Wednesday, 26 March 2014

Been a busy boy

Been very busy with the day job and too busy playing radio so this post will be a bit of a catch up!

JT-65HF
I have been using my newly built datamode interface in anger.

As well as running WSPR on occasion I have also been active using JT65-HF.

JT65 is a communication mode developed by Joe Taylor, K1JT, (specification here) originally intended for amateur radio communication with extremely weak signals such as Earth-Moon-Earth (EME) contacts on VHF it has gained popularity on the short wave bands using JT65-HF an adaptation of the JT65A protocol.

Being restricted to 10W it is an attractive method of making contacts. The protocol includes error-correcting features that make it usable even when the signals are too weak to be heard or are being subject to interference.

There are several how-to guides available
Get On the Air with HF Digital (from the ARRL)
JT65-HF -- an 'Odd' but Fun Digital Mode (from eham.net)

A number of software packages support JT65, the most popular being JT65-HF originally developed by Joe, W6CQZ. Sadly Joe is no longer developing the software, but the last version released still works, and is available at http://sourceforge.net/projects/jt65-hf/ 

Thankfully the project was open source and Beat Oehrli, HB9HQX as developed his own version with the catchy title JT65-HF-HB9HQX-Edition, available at http://sourceforge.net/projects/jt65hfhb9hqxedi/ This is the version I have been using with great success, the colour coding and simple button pressing makes a QSO straight forward and the built in logging and exporting make uploading to QRZ, eQSL and HRDlog painless.

Whilst to a traditionalist amateur operator it is perhaps a little slow, remote and impersonal (each exchange occurs during alternate minutes) I really like it! One advantage is I can set up the radio in the shack with CAT control via HRD and then have QSOs while VNC'ing into the computer from the laptop whilst in front of the TV with the wife and the dogs! (Thanks Tim G4VXE for that suggestion!)

I have been active on the 10/20/30 and 40M bands over the past few weeks making contacts with Bulgaria, Canada, Denmark, Germany, Greece, Iceland, Kazakhstan, Poland, Russia, Serbia, Sweden, Thailand, Ukraine, USA and Venezuela.

Contesting 'DX' Headset and Interface

I have become hooked on the RSGB UKAC VHF contests, operating on a Tuesday evening on different frequencies (50MHz, 144MHz, 432MHz depending on which week of the month) Whilst my results are small-fry compared to the big guns I have been more than happy with my modest antenna set up and less than ideal location (previous blog posts)

I soon appreciated that using headphones rather than the speaker made life easier but I was still using the stock supplied hand microphone. Several times I have found it difficult to make myself understood and suspected that not only am I plagued by my 'Black Country' accent and poor enunciation but maybe the microphone wasn't quite cutting it.

Not able to afford or justify the purchase of a Heil headset just yet I took inspiration from Charlie M0PZT and his recommendation for a budget solution using a £10 computer headset from CPC (product AV21444).

On the Yaesu FT-857D the microphone connector is a 8-pin RJ45 socket which is behind the removable front panel with the lead coming out of one of a number of openings. Whilst the panel is easily removable I didn't want to keep removing it when switching between microphones, also re-purposing an obvious CAT5 network lead was problematic as they are often thicker than the openings.

The lead removed from MH-31, RJ45 on interface
A quick look at the supplied Yaesu MH-31 microphone revealed it can be unplugged, so what I needed was a interface box where I could plug in the headset and the microphone lead. This would also allow me to try different headsets in the future.

Mic lead connected and headset
The budget 'dx' headset
My solution as pictured above is quite simple, I won't include any pictures of the interior as it is a bit messy and not my best work! It is built from salvaged parts, including the box. The RJ45 socket came from an old network adapter, but beware some sockets are only 6 pin not the 8 as needed here. The headphone part of the headset is a simple connection to the rear socket on the FT-857D (the grey cable on the picture above)
Yaesu FT-857D mic socket as view from front
Most microphones designed for computers use electret elements which require a bias voltage, this is quite simple as the Yaesu microphone connector supplies 5V, so a simple resistor (8.2K) will supply this, also by using a couple of different capacitors and a switch I can select a 'thin' higher frequency response (for DX work) or a more normal 'fatter' response. A circuit can be found on George Smart's webpage, the bias is simply applied to the tip of the microphone jack.

The box also has a PTT switch, this could have simply grounded the PTT line but I wanted to have a LED indication on the box and again I could have just wired a LED and resistor to 5V and to the PTT line so it would light when the switch was closed, pulling PTT to ground and completing the circuit. I opted to use a simple transistor open collector switch to add a little isolation.

The interface works well and I used it for the first time last night in the 50MHz UKAC with my homebrew MOXON antenna...

6M/50MHz MOXON
My first contest back in January was the 50MHz UKAC and as I blogged I made a solitary contact due to antenna issues, i.e I didn't really have one!

I missed the February contest so this month I really wanted to have a decent stab at it which meant building an antenna. I decided early on that a Moxon was probably the easiest to construct, so I downloaded the MoxGen program to calculate the element lengths.

Using 1mm diameter 'garden wire' for the driven element and reflector. I had various bits of flexible plastic pipe kicking about and decided to use them to construct an x-shaped spreader, unfortunately the pipe was obviously from different batches and as soon as it was tensioned by the wire it bent into all sorts of strange shapes due to the different elastic properties so I abandoned that design.

I had left the build to the last minute and needed a quick solution, so yesterday morning plan-B was to go an get some cheap timber from the local B&Q on the way to work and build a simple frame to wrap the wire round.
Moxon on garage floor
Coax and common-mode choke, and sturdy support!
I impressed myself by completing the construction of the frame in the short time I had at lunchtime!

One thing I hadn't appreciated was just how big the final antenna was, it wasn't heavy just big! So last night an hour before the contest started I fitted the choke balun and coax to the terminal block. To be safe I removed the other antenna from the mast and hoisted her up.
Up in the night sky

Moment of truth, thankfully the VSWR was around 1.5:1 at 50.2MHz, rising to nearer 2:1 at the top end of the band. Not ideal but close enough. The VSWR measurements would suggest that the Moxon is a little bit long, interestingly some online Moxon calculators suggested dimensions for a slightly smaller Moxon than the downloaded Moxgen program did? Something to tweak/experiment with possibly using some thicker wire to increase the bandwidth.


50MHZ UKAC 25 March 2014
I was sorted! Moxon antenna up, contesting headset and interface plugged in and a quick scan up and down and I could clearly hear several stations testing and setting up. I poured myself a beer and soon the contest started.

Time between QSOs for a 'selfie'
I finished the night with just 14 QSOs, more would have been nice and it wasn't through lack of trying I could hear many more operators but simply couldn't make myself heard either because the antenna was in wrong direction or due to low power and getting lost in the pile ups to stronger stations.

I was not disappointed in fact I was quite happy with what my 10W, my new headset and home brewed antenna had achieved. The Moxon showed great promise and directional characteristics but for some reason just couldn't get south as the map indicates.


Out of interest I wondered what the line of slight view from my mast looked like so I strapped a camera on to the moxon this afternoon..


Need more height I think, especially if pointing South and a rotator would be nice!
Well that wraps it up for the moment.. 73

Monday, 10 March 2014

Datamode Interface built

This weekend I finally got around to sorting out my digital/data mode interface for the Yaesu FT-857D.

To transmit and receive digital/data modes you need to connect the radio audio in/out to the computers sound card in/out, the computer then runs the necessary software to encode/decode the signals. I want to try out WSPR, PSK, JT65 and some SSTV for starters I have spent too long just receiving and decoding...

There are a number of inexpensive commercial interfaces available, but many of them use the same basic design originally intended for eQSO/Echolink operation. I nearly succumbed but I had built an eQSO interface many years ago when using PMR446 and had most of the parts to build another.

I nearly took the easy route and got a commercial one since connecting up some home built circuitry to a £20 hand held is slightly less daunting than plugging it into an expensive rig!  My original interface has been modified and reused over the years and was a bit of a mess, but being brave I decided I could tidy it up and I couldn't really damage anything if I took my time... actually the truth was I discovered I didn't have the necessary optocoupler IC so couldn't build a new one just yet...

A simple internet search for digital/data mode interfaces will bring up a great deal of information, schematics and ideas for home brew solutions. The basics can be found here for example.

The simplest form of interface is just a simple direct lead with the transmitter operating in VOX mode. However levels can be a problem as the line/speaker output from a computer can be too high for a transmitters microphone input. Also connecting a radio to a computer directly can lead to problems with ground loops and interference.

The computer can be made to control the Push-To-Talk (PTT) on the transmitter using a serial port with the software controlling one of the handshake lines (RTS/DTR) Some data mode software support CAT to allow control of the PTT as well as tuning the transmitter, but the serial port method is more universal.

The preferred interface, and the one I had built isolates the computer from the radio by using two audio transformers and an optocoupler. There is no direct connection between the two devices so keeps interference to a minimum.

I could have used the microphone and speaker output on the radio, but the FT-857D has a convenient data connector on the back. This is a 6-pin DIN socket as used by older (PS/2) computer keyboards/mice. Note the diagram shown in the FT-857D manual (as below) is the view as you look at the socket.

FT-857D Data connector as in the manual
The connector has two "data" outputs but they are simply fixed level audio outputs from the receiver. The one of interest for most modes is the 1200 baud output (the 9600 baud output is more akin to a discriminator tap and is only of use for FM packet) There is a data-in (TX-audio) and a PTT control line.

Like many people I initially thought I could cut a lead off a mouse/keyboard and repurpose it, however I discovered most only use four wires and they don't use the necessary pins! You might be lucky especially with older keyboards or alternatively if you have an old keyboard extender cable they usually have all six wires present. Alternatively the plugs are readily available from the likes of CPC/Farnell.

I had a hunt around in a junk box and located a suitable keyboard extender cable. I chopped off the useless end and metered out the pins to identify the appropriate wires. Remember when looking at the plug the pins are swapped left-to-right compared to the diagram which is the socket view.

Well here is the insides of the interface.. and as you can see I completely failed to tidy it up! Not my best work, but I did put it in a new box and I did tape up all those unused wires!

The messy internals of the interface
One annoying issue I had was the audio from the computer wasn't getting to the radio, it worked and scoped out okay when out the box, but in the box it stopped working. I suspected a bad solder joint and redid them all, but still showing the same intermittent issue. I did notice flexing the board slightly out the box cause the fault and soon located a track on the vero-board which appeared to have a hairline crack, I couldn't see anything obvious but a wire soldered along it cured the issue.



It looks better with the lid on..
I soon had it connected up and fired up WSPR

Computer, radio and interface

It was straight forward setting up WSPR to use a combination of CAT for tuning and the RTS PTT control and soon had some encouraging results, in fact these are some of the spots of my 5W signal on 10m/20m and 30m, I was grinning from ear to ear!

10M Spots

20M Spots

30M Spots
I had simply set up the FT-857D for basic USB transmission, however it does have a dedicated DIG mode, the manual refers to setting it up for RTTY/PSK, I very briefly had a go with PSK31 and Digipan and was successfully decoding signals and put out a few CQ calls (again on 5w) but got no immediate response. However checking PSK Reporter later it seems I had been heard by VC3S, OH1FOG and ES1JA maximum distance was around 3260 miles

Looking forward to spending some more time experimenting with the data modes.

Monday, 3 March 2014

Cheap GPS module

Several of the Arduino projects I have been experimenting with have used a GPS module to provide accurate time and/or location information and in the case of the QRSS/WSRP QRP beacon a highly accurate GPS derived 1 second pulse is used for frequency calibration. A number of people have enquired about the GPS module I am using.

Most GPS devices have a limit on the altitude they work at, normally 60,000 feet or less. This is a legacy of the now defunct CoCom (Coordinating Committee for Multilateral Export Controls) restrictions. For my HAB project this restriction needs to be disabled and the GPS must be switched into 'flight mode' In the HAB community the favoured devices are made by U-BLOX

Therefore when I was sourcing a GPS I had search specifically for a inexpensive device using a U-BLOX.

s
The GY-GPS6MV2 as supplied
I soon found something called a GY-GPS6MV2, it appears to be a generic design and is readily available on eBay from suppliers in China, Hong Kong and Singapore and can be purchased at the moment for around than £10 (approx $15) including postage!

It is also available from domestic suppliers but often at a much more inflated price, but you don't have to wait several weeks for them to be delivered.

There are many other GPS modules available but this module seems to be one of the cheapest available. it is often listed as a NEO6MV2 GPS Module Aircraft Flight Controller.

The module consists of a small PCB 25mm x 35 mm size with a separate ceramic antenna connected by a small lead which is 25mm x 25mm in size. The Antenna is quite heavy and isn't suited to Pico HAB payloads but for other uses is more than satisfactory.

On the board is a small button-cell battery to provide backup to the GPS chip and a small EEPROM connected to the GPS chip which I believe can store configuration(s). I haven't used it myself just using the module in it's default set up at the moment. For a schematic click here

The board has four connectors VCC, GND, TX (Transmit) and RX (Receive) and can be powered by the 5V supply on Arduino boards since it has a small regulator to provide the 3.3V needed. 

In most projects all that is required is data out of the GPS. The GPS TX (data out) being connected directly to the microcontrollers RX (data in) The (0V and 3.3V) level shift of the signal is compatible with the TTL input of the microcontroller.

The GPS by default will start up and output standard NMEA sentences at 9600 Baud, until GPS position lock is achieved the NMEA sentences won't have a long/lat location. The module also has an LED which will start flashing once a lock is achieved.

There is no direct connection for the highly accurate 1PPS (pulse per second) signal that can be used for frequency calibration, but the flashing LED is driven by pin 3 of the GPS module which is the 1PPS (pulse per second) signal required.

The 1PSS signal, like the TX is either 0V and 3.3V, in order to use it a small lead will need to be soldered onto the board, either directly onto Pin3 of the GPS chip, or alternatively on to the small current limiting resistor used by the LED, as indicated below.

Showing the GPS 1pps points

Monday, 24 February 2014

Welcome new readers

Firstly welcome to all my new readers via AmateurRadio.com

I was very surprised, shocked even, to be asked to syndicate my postings to the site. Hopefully my posts will be of interest to a wider audience.

I have been a licensed amateur operator for six months currently on the bottom of the UK licence structure, the so called Foundation licence, but am hoping to take the Intermediate licence soon.

The main driving force for wanting to progress is I want to build things, to experiment and learn.

In a natural extension/diversion from my day job I have already been experimenting with the Arduino platform, initially with the intention of developing a High Altitude Balloon tracker but more recently with other radio related projects including a satellite tracker and using it in conjunction with DDS modules for WSPR/QRSS purposes. I have just built a dedicated Ultimate 3 QRSS kit from Hans Summers (G0UPL)

The DDS module are particularly interesting and I have some tentative plans for an Antenna Analyser and a Power/SWR meter capable of working down in the mW range which I stumbled across on the website of Loftur E. Jónasson - TF3LJ / VE2LJX. This is of particular interested to low power QRP operating. Did I mention that I have joined the GQRP Club?

Progressing from a couple of Baofeng VHF/UHF handhelds (which I hardly use) to a proper rig last month with the purchase of a Yaesu FT-857D I have been dipping my toe into the frightening world of operating!

It is common for new amateurs to be "Mike Shy" and I admit to suffering terribly. Not being the most outgoing or confident person being confronted by a barrage of rapid fire abbreviations, codes and etiquette it took a while before I had the courage to key up.

I plucked up the courage to have an attempt at some of the RSGB UKAC VHF evening contests and after gaining a bit of confidence I ventured properly onto the HF bands this weekend making a few simple signal report QSOs.

I should like to thank all those who have been patient with me as I fumble along.

Because of the shyness the use of data 'digital' modes is a strong draw since it uses computers and you don't have to talk! I am salvaged some suitable connectors to build a new computer data interface for the FT-857D, I built one several years ago but it got slightly cannibalised when experimenting with an ARPS gateway.

I can afford a commercial interface but why should I pay over the odds for something I can easily build myself? The desire to homebrew isn't just driven by cost, but lets be frank this can be an expensive hobby! Nothing gives more satisfaction when something you built works.. and yes they may be famous last words.


Monday, 17 February 2014

Ultimate3 QRSS Beacon kit built!

At the start of the year I did some experimentation with cheap DDS modules based on the Analog Devices AD9850 connected to the Arduino board, making a rudimentary WSPR transmitter prototype.

My current licence restrictions prevent me using anything home-brew for transmitting except for commercial kits. So I ordered an Ultimate3 QRSS beacon kit from Hans Summers (G0UPL) thinking that it would be okay. I subsequently learned that any commercially available kit must satisfy IR 2028 which is all a bit vague and unclear but sadly I don't believe this particular kit does.

All was not lost, building this kit should more than satisfy one of the practical assessments of the intermediate examination, which will get me around this problem.

The Ultimate3 kit is extremely popular and so I had to wait a little for delivery and it arrived on Friday. After the last few weekends of non-radio activities I had planned to get my antennas backup and do some proper operating. Like many people I had been forced to take everything down due to the barrage of storms and high winds the UK has been experiencing recently.

A tidy workbench

Saturday saw no let up in the wind, so I decided to spend a few hours building the kit instead.

The instructions were extremely clear and straight forward and soon had it built up, though it is high time I invested in new soldering station. I have a basic Antex 25W iron. I cannot remember exactly when I brought it but it is well over 10 years ago.  It was more than adequate to build this kit and for soldering connectors but I could do with something adjustable and more comfortable.

Taking shape
The only issue I had was winding the first toroid, 25 turns later I realised I had wound it the wrong way round so the leads didn't line up with the holes in the PCB. I could have made it fit but nope I will do it properly so I unwound it and did it again.

I also made the mistake of not scraping the enamel off the toroid wire and tried the heat it and bubble it off method, except I think my iron just isn't hot enough so ended up using a piece of wire wool to remove the enamel.

Lessons learned I soon had the other three toroids correctly wound and wire prepared for the low-pass filter board.
Close up of the LPF
   A final visual check and powered it up and it worked first time!

All built
It works!

Setting it up
Full of confidence I grabbed my trusty GPS module which has been pressed into service on a few Arduino projects including the HAB project. Quickly soldered some connecting wires and powered everything up.. all was well or so it seemed when the display suddenly went blank, backlight was on, just no characters.

Pressing the button I occasionally got some random characters and a flashing cursor! I de-soldered the GPS and still nothing. I suspected the display was faulty but trying it on the HAB prototype board confirmed it was okay. I checked the display connector continuity and everything appeared okay.

Out with the oscilloscope I started probing, everything checked out. Crystal was oscillating and data pulses on the display control lines. Then I checked the supply pin on the display and it was only reading 4.1V, this under-voltage would explain the odd display behaviour.

PSU output was 5V, micro-controller was 5V, DDS module had 5V. All very puzzling till I removed the DDS module and spotted a discoloured track on the PCB, touching it with a screwdriver and the lacquer fell away revealing a tell tale scorch mark, somehow I had made a nice resistor!

Burnt track to right of micro-controller
A quick wire link soldered in place and everything was back to normal.

What caused it? Checking the de-soldered GPS connecting wire I spotted a stray single strand of wire on the ground wire. I suspect this must have shorted to the adjacent 5V line and since I was using a nice beefy ex-PC PSU as a bench supply it had popped the track without the hint of a flicker. The GPS has been rewired properly and is working nicely, now to connect a dummy load and experiment some more.

Sunday was a lovely day, wind dropped so antennas have been put back up and I took the opportunity to tidy up the installation a bit. I also dug out an old fibreglass pole to put the M0CVO HW-20HP back up. I didn't get to do any operating in the end as by the time I had done this and made up a couple of decent patch leads it was time for roast beef and all the trimmings and an evening in front of the TV.

The HW-20HP back up
Putting PL259 and N-Type connectors on coax is also part of the intermediate assessment, so perhaps I should have videoed making up the patch-leads as proof ;-)

Wednesday, 12 February 2014

432MHz UKAC - 11 February 2014

Another enjoyable evening getting familiar with my radio and competing in the RSGB 432MHz UKAC.

I rewired the 7-element ZL-Special on Monday night, and adjusted it to get an excellent VSWR of nearly 1:1 and mounted to the pole.


Setting up last night I raised up the pole around 19:30 and a quick check showed the VSWR was over 1:2!

Yesterday it rained and sleeted very heavily, as suspected the culprit was where I joined two pieces of coax. I had used plugs and a coupler but had run out of self-amalgamating tape to waterproof it, so had resorted to wrapping it in insulating tape... bad idea! Removing the tape it soon became evident that everything was very damp, I quickly dried all the connectors down and gave it a quick blast with a hot air gun. All sorted, the VSWR was back to just over 1:1 (must visit Screwfix for some more tape)

I was much more relaxed for this contest, it was an enjoyable but difficult evening and made just 8 contacts, claiming 762 points. I heard quite a few calls but just couldn't make myself heard. I kept popping out the shack to turn the antenna, listening to other QSOs I was able to use the locator to determine the optimum bearing.

One observation I made was the apparent poor front to back ratio, some calls coming in loudly despite the antenna being in the opposite direction which suggests the phasing isn't quite right.

The map below shows my results.

A night off next Tuesday as it's the 23cm contest, but hoping to be better set up for the following weeks 50MHz contest, hopefully getting better results than I did last time.



View UKAC 432MHz 11-Feb-2014 in a larger map

Monday, 10 February 2014

A Radio Free Weekend!

No chance to do any radio this weekend as was away with the XYL in North Yorkshire. Packed the Baofeng but never got chance to turn it on..


I did manage to get along to Maplins at the end of last week and grabbed some expensive N-Type connectors (as well as some other connectors, a cheap dummy load and an antenna switch!) So this evening I am hoping to sort out my Moonraker 7-element 70cm ZL-Special for the 432MHz UKAC contest tomorrow night.



I have been reading up on the ZL since I have always been a bit confused by the antenna.

The assembly instructions for the Moonraker one were very poor and the joining of the two phased elements was achieved using simple straight wire, rather than the twisted transmission line I was expecting. It has worked reasonably well as a RX antenna but I haven't used it for TX yet.

I have found a small section of ladder line from an old FM radio antenna, so will be using that now that I have more of an understanding of how it works, the front element and the larger rear element are supposed to be approx 1/8 wavelength apart (I haven't measured it yet) the two are joined using a twisted section of transmission line 1/8 wavelength in length.

There is also a trimming capacitor to help with the matching, so with this information I hope to get things tuned up nicely, the only draw back is only have RG-58 coax at the moment which isn't ideal for UHF, but it is only a 10m length and will be using proper N-Type connectors.