Author Archives: Gavin, M1BXF

EME Elevation System

May 3rd, 2013 | Posted by Gavin, M1BXF in General - (0 Comments)

So progress is being made on the elevation system.  We have the mechanical side complete, the controller/feedback had some issues but a solution is now sorted.


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You can see the milled and turned pieces of metal Dave M0VMC has produced for us.  Dave was on the 2008 DX’Pedition and has access to a wide range of tools.

The left round bar fits in the top of the Flossies mast with the 2 smaller bits forming a hinge when assembled (see left photo below), the larger bar is the lower Jackarm mount (see right photo below).  The Jackarm attaches between this lower bracket and a similar bracket attached on the upper pole where the antenna also mounts.  This means when the Jackarm extends then pole the antenna mounts on is forced to move  at the hinge point and thus you have elevation.

P1030288 P1030289

Control and Feedback

This was always going to be the challenge, you can see how much fun it was testing a few options by this photo

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There are 3 ways we could get elevation position feedback

  1. The Jackarm has a reed-switch and magnet in it which gives 1 pulse per revolution, count the revolutions for 0 to 90 degrees and you can calculate the position.
  2. Attach a potentiometer somehow to the hinge so we know the mechanical position of the hinge
  3. Use an accelerometer like the one Gavin M1BXF used for his own EME system.

Each of these systems have advantages and disadvantages.

Option 1 – Jackarm Rotation Pulse

There are 2 disadvantages to this option. First, due to geometry this system is non-linear.  When at 0 degrees (everything a right angles, right photo of the system on the grass above) an extension of the jackarm by 1 inch will say be 1 degree, but at 45 degrees or so then an inch of the jackarm might only be 0.5 degrees.  This can be calibrated out in code or a custom analogue meter scale.  The second issue is of the system is powered off when not at 0 degrees the when powered back up there is no way to know the angle and so the antenna must be elevated back down to 0 degrees  to get a known position.

Option 2 – Potentiometer

This would have been the best option, 0v on one side, 5v on the other and the wiper to an analogue meter.  However we would have had to machine the metal to allow mounting a potentiometer which we never done, maybe in rev 2 Smile

Option 3 – Accelerometer (MXD2125)

This is a known working design but needed modification to allow displaying the position as previously it was connected into a G6LVB rotator interface which only needed an analogue voltage.  In reality this was just a little bit of extra code which overall turned out to be the best option.

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This system will be made up of 3 elements, a box to control the Jackarm motor which is 12v, the outside box housing the MXD2125 accelerometer + PIXACE-18X chip which attaches to the pole above the Jackarm near the antenna and the display unit.

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The Jackarm extends or retracts by simply reversing the polarity on the motor.

A video showing the final assembly in action;

Gavin, M1BXF.

ICQ Podcast – S06E08

April 22nd, 2013 | Posted by Gavin, M1BXF in General - (0 Comments)

ICQ Amateur / Ham Radio Podcast

Series Six Episode Eight of the ICQ Amateur / Ham Radio Podcast has been released. The latest news, listener mailbag feedback and Martin Butler (M1MRB & W9ICQ) are joined by the Cambs-Hams to discuss their upcoming DXpedition to Mull.

Rob M0VFC, Lawrence M0LCM, Dom M0BLF and Gavin M1BXF chat to Martin M1MRB about the Mull2013 DX’Pedition, download the Podcast here: http://icqpodcast.com/download-the-show/2013/4/21/series-six-episode-eight-cambs-hams-dx-preview

Also covered in this episode;

Mull2013 Clothing

March 30th, 2013 | Posted by Gavin, M1BXF in General - (0 Comments)

Every year we go out and get branded clothing for the dx’pedition.  This year we changed supplier to RebelScum Workshop after one of our group recommended them to us and the decision was a very good one it turned out.  Not only was the price cheaper than the competition but the quality was fantastic and the detail much more.


The detail is the colour shading in out logo which was missing from our previous supplier, but RebelScum Workshop was able to provide. See the semi-circles around our groups name in the first images is solid yet in the RebelScum Workshop version below has shading.

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As a guide these are prices we paid, this was in volume (26 items in total) and include the logo on the left breast and name + callsign on the right;

Item Price
  SS11 Fruit of the Loom Pique Polo Shirt   £15.50
  GD57 Gildan Heavy Blend™ Hooded Sweatshirt   £21.00
  RG150 Regatta Uproar Softshell Jacket   £39.00
  FR1 Front Row Original Rugby Shirt   £24.50
  RS36 Result Active Fleece Jacket   £25.00
  510M Russell HydraPlus 2000 Jacket   £49.50
  GD52 Gildan DryBlend ®Sweatshirt   £18.00

Here is Gavin M1BXF showing the 510M Russell HydraPlus 2000 Waterproof Jacket.

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Something we also done new this year, which our previous supplier couldn’t manage was vinyl printing on the back of the clothing which allowed additional callsigns or logos, here is another example of what RebelScum Workshop could do, for an additional £1.50!

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If you are after items of clothing for a group you are in then give Martin at RebelScum Workshop a shout on info@rebelscumworkshop.co.uk – they do a lot more than just embroidered clothing…

IO76EJ Path Plots

March 28th, 2013 | Posted by Gavin, M1BXF in General - (0 Comments)

Just done a HEYWHATSTHAT plot of the Mull 2013 site, it looks good: http://www.heywhatsthat.com/?view=ATC92334


It shows that from North to South looks reasonably clear, much better for VHF than last year where Microwave Hill was in the way!

Mull 2013 Meeting #1 Notes

March 10th, 2013 | Posted by Gavin, M1BXF in General - (0 Comments)

So at the end of February we had out first meeting about this years dx’pedition.  All went well and I thought I’d post a few notes about where we are;

  • 472kHz is progressing – TX is transverted from 80m on an FT-817 with RX direct with FT-817; With noted from other stations we are making a 472KHz BPF.
  • We plan to modify the Camb-Hams trailer to allow us to take 2x SCAM12 masts giving more options for beams on HF.
  • The outcome of this is we will have a 15m mono-bander.
  • We are constructing an elevation system for Flossie’s mast so we can be more active on EME, however the moon conditions are not best that week.
  • There are 2 contests we plan to be active in while in IO76.

    • Sunday 12th May – 70MHz CW
    • Tuesday 14th – 70cm UKAC, we might go to a better location for this contest.

    We plan, when a band is not running or overnight, to run WSPR beacons so we can;

    • See when spots start to appear on the spotting network and thus know a band might be opening.
    • Allows us to see the propagation and antenna patterns to allow tweaking of our operation vs band schedule
    • WSPR beacons will also be run on VHF, that is 6m, 4m and 2m when they are not active also.

    More items where discussed but these are the main points which will impact on how we have QSO’s and might help you best work us.

    Request QSL via Buro

    May 14th, 2012 | Posted by Gavin, M1BXF in General - (0 Comments)

    If you are reading this then I hope we managed to work you while on Mull.  It was our best year yet for QSO numbers and we had lots of fun doing the DX’Pedition, speaking to so many people all around the world and we managed to work stations in over 100 countries without trying, DXCC it is then.

    If you did work us and wish to receive a QSL card from your QSO via the buro then we can save you the time and effort of you sending us one.  Making use of Michael G7VJR’s brilliant Clublog you can check your QSO history with us and then request a QSL card online, saving you sending us one.  This is not a replacement to direct QSL cards, which should still be sent via M0VFC, but it saves you and us time organising buro QSL cards.


    Use the search box to start.

    CQ BBC Radio Cambridge

    May 3rd, 2012 | Posted by Gavin, M1BXF in General - (3 Comments)


    So this morning Dominic M0BLF had a different type of sked to keep, this one was with Jeremy Sallis on the BBC Radio Cambridge breakfast show.  Dominic was live on the show just before 07:00 GMT.

    You can hear Dominic’s QSO with Jeremy on BBC iPlayer which starts at 1h55m32s into the program (the link should take you there).

    SOTA chasers

    May 2nd, 2012 | Posted by Gavin, M1BXF in General - (0 Comments)

    I’m loving SOTA chasers today. Just come back from an activation of Ben More, GM/SI-003 with my 40m CW rig. The first time I took it out I was worried that no-one would come back to me, and that my CW wouldn’t be good enough to actually work anyone.

    Three times this week I’ve called CQ on 7.030+/-, and every time someone has come back to me and patiently accepted my ropey morse code.

    While I love walking up mountains, you guys who keep the radio on in the shack and work SOTA activators deserve a shout.

    Thank you.

    GS3PYE/P (M1ACB) as heard at M0MVB QTH in Cambridgeshire

    May 2nd, 2012 | Posted by Gavin, M1BXF in General - (0 Comments)

    VHF Squares Worked (6m, 4m & 2m)

    May 1st, 2012 | Posted by Gavin, M1BXF in General - (0 Comments)

    As of 13:00z on May 1st 2012 here are the squares we have worked;



    Squares on 6m: IM57, IM58, IM59, IM87, IN50, IN52, IN53, IN70, IN72, IN73, IN78, IN83, IN89, IO62, IO63, IO70, IO74, IO75, IO82, IO83, IO85, IO86, IO90, IO91, IO93, JN37, JN58, JN76, JN78, JN99, JO01, JO02, JO20, JO21, JO22, JO31, JO32, JO33, JO41, JO43, JO48, JO55, JO59, JO62, JO63, JO65, JO66, JO72, JO77, JO79, JO80, JO81, JO82, JO83, JO90, JO91, JO92, KN09, KO02.



    Squares on 4m: IN89, IO62, IO75, IO82, IO83, IO85, IO90, IO91, IO94, JN79, JO01, JO10, JO20, JO21, JO22, JO30, JO32, JO33, JO45, JO46, JO48, JO50, JO54, JO55, JO65, JO70



    Squares on 2m: IN97, IO75, IO81, IO82, IO86, IO87, IO92, IO93, IO94, JN25, JN37, JN49, JN58, JN65, JN78, JO11, JO20, JO21, JO32, JO33, JO40, JO41, JO47, JO50, JO51, JO53, JO55, JO61, JO63, JO64, JO72, JO77, JO89, JO94, KO93, PM95