Tuesday, 4 November 2014

WSPR Presentation

Here is a presentation on WSPR which I gave a few months ago:
PowerPoint
PDF

Sunday, 2 November 2014

Homeplug Noise on 27.245

A video I made of noise from the Netgear homeplugs. A single adaptor waiting for a connection.

The amateur bands are supposed to have some more filtering with these but it won't be perfect.

Saturday, 1 November 2014

Plug 'n Talk

A pair of Homeplug power line networking adaptors arrived in the post today (no, they're not for use here!) and it reminded me of how far we've come with power line communications in the last few years - who would have imagined that we would have 500 megabit networking down mains cable (or over any other sort of cable)?
I tested the Homeplug (200 megabit) adaptors copying a large file, from one side of the house to the other and the real throughput was more like 35 megabit (around 4MB/s). This is still about twice as fast as WiFi (even using type-N speeds) over the same path though.  Good enough for what they will be used for (extending an ADSL internet connection to a garage).

Back in about 1992, I was playing around with a pair of Radio Shack/Realistic/Tandy Plug 'n Talk intercoms. They used 230KHz FM to transmit down mains wiring. That was in the Long Wave broadcast band, and even though they used FM (narrow deviation), they could still be received on 225 and 234 KHz AM broadcast channels (by slope detection, being a few kHz off the centre frequency).

I don't have them any more but here's a picture of what the box would have looked like. Model number 43-207

They had a locking PTT button, so could be used as a baby monitor and one of the ones I used had been modified to have a line in jack socket. This made it a really lo-fi version of today's iPod FM transmitters, I could broadcast to Long Wave radio receivers in the house. The signal actually extended beyond the house, either along power cables or direct radiation. It could get up to around 250 metres depending on where the power cables were coming from, also holding a portable radio by telephone poles improved the signal greatly.
At that time there were also some intercoms that used lower frequencies of around 80 - 140KHz (a 4 channel model with 20KHz spacing?) but these would have been no use for my microbroadcasting activities, being below the Long Wave band.



Eurosonic Ultimate



Bought this Eurosonic Ultimate 80 channel CB handheld in 2000, I think it was cheap as Barrow Tandy was closing down.
The short antenna had a TNC connector but the plug was glued tight as if they didn't want anybody to use it with an external antenna!
There was also no external power connector, the battery pack (8 AA cells) had a charging circuit built in and a power jack. I've connected this directly to the battery contacts so it can be used with external 12V DC, as I don't think I'll be using it on the battery very often.




More power on 28MHz

I've been using JT65 on 28MHz quite a bit recently, with 5 watts from my FT-817. I thought I'd try using a bit more power, remembering I had a Euro CB EA-150 amplifier that I'd not used for a long time.
With 0.5 watts input (the lowest power setting on the 817), it was already putting out around 35 watts at 28MHz, which was quite enough for a weak signal mode and transmitting continuously. I think it will do about 100 watts, which means that at a normal CB type drive level (4 -12 watts) it wouldn't be a very clean SSB signal.
The transmitted signal is OK, I'm getting received by some stations on 28.076.

Tuesday, 28 October 2014

Eurosonic ES200LCD

Eurosonic ES200LCD CB handheld (video).

I bought one of these in 1995 at Tandy in Kendal and remember going a walk up Whitbarrow Scar on the way home.
Like most CB handhelds of the 80s and 90s, it used no fewer than 10 AA cells, before we could get 5 watts from a 7.4v Li-Ion battery.
One thing about this radio was the extremely low S-meter, I measured the bar graph segments as:
S1 = 6uV
S3 = 15uV
S5 = 50uV
S9 = 150uV
S9+ = 1mV
This was actually quite useful as not everyone was 9+
There was also an ES200 with a LED display and no signal meter.

Monday, 13 October 2014

10 Metres JT65

28MHz is getting better now, and I've been trying JT65 on 28.076 for the last few days. My antenna at home isn't very good for this band but even with 5 watts I've been getting quite a few reports via PSK Reporter.
Compared to WSPR, JT65 seems to have a lot more activity on the higher HF bands, especially on 21MHz. Also, with WSPR I was getting out further than I was receiving, which I put down to background noise at my house. But on JT65, I'm receiving stations from the Far East of Asia and West Coast USA. Maybe it's the extremely low power being used on WSPR by a lot of stations or JT65 being more popular.
If I put a CQ call out on JT65, I can get 10 stations spotting me via PSK Reporter, but not one single reply to the CQ call. If there hadn't been a network of stations automatically spotting then I could have called CQ, got no reply and given up.
If someone does reply to my CQ call, the QSO is often never completed because conditions have changed over the 5 minutes it takes to finish a JT65 exchange of reports and RRR.
I don't really mind if nobody does reply to the CQ call and often I'm not even at the radio so it's a bit fiddly clicking stuff through TeamViewer on my phone to reply to people. 
Is it worth sticking with the traditional idea of a 'QSO' for certain data modes, or would it be better to try for the most transmit or receive reports your station allows (maybe the lower of the two if it was for some contest or award).