Friday, 10 August 2018

Vintage Vodafone Mast

On the way back from Airdrie today, I stopped at Happendon Services by the M74 (grid reference NS850338).
In the car park is a Vodafone mast which has been there from the early 90s or earlier. There aren't many of these left, with two omnidirectional antennas for the 900MHz band. I know this one was active in 1995 with their analogue phone service (control channel 935.7625 MHz), probably GSM too by then. 
Since then, other masts have appeared, the one in front of the Airwave mast looks like newer Vodafone 900 and 2100MHz panels.
And at the far end of the car park, the antennas on that mast may be the ones which are actually in use now, as most sites now only use two sets of panels, one for Vodafone/O2 and the other for EE/Three.

Monday, 30 July 2018

Network Radio

One of the latest things to hit amateur radio is Network Radio. What is it? Devices based on Android mobile phones which are designed to look and act like a traditional mobile or handheld radio transceiver. They give a proper Push To Talk interface to voice chat apps such as Zello (any app which can recognise a hardware button as PTT), while also being usable as an Android mobile device.
It's not really a new idea though, Voice Over IP has been around for years in various forms, and radio amateurs have used it for both internet linked repeaters and privately without connection to any transmitters. It's just the range of PTT enabled gear has recently expanded and been marketed to radio amateurs.


Review of a SenHaiX mobile network radio by Ringway Manchester

One brand of network radios from one amateur radio dealer: 
 You can see they look almost exactly like proper VHF/UHF handheld and mobile radios, except they have no transmitter and receiver except the standard cellular/Wi-Fi radios you would find in a mobile phone. The intended market for these is the business radio user who needs to cover a wide area without setting up or renting a business radio system. E.g. a travel or haulage company. Even though mobile phone coverage now means that private business radio systems aren't essential, there will still be users who need PTT type communications (group calls, instant transmission for urgent calls).

So why does this affect amateur radio, these don't even transmit on any amateur bands (unless you count 2.4 and 5GHz Wi-Fi, which do share some of the same frequencies)?
Radio amateurs have been setting up channels (group chats) on some of the VOIP applications to have conversations in pretty much the same way as they would over the air. In fact, you could be mistaken for thinking you were listening to one of the internet linked DMR repeaters or even a QSO on the 80 metre band, but with better audio. Callsigns are given regularly (even the correct regional locator when travelling around the UK), people 'transmit' for 2 or 3 minutes before the next person takes their turn. Channels are moderated to keep them limited to people who have a genuine interest in amateur radio.
Here is one of the most popular channels used for amateur radio talk, mainly in the UK. There are a few alternative channels run by the same people in case the main one is busy. 
At present, over 3000 Zello users have added this channel, and at times there are over 100 connected (95% of those will be just listening, which shows what a nosey lot radio amateurs are, although a 100 person 'net' would be hard work).

Is it going to be the end of 'real' amateur radio?
Probably not, if the hobby was to end, it wouldn't be because of Network Radio.
Listening to the amateur radio channels on Zello, the users are the same kind of people as you would find on any repeater (callsigns from G3 through to M6). As with repeaters, those people will have other interests within the hobby that are related to 'real radio'. Now that weak signal digital modes allow long range contacts that would be impossible using any voice mode, there may be some people who can set up a station which is good enough to work on data modes or CW using limited power or high receiver noise, but struggle to have the voice QSOs they would like. Network radio channels can make up for this missing part of the hobby.
To a complete newcomer though, who had not been used to traditional amateur radio or CB voice contacts, this might not be as important, not enough to attract a younger generation, although it does give them a chance to listen to what they are (or aren't) missing.

But it IS radio, it's using the 800/900/1800/2100/2400/5700 MHz bands!
It is, but there isn't very much you can do to experiment with the transmission and reception on those bands, and it's nothing you can't do with any other mobile phone or Wi-Fi device. As the device always selects the base station with the best signal, unless you were in a very remote area with no normal cellular coverage, experimenting with different antennas or locations would make no difference.
But, as the network radios have external connectors for the cellular antenna, in those remote areas, you could always build a high gain antenna to access a distant 'repeater'.
Apps such as Cellmapper are available to see which base station you are connected to and what frequency that is on, so you can even have a frequency display on your network radio (or phone).
Private LTE (4G) networks are also a thing, at the moment they are only used by some large organisations because of the cost and few available frequencies. The LTE specifications support networks in the 400-470MHz band (but a standard mobile phone won't have any 400MHz radio in it), with narrower bandwidths than used by the public cellular networks (5MHz minimum in the UK). There is also simplex (DMO) LTE communications, without the use of base stations, again this isn't  standard on any phones. Maybe in the future the technology could be easy and cheap enough to use by radio amateurs.
The only gear I've seen for use on private LTE networks is from Huawei, with their eLTE Broadband Trunking System, and for those of you wanting a slightly different 70cm repeater project, try the Rapid Deployment Broadband Trunking System
Huawei's commercial for their network radio system and Rapid Deployment deserves to be developed into a feature length, straight to DVD, movie.

As well as being used for 2-way amateur radio style conversations, the VOIP apps are also useful for remote control or monitoring of your own radio. Zello has VOX so if used with a radio that also has VOX control, you have an simple personal gateway that you can limit to only yourself. It can be used for receive only audio too, there are channels on there which broadcast someone's receive audio while they scan around the bands.

Would I buy a dedicated network radio?
I don't think so, I rarely use radio based repeaters, and spend more time programming in channels for repeaters than I do talking on them. There's always the phone or PC to join in with.

Should you buy one?
Have a listen through the different apps first, that costs nothing. If you find yourself spending time talking, a dedicated network radio might be more comfortable.

Saturday, 9 June 2018

950MHz 2G Spectrum

Here are some spectrum views of the 900MHz GSM phone band, captured with a SDRPlay RSP-1 and a 1/4 wave ground plane next to an upstairs window (looking north).
My Comet GP-15 tribander on the chimney, with over 25m of coax gave roughly the same signal for a mast which was line of site except for a few trees (the sector facing me is on 959.4). A mast only a few streets away with my best sector on 953.8 was much better on the GP-15 (about 15dB), it's on the opposite side of the house.
Vodafone using 951.4 - 954.8 (18x 200KHz channels 82-99), O2 using 955.2 - 959.8 (24x 200KHz channels 101-124). Most sites are now Vodafone and O2 into the same antennas. It looks like a lot of the newer sites which were built for 3G coverage (usually roadside poles) have been fitted with 2G 900MHz. 2G GSM is nowhere near finished yet in the UK, the cheapest phones are 2G only, and as the turnover of smartphones is faster, support for devices without 4G could be cut down to 2G voice/texts only before too long. 3G capacity is already being cut by refarming the 2100MHz band to 4G for up to 2/3 of the bandwidth. 2G GSM is used by a lot of remote control and slow data applications too, things like tracking devices, digital signage where the speed of sending a txt or GPRS data doesn't matter.
I'm not sure what's happening with the channels like 955.8MHz where the signal isn't continuous, seems to be an extra channel from the same sites.

Monday, 28 May 2018

FT-8900 Programming Errors

50MHz FT8 was full of stations today around 50.313, all over Europe. Also I had a go on 24MHz with my random bit of wire and 10 watts, made some contacts into Germany and the Netherlands, also received by 2 stations in the UK in the Bournemouth (M1HHL) and Medway (M0OLA) area.

Today I went to the car and connected up my laptop to the FT-8900 to download a new set of memories to it. Using the FTB8900 software as usual, I started off with an upload of the existing settings, and everything was OK. Then when doing the download, it got to the end and then the radio displayed 'clone error' and the software displayed an error message saying it did not receive the final confirmation from the FT-8900.
I was using one of the very cheap USB to serial adaptors which I bought last year, instead of my usual Prolific chip based adaptor (fake chip so need to use an old driver). These new adaptors use a CH340 chip (never heard of it until I plugged one in, expecting a Prolific chip) instead, drivers aren't included with Windows 10.
Well the failed download completely reset the radio, clearing all the memories and other settings. I tried again later, after the temperature had dropped a bit - when I was trying to get the radio to program earlier the car was showing the temperature as 27C and not very comfortable sitting there with a laptop. With the old Prolific adaptor the download worked OK.
I've had trouble with the CH340 cables before, with the WSJT-X software, I had to increase the CAT polling interval from 1 to 2 seconds on a Yaesu FT-847 otherwise it would sometimes get CAT errors.

Downloading to radio - this time it worked

Bargain basement USB-serial adaptor with CH340 chip

Good old Prolific USB-serial, bought at Llandudno Maplin a few years ago

USB device details for the USB-serial adaptors

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