BiCraft“Bundu Basher”
40metres to 10 metres Long Wire Antenna [Aerial]
The“Bundu Basher” came into being because of a need for an extremely simple antenna that could be used by caravaners, campers, holidaymakers, and even an almost invisible device that could be used in a retirement village complex, as a fixed antenna, where no big antennas or towers are allowed.
This antenna is so simple; it consists of a matching toroidal transformer built into a waterproof ABS plastic housing, a radiator wire of about22 metres long, a counterpoise wire of 4 metres long and a SO239coaxial socket to feed the transceiver. Please note that only 40m,20m, 15m, and 10m can be used, as they are harmonically related, for other bands – use an antenna tuner.
The antenna has been successfully tested at Ramsgate, KwaZulu South Coast, the Drakensberg near Champagne Castle, and Honeydew in Gauteng, with extraordinary results, particularly from the Drakensberg where “man-made noise” is virtually non-existent,ideal for test purposes.
The antenna was tried at heights of 2 metres, 2.5 metres, 3.5 metres and8m above ground level. The SWR on all bands remained very constant in all cases.
An ideal mounting would be as high as possible – can be horizontal to ground level or as a sloper from a suitable pole or tree. Using the Bundu Basher Aerial on 80 metres. [PDF]
Contacts;first time out:
On 20 metres, with a power of 50 watts: (Drakensberg)
Naples– Italy 5 & 6 on SSB
Tsumeb– Namibia 5 & 8 on SSB
Reunion Island 5 & 6 on SSB
On40 metres, with a power of 50 watts:(Drakensberg)
Hoedspruit 5 & 9 on SSB
Port Elizabeth 5 & 8 on SSB
Ficksburg5 & 9 + on SSB
Eshowe5 & 9 + on SSB
The antenna is capable of handling 100 watts on SSB.
Once tuned, the antenna has outstanding SWR figures throughout the band,as indicated below on a graph supplied, by Nic van Duffelen, ZR6AEZ – Senior Radio Engineer at a large two-way radio company in JHB.
Tests conducted on the BiCraft “Bundu Basher” Antenna
[Thesemeasurements were made on very sophisticated RF laboratory testequipment. Thanks Nic!]
Tuningthe antenna is relatively easy, in that one would need the use of anaccurate SWR Meter, or something similar to the MFJ Antenna Tunerunit.
Theantenna is initially tuned on 40metres, and because the hamfrequencies mentioned above are harmonically related, all the otherbands fall into place as far as SWR is concerned. (See graph)
Itis however, to be noted that the SWR on 80 metres and 160 metres isway out – no tests were conducted with an antenna tuner to trythese two bands!
Pleasenote; below that each peak is a high SWR and each dip is the lowestSWR for each ham band, as indicated in the adjacent table of thegraph.
Testsat various heights were conducted, and there was very little changein the SWR levels.
Figure1
Installing your “Bundu Basher Antenna”
Find a suitable place to mount/hang the plastic housing of the antenna –this could be in your ceiling, or under the eaves of you house, you decide.
String the 22 metres of cable out in a straight line – if possible; at a minimum of 2metres above ground level. The counterpoise can be strungout on the ground, or hanging down from the eaves, or just dangling loosely in the ceiling, it may also be electrically attached to a“copper weld” earth spike. Six to eight metres of RG58 or a heavier coax may be used to feed the transceiver.
Attach an SWR meter between the transceiver and the antenna SO239 socket.
Select the 40 metre band, and apply a low level CW signal to the antenna. If the SWR is low, say below 1.8, then the antenna is OK, and the balance of the bands, i.e. 20, 15, & 10 metres will all line up with almost the same SWR readings. (10m maybe a bit higher)
Should the SWR be too high, then proceed by trimming the 22 metre length by15 centimetres at a time, until the SWR is satisfactory. Do not trim the counterpoise!
Notes:
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The higher the antenna is above ground level the better!
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When tested at various heights up to about 8-metres, the SWR did not change significantly.
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Tests were also conducted with bends in the radiator wire, without any major changes in the SWR.
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It would be advisable, as with any antenna, to disconnect during any stormy weather conditions!
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The end of the radiator wire must have an insulator attached before tying to any object.
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Try to keep the radiator away from metal objects as much as possible.
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The direction of the radiator did not seem to matter.
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There are several “lobes/nodes” on the sides of the antenna wire where there will be better radiation than in other positions. See details on the Internet.
Kit comprises of:
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Internal toroid matching transformer.
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22 metres of 1mm flexible cable terminated with an “eye” crimp connector.
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4metres of 1mm flexible cable terminated with an “eye” crimp connector.
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AnIP64 100x100x50 mm plastic housing, with connectors.
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Instructions documentation.
Bob Innes
BiCraftElectronics
Email:innesbob@gmail.com
Landline: 011 958 1479
Mobile Phone: 083 625 0294
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