Friday, 19 September 2014

Radiosonde Decoding

Weather balloons have been routinely launched into the atmosphere for many years by government and commercial organisations for the purpose of scientific and meteorological observations and research. Hundreds are launched daily around the world, using predominately renewable Hydrogen as the lifting gas.

These balloons invariably carrying radiosondes, a battery powered telemetry instrument package to measure various atmospheric parameters and transmit them to a ground receiver. Worldwide they operate on radio frequencies around 400MHz and 1680MHz.

Last year I discovered the hobby of High Altitude Ballooning, where enthusiasts send up their own balloons loaded with experimental payloads and radio telemetry trackers using low power transmitters and amateur radio data modes and frequencies. I have since had a great deal of enjoyment receiving and decoding these as well as developing my own payload.

I decided last year to also try my hand at decoding the commercial radiosondes. Reception of the telemetry signals is relatively straightforward as they are of higher power than the hobbyist transmitters and decoding can be done by the Sondemonitor program from COAA available to individuals to produce graphs and charts of temperature, pressure, humidity as well as the location (if transmitted) and height of balloons.

The software is available for a 21 day trial but when I attempted to install it I was thwarted by a licensing issue caused I believe by installing trial versions of COAA's ShipPlotter and PlaneSpotter programs in the past, despite this I still decided to purchase a software licence for the princely sum of €25.

However this was just before the Christmas upheaval and the dismantling of my receiving set up and so it got mothballed and I have never got around to using it till now.

It was quite by chance that I was flicking around the SDR yesterday using my original (Version1) FUNCube Dongle PRO when I spotted a Radiosonde signal on 404.2MHz, my interest was piqued. (It should be noted the later FUNCube Dongle PRO+ unfortunately has a coverage gap on this frequency so cannot be used)

I connected to my magical HAB antenna and using SDR# and the Sondemonitor program I received and decoded my first radiosonde early this morning and a second flight around noon.


The program produces some interesting graphs showing temperature, humidity, pressure and other measurements during the ascent and after the balloon burst, as well as Tephigrams.


 
I am not sure where these balloons are launched from. The Radiosondes are identified by the software as Vaisala SGP models (but have no GPS data?)  Checking the Vaisala website there are a number of devices and one downloadable document is a comparison of the Vaisala Radiosondes made by the UK Meteorological Office in 2013 (pdf file) which mentions a site in Camborne in Cornwall, but I have also seen mention elsewhere of a site in Larkhill on Salisbury Plain.

The Met Office document also hints that the Radiosonde currently used by them is one of the Vaisala RS92 range, indeed the RS92-D appears to be a device which has no on board GPS and would fit with the GPSless decodes I have made.

Definitely another interesting radio diversion and if you are interested then reception can be made using RTL-SDR receivers as this tutorial on RTL-SDR.com demonstrates, but bear in mind the demonstration/tutorial shows GPS information being received which I have not seen on either of the two launches.

Wednesday, 10 September 2014

Repairing a Kenwood TR9500, Part2 - TX working, SSB RX not

As I suspected the microphone amplifier Q1 in the Kenwood/Trio TR9500 was indeed faulty. The replacement arrived next day and within an hour I had successfully soldered in the new 2SC2240 transistor and it now had audio on transmit.

Transmitting into a dummy load and monitoring on my FT857-D the FM transmission was fine, the SSB was okay, perhaps slightly over driven. I suspected that maybe the previous owner might have twiddled something to compensate for a failing Q1.


In the adjustments section of the service manual VR6 on the IF unit controls the SSB MIC gain. To check the settings it was a case of setting the transmitter to 432MHz and putting an audio frequency signals of 1.5kHz of amplitude 1mV and 10mV from my signal generator on to the microphone terminal, and observing the RF power output, which were the 5W and just over 10W as required. As this didn't need altering I left it alone and boxed it back up and returned it to the happy owner.

Last night was the RSGB 432MHz UKAC Contest and I was hoping to here it on the air, sadly I didn't. It now transpires that there maybe another issue with it, something I should have spotted.

I do remember something strange when doing the initial testing. Connected to a dummy load and in SSB mode the S-meter showed S9+ when in receive but with no audio, turning the RF gain control the meter dropped to S0 and normal white noise static could be heard. It received a SSB transmission from the FT857-D with no issue so I thought no more of it. Being over eager and not experienced with using different rigs I had mistakenly dismissed it and should really have read the operating manual more extensively.

The anomalous S9+ meter reading and no audio occured when the RF gain control was set to the maximum which is the normal recommended setting for operating, I'd simply turned the RF gain control to the minimum mitigating the issue.

Obviously the rigs owner had put the RF gain back to maximum and was now reporting it wasn't switching back to receive. In fact it is but nothing is being heard. Checking the service manual this morning and it appears there is an issue with the AGC circuit (description and block diagram below)


RECEIVER CIRCUIT
.... The signal is picked up from the last stage of the IF amplifier (Q23), then detected and amplified to generate the AGC voltage. The AGC time constant is automatically set according to the mode : FAST for CW; SLOW for SSB. The AGC voltage is applied to IF amplifiers Q21, Q22 and Q23 (3SK73(GR)) and RF amplifier Q51. It is also used to drive the S meter.

It seems the rig may well find itself back on the bench, however this repair could be more problematic!

As I mentioned it was the 432MHz UKAC last night and I had a decent night of search and pounce. Conditions were very strange, lots of fading and strangely some of the usual local operators were not heard. I was very pleased to catch some lift and made a couple of decent DX contacts in Northern Ireland, The Isle of Man, Northumberland as well as Essex and Cambridge.
In a few weekends it is the National Hamfest, which is held in my home town and I hoping to pick up some bargain gear to improve my UHF set up, however from past experience that may prove difficult.

Friday, 5 September 2014

Repairing a Kenwood TR9500, Part1 - The Diagnosis

A fellow SKARS club member picked up a nice condition Kenwood/Trio TR9500 70cm all-mode transceiver (circa 1980) from the Hamfest last year for not a lot of money and he hoped to use it for the UKAC contests unfortunately it proved to be faulty.

From the description of the fault and studying a downloaded service manual I suspected a relatively simple fault and saw an opportunity to acquire it and offered to buy it for the price he had paid. However I have decided to be more charitable rather than mercenary and have offered to give it a look over and repair it for him if I can.

The fault as described was the rig receives okay but on transmit there was a carrier on FM with no audio and a very quiet SSB signal. A faulty microphone had been ruled out and someone had suggested a bad connection internally. Due to the compactness of the unit and the difficulty in dismantling no one had felt confident to attempt any further inspection. I wasn't so sure this was the issue so at the last meeting I picked up the rig and currently have it on the workbench.


TRANSMITTER CIRCUIT
The microphone signal is amplified with the microphone amplifier Q1 (2SC2240(GR)), which is commonly used for both SSB and FM transmission modes and is incorporated in the carrier unit (X50-1720-XX). The amplified signal is then fed to both the SSB and FM circuits.
Looking at the block diagram of the carrier unit and the above functional description in the service manual I suspected the microphone amplifier Q1 to be faulty.

I want to confirm the fault first and so I connected up a dummy load and RF power meter and using the FUNCube Dongle SDR I could observe and monitor the output signal. Sure enough on FM there was a nice carrier at 10W with very faint audio, on SSB there was a small visible signal again with very little modulation. Whistling, blowing and tapping of the microphone could be seen on the waterfall... just!

I connected a switch to the Morse key input and confirmed the rig transmitted in CW with no issue.


On the block diagram there is a switchable tone burst oscillator for repeater access and the output of this is joined to the output from the microphone amp. Encouragingly the tone burst can be clearly seen and heard in the transmission again pointing to an issue with the microphone amp.


To get to the carrier unit PCB it was a simple matter of removing the bottom cover. The PCB is held in a metal frame mounted with five screws and can be lifted out, as pictured above. But before I did that I checked the continuity to the microphone socket and the 8V supply to the amplifier circuit and both were fine (see diagram below)


The poor quality image from the scanned service manual shows the bottom of the carrier unit, this is the side of the PCB visible without needing to remove it. The microphone connector is in the top left, putting an oscilloscope on the microphone input (pin1) a signal was observed, however the output (pin8) had an almost identical signal with little or no amplification. Injecting a low level audio signal from the a generator on this pin could be seen and heard in the transmitted signal. This observation together with the tone burst seemed to confirm the other audio circuitry was functioning normally and the microphone amp wasn't.

Actually removing the carrier unit PCB proved a bit tricky as it has a number of small and very secure connectors with ageing and delicate wiring, but I did manage to extricate it and a visual inspection didn't show up any obvious issues such as broken tracks or joints.


This is the detail of the microphone amplifier section from the schematic. Using a meter I have checked the continuity of tracks and have checked all the resistors for shorts or open circuits and they all read the correct values. The capacitors all look okay and checking the signals either side of C3 the C7 coupling capacitors show they are functioning correctly. This left Q1 a 2SC2240(GR) transistor as the likely culprit and I have ordered a replacement which should arrive in the next few days. I am hoping this will make it spring back to life.

Wednesday, 3 September 2014

Logging and datamodes with PZTLog

Organisation isn’t one of my strengths and my logging of contacts has been pretty woeful. It consisted of a spiral bound note book full of various scrawls sometimes tabulated for contests but more often than not a free form mess. With good intentions I purchased a proper RSGB Deluxe log book months ago but that has remained pristine and has just become a handy band-plan look-up!

Until recently I had only made a small number of voice QSOs on HF and had entered those manually into the online eQSL, QRZ and HRDlog logbooks I maintain.  JT65 data mode logging was handled by the JT65HF program itself and for the UKAC and other VHF contests I have been using the MINOS logging program - all in all a bit of a mishmash.

Now my operating confidence has grown I am making more contacts and so I really need to computerise and centralise my logging. After  looking at a number of programs I opted to give Charlie Davy’s (M0PZT) freeware PZTLog a try and after using it for a couple of weeks I am very impressed.

http://m0pzt.com/?pztlog

The program has a multitude of features but at the moment I am using it to simply enter and log details of contacts, combined with the CAT interface to the FT857-D and the OMNIRIG control the mode, frequency, band and power settings are automatically populated.

The really nice selling point for me was the inbuilt data mode operation. I have tried PSK and RTTY before using other programs but I often found myself confused and intimidated by the interfaces and jargon.

PZTLog uses the MMVari engine to operate PSK/RTTY and it uses a familiar waterfall display. The TX/RX window and  QSO macros are easily accessible and I found the interface much more intuitive than other programs I have used. On installation, the macros are already populated and labelled sensibly and are easily editable. By double-clicking received text you can set Callsign, Locator, RST/Serial, Name/QTH quickly and with ease.

In a short time I have made a good number of PSK QSOs as well as a some RTTY contacts, even giving some points away in the fast paced SCC RTTY contest last weekend.

Importing and exporting of logs is very easy and it has inbuilt eQSL uploading, but at the moment I am having trouble making that work reliably but that I think is me rather than the program.

PSK is a great mode, running no more than 30W, often less I have made a number of nice DX contacts and countries including Argentina, Oman, Japan and the Dominican Republic.



Thanks to Charlie’s program I now have a better understanding of how the mode and QSO works so may try some of the more sophisticated programs, or I may just stick with PZTLog for a while. Check out Charlie's page for lots more interesting information as well as some very funny light hearted audio features poking fun at the hobby.

In other news the VHF UKAC contesting is improving. Last week I made a last minute decision to lower the pole and put up my homemade wooden 6m MOXON but glad I did. Conditions weren’t good but still made a respectable number of contacts but not a lot of distance. I’ve climbed to 30th place in the 50MHz low power AL section.
Last night was the 144MHz UKAC and what a great night it was, conditions were brilliant and it was very busy on the band. Still operating search and pounce mode I snagged just 32 contacts, but with 13 multipliers giving me by best score so far on that band.  Operating in the low power AL section as M6GTG it is hard work getting through the pile ups but it was great fun trying.
Finally I became a licensed ‘foundation level’ amateur a year ago this month (M6GTG), and have since become an ‘intermediate’ (2E0NRD) and have now taken the bold step of applying to take the ‘advanced’ examination next month. I say bold because I haven’t taken a course or studied for it per se but with my background and education I have covered most of the theory even if it was over 25 years ago – with a bit of serious reading, revision and dusting off of the memory banks over the next few weeks I hope to be ready!

Tuesday, 19 August 2014

Portable in a very windy Cumbria

Before amateur radio took over my life my main pastime was competing at dog agility which I did moderately successfully for many years, for several of those I was even the chairman of a Nottingham Agility Dog Training Club and organised one of the larger Kennel Club Championship shows as well as judging at many events. If you search my YouTube page there are a number of videos showing me and the dogs in action.

Things change and sadly I became disillusioned with the sport as seemingly endless rule changes and its increasing popularity saw it losing its core ideal, what was meant to be fun for dog and handler had sadly become too competitive, professional and commercial, too many people now make money out of the sport and what was once an enjoyable social activity is now spoilt by unsportsmanlike behaviour, complaints and bitchiness.

When my dog Boris suffered a cruciate injury the enforced time-out made me realise I didn't want to do it anymore and so I don't.. well apart from the odd exception, last weekend was the West Lakes Agility Club Show held in the small town of Haverigg on the Cumbria peninsula (Locator IO84IE)

This is a lovely old-style small friendly show with the bonus of being held just a stones throw from the sand dunes and beach. I had agreed to go and like the recent holiday in Skye it was initially planned with no thought for any radio operating.

We would be caravanning at the show for the best part of four days without any electrical hookup and the wife had volunteered to help on Saturday leaving me on my own for most of the day... so a plan was hatched at the last minute.


I purchased a nice new 'spare' 100A/h leisure battery and smuggled on board the FT-857D with some suitable battery clips, headphones, a fiberglass pole, some antennas. I don't own a suitable 'portable' ATU at present,  having borrowed one from SKARS on several occasions but as this was a last minute thing I would have to chance operating without it. I took the M0CVO HW-20P OCF-Dipole, which has a usable VSWR on 20m, 17m, 15m, 12m and 10m without an antenna tuner and the M0CVO Magitenna, but wasn't sure what I would get from this as I'd only ever used it with a ATU.

The weather was difficult all weekend, we arrived on the Friday to be met with warm and sunny conditions but a steady strong wind. There was bit of a battle to get the caravan awning up but we managed it.Saturday the wind just got stronger, the forecast for Sunday was for even stronger winds so it was dismantled and packed away, indeed it was worse around 25-30mph with must stronger gusts.

Undeterred I got the antennas up,  however the fiberglass pole I have must be getting on for 10 years old, and would often fly a pirate flag when camped at agility shows. It had already lost it's top section many moons ago but was still quite tall and so I hoisted up the OCFD balun and coax and the end of the magitenna wire in the buffeting wind and it was swinging around wildly - almost inevitably it proved too much and the remaining top section splintered!


Despite losing over in a metre in length I tried again and managed to get everything up, the OCFD wires were tied out to form a sort of inverted-vee using a handy nearby fence, the Magintenna was pulled to form a sloper across over the front of the caravan, but due to the lost height actually touched the front of the roof. Amazingly I got an almost 1:1 VSWR on 40m and loud and clear RX.    



This weekend was the International Lighthouse and Lightship Weekend (ILLW) this annual event has been going since 1995 and promote public awareness of lighthouses and lightships and their need for preservation and restoration, and at the same time to promote amateur radio and to foster International goodwill.


The bands were kind and I had an enjoyable Saturday afternoon and a few hours on Sunday making QSOs with a number of UK and European lighthouse stations on 40m and 20m and it seems the whole event was a great success. Alas the wind proved too much for the remainder of the fiberglass pole and it developed a large crack in the bottom section forcing me off the air.


By coincidence Haverigg has two lights, the old Hodbarrow beacon and the restored Hodbarrow Point lighthouse (pictured above from the beach). Last year we walked to the restored lighthouse but since the restoration was completed in 2004 it is sadly looking in need of some remedial work.


I only learned of the ILLW event at the last minute and sadly neither of the Haverigg lights were activated that weekend, next year if the show is on at the same time I may look at trying to operate from them.

Oh and the wind? Here is a video of a walk on the beach on the Sunday morning..

Friday, 8 August 2014

FUNCube-1 & FUNCube-2 Decoding Update

In the film "Willy Wonka and the Chocolate Factory" there is a scene where the lucky children (and parents) enter the "Land of Candy" where everything is edible and they run around grabbing a taste of everything. I am beginning to know how they felt.

Amateur radio has so many different things to try and over the last year I have found myself jumping around having a dabble at new things. Doing this and time being scarce has inevitably impacted the HAB payload and other Arduino projects. I have also neglected some of my previous satellite monitoring activities.

I had been regularly decoding the FUNCube-1 (AO-73) telemetry and uploading packets to the data warehouse (see earlier posts). To do this I had been using a discone in the loft and a FUNCube Dongle on the ageing main computer in the house.

This computer was on 24/7 but I couldn't leave the FUNCube dashboard running continually as the processor load would cause the noisy fans to kick in, besides for most of the day there wasn't a receivable pass. So I would just start up the dashboard when needed which meant remotely logging in from work. Due to an increasingly busy work load I would often forget or be unable to start it up and have got out of the habit. I therefore missed many opportunities to climb up the uploading ranking chart (it is really for the science honest!)

Of late there have been a large number of new satellites launched including the UKube-1 and the QB50 satellites which have modules and transponders as part of the FUNCube project.

Catching up with news after the holiday to Skye I noticed the announcement that an enhanced version of the FUNCube decoder dashboard has been released promising improved performance. The dashboard will also capture and upload (but not display) the FUNCube-2 telemetry transmitted from UKube-1

Looking at the FC1 upload ranking list I saw I had dropped down significantly and decided it wasn't acceptable!


As part of my antenna upgrade I have put up the X-50 dual-band collinear on the top of the pole feed with nice low loss RG213. This is currently connected to the FUNCube Dongle Pro+ dongle on the shack laptop, with the latest dashboard software installed.



It has been running 24/7 for the majority of the last week and has captured close to 2000 telemetry packets from FC1 a significant performance increase compared to my earlier set up, and I have now surpassed the 10,000 packet milestone (currently 11,626). I have also uploaded over 500 telemetry messages received from the FUNCube-2 on UKube-1. I have actually received more but a fault in the warehouse meant a lot were rejected due to a incorrect data field.

The FC2 subsystem on UKUBE-1 may not be enabled on every pass while the satellite is commissioned and the FUNCube team will be releasing an updated dashboard shortly for when it is operating full time.

At present both satellites are passing one after the other, with UKube-1 gradually gaining. So as FC1 goes LOS (loss of signal) UKube-1 rises elsewhere for AOS (acquisition of signal)

On one pass yesterday I thought I would capture some screen shots and show how I've got the dashboard set up for both payloads.

As already mentioned the existing dashboard can be used to receive both FUNCube-1 and 2, if using the FUNCube Dongle Pro+ by setting the central frequency to 145.905MHz and adjusting the upper and lower filter curtains both payloads can be received.

On the Orbitron prediction software you can see FC1  is overhead, with UKube-1 over the North pole.


The reception window on the dashboard is limited by moving the curtains. I have the lower one set at 145.906MHz just enough to filter out the centre SDR spike,  the upper one is at 145.945MHz. The telemetry signal on FC1 is at 145.935MHz but due to the Doppler effect the received frequency will vary above and below this nominal value, 10kHz either size is sufficient to compensate.

If you were just interested in one satellite you would move the lower curtain to around 10kHz below the nominal download frequency. However since UKube-1 is on 145.918MHz the lower curtain is set to below this again to compensate for the Doppler shift.

The resulting receive window will allow both to be received. However this does risks problems should QRM occur in the pass band as the decoder can lock on to this, luckily the improved dashboard software discriminates between the signal and noise much better than previous versions.

The dashboard below is receiving the FUNCube-1 signal (click to enlarge)
 

The data is being uploaded and checking the real time display on the warehouse confirms this (my old callsign M6GTG) however you might not show up every single time and the FUNCube-1 Flight Model tab must be chosen as seen below.


As the pass finishes and UKube-1/FC2 comes overhead and due to the omni-directional X-50 I don't need to change anything.


The dashboard soon detects the new signal at the lower frequency and begins decoding.


The received payload ID is shown in the bottom right of the dashboard


Again the upload can be confirmed by viewing the real time data page on the warehouse by selecting the UKube-1 FC2 Payload tab. It should be noted that it seems FC2 is sometime sending spurious data elements in the telemetry which the warehouse is rejecting so some uploads may not be displayed.


It is really that simple.

Tuesday, 5 August 2014

Noises Off - WiMo QRM Eliminator

As I posted at the end of June I was almost on the point of giving up on HF due to the high levels of QRN/M suffered at home.

In desperation I had been looking at some of the noise cancellers available from MFJ and others. I had heard conflicting options on their effectiveness but was willing to try one if I could obtain one cheaply. The MFJ units are in my opinion expensive to purchase new so I bid on several that came up second hand on eBay but they invariably also went for silly money. I was even contemplating building an home-brew one from the numerous designs available.

Then I discovered the WiMo QRM Eliminator, made by the German company WiMo Antennas and Electronics. Several online reviews and numerous YouTube videos seemed to indicate its effectiveness and taking up the then summer discount offer I ordered one for the princely sum of €147 including postage, around £116.

Due to heavy demand and low stock levels following the International Ham Radio Exhibition at Friedrichshafen I was told the unit wouldn't be available till the middle of August, so I was pleasantly surprised when the unit turned up last Friday morning.
I have connected it up and briefly tried it out and am impressed, as this video illustrates.


Even using one for a short time I would agree that they are something of a black art to set up and use and can understand why people might consider them useless, but this may be due to lack of understanding of how they work.

I have created a diagram showing a typical scenario.

The operators main antenna is designed to pick up distant signals, not necessarily DX but signals not emanating from the immediate vicinity, however they will also pick up locally produced QRM as shown, perhaps generated by a neighbours TV or PLT device. 

The QRM eliminator has a second antenna which isn't as efficient as the main antenna and ideally just receives the local QRM at a similar level to the main antenna. The device then takes this second signal and inverts the phase so when it is mixed with the main antenna signal the QRM is cancelled out.

The principal is quite simple, if you take two in phase signals and combine them you will end up with a signal with a larger amplitude. However if the signal is 180 degrees out of phase, the positive and negatives of the waveform cancel each other, producing a null signal. 

The tricky part is making sure the noise antenna just picks up the noise, if it picks up the main signal then that will also be cancelled out. The WiMo unit has three controls a gain and two phase controls it is a case of altering all three to maximise the cancelling effect without losing the main signal.

At present I just have several meters of wire running as the noise antenna along the side of the shack and this seems to fairly effective.

The unit is powered from 12V and can be left in line, but requires the PTT/TX-GND signal from the CAT/Linear socket from the transceiver to activate a bypass when transmitting and I don't have the appropriate 8-pin plug at present. If the unit is powered off the bypass is automatically engaged.

All in all, first impressions are good and looks like a worthwhile purchase.