Monday, 27 March 2017

Good VHF/UHF Conditions

On Saturday, conditions on VHF and UHF were really good. Hearing a lot of activity from Ireland, and even signals from as near as Blackpool were a lot better than normal.

The video is just my radio scanning round 2m and 70cm, showing what kind of signals I was getting from some DMR repeaters, the best propagation was to GB7UL on 439.525 at Carrickfergus.

On 145MHz, GB3MP on 145.750 was a bit stronger than normal, you can hear some interference on all the VHF signals, like a clicking noise. This happens at certain times of day, and is on top of the already high noise level - if I turned the squelch down on the FT-7900, it would be showing S3 of noise right across the 144MHz amateur band.

I could hear a repeater on 439.100 which had an Echolink conversation on it, that isn't a repeater frequency used anywhere in the UK for analogue or digital, and the only mention I could find online was a repeater in Germany. I couldn't find any CTCSS tone when scanning for one either.

Friday, 17 March 2017

How Cheap?

Think £20 for a dual band handheld is a bit too much? Well how about £9.36 for two?
If you look through enough search results on Ebay for Baofeng radios (either the UV5 or the BF888 single band 16-channel) you find the odd one on sale for ludicrously low prices.

Here are UHF handhelds for under £2 each
At this sort of price, even if the battery or the radio was faulty when delivered, the other half would still be worth the money as a spare.

Friday, 3 March 2017

Audio Transformers

I ordered a Ground Loop Isolator from Ebay a few weeks ago for about £2 - a box with 2 audio transformers in it, usually for installing in a car between the line out of a car stereo and an amplifier. I got it for connecting between a radio and PC, in case there were problems with ground loops and other interference.

And here are the transformers inside
I have my Yaesu FT-7900 connected to a Edirol UA-25 USB audio interface using a 6 pin mini DIN to phono cable. One phono plug for discriminator audio (9k6 packet out) and another for normal (voice) audio. The first test I did was to try decoding some DMR using DSD+ software. This normally works OK using the 9k6 packet output.
DSD+ was trying to decode the DMR but there were so many errors it could not even get the correct colour code on a strong signal. Definitely the transformers causing the problem.
I checked their frequency response by looping the UA-25's output back to the input and playing some test tones through it, then comparing with a straight through cable.
The table below shows the insertion loss at each frequency compared to a straight through cable.
The -3dB point is somewhere between 50 and 100Hz, this would be OK for voice and data which used frequency shift keying only within the normal audio bandwidth of a radio, but for DMR (and probably other data modes using the same modulation), this is no good. It cuts off a bit high for music too, at least with a good amp and speakers.


Last June I started trying to be a bit more fit and healthy so as well as joining a gym, I bought a fitness tracker "smart watch" device, a Garmin Vivofit 2
It's purely a fitness tracker, it won't show messages or do any syncing with a phone other than to (slowly) transfer my activity data.
But, unlike a lot of other wearables, it uses a non-rechargable lithium cell (CR1632 - not a very common size, couldn't find any in Poundland so ordered some spares online) which can last up to 12 months. I've not had to change mine in the 9 months I've had it. It's waterproof and I've never needed to take it off.
As well as steps, it can measure heart rate (with a chest strap which I've never tried) and sleep (by tracking movement, not by brain waves or anything as clever). I usually keep an eye on steps and distance throughout the day, walking a bit more in my lunch break since I've got it.
At the gym it's sort of useful, some of my gym activity adds to the step and distance count but it's no use on the bike and might not be that accurate on treadmill and cross trainer as the movement isn't natural walking or running. The daily step target varies depending on how well I've done over the last few days, it's usually over 10000 unless I've spent a few days off work doing nothing.
Here are a few screenshots from the Android app, Garmin Connect. I find that to sync the device, I need to start the app, kill it in the task manager and then start it again before pressing the sync button. The app also needs internet access to work at all, it won't even sync offline as all the data is stored on Garmin's servers.

 My best 28 days was around 400000 steps, in the summer.
My phone also has an activity tracker, Samsung S Health, which is always running but I don't take much notice of it as I don't always have my phone with me when exercising. It usually says I've done enough steps each day anyway but I think the target is set to something really low like 6000.