70 MHz Trophy Cup

The RSGB 70 MHz Trophy Cup ran from 11 till 5 on Sunday,  Team SNBCG assembled at the Kelvedon Hatch Secret Nuclear Bunker. The contest promotes activity on 70 MHz, but it just one of many contests run by the RSGB to promote activity on the amateur bands.

The beam was homemade, 6 elements on 70 MHz using a 4m boom.

Setting up

Checking the antenna

We used John M0UKD newly acquired Icom 7300 and George M1GEO Expert 1.3K-FA amplifier to provide 160w PEP. The contest exchange was a little more involved than some and included signal, serial, locator and first two letters of your postcode.

A 12m push-up mast provided the support for a homebrew 6e beam. The beam had recently been reworked with some new insulators and the boom has been split into 2 parts to facilitate easy transportation in the car.

We operated alfresco using a 2Kw Honda generator to provide the power for both the amplifier and radio.

The screen on the Icom 7300 looked very nice, and the waterfall was helpful in finding band activity.

The band had a fair level of activity, with a number of the regular contest stations evident on the bands. We managed to work 74 stations in 7 countries. England, Scotland, Wales, Northern Ireland, Gurnsey and the Netherlands.

Audio clip from working Alex GM4NFC (518KM)

Audio clip from working David GI4SNA (524 KM)

You can view the claimed scores online

A map of the QSO can be seen below.

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MFJ Versa Tuner III MFJ-962C review

The MFJ-962C is a high power 1.5kW manual ATU capable of matching balanced or unbalanced antennas typically from 1.8 to 30 MHz. It uses a T matching network, and the ARRL has provided an interesting article on “Getting the most out of your T match without snap crackle and pop


The ATU has a rating of 1.5kW, but this power rating must be taken as a guide, for example, try matching a 1/2 wave on 80m using 800w. The power rating will depend on the suitability of the antenna, and working on the principle that a poor antenna matched is still a poor antenna.





You have the possibility of 2 antenna positions, and a coax direct option allowing you to connect 3 antennae to your transceiver.The inductor in common with most ATU is switchable from A to L allowing you to select progressively larger {or smaller} inductance.

The capacitors are large enough to cope with the high voltages often found in a QRO ATU, and should with care provide many years of service. The internal quality of my ATU looks good, although I have found the level of finish does vary quite a lot of MFJ products. If you purchasing a similar product I would suggest you give it the shake test and listen for rattles.

The ATU is quite large, 27cm wide, 38cm long and 12cm deep.

The capacitors used are 12cm long by 6cm wide.





The case is made from aluminium and uses 12 screws to provide a rigid construction. I have used the ATU with a selection of doublet antenna, using my own 1:1 balun on many of the HF bands, power has often been at the UK maximum 400w without an issue.


The ATU has a cross needle VSWR and power meter, wth low and high power settings. The power meter can be adjusted with the pots inside the ATU, although I have found mine to be accurate. You also have an average or peak hold setting on the meter, this is helpful for SSB when trying to read the PEP.




12v can be used on the rear to provide a light in the metering, but otherwise, the unit can run without power.

The ATU was recommended to me from John M0UKD and purchased second hand, and its performed very well over the years.

These are no longer produced new but do come up for sale on Ebay or your local amateur radio store.

Here is a look at the high power 1:1 balun I use with this ATU.

You can download the manual for the ATU online.

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QRO portable from Cromer North Norfolk

I have always enjoyed operating portable HF as you can put up antenna and work bands not possible at home. This coupled with finding an RF quiet location can make HF portable very enjoyable.

Using a 12m spider beam roach pole, an 80m doublet fed with 300 Ohm ribbon cable and Icom 7100 I parked in a rural country lane surrounded by fields. The doublet was cable tied to the roach pole at around 11m, and the pole secured to a farmers fence.



The Icom, Expert 1.3KFA linear and ATU was placed in the boot of the car, and power was provided by an EU20 Honda generator. I started operating at 19:26 with the first call in the log G4JXC Bob from Bristol, signals seemed very good with reports usually over s9, sometimes s9+40.

At times I had a pile-up, really hard to pick out any calls, I did try and pull out a few QRP stations some running just 3 and 4w.

The amplifier definitely helped, but getting a large antenna in the air inverted V means a lot of the RF goes up in the air. Over the next couple of hours, I worked 57 stations in 10 countries. As darkness descended the skip did lengthen out a little, with stations calling me from Sweden, Germany, Spain and the Netherlands.


I was also able to monitor my own signal on my KiwiSDR located some 100 miles away. It was fun to work some stations that had also used my SDR, and also catch up with some people on twitter.


A enjoyable was to spend an evening, thanks to everyone who called.


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70 MHz Cumulative Contest #4

The RSGB CC run a series of cumulative contests through the year, you can partake in either a fixed station or out portable. I prefer to operate out portable, as this gives me a significant advantage to attempting this from home.

Using our contest site at Kelvedon Hatch SNB and with the assistance of John M0UKD we set up the following station.

12m Racal 714 push up mast

Homebrew 4e 70 MHz beam a DK7ZB design

Icom 7100

Honda EU20 generator

Expert SPA 1.3k FA Solid state amplifier

The weather was forecast to be dry and breezy and so we opted to set up in the fields overlooking the bunker and the mast. The contest ran from 3 till 5 pm, and with around 1hr setup time to organise the portable station, you can maybe see why some people operate from home. It’s quite a lot of effort for a 2hr contest, but on the positive side, you would expect the activity to be condensed into this short timeframe.

Setting up the beam.

The makeshift shack was constructed to keep out the wind, and the odd  spot of rain.

The beam worked really well, having very good directivity and F/B ratio despite its small size.

Over the course of the next 2 hrs, we worked 45 stations, in 4 countries. England, Wales, Guernsey and Northern Ireland. Our best DX was  GI4SNA at 527 KM.

You can view the claimed scores online.

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The Good the Bad and the Ugly Part 3

The good, the bad and the ugly Part 3

If you haven’t already seen this started with Part 1 and Part 2

This evening I tested 2 common micromagnetic aerials often used as quick fixes for using the handy in the car. The last antenna is a stubby found on the Motorola MT200 series handhelds, often used by amateurs for 433 MHz.

Our first micromagnetic antenna is around  300mm (12 inches) long and has the very lossy thin coax.The antenna surprising has a match point on both 145 and 433 MHz




You can see from the VNA plot it makes a good effort on both frequencies.

Our second micromagnetic antenna doesn’t fair as well, providing a poor match on 145 MHz, and a poor match on 433. It’s slightly shorter than the first version around 25cm (10 inches)

The VNA plot shows the match at both 145 and 433 MHz

Our last candidate is the stubby found on Motorola MT2000 handsets, these are often used on the 433 MHz amateur bands. The handheld and antenna look like this.

The antenna doesn’t do too bad on 433 MHz but it’s clearly been optimised for further up the PMR band.


It’s worth noting on 433 MHz using the very thin RG174 coax you should expect to lose 50% or more of you power before it even reaches the aerial. Yes, they will often work better than the stubby in the car, and they may very well do exactly what you want for local repeater access but it’s worth knowing the limitations.


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50 MHz Trophy Cup

I once again took part with the in the 50MHz trophy cup with the SNBCG, the contest runs for 24 Hrs from 3 PM on Saturday. This year the contest had been booked for one of the hottest days of the year, with temperatures reaching 30C (around 220F in old money)

We set up Saturday morning,  using the 5e 50MHz beam and a 10m pump up mast.  A solid state amplifier provided 400w and a light weight tent to keep off the sun.

The most important issue throughout the weekend was trying to keep cool, with copious cold drinks from the fridge. Fred G3SVK was kind enough to lend us a fan and this became an essential item for the shack.

Fred spent some time operating on CW, working mostly EU with the odd notable exception.

In total, we worked 250 stations, with our best DX being 5B4AAB at 3161KM. You can view the claimed scores here and map here.

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© 2015 Dave, M0TAZ