Wednesday, 1 June 2016

Brant Fell and New Car

On Saturday I was at Windermere in the morning so I had a quick walk up Brant Fell (WOTA LDO-113) on the way home. Just took the Alinco handheld up there and made 2 contacts, M0AYB/P who was on the way up St Sunday Crag from Patterdale, and M0LKB at Ulverston.
Parked at SD413961 on the road to the east of the fell, where there is a parking space at the start of the footpath.










On Thursday I picked up the new(ish) car, a Nissan Note N-Tec 1.4 petrol. It has built in satnav, Bluetooth and USB music playback.
No less than 3 12v sockets - one below the dash, one behind the front seats and one in the boot. Also some good places to keep a radio out of the way.



Fixing the FT-8900 head unit to a phone holder. Screwed back together after putting cable ties through.
 




Sunday, 1 May 2016

Car Electrics

In the last few weeks I'd been having some trouble with the Yaesu FT-8900 radio which I have in the car. When switching it on, it displays the DC voltage and I'd noticed that it was very low. Under 11v with engine off. I've got the FT-8900 wired up the way that every instruction manual ever written tells you not to - through a cigar lighter plug. This is not usually a problem, I've never had a radio connected any other way in the car and never used over 20 watts mobile from the FT-8900. Also, the radio is transmitting APRS while I'm driving, with around a 1% duty cycle and 20 watts.
At first I thought the car battery was not charging and would soon be completely dead, but I did a check with the engine running and the voltage did go up, so the alternator was OK. The voltage while charging did seem a bit low, maybe 12.8v. This was while I had the radio on receive, but when switching it off, the voltage went up to the normal 14-ish. That's a big voltage drop for something drawing under 1 amp on receive. I checked the voltage drop between the negative wire on the radio and the car body, and it was very low.

It turned out the connection between the lighter plug and the socket was bad, because there was something that looked like a burn mark on the centre contact of the socket. Something had probably knocked the plug out slightly and the resistance had increased.
I cleaned the contacts up and the total voltage drop with 20 watts transmit power is around 0.3v (including the wiring from the battery).
 With the engine running, there must have just been enough voltage at the FT-8900 to let it transmit (or at least look like it was - nobody picks me up on APRS round here anyway!). I'm guessing below about 9v the radio will shut down.

One other thing I learned from all this is that the Nissan Juke (and probably lots of other cars) doesn't keep the battery charging all the time when the engine is running. This is something I'd never thought of before, normally you would leave the engine running if you wanted to power something that might drain the battery - like a high power transmitter.
After starting the car, the alternator is connected to the battery, but once the battery voltage reaches a certain value, it cuts off when the car thinks it is fully charged. Now this is a problem because I don't think the "fully charged" voltage is really fully charged, and it just replaces what energy was used the last time the car was started, and then cuts off. Searching online, I found that this is a known issue with certain Nissan Jukes and the batteries never charge properly. It also effects add-on lights which detect the battery voltage to switch on when the engine is running. Putting a load on the battery (the headlights usually work) can switch the alternator back onto the battery as the car sees a voltage drop and thinks the battery needs charging.

Monitoring battery voltage (engine stopped) with a CellLog 8S

Wiring to radio and APRS tracker. The FT-8900 cable is soldered directly inside the 3-way splitter. The APRS tracker is on the lighter plug, so I can disconnect it when not wanting to transmit data.

Sunday, 10 April 2016

WotIHeard

I've started a SoundCloud page where I upload recordings of radio activity, usually 145.500 at weekends and bank holidays.
These have the gaps taken out, and I try and get at least 11am - 3pm (peak time for SOTA activations etc.) when I'm not at the radio.

I'm using a Yaesu FT-7900 and Comet GP-15 triband antenna. At 145MHz the coax has about 1.5dB more loss than it really should do, because of some RG-58 extending it out of the loft. But on VHF, the receiver is limited by external noise, there is always some reading on the signal meter with an antenna plugged in (only the 7900 has a meter sensitive enough to show anything on external noise). No, even on 145MHz you can't get away from noise generated by electronic devices in a built up area.
Audio comes from the 'data' socket on the 7900, directly to the unbalanced input of a Edirol UA-25 USB audio capture. The UA-25 has a peak limiter enabled on the input, this only operates on bursts of noise or very high deviation signals.
Recording is threshold activated on the PC, at -29dB and 1 second release delay. The FT-7900's squelch only cuts the 'data' output by about 30dB when closed, so this is as low as the threshold can be without unwanted recordings.
After recording, I copy the left channel to both left and right, apply another limiter (in software) with a -6dB threshold to cut down the 'clicks' when the squelch opens/closes and level out differences between people using a mix of 2.5 and 5KHz deviation (I don't think the FT-7900 has narrow and wide filters based on the transmit deviation setting, like the more expensive Yaesu mobiles).
I should also do a low-cut filter too, it doesn't sound like the low frequencies are rolled off much in the radio, and as well as the DC clicks when the squelch opens/closes, I can hear who has their CTCSS left on when not on repeater channels.
I also use the Edirol UA-25 when I'm running the APRS gateway, with the PC's internal audio used for HF data modes. The red plug in the photo also comes from the 'data' 6-pin DIN socket, but that is from the 9600 baud packet output, giving unfiltered, unsquelched receive audio. This is good enough to use with digital voice decoding software like DSD+ to receive DMR transmissions. I don't think it works quite as well as a proper DMR radio but it's handy because if I find a DMR signal when using the FT-7900, I can quickly start up DSD+ and check it out, rather than having to change radio.

Thursday, 11 February 2016

WSPR in Linux

I'm typing this from Linux Mint 17.3, while running WSPR. It was quite easy to install the Windows version of WSPR 4 using Wine. The only problems were no choice of sound devices (I have both internal and USB audio, often a different radio application is using each one) and the list of serial ports for CAT control of the radio still showed COM1 etc. which don't exist in Linux. I think these can be set up to use the proper device but I just chose VOX to transmit.
When I was installing Linux Mint I chose to install it alongside Windows, and it installed itself on an external USB HDD (with the boot menu on the internal HDD).
You can see on the screenshot where I had to turn the input level up from its default of 0. It still managed to decode 2 stations with only half the time slot though.


Friday, 5 February 2016

DMR

Everyone else seems to be getting DMR equipment so I thought I'd get one myself - a Retevis RT-3 UHF handheld. It's a clone of the Tytera MD-380 and one of the cheapest, at under £120.
I've used it on my local repeater GB7MB (Heysham, Colour Code 1, 439.700 MHz) and also simplex where there is quite a bit of activity on 438.5875 MHz round the Barrow-In-Furness area.
I've not been much of a repeater user but I like the way you can see the activity on any repeater using the DMR live monitor
GB7MB log 
I can also receive a few other DMR repeaters at home:
GB7PN 439.425 Prestatyn (2nd best)
GB7CA 430.925 Douglas, Isle Of Man
GB7TP  439.6875 Keighley


Friday, 11 December 2015

Spain

Some radio related photos from our holiday to Lloret De Mar last month:

Radio mast above the town - some FM broadcast on here

VHF antennas on building across from hotel. Are they for transmitting? They look like around 150MHz. 

Never heard one of these working but they have some UHF antenna on them

Lots of buildings have long distance Wi-Fi access

More Wi-Fi 

Fire station

Band 1 TV reception

Telemetry link from electricity substation
 

UHF folded dipole on some museum or information centre - could be to do with the remote controlled loudspeakers seen along the beach


There is an amateur repeater on 438.950 near the town of Blaines, a few km west of Lloret De Mar. Never heard any activity on it except it giving it's ID. Further away there are some Echolink gateways around 431MHz and I heard some APRS activity on 144.800.
The area has a lot of air traffic and also business radio users seem to be mostly between 152 and 154MHz.
One thing you think about when outside the UK is how much more effort they have to put into receiving TV broadcasts. Because there are lots of tall apartment and hotel buildings, along with land rising up sharply inland, it's hard to get a line of sight to any mast, even if it close by. Going along the motorway towards Barcelona I saw some blocks of flats which must have had a large TV antenna on 20 metre guyed mast on top of a 30 metre building, to get over the hill. The same goes for satellite reception, no little 45cm dishes, even when they are not trying to get UK channels. But we're a small island which can be covered with a narrow beam.
We're lucky with our little Sky dishes and cheap 10 elements. But I think a lot of people would have gone over to internet streaming or cable - when I was in Malta 2 years ago, it seemed to have gone that way with no RF receivers at all in houses.

Saturday, 5 December 2015

GP15 connected again

After nearly 6 months of the coax from my 6m/2m/70cm antenna coiled up in another room, I finally got round to connecting it into the new shack, by running it up into the loft and joining to an extra piece of coax I'd put in for a temporary 2m dipole.
It's not perfect - it's 7 metres of RG58 I'm adding, giving up to 3dB loss on 430MHz and 1.5dB on 144MHz, RG58 being what I had handy and easy to wire into a dipole centre.
When I put the GP15 up, I'd left enough spare coax (Westflex W103) to reach out of the room and across the house, but I wouldn't be very popular if I just trailed it along the floor through open doors to reach the shack.
I'll do a direct run of coax some time and get the Comet GP15 down to check it, it's still working fine but it doesn't sit exactly straight so I hope the screw holding it into the tube hasn't snapped (they often do on that kind of antenna).

For HF I'm still using a wire along the gutter, fed with an UnUn and sticking mostly to 10 and 14MHz. The other wire is still up in the back garden but the coax is left coiled up in the old shack.