Category: Electronics

Sending Sounds into Space

Sending Sounds into Space

Early in 2018 the club was contacted by artist Sian Hutchings who was in her first year of a masters degree in fine arts at Northumbria University, Newcastle and she wanted some help with a project that was going to come to a head with an event at the Baltic Centre for Contemporary Art in Gateshead on the 15th March.

The club is no stranger to working with artists having previously been involved with the Waygood group and an event called Scatter in the AV08 Festival involving artist Marco Pelijhan again at the Baltic Centre for Contemporary Art in 2008.

Anyway Sian’s project centered around the ‘Voyager Golden Record’ which were two phonograph records that were included aboard both Voyager spacecraft launched in 1977. The records contain sounds and images selected to portray the diversity of life and culture on Earth, and are intended for any intelligent extraterrestrial life form, or for future humans, who may find them. The records are considered as a sort of a time capsule.

Sian wanted to update the recordings stating that she considered the recordings didn’t reflect the way we live in the 21st century and weren’t a true reflection of modern society.

Sian planned to record an updated version of the golden record and transmit the recording herself so she contacted the RSGB to find out how she could do this. Sian was informed that she would have to complete the Foundation licence course in order to do this and due to her timescale it wasn’t a feasible thing to do. The RSGB did suggest that she contact a local amateur radio club to see if they could help and gave her our contact details, in due course Sian did contact us which resulted in Glen and I going into Newcastle to have a meeting with her at her studio.

At the meeting Sian outlined her idea to update the golden record and Glen and I told her how we could help which basically meant that we would be able to transmit her recordings, also we would be able to let her see the transmission via an SDR radio receiver but this would all be dependant on whereabouts in the Baltic we would be based in relation to siting antennas. A follow up meeting at the Baltic was arranged and I took a dual band 2m/70cm antenna to show Sian what we might use as Glen thought that 70cm might be a better frequency to use as trying to find another amateur on the band was as likely as finding teeth in a hen and it therefore hopefully wouldn’t cause any disruption to what Sian wanted to do, also it is a frequency that is suited to satellite (space) communication. We also took along a couple of radios to test the suitability of the location.

We were to be sited on the first floor and there weren’t a lot of options for feeding coax to the exterior and then onto the roof to feed antennas, it was decided to set up in the outside lobby area and fire the radio signal out of the glass windows running the full height of the building. This would be an easier option as we were right in the heart of the building and all other options quite frankly would have been a nightmare to sort out. 

Having completed the recce Glen and I had a better idea of what we could offer, Sian arranged workshops to record the sounds and on the allotted day Glen and I arrived at the Baltic in the afternoon and set up our station which consisted of my 70cm yagi antenna that was mounted on a microphone stand angled at about 45 degrees to the horizon, Glen’s Yaesu FT 817nd provided the transmit option along with a laptop which used a USB drive with the recordings provided by Sian from her workshops. I took along my SDRPlay RSP1 software defined radio to receive the transmitted signal and projected it onto the large screen in the cinema for a visual effect.

Sian was given a handheld transceiver to start each transmission using with the callsign that had been applied for GB8NOE, this related to our 2008 involvement at the Baltic and there is an 8 in 2018 (very tenuous I know). The letters related to the name of the group of artists also involved with Sian called the Noematic Collective.  

Sian transmitted four three minute recordings of sounds from her workshops and the people at the event were able to move between the theatre where I was projecting the image of the received signal from my SDR receiver and the corridor area where Glen was at the transmitting end of things.  There was an additional twist a vinyl recording was made of Sian’s recordings on an original recording machine from around 1930 I believe.

The event seemed to go well and Sian was very happy with the way that things went, the people attending also enjoyed it as well.

Check out our video page to see Sian’s video of the event.

 

 

 

 

73’s Graham M0GAE

 

 

 

 

 

LiFePO4 Portable Power Kit

LiFePO4 Portable Power Kit

Recently I was researching an alternative to Sealed Lead Acid Batteries (SLAB), the cause of this research…back pain. While SLAB’s have performed ok for my car portable use, I was reminded just how heavy a 50AH SLAB is after straining my back putting it back on the shelf. So having seen a number of posts and videos on the Internet about the weight advantage I needed to give alternatives some serious thought.

I suspect like me, many of you will have heard of Lithium batteries but what I hadn’t realised is that there are different types and specifications. I was looking for three things in a new battery; appropriate voltage for amateur radio use (13 to 14 volts), low voltage sag (little voltage drop when under load), and a high number of recharge cycles (reduced cost of ownership).

Lithium ChemistryNominal Voltage
(4 cells in series)
Recharge Cycles
Lithium Titanate9.6v3000-7000
Lithium Nickel Cobalt Aluminium Oxide 14.4v500
Lithium Cobalt Oxide14.4v500-1000
Lithium Manganese Oxide14.8v300-700
Lithium Nickel Manganese Cobalt Oxide14.8v1000-2000
Lithium Iron Phosphate (LiFePO4)13.2v1000-2000

 

I hope you agree that Lithium Iron Phosphate (LiFePO4) came out as the most suitable. I was also fortunate that while away on a DX’pedition to the Isle of Barra with Bob (M0KLO) he kindly lent me his KX3 and a small radio model style 13v LiFePO4 4.2AH battery pack to try. It was certainly compact in size, light weight, and an ability to maintain voltage during transmit but the total capacity of 4.2AH I felt was a bit small for what I had in mind. 

A battery of about 15AH seemed to be about the size suitable for my needs based on my initial transmit tests with a Yaesu FT-891 “field” radio which suggested about 8 amps on transmit was a good target if I wanted 3 hours of operating time on a single charge. Remember that this is not an exact science as less current is drawn when listening as to transmitting and whether you use CW, Data, or SSB.

A search on the Internet provided a range of options from which I produced a shortlist:

  1. “radio control” style soft battery packs to make up a battery of 17AH. Various comments on the Internet suggested quality control of these packs is variable. Costs today (Mar’2018) for a 8.4AH pack is £ 52.83 + p/p. Due to the manufacturing process if one of the internal cells develops a fault the whole battery is a right off. Requires a balance charger to maintain cells. https://hobbyking.com/en_us/zippy-flightmax-8400mah-4s2p-30c-lifepo4-pack-xt90.html

 

  1. Electric Golf Cart suppliers have a good selection of LiFePO4 batteries in capacities from 15-40AH available with chargers and 3-5 year guarantees. Mainly sealed units with an internal Battery Management System (BMS), while this is perhaps convenient it has the drawback that if a cell or the BMS develops a fault the battery may be a right off. Generally supplied with a simple charger. Costs depending on capacity and warranty term but are generally £150  to £300 per unit. NB: Always double check golf cart batteries, are they definitely LiFePO4?www.topcaddy.co.uk/category/batteries/lithium-batteries/

 

  1. Electric Bikes commonly use LiFePO4 packs of various sizes (8,10,12,15AH), individual cells can be purchased and made into a pack. All of the required components can be purchased online or from an electric bike components supplier. Costs increase as cells capacity increases. For 4x15AH cells + cable bits to make 13.2 battery (Mar’2018) approximately £100. Simple chargers are available similar to the ones provided by the Golf Cart suppliers, but would recommend radio model style balance chargers suitable for LiFePO4 batteries.
    LiFePO4 (UK) Battery supplier
    http://eclipsebikes.com/index.php?cPath=25_10
    ISDT T6 LiFePO4 charger
     https://hobbyking.com/en_us/isdt-t6-lite-600w-charger.html?___store=en_us
    ISDT Battery Checker
    https://hobbyking.com/en_us/bg-8s-smart-battery-checker.html

 

I decided on option 3, if there was a problem with an individual cell I could replace it at minimum cost and it allowed me to take control of the management of the battery pack and individual cells. As a self-build I could also choose on different form-factors depending on requirements and components. It is also a simple task to increase the capacity of the pack by putting another one in parallel if needed at a later date. I also purchased a radio control style charger (ISDT T6).  This charger provides greater control of charging and also includes storage charge and discharge options and very importantly it allows charging of cells without a balance lead connected as I would be Bottom Balancing. Note that some LiFePO4 chargers will refuse to work without a balance lead connected. I also purchased the ISDT Battery Checker for more precise measurement of individual cell voltages on charge, storage, and discharge.

The rationale for bottom balancing is that I want the cells to converge to the same state of charge when discharged, before use and I charge the whole battery as one, rather than have the charger bulk charging the cells and top balancing them when using balance leads. I’ve included the following YouTube links for the background to bottom balance and not using a BMS. 

Bottom or Top Balancing
https://youtu.be/0KSFitqvap0

One example of how to Bottom Balance a battery pack
https://youtu.be/J2WvQre8sAQ

To achieve bottom balance I discharged the individual cells to 2.7 volts each and measured the voltage variation (after a settling period of 24hr) between the cells using the ISDT Battery Checker via the balance leads to achieve a variation between cells of a couple of mV. I then charged the cells to 3.4 volts per cell using the chargers (ISDT T6) upper storage charge setting of 3.4v and a charge current of 1/10th the pack capacity i.e 15AH divided by 10 = 1.5 Amps. The cell voltage variation at 3.4v across the pack was 8mV. I’ve found that if the individual cell charge voltage is increased to 3.6v, the cell voltage difference will also increase to 100+ mV. Also if the charge current is increased for example to 5A then the cell voltage variation will increase at top of charge. This in itself is not a problem and is predicted however monitor the voltage to make sure no individual cell goes beyond the 3.6v manufacturers specification.

My final choice was for 2×2 rather than the 4×1 cell pack, mainly because it fits neatly into a box that I subsequently purchased and it also fits better the compartment underneath the boot-floor of my car. The red/black leads with PowerPoles fitted are for the high current connection to the radio, and are also used when charging and discharging, the white leads are the low current balance leads that are used for voltage monitoring. If the ISDT T6 Lite is used to perform a discharge the balance leads are connected and the T6 will not let a cell go below 2.8v. While using the battery pack with my radio a small voltmeter is connected to the balance leads which cycles continually indicating pack and individual cell voltages during use. The audible alarm is set to 2.7v, if any cell reaches this lower limit an alarm sounds and I stop transmitting and disconnect the battery to prevent further discharge. After use the pack gets a storage charge and stored in a dry and cool place in the garage. 

Enjoy your radio
Glen G0SBN/P

Amateur Radio with a Clansman PRC351 / PRC352

Amateur Radio with a Clansman PRC351 / PRC352

This particular radio consists of a transceiver, a 24 volt battery, an antenna tuning unit, a 20 watt amplifier, a telephone style handset and a combat whip antenna.

Why does this Clansman have the number 351 and 352? Well it all depends on whether the amplifier is attached. The 20 watt amplifier on the right of the picture above, the one with the heat dissipation fins, is what turns the PRC351 into a PRC352. Note that when connecting the amplifier the whip antenna can no longer be used, it requires a ground spike, and a resonant antenna such as a dipole or the Land Rover FFR Antenna Tuning Module and Whip. Also remember that the output with amplifier is 20 watts so it exceeds the maximum permitted power limit of a UK Foundation Licence.

The transceiver unit of the PRC351 provides an RF output of 4 watts on transmit, with a frequency range of 30 MHz up to 75.975 MHz NFM. So for Amateur Radio I plan to use the PRC351 on the 4m and 6m bands NFM segments of the UK band plan.

But before I start I need to assemble the separate components that make up the radio and make sure it works. Having completed the PRC351 assembly I planned to confirm the operating frequencies of the PRC351 on 4m and 6m with a SDR receiver. I tuned the SDR to 52.000mhz (6m) and tuned the PRC351 using the frequency control knobs. I then set the “ON” knob to the “*” position to remove any squelch, and selected the “L” setting for local. The next step is to match the antenna with the radio’s ATU, the ATU is designed to provide tuning to the whip when fitted. On completion I pressed the PTT button on the telephone handset. Unfortunately I noticed that there was a noticeable buzzing sound and no transmitted audio.

On close inspection of the telephone handset the probable cause was clear to see, the microphone mouth piece slots were full of mud. I stripped the handset and cleaned away any debris and gave the speaker and microphone a check over using the multi meter. Now that the handset was reassembled, another test, and I had audio, however there was still an annoying buzz. I did a bit of research on the Internet and it turns out that the PRC351 radio has tone squelch of 150khz. I haven’t found any information so far on how to disable the feature, so I plan to use the PRC351 with the squelch OFF as the background noise isn’t too offensive through the handset, and inhibit the tone as much as possible during transmit.

 To do this the unit needs to be opened which is simply undoing 8 Allen bolts, being very careful not to damage the internal brown ribbon cable while removing the end panel and unplugging it. Once apart disabling the 150khz tone is quite simple, locate the module “13” and gently turn pot “R9” fully ant-clockwise. Now that the PRC351 is re-assembled I conducted another transmission test, The SDR demonstrated it was on frequency and with clear modulation, and no annoying 150khz tone.

    

If you’re like me now’s the opportunity to tidy up the radio with a quick clean and paint job, gently removing the labels to be re-applied later.

Power to the PRC351 is from a Nickel Cadmium rechargeable battery pack which includes a “state of charge” indicator. The label on the battery provides some relevant battery information and a date of manufacture of 2005, so I’ll probably replace the cells in the pack with new lithium equivalents and include a charging circuit.

  

Hope to hear you on the 4m or 6m bands using my refurbished PRC351…

Ray M6OZA

M6OZA on ADSB Flight Tracking

M6OZA on ADSB Flight Tracking

So if you’re like me, a bit of a geek or maybe handy with technology, you’ve probably got drawers and shelves at home full of bits and bobs that “may come in useful one day”. This article is about how I made some of my “bits and bobs” into something quite useful…

I’ve always had an interest in radio, technology, and programming so when I was given a Raspberry Pi and a RTLSDR dongle for Christmas a few years ago I wanted to combine them into a radio project.

Up to this point the Raspberry Pi had spent a few short weeks being a Kodi box, and then a WiFi repeater, before being destined to the bottom drawer. My first experience of Software Defined Radio (SDR) was with the RTLSDR dongle, an entry level model, but it had done the trick of luring me back into radio monitoring and listening to shortwave. After a while I upgraded to a better model but having explorered everything I thought I could, it also ended up in the bottom drawer.

I’d started to acquire a small collection of old 1980’s – 1990’s Realistic scanners, these analogue scanners had served me well. Military air scanning had become “my thing” and I found myself scanning the frequencies after work listening to transmissions from practice flights off the North East coast. These flights were mainly controlled out of RAF Boulmer, not far from my location at the time. However, after a while I guess listening wasn’t enough and I was on the hunt to improve my setup when I came cross ADSB and MLAT aircraft tracking. I read up on the subject and eventually found an article that described how it was possible to use a Rasberry Pi and a RTLSDR dongle to make a suitable receiving station. I’ve included a link to the original article here.

I suggest you simply follow the instructions on the website to upload the software onto an sdcard and install it in your Rasberry Pi. All you then need to do is plug in your usb RTLSDR dongle and you’re ready to go.

So what type of antenna do I use, as the ADSB aircraft signals are on 1090MHz? As with a lot of things today the antenna can be purchased online, but why not make your own. You’ll need an empty beer can, if you don’t like beer a lager one will work just as well 🙂

The picture below is one I made. The beer can acts as a ground plane and the short vertical wire (1/4 wavelength long on 1090MHz) is connected to a sma connector.

The paint was just for practical reasons, to stop rain water shorting out the antenna to the can (groundplane). I happened to have Citroen saxo blue in the cupboard, but any colour will do. A blob of silicone around the connector would serve just as well. The measurements should you require them are: Antenna length 69mm, Can length 69mm.

For maximum receive range mount the antenna on a non-conductive mast, mine is on the chimney stack as a temporary measure. At this height I’m seeing a range of 100-150 miles from 200-350 tracked flights a day. It will work at ground level but range will be much shorter and the number of heard aircraft will be less.

Now I don’t only hear them I can see them as well…brilliant !

A year or  so down the line, I have now upgraded my system to include a flight-aware dongle to replace the RTLSDR, a 1090mhz pre amplifier, and I have upgraded the antenna to a high gain 8 section co-linear. Although not needed to get started, these upgrades have improved my receive capability significantly.

 

So don’t throw away your “bits and bobs” as they may come in useful one day. Have fun building your own ADSB receiver. If you liked this article please give it a thumbs up.

73 Ray M6OZA