Thursday, 15 March 2018

FT8 - 4 Weeks On

I've been using 144MHz FT8 for about a month now, and it's getting more popular. I've been leaving the radio on 144.174 all day while I've been out, and operating remotely using TeamViewer on my phone.
There must be quite a few people doing the same as if I call CQ at any time of day, someone will have received me and there's a spot on PSK Reporter. Because of the extra range of FT8, there's more activity on there now than on 2m FM. Some days I'll put a CQ call out and not get a reply, but it's not a waste of time as I could have been received by someone new.
At the moment conditions on the HF bands aren't very good above 10MHz so it's good that there's something else to do with an SSB radio.

I put a CPC order in today for a few bits and pieces, and ordered some coax adaptors on AliExpress. AliExpress is usually pretty slow (a month or more) but that means it's a nice surprise when something turns up after you've forgotten all about it. One of the things in the CPC order was a dishwasher cutlery basket, but all the others were more electronics related. Ordered 2 optical audio cables as I'd used one for connecting up a sound bar then realised I didn't have any more to connect my PC up to the amplifier.
With CPC, I tend not to use the website to search or browse through the products because the cheapest of anything is usually in the paper catalogue updates I get through my door, or in the PDFs on the website. Most popular things are in the catalogue update, and I like catalogues, it's sometimes better to have a look through pages with pictures and things ordered nicely, rather than a list of search results.

Thursday, 22 February 2018


After reading on Twitter that some people were trying the very popular FT8 data mode on 144MHz, I had a go. I don't have anything like a VHF DX station at home, with just a Comet GP15 vertical on the chimney, fed with a bit too much coax.
The frequency for 2m FT8 is 144.174.
I started off using my new SDRPlay receiver and found that I was able to decode a few stations, outside my usual VHF range (G4KUX in IO94 and GM4FVM in IO85).
After connecting up a transceiver, I was able to make some 2-way contacts at this distance, and was even getting reception reports of my signal via PSK Reporter from up to around 300km. This makes the 2m band a bit more interesting, and because data modes software like WSJT-X automatically sends reports to PSK Reporter, even if I'm away from the radio, it's still worth leaving it on all day just in case someone calls CQ.
At the moment, there aren't really any 'lift' conditions on 144MHz, at least not which you would hear if listening to FM or even SSB, and most of the long distance propagation is from reflections off aircraft. Reflections off fast moving objects like aircraft shift the frequency from the doppler effect, and it can be over 100Hz. With FT8, the bandwidth is very narrow, so if there are multiple paths, the same signal can appear on 2 different frequencies. See below for some FT8 activity where there are multiple decodes.

On some days I've received 10 different stations on 144MHz FT8.

Saturday, 3 February 2018

Because I Hadn't Posted Anything Since Last Year

Happy New Year 2018

 USB load - switchable between 1 and 2 amps

 Barrow BBC MF/DAB broadcast site, is the colinear lower down the mast for smart metering because nothing else is from the site ?

Majority Huntingdon DAB/FM/CD system

New drill

Thursday, 7 December 2017

Saturday, 28 October 2017

More UHF APRS Testing

I tried the E32-TTL 1 watt 70cm LORA module a bit further away from home, again using APRS software to send the position to the internet.
The location I tried first was some high ground just off the A65 to the west of Settle (grid reference somewhere around SD786669) on the narrow road above the Austwick TV mast. This has a good take off towards the west.
Instead of the mobile antenna I put a short antenna directly on top of the module and taped the thing to a mop handle so it could be as high as possible while operating. This also gets rid of any coax cable loss.

 Video camera also fixed to mop handle

 View to the west from near Settle

 But did it work? Yes it did, at a distance of 37.7 miles (60.7km), with more than one transmission being received as I moved around the parking area.
I tried another two locations further south, which weren't on high ground, but received nothing. These were at the Lancaster (Forton) M6 motorway service area and just outside the boundary of the Charnock Richard M6 motorway service area.

My next experiment was to compare the performance of the LORA module against normal 1200 baud packet radio using an FM mobile transceiver.
Using the same antenna as in my last blog post (it's a small Moonraker dual bander, about 40cm long, on a mag mount), I transmitted APRS beacon messages from my Yaesu FT-8900 on its 20 watt setting. The frequency was the same as I had used for the LORA test.

See the results of the LORA test below

Result? A lot worse than the 1 watt LORA transmissions. Because the car APRS tracker has no logging function, I could only guess where any failed transmissions were from. I know that it beacons every 110 seconds so I've put red Xs in rough locations of where it should have worked but didn't.
The blue O shows where it actually worked but no location was sent (my tracker is programmed to send some other information every few beacons instead of the location). I had stopped the car there, which would have helped as I wouldn't have been passing through any multipath dead spots while transmitting.
So with 13dB (20x) more power on the same frequency, traditional packet radio is still worse than LORA when used mobile. Even if you compared VHF packet with UHF LORA, I don't think 20 watts VHF (to a 0dB gain antenna like the Moonraker) would get much further than 1 watt UHF.

And here is Dales Radio's Ingleton antenna (103.0 MHz), covering the area further west of Settle, with Settle itself on 104.9 MHz.

Thursday, 19 October 2017

433 MHz LORA

Experimenting with a couple of 1 watt 410 - 441MHz LORA based modems.
The part number is E32-TTL-1W (there are also 100mW versions available).

Manufacturer's website and data sheet

Only about £12 each on the usual sites

With most electronic equipment shipped from overseas, the specifications are usually quite 'optimistic' so I wasn't really expecting 1 watt from them. Especially as the 100mW version looks exactly the same. But they really do put out around 1 watt.

They fit nicely inside a Choc Box once you cut out the bit which is supposed to go through the terminal block. The cable is a USB to TTL serial adaptor, they were less than £1 each.
The power is supplied from the USB cable (red wire), with the current on transmit 670mA (I couldn't actually measure this using a USB tester, maybe the quick variation in transmit power confused it).
Although they draw quite a high current from the USB port, I had no trouble using them on a PC USB3 port and my phone's USB-C connector (through an On The Go cable).

Programming software. These settings are for the highest power output and slowest transmission rate (greatest range). There are 65536 addresses available, but #FFFF can be used as a broadcast address.

Only 1 MHz channel steps are available, and the transmission is 125 KHz wide, centrered on the MHz.

How far do they go? LORA is supposed to work with very weak signals at the lowest transmission rates. I connected one modem to the car antenna and the other to the base antenna on my chimney. The data I transmitted came from an Android App on my phone APRSDroid and was received by APRSIS32 in Windows.
To these applications and the APRS internet servers, it looked just like I was using packet radio TNCs and the normal APRS frequency (in the UK) of 144.800 MHz.

Transmitting at least once every 2 minutes, I drove to a point over 8km away. At this distance there was no line of sight. It even worked in Dalton town centre, behind a hill. Over the route there were only 2 locations where the signal was lost, see the Xs on the map below
These locations are at the back of a hill, I would have expected it to be worse in the town centre than there but at least I know where to test in future.
Range would have probably been well over 8km if I'd carried on further east along the A590.
These are good results for 1 watt, probably as good as 10 watts on VHF APRS using normal 1200 baud packet radio.

This would be interesting as a weak signal mode when propagation is good on UHF. Using terminal software you can just type and they transmit, much like PSK31 but with error correction.

Thursday, 28 September 2017

WSPR House vs Car

A test comparing my home and car antennas on 14MHz using WSPR

At home, I used 5 watts into an end fed wire that was run along the gutter, with the feed point just inside the upstairs window. This isn't cut to any specific length except to fit along the front of the house and isn't much more than about 7 metres long.

This is fed through an LDG auto tuner

In the car I used a Watson Multi Ranger 9 band whip on a small Sirio mag mount. The mag mount should really be bigger for the HF bands (except 28MHz - this type of mag mount was also sold with a Sirio CB antenna). The transmitter was a SOTA Beams WSPRLite, with 200mW output.
The car was parked on the road outside my house.

Both the wire and the car are on the north side of the house, with the axis of the wire about 20/290 degrees. To the north there is a field across the road, then more houses around 100 metres away.

During the test, both transmitters activated simulatneously 3 times in their random sequences. There was some spacing between the frequencies so they didn't overlap, around 50Hz. 

With equal gain on both antennas, there should have been a 14dB difference between the house and the car. Most reports had less than 14dB, showing the car antenna was performing better. In some cases the car was better, even with 14dB less power. The best performance of the mobile antenna seems to be towards the north (OH - Finland, LA - Norway) and worst towards the south (EA - Spain). This makes sense with the open area towards the north allowing a low angle of radiation and the house to the south blocking anything in the direction of Spain.
From those results, it looks like the mobile antenna would be best for all directions in an open area.

There were some stations who I was received by only when using the wire antenna and 5 watts, including those in the USA and Canada. Without the extra power, none of these stations would have received me as there was much less than 14dB margin above the limit of WSPR reception. The 200mW to a mobile antenna has got to the USA quite a few times before.