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Archive for March, 2016

Making Waves–White Noise and Woodpeckers

Well, here we are, half way through March 2016 and looking forward to the sporadic e season on the 6m band.  Quite looking forward to some 6m DX this year now I have the hybrid quad up.  However, currently when listening to the 6m band all that is heard is white noise.  Nothing, it seems, is getting up this high in the Northern Hemisphere as yet.  Will keep monitoring it though as you never know when something may break through – especially on the magic band.

Then we get onto woodpeckers.  Pretty little birds that tap the bugs out of tree trunks and nest in holes but very little to do with radio… Wrong woodpeckers, what we are speaking of is the Over The Horizon Radar (OTHR) that keeps popping up on 15m at the moment.  In the past both Russia and China have been guilty of using high power OTHR on the amateur bands producing that familiar tapping / knocking sound but now I believe the UK and the USA are as guilty.  Anyway, on Sunday afternoon I was trying to work a station from the Democratic Republic of Korea (nice DXCC) when up it came and totally wiped out the portion of the 15m (21MHz) band being used.  This has been heard on other bands also and was commented on by some twitter users at the weekend.  So much for international IARU agreements banning the use of OTHR in the amateur bands. 

Have been busy designing some 5th Order Low Pass Elliptic filters for 40m (7MHz) and 20m (14MHz).  These are done with SMD technology – coils with a physical dimension of only a few millimetres in length and 1.2mm across. Whilst certainly not aimed at the QRO operator they will be fine for very low power (QRPP) transmitters such as those used for WSPR or QRSS beacons.  It is an ongoing project at the moment so no photos of completed units but I do have some graphs – one of which is at the bottom of the page showing the 7MHz filter properties. 

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Making Waves: DX Power

March 5, 2016 1 comment

For many years now I have been a radio amateur.  I started out in the 90’s as a B licence holder (M1DKN) (VHF, UHF and above) and then, in 2000 took and passed my 12wpm Morse test and gained my HF licence (M0CVO). 

As M1DKN I enjoyed some relative DX from difficult locations building and using quad yagi antennas and ZL Special antennas, once managing Cromer (Norfolk) to Moscow via strange tropospheric propogation and Cromer to Caithness Lighthouse via auroral scatter.  Being limited to VHF and above certainly encouraged one to learn as much as possible about weather systems and phenomena to enhance communication.  Getting as much power into the antenna and then out of the antenna into the air was also crucial so one made sure that the coaxial cable or feeder of choice was of the highest quality and lowest loss.  It also gave one encouragement to build and test various antennas to obtain the highest gain and best results.

Then I got my HF licence and this opened up the rest of the world for me (as far as spectrum went).  Due to restrictions (garden size, local authority, planning, etc.) I have always limited myself to wire antennas that could be called “stealthy” but I still managed to work most of the world even though it was sometimes a struggle.  This proved easier to do using CW (Morse) or, occasionally, other data modes such as PSK or JT65.   However, I was never really set up as a DX station.  Recently I looked at the situation and decided to give something new a try.  So I obtained an HF beam.  Actually, it is a mini-beam as I would not be able to fit a full size HF beam (even for 10m) in my small garden without it overlapping the neighbours’ properties on either side.  The beam in question is the TGM Antennas MQ-1.  This is a four band beam for 20m, 15m, 10m and 6m.  The longest element is 11ft (3.35m) and the boom is 4.5ft (1.37m).  The reflector is a hybrid quad element in a diamond shape that stands 48” (1.22m) high.  Tuning is done with a series of coils and capacitor caps consisting of adjustable spokes.  Total weight is 16lB (7kG).

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The MQ-1 in place beneath the 144MHz 10element Yagi

Performance wise it is astonishing.  First contact was with NC1I at 57 / 59 on 15m and then with VE8EV on 20m (59/59).  The quoted gain figures are:

6m: 6.5dBd, 10m: 6.0dBd, 15m: 5.5dBd, 20m: 4.4dBd.

Going by the performance and comparing with a straight dipole I can well believe that they are correct.  So now I have a good DX setup and with the 300W linear that I occasionally use should be able to work some of those rarer stations.

Have a good weekend and good DX.

73 DE M0CVO.

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