Two Flags For The Price Of One!

Being a greedy DXer I like to have it both ways - I like to have an antenna towards Asia and another towards the Americas. :O) That's not easily achievable at the new QTH. Although we have lots more garden space than at our last QTH, the gardens are narrower. Well, you can't have everything. Or can you?

 

     Asian flag antenna at 028 degrees                 North American feed at 355 degrees    

Flag antennas are usually fixed, with the vertical sections being anchored. Moving the flag is not one of the easiest exercises in the world. OK, it's not the most difficult either, but it takes a good hour or more, Sod's Law permitting, for me to relocate my flag.

Some DXers have constructed their flag antennas on a large wooden frame and plonked them on a rotator. Nice if you have that kind of room. No section of our garden is quite wide enough to achieve that, so I had a good think about how I could have two flags for the price of one. This part was actually quite simple, but I wanted to experiment by having an additional wire connected in order to make the moving part simpler and assess its impact on directivity.

 

'Portable' Asia feed on the left. Fixed resistor box on the right. Click to enlarge

Some basic info to recap. The flag antenna, also called a 'ewe' and sometimes a 'pennant', is a unidirectional antenna with a low reception angle. It's been a must-have for medium wave DXing for me for years and out-performs the loop, the ALA1530 and even has similar reception characteristics to those of a Beverage. The front lobe is fairly wide, accepting a good 50 or so degrees spread, but the rear null is also wide, and usefully consistent across the whole medium wave.

My existing flag was pointing at 28 degrees, based on figures obtained from Google Earth maps. 28 degrees points straight at Japan from here. I needed a second flag at around 300 degrees for west coast North america. Providing I could permanently anchor one end of the flag to the wooden garden fence, I could make the other (feed) end by ensuring it can be lifted from its moorings and carried to another mooring point in the desired direction. That bit was easily achieved. But what about the connections?

The use of a few banana plugs and sockets would make the job much easier, only I didn't have any. Time to call in that infamous duo Bodgitt & Scarper. Connections aside, I wondered if I could have two base wires connected at the same time in order to make the move simpler. The existing 28 degree base wire was buried behind plants and bushes, so I left that in place and affixed an additional base wire to the other anchoring point. This made no difference in the reception and directivity AT ALL! I used my usual checkpoint, semi-local BBC Radio Cambridgeshire on 1026 kHz. I can get this right down in the noise. The null was unaffected by the second base wire. From all measurements and recordings taken I could not see any differences whether the second base wire was connected or not. So now, moving the flag to its North American direction could be easier than ever! All I had to do was lift one end of the flag from its moorings and plonk it in the other. 30 seconds and two simple connections later and my Asiatic flag becomes a North American flag.

A DXer recently asked me what effect the base wire had when it was lifted off the ground and how did this affect reception when the base wire was lying on the ground. Well, the answer is another simple one. It is only the vertical sections of the flag which have the pick-up. The directional effect is achieved by phasing the vertical sections against each other. The horizontal sections are not supposed to receive anything, so it doesn't matter if the top wire sags a little, etc. I tested this further by lifting the base wire slightly above the height of the bottom of the vertical sections and I didn't notice any difference. I even extended the bottom wire so I could direct it in some grooves in the concrete path on the garden so it could be hidden and, again, it made no difference.

Whether there are any differences on paper when making these adjustments to the base wire I do not know. Perhaps somebody could model this. There may be something of course, but I did not observe any detrimental effects while carrying out these experiments. Also bear in mind I am not a 'techie' so my apologies if I have stated anything incorrectly above. I am a Bodgitt & Scarper man and proud of it! If it's help together with sellotape and it works well I don't care too much.

BUT ... since the vertical elements of the flag are the crucial part, ensure these really are properly vertical and straight as this is what helps you achieve those nice deep nulls. You will benefit by NOT employing Bodgitt & Scarper tactics on this part.

Keep the supports absolutely vertical if you can

To clarify, this is one flag antenna and not two. I merely move one side of the flag to a different location in order to make the most of two different directions. 355 and 028 degrees are fairly close for an antenna with such a wide forward lobe, but there is a clear difference in reception, so this has been a worthwhile exercise.