on the magnetic loop than the dipole, stronger enough to surely make a difference given that signal strengths were marginal in any case.

Using 40W to the attic mounted magnetic loop I worked FG5LA (Guadeloupe) and then, after several tries and witnessing some of the kind of bad mannered operating that makes me think it might be best to stay off the radio at weekends, JI1FGX/DU9. KComm said this was not a valid call, so after the contact I fired up the Lazarus development system and had another attempt at rewriting KComm's callsign validation routine. KComm still thinks the contact is with Japan not the Philippines so that is something I still have to look at.

I could of course have tried to work these DX stations using the K2 and 5W but I doubt if I would have been successful. This made me think that it would be handy if there was an easier way to switch the magnetic loop between the K2 and the K3 than groping round the back of the rigs and unscrewing the plugs. In my junk box I had one of those die-cast coaxial switches that are intended to switch one radio between two antennas. In theory I could use it to switch one antenna between two radios, but would there be sufficient isolation on the disconnected port that I wouldn't blow up the K2's front end while running 100W from the K3?

To find out I connected the antenna switch between the K3 and the magnetic loop controller and connected my QRP wattmeter to the other input. While transmitting a 40W carrier I observed no movement at all on the QRP wattmeter on its 1W FSD scale so I think the isolation between the two ports is good enough. I got the drill and fixed the switch to the wall so I can now change the magnetic loop between the K2 and the K3 at the turn of a switch.

And that was Sunday's ham radio activity in the G4ILO shack!
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