Monthly Archives: December 2013

New Baluns for Flag Antenna

I recently revamped my Flag antenna which has served me so well for MF dxing in this very suburban London location. It was around 8m by 3m but I made the vertical sections longer and the horizontal section slightly longer as well so it is now 9m x 4m.

The major change was that I constructed a balun. I had been using a balun made for the Flag antenna by eBay seller kafa2500 which was well made, waterproof and reasonably priced – however i thought I would have a go myself. In the end I ended up making two baluns which i’ll describe and show here.

Remember the purpose of the balun is two fold – primarily to transfer the wave energy of the desired signal from the antenna to the feeder cable – RG58 in my case. The second purpose is to prevent common-mode currents flowing along the balun which could cause RF problems in the shack. The latter is not an important consideration for the receive only paradigm. The balun will not help with directivity or nulling. The energy is transferred by the balun using magnetic induction which is a manifestation of the Work form of energy transfer  –

The first balun was constructed using a pair of largish monocular toroids picked up a the Kempton ham rally, bound together in a box picked up for £1 at the same rally. The windings ratio is 11:3 using 24 swg magnet wire from Maplins. I was intending for 12:3  following advice from N2VV but could not get the 12th turn through! Believe me it’s not critical.  The SO239 and phono antenna sockets I had in stock.  Here’s a close-up picture of the beast: 


and here is how it looks with the box top screwed down- all connections are wrapped with self-amalgamating tape with black electrical tape on top and liberally smeared with vasoline to further combat water ingress, especially the box top screw holes.


For context a picture of the garden showing part of the Flag antenna wires and balun box:


This new Flag antenna works very well with excellent signal/noise characteristics from LF up to 26 Mhz and beyond. It also delivers a decent signal strength hence not necessitating the use of a pre-amp.

I also made a similar balun with an Amidon binocular toroid BN-73-202 kindly sent to me by N2VV. The BN-73-202 is very highly thought of by serious low band dxers. I aimed for  the same turn ratio but think I ended up with 10:3 – again it works very well but for the moment I am long-term testing the larger toroid model. Here’s a picture:






I think the reason people complain about low signal strengths from Flags and lack of coverage above 4-6 MHz is purely down to the choice of toroid and the turns ratio used. You can’t just use any old toroid and a random turns ratio – source a proper high quality toroid and use an appropriate turns ratio.


How to be a Successful HF Dxer Part II

Welcome to the second of an irreverent and not too serious look at how to be a successful HF DXer.  Last time we look at how we defined DXing, what is a DXCC entity, band slot and the fundamental steps you need to take to start DXing. Today we’ll look at how you cam maximise your chances of filling bands slots.

The DX Cluster is a much abused but very useful tool to see what DX is on the bands at any moment. The Cluster is simply a list of DX stations, their frequency, time spotted (you always “spot” to the cluster), the spotting station and a comments field. Originally this list was propagated by packet radio on 2m – however this method has now gone the way of DR-DOS (i.e. obsolete but one of two people still run it and consider it to be the future). 99.9% of people now access the Cluster using an Internet connection. Technically the Cluster program is a telnet application (you what?) and it really comes into its own when you have an always-on broadband connection. Run the cluster 24/7 and you will have a record of what has happened and what is happening at the moment on the bands.

I’ll not explain the details of how you set up the Cluster program here but googling DX Cluster will give you loads to read and going to will fast track you. The ve7cc program is the one I use so help is available if you go that route.

You will need to “filter” the spotting stations or else there will simply be too many station spots on the screen to comprehend. I always set my filters so that US and Canadian spotters are excluded (too many of them, I’m not interested that Japan can be heard in Iowa,…) along with Italian spotters (too excited, always spotting that North Korea is 59+60 on top band at noon). You may think it is a wise move to only allow UK spotting stations – it is if you want one spot every 10 hours.

The Reverse Beacon network (skimmer) has really taken off in the last two years. These are automated programs that decode stations sending CQ using CW, RTTY or other digital modes and report them. ve7cc contains an option to turn on these skimmer spots so you can get an immediate indication that a station is on the air even before it is spotted by a human. Some people don’t like this degree of automation – however it can give you 30 seconds advantage to try for a station before the EU pack descends and chaos reigns in the dx zoo.

Let’s move on to Contests. Yep, those guys shouting 59 569 all over the bands when you just want to chat with your mate in the North about your latest hospital appointment (you have heard about telephones?).

Contests are very useful to the DXer as the good contests mean that a lot of stations will enter including rare DX stations. The QSOs are quick and especially on the 2nd day of a 48 hour event you can often work the DX station on 1st or 2nd call as the big boys will have bagged him by then. Contests take place on all the HF bands except 30m, 17m and 12m (so-called WARC bands – google it Joe).

You can safely ignore all the RSGB contests (working loads of G3s will not improve your DXCC count) with a couple of notable exceptions. The Commonwealth CW contest in March is your best chance to work VK, ZL etc with NO EU QRM. The contest is limited to Commonwealth countries and try as they may to persuade the DX station otherwise Italy and Ukraine are not in the Commonwealth. Hence Luigi and Vlad have to sit and weep at their 10KW stacked yagis station while you work ZL3 with a Yaesu 817 and a miracle whip (ha ha!). Even if you don’t do morse you can use programs like cwget and cwtype to decode and make the exchange (again google them Joe).

The other useful RSGB contest is the IOTA in July which normally has a big turnout of stations on islands – some from exotic locations like Anglesey. Oh no, wait the IOTA committee in its infinite wisdom don’t consider Anglesay to be an island while the UK is…

Good places to see what contests are on are and

Well if the Cluster and Contests don’t improve your DXCC score there’s always your local 2m/70cm  to play with. Bip Bip!

Radio North 846

Radio North 846 from the Irish/Northern Ireland border area (Donegal?) is a consistently good signal into London these days. It is audible from mid-afternoon and as late as 09/10.00 in the morning.

Here’s how it was sounding this early evening just after 18.15:

If YouTube has blocked the video due to the brief Glen Campbell song then try this one:

The signal is so consistent it is my MF beacon with which I test the Flag antenna and various baluns.



Rare Peruvian Radio Carraviz heard in London

Yesterday I heard the rare Peruvian Radio Carraviz OAU72 from Juliaca at 0357 on 1570 kHz following a tip-off from Paul C:

Despite the distorted audio you can clearly hear the “La Voz de la Liberacion” id at 03:57:55. Receiver as ever was the Perseus SDR and a 10x4m Flag antenna with home-brew dual binocular toroid balun.

Beauty of MF dxing is that you never know when a new rare one will pop up. Normally 1570 is dominated by the Canadian French popster CJLV out of Laval. If Latin America dominates it is usually Bethel Radio from Lima.