Monday, November 14, 2011

JT65A, propagation and data visualisation

When I met Dave WW2R/G4FRE back in the spring he mentioned that after you've played with JT65A on HF you really don't want to do HF any other way. Having had a good weekend playing with the mode, I'm inclined to agree! Of course there are provisos - this is a mode to make bare bones contacts with minimal power or poor propagation. It's certainly not a mode for chatting!

Having said that, I have loved having the receiver running all day hooked up to the wonderful JT65A-HF program from W6CQZ with the data being uploaded to both the Reverse Beacon Network and the PSK Reporter network

The other thing about this is that when you call CQ or work someone, you can readily see who else heard you, which is absolutely fascinating.

Over the weekend I think my signals have been heard in all continents on 28MHz running anywhere between 10 and about 50 watts (depending on conditions) to the vertical. I have had some fascinating contacts and found some interesting openings.

Mike M0PRL is interested in visualising propagation data to look for openings and he kindly put together a fascinating time lapse sequence of the stations that my JT65A receiver hears over a period of 24 hours (though I confess it's usually switched off overnight, as you will see). Congratulations Mike, this is a really great visualisation!


Wednesday, November 09, 2011

My first QSOs on JT65a

I've mentioned before that I wanted to try out JT65A on HF but had hit some problems with the laptop's sound card and the software. Having got things going on WSPR yesterday; my 1W 20m signal got as far as VE6PDQ/1 in Edmonton. Having had an insight as to what I thought the sound card issue was with the JT65A-HF software was, this afternoon I connected it all up and started the software.

It worked!

First of all I tried it out on 20m and got a decode, having sorted out the levels to the sound card. It seemed that the JT65A software needed a slightly higher input level than WSPR. Having done that I was delighted to work DL1AAH on 20m running about 1W.

I wondered what 10m would be like and sure enough it was busy! I answered a few CQ calls, but a particularly nice QSO was with W7YES - I was running about 10W to the vertical.

By about 1830z the band seemed to have faded but I left the software running whilst we had supper. To my surprise, when I popped up later, the band had opened again and the software had logged some further US stations including WY7LL.

I'm pleased to have this working and suspect I shall have a lot of fun with it.

Tuesday, November 08, 2011

What's that signal on 433.075? "Beep Beep - 500 feet!"

I was passing through the shack quickly on Sunday and popped the FT7900 FM rig on to see what was going on in both the 145 and 433MHz bands. To my surprise, the receiver stopped on 433.075 - the output of the local Swindon repeater, GB3TD. However, what I heard was not GB3TD.

At strengths between S2 and about S4, fading up and down, was an FM transmission, consisting of a series of tones followed by an occasional announcement of "500 feet". I'd never heard this before and wasn't entirely sure what it might be. To start with, I thought perhaps it was a data from a balloon flight, but as the heights were increasing and decreasing quite rapidly, I suspected that was unlikely.

However, GB3TD sprang into life and Andy, G0BEQ popped up, testing his new Baofeng UV-3R (which sounded great!). I told Andy what I was hearing - and interestingly, about 15 miles away from me, he wasn't hearing the interference. He was able to tell me what it was though; equipment for model aircraft that reports the altitude of the model plane back to a receiver on the ground.

Oddly, after Andy and I had been speaking for a few minutes, I noticed that the transmission stopped. A coincidence perhaps, or perhaps the signal from the repeater being rather stronger than the few milliwatts from the plane had caused the altimeter to stop working whilst the repeater was active.

Not sure about the legality of these devices - although my suspicion is that they come under the heading of the low power devices and can thus be operated legally. However, if you are a model aircraft enthusiast reading this and you have one of these devices, may I ask you respectfully (genuinely) to try and use a channel that amateurs do not use. If you are in doubt - then your local amateur radio club can probably advise you which frequencies are likely to be in use local to you.

It's surprising how far a milliwatt or two of FM on 433MHz will travel!

Sunday, November 06, 2011

Making VHF go further: Morse can help!

The first weekend in November has always been one of my favourite VHF contests. There aren't many purely CW contests on VHF these days, but the Marconi Memorial 144MHz is probably the best known. The nice thing is that all over Europe many of the top VHF contest stations and groups take part in the 24 hour event. Quite often at this time of year there is some tropo around and there's always some meteor reflections too - so there are tantalising hints of contest stations some 1500 or 2000 km away!

These days I don't treat the Marconi Memorial as a contest but as an exercise in DXing and to see what I can hear and work on 144MHz. This year despite indifferent conditions I was pleased to work TM0W in JN36 at just under 800km - it's a path that works quite well from here as I see I have worked that station before. DF0MU in JO32 was a nice one too as well as a number of other closer French and Belgian stations. There were hints of more distant Italian and Czech stations, but nothing solid copied.

Although I wasn't looking to work UK stations this weekend, I did get the impression that there were a few more people from the UK taking part which is good to hear


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