Thursday, 26 March 2015

I am now the Chairman of a radio club!

Firstly my apologies, last weeks post about the Eggciting Eggsplorer-1 HAB project and the talk and demonstration on SSDV wasn't posted on Amateurradio.com due to an error.

This week South Kesteven ARS (SKARS) held an EGM where I was voted on as the new Chairman. Nigel Booth M0CVO has stepped down following four years in the position citing increasing business commitments. Nigel intends to remain an active member, I and the other members wish to thank Nigel for his efforts over the years and wish him well with his business ventures.

SKARS has a small membership at present which we hope to increase but the committee finds itself in the  Catch-22 position of not having a lot of funds in order to put on activities and promote ourselves to increase the membership.

I have created a social media presence in the form of a Facebook page and twitter account in addition to updating the societies web page.I am hoping that permission willing the GB2EGG and Eggsplorer-1 project will significantly promote the society and the hobby.

I know running a club/society isn't a trivial undertaking, especially if working full time having chaired a large dog agility training club many years ago. It can take a lot of effort and time and it can sometimes be a thankless task.

Indeed my first twenty-four hours has Chairman saw my first sacrifice, a lovely Yaesu FT-450D was delivered yesterday and I have yet to take it out of the box!

 
Something to be remedied this evening.

Friday, 20 March 2015

Eggciting HAB projects

I have a new high altitude balloon project, this one is very Eggciting.

In June my club South Kesteven Amateur Radio Society (SKARS) will be operating a special event station at the Swaton Vintage Day held at Thorpe Latimer in Lincolnshire. 

The 2015 Swaton Vintage Day will also host the 10th World Egg Throwing Championship  and in recognition the special event station will have the call sign GB2EGG. This popular annual show raises money for local, national and international good causes.

Egg Throwing is recognised by the English Sports Council and the sport is taken very seriously by some competitors. Hundreds of competitors from Europe and around the world are expected to compete this year. Last year’s event attracted teams from Germany, Slovenia, Hong Kong and Brazil.

While planning the special event station I jokingly suggested throwing an egg in to space on board a balloon, I shouldn't have yoked as it is now a serious project. The idea coming from Dave Akerman's Spudnik flight for Heston Blumenthal’s Channel4 television program.

Image with the permission of Dave Akerman
Subject to Civil Aviation Authority clearance and weather conditions I will hopefully launch a high altitude balloon carrying one lucky egg into the edge of space and then dropping it back to earth under a parachute. In addition to the plucky Eggstronaut the balloon I have called Eggsplorer-1 will carry a radio transmitter to broadcast its position, altitude and live images of the journey back to earth.

On board cameras will record the journey to be recovered on a successful return to Earth. Radio enthusiasts all around the country will be able to assist receiving the data and pictures and track the progress of the flight via the UK High Altitude Society tracking website.

More details and progress will be posted on here and on the Eggplorer-1 website  and you can follow developments on twitter @eggsplorer1 South Kesteven ARS welcomes anybody with an interest in radio communications, so if want to be involved in this and other events like this please visit us at the show or visit the South Kestevan ARS website and on twitter @M0SKR

I have already begun development of the payload, unlike the moth-balled NERD-1 payload this one will use one of the Raspberry Pi boards since I want to transmit SSDV images live and it supports its own specially designed camera modules. NERD-1 will still fly as a backup tracker.

Dave Akerman (M0RPI) and Anthony Stirk (M0UPU) have developed the Pi-In-The-Sky ready made boards and the design and software are open-sourced, using this as a starting point together with Phil Heron's (MI0VIM) SSDV software I quickly had a prototype dubbed NERDPI running.


I did have an issue since the GPS module I currently have only outputs serial data so had to use one of those small TTL USB-Serial adapters and spun some of my own code to get the data out and was soon successfully decoding my own transmissions from the shack and uploading them to the Habhub system.


Today has seen the spectacular partial solar eclipse here in the UK, during the eclipse several HAB flights were launched to try to capture images above any cloud cover (details here)  Fellow SKARS members and members from the Grantham ARC were keen to decode the SSDV images themselves as the BBC Stargazing Live balloons were flying from nearby Leicester.

So on Wednesday I did a talk and demonstration to show how to track and decode the images, it was well received and I uploaded pictures of the audience to the system.



Unfortunately technical issues prevented live images from the Stargazing HABs being transmitted but I was able to decode some images from the University of Southampton OLAF payload They were only lo-res but still pleased to get decodes here it was a good distance from me.

Here in Newark the sky was beautifully clear so the eclipse was visible and spectacular, where OLAF was flying was covered in cloud, so the mission was a success.







   

Thursday, 12 March 2015

A dark cold evening in a layby

True to my last post I drove out to some higher ground to operate portable for the 70cms UKAC on Tuesday evening.

Several hours sitting in the car on the side of a deserted road in the dark and cold was worth it. Despite some initial trepidation I really enjoyed the experience until I got spooked at the end.

Like the last time I operated from this location I put the small yagi approximately 3-4 metres up on the top of my 'painters' telescopic pole stuck in to a parasol stand. I sat in the car and reached out the open window to rotate the pole as required. I wrapped up well and had a blanket over my legs and a woolly hat on and kept surprising warm despite it being just 1°C, turning the courtesy light on only when I needed to write in the log.

It was nice to be noise free and I made 29 contacts, nothing earth shattering but with a modest set up and operating in the AL section (10W max) I was more than happy and got my first contact in the Isle of Man.


From the reports posted on line it seems conditions were flat and activity was low. Frustratingly several times I found a distant station only for it to be drowned out by splatter. I know some of this is down to my radio and the antenna but the source is nearby and so strong that even turning the beam makes little difference. Ironically being higher up meant the signal was even stronger than I experience at home.

The annoyance is compounded by the operator's habit of regularly changing calling frequency seemingly with little regard of who is currently operating there. This SDR screen capture shows an example of the same contesters signal during a recent 2m UKAC. Captured using a vertical collinear several strong clean(er) signals are clearly visible even with the mismatched polarisation. Sadly it is not a one-off and I have observed similar splatter from this source during both 70cms and 6m contests.



It was very dark and eerie on the quiet road and I'm afraid I got spooked with 20 minutes of the contest left, a 4x4 drove past slowly and appeared to shine a spotlight at my car. I was midway through a QSO writing in the logbook so I only caught it out of the corner of my eye so wasn't sure if they did. But a while later I saw what looked like torch beams moving in the nearby field that seemed to be getting closer. In retrospect it was nothing untoward when I checked the map later there are farm buildings in that direction but I've seen one too many horror films so decided not to hang about so threw everything in the car and headed home with out looking back..

you can't get rid of the Babadook
.... you'll see him if you look 

Tuesday, 10 March 2015

Operating /P for the 432MHz UKAC tonight

The 432MHz UKAC contest is usually a pretty dismal experience for me, low elevation, local noise and a mediocre antenna makes for a difficult evening. Last weekends VHF/UHF contest and some tests with fellow club member Stewart​ (M0SDM) on Sunday evening convinced me to try operating portable this week.

I have a small Moonraker 7-element ZL-Special on the main antenna mast, purchased originally for monitoring satellites and was pressed into service for SSB when I got licensed. It has never wowed me performance wise and I have been intending to replace it for quite a while but since I only use it one day a month it hasn't been a priority. So the mast came down last night and I removed it so I can take it out with me to operate portable from some higher ground tonight.

Using the 2m delta beam in June 2014

Last year I had a go at operating portable from the car and posted a write-up. It is my intention to repeat this exercise but with the 70cm antenna on top of my 'painters pole' mast. I have serviced the antenna and fitted a new short run of quality coax and spent a far amount of time with the AW07A analyser adjusting the antenna's tuning capacitor and have got the VSWR right down to 1.1:1 on 432.200MHz so things should be optimal.

I am looking forward to this evening, hoping it pays some dividends.

As I mentioned the 24 hour March 144/432MHz VHF Championship contest took place last weekend. I took part to give away some points just grabbing a few short sessions with the radio. I concentrated on the 2m band due to my issues on 70cm.

In my AW07A analyser review I mentioned some issues with my 2m LFA YAGI, thankfully these have been resolved. The use of some wire wool to remove some corrosion and a hacksaw to take 10mm from the long elements of the loop allowed the end elements to 'trombone' in sufficiently to get the antenna resonant and the VSWR is down to 1.2:1 on 144.300Mhz.

I only made 18 contacts, but was happy with the distances achieved with 30W, getting a lot further south than I normally do, given I am 18m ASL. There was also some local wideband noise (I captured a screenshot on the SDR) and the conditions gave some interesting fading.

M0NRD QSO map March 144 VHF

Noise across the band



   

Monday, 23 February 2015

More SSTV from the ISS

Like many others around the globe I spent yesterday attempting to receive and decode the SSTV transmissions being broadcast from the International Space Station by the Russian Cosmonauts.

The SSTV activity had been due to last three days starting on Saturday but commencement was delayed by the NASA space walk.

Receiving the signal and decoding is relatively straightforward due to relatively high power used (around 25W) however getting a perfect image is a challenge and dependant on a number of factors.
  • The timing of the overhead pass. Due to the time taken to transmit the image and the three minute delay between each image it is possible to only be in reception range for the end of one image and the start of the next. 
  • The ISS is moving quickly and so the transmission suffers noticeable Doppler shift. FM is more immune to the effect but for optimal performance adjustment of the tuned frequency is required especially on high elevation passes (more information).
  • The ISS moves position, both in direction and elevation as it moves across the sky and will show up the peaks and troughs in a static antennas radiation pattern. This leads to bands of noise when the signal level falls. The use of a rotatable (and if possible tiltable) antenna (or even an handheld one) is the dirigour mode of operating satellites (and the ISS) for serious enthusiasts. 
  • Noise and local interference will also obviously affect the image.
Mission Control

I opted a two pronged approach, the Yaesu FT857D connected to my rotatable four element YAGI which is mounted horizontally for SSB and the old TRIO/KENWOOD TR9000 was connected to the X50 dual-band collinear mounted vertically.


I had two copies of the MMSSTV program running on separate laptops The TR9000 was left running largely unattended tuned to 145.800MHz, while the FT857D was tweaked to the optimum frequency while the YAGI antenna was rotated to the correct azimuth during the pass.

All adjustments were done manually and I use the Orbitron program for prediction and under the Rotor/Radio tab the frequency and azimuth are shown and updated during the pass (as can be seen in the screen show below)


I missed the first low elevation at 11:07UTC, but was able to monitor and decode images on all the remaining passes during the day, with some excellent results, the images show the full images decodes on both radio set ups as a comparison.

FT857D - Yagi

TR9000 - Collinear

FT857D - Yagi

TR9000 - Collinear

FT857D - Yagi

TR9000 - Collinear

FT857D - Yagi

TR9000 - Collinear

FT857D - Yagi

TR9000 - Collinear

I was especially pleased when one of my best images was featured on the Amsat-UK and the Southgate Amateur Radio News websites.

What was slightly worrying and it also happened during the last SSTV activities were some operators transmitting on the downlink frequency even during a pass, what sounded like someone keying up was responsible for the single noise line on another perfect image. I even received an unexpected SSTV image, complete with a call sign while the system was waiting for the next pass. I won't publish it here as everyone makes mistakes.

The experiments are continuing today but I am in work so will just leave an automated set up running on the collinear.

Judging by the messages on social media these SSTV activities seem to have captured the imagination of a lot of operators and several members of my local club South Kesteven Amateur Radio Society (SKARS) had their first go with some excellent results and are hooked! The images can seen on the SKARS Facebook page

Long may the activities continue, hopefully started to transmit some live images from space.

Tuesday, 3 February 2015

Repairing a Kenwood TR9500, Part4

The troublesome TR9500 has developed another fault, well it has likely had this fault since I've owned it but I have only just spotted it.

After making repairs to the microphone amplifier and the receiver pre-amplifier the rig seemed to be working fine, I'd even used it several times during the UKAC contests with some success.

The 70cm band is under used locally and activity seems largely restricted to repeaters. Due to it's vintage the TR9500 doesn't have CTCSS tones and so cannot be used to access repeaters without some modification and I've been looking at adding a CTCSS board.

In the meantime I really wanted to use the TR9500 a bit more and was hoping to make it part of a satellite station, the TR9500 acting as the UHF uplink transmitter (LSB) and the VHF 2m TR9000 as the downlink receiver (USB) for the AO73 (FUNCube-1) and other satellites.

The satellite portion of the band plan is at 435-438MHz and it was when setting this up I discovered the TR9500 neither received or transmitted in the upper part of the 70cm band (435-440MHz) below this everything was hunky-dory.


It hasn't taken long to locate the issue, the HET unit employs two crystals L33 (36.6222MHz), L34 (37.1777MHz) which are switched in to the oscillator Q1 depending on the selected frequency. L33 being referred to as low band, L34 as high band the switching occurring around 435MHz.


The switching HL signal (via R10) and transistors Q3/Q4 are working correctly it is just crystal L34 is not resonating. The surrounding diodes, capacitors, inductors and resistors all look fine, no obvious shorts or broken joints.

I have to do some more diagnostics to rule out any of the passive components but if it is the case that the crystal has failed then it may prove difficult to source an economical replacement.

Sunday, 18 January 2015

Feature Tech AW07A Antenna Analyser - First impressions

Christmas seems such a long time ago and one of my presents was a Feature Tech AW07A HF-VHF-UHF Antenna Analyser which I have finally been able to try it out.


It is about the size of a thick paperback book and is a powder coated steel case similar in style to that used by MFJ equipment, indeed the MFJ-266 analyser appears to be a re-badged version albeit for a lot more money than this unit can be purchased.

It can be powered by batteries fitted internally or by an external supply and is supplied with a power cable for connection to an external supply, mine was white/black rather than the normal red/black cable. It has a N-Type socket for the antenna and comes with two adapters for PL259 and BNC connectors.


It has a power button near the external power socket, two buttons on the top select HF and VHF/UHF operation and two other buttons marked UP and DOWN to select operating mode and/or the frequency band being used. Unfortunately one thing it doesn't come with is a manual but a copy can be downloaded from QSL.net or a slightly different version from the manufacturers website. But I actually downloaded the manual for the MFJ-226 has it is much more detailed.

The front panel decal and manual state it can be run from 10.8-12V, in fact the manual states it should ideally be less than 12.5V and no more than 13V. While doing some research I found the reason for this limitation hidden away on this aliexpress webpage "Avoid higher than 13V power supply circuit for the UV segment may be damaged due to excessive power dissipation." So this would seem to rule out using a standard 13.8V power supply.

It can be fitted internally with eight AA batteries and this is the way most people would use as it offers portability. Removing four screws allows access to the battery compartment and the internals electronics seem well built.


It takes eight AA batteries, in two boxes. The battery boxes have lids secured with a small screws and are fixed to the case using simple sticky pads, while secure at the moment I can imagine in time the adhesive could dry-out and become unstuck leaving the battery boxes loose inside the unit.


The display is a simple two line LCD with an optional bright back light which can be turned on during the power up sequence. The display shows the battery or supply voltage and pressing Down puts the unit into a frequency counter mode. Pressing Up puts into the antenna analyser mode.


In the analyser mode it is a simple case of selecting the HF, VHF or UHF mode. VHF works from 85-185MHz, UHF is 300-390MHz, the HF is split into six overlapping bands A: 1.5-2.7 MHz B: 2.5-4.8 MHz C: 4.6-9.6 MHz D: 8.5-18.7 MHz E: 17.3-39 MHz F: 33.7-71 MHz selected using the Up/Down buttons.

Turning the vernier  tuning knob adjusts the generated frequency the antenna is being tested against. I connected the analyser to my 2m YAGI antenna and turned the knob to find the lowest SWR


The manual describes what is being displayed (on UHF just the SWR is shown)

“139.763 MHz” is the frequency
“V “is the band (A,B,C,D,E,F in HF, V in VHF and U in UHF)

The bottom row shows the complex impedance Z = R + jX, so on this screen 

“41” represents R = 41 ohms the resistive component
“18:” represents the reactance component value, jX = 18 ohms
“45” is the overall complex impedance magnitude Z = 45 ohms
“1.5” is the SWR value

As you can see for a 2m antenna something isn't quite right! The antennas were down due to last weeks strong winds so I was taking the opportunity to do some maintenance and tweaking of the 2m antenna since I'd seen an increase in the SWR during recent UKAC contests. I had suspected feeder issues, possible water ingress but I tried a dummy load at the antenna end but that read as expected (Z=50ohms) and metering the continuity of the feeder showed no issues, it just seemed to be resonant at too low a frequency.


The analyser confirmed what I'd observed with a normal SWR/Power meter a higher than desired SWR in the middle of the SSB section of the 2m band.


Unfortunately I was unable to get it any lower than 2.5 and most adjustments seemed to increase the SWR.  For peace of mind I double checked the analyser by swapping the feeder on to the 2m/70cm collinear and that was spot on


again I double checked the SWR readings back in the shack using the normal meter


While I try to sort out the antenna issue I can say the analyser seems to do its job well. The tuning knob is a little twitchy and has a bit of play which makes setting the frequency accurately a little harder than it should be but hopefully that might improve with use.

The unit also has other functions none of which I have used yet but it is bonus to have some useful test functions available in the shack.

The AW07A can be used as an inductance/capacitance meter by powering it up with the U or D button held down. The inductance or capacitance of a component fitted across the antenna socket is then displayed and this can be done for any test frequency by selecting the band and turning the tuning knob.

As I mentioned earlier the unit can also function as a frequency counter that can measure signals between 1 and 500 MHz and can be used to give an indication of relative RF field strength. A signal source or an external antenna that yields a usable signal level may be connected to the analyser’s antenna jack. The usable signal range is quoted as -20dBm (30mV)  to +10dBm (1V). Note that the display reading is a RMS value.

Obviously in the antenna analyser mode the output which is approximately 2V in magnitude can be used as a signal source, with 20dB of second harmonic suppression. 

The MFJ manual goes into some detail of how this all works and how to use the analyser for a number of common tasks such as checking baluns, making 1/4wave stubs or measuring velocity factor of coax.

While the AW07A has some obvious shortcomings and may not be a precision device I am impressed with it and what it can seemingly do. It is shame about the lack of a manual but I am not sure getting one is justification for the premium price of the near identical MFJ unit.