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Spiderbeam (eng) P1/5

Antennas > Spiderbeam

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Photo1 - Spiderbeam 12m on the ground


History of the Spderbeam antenna

Monday, 03rd of september 2007

The Spiderbeam antenna is a revolutionary antenna, largely used in portable operation by many DXpéditioneers, its ultra light weight (6.5kg) classes it among the favorite antennas. One can also install it into fixed, at home, but its weight then, is approximately 11kg which is explained by the reinforced use of the fiberglass rods and the thickness of metal parts (2mm) made of aluminum.

It is presented as a tribander or multibander Yagi aerial in spider shape, so i personally opted for a 5bander model 10-12-15-17-20m Heavy duty. Its design is really particular, it is composed of two long fiberglass poles 10mx10m, which are the boom element and lateral spreaders where all conducting elements are fixed:

* Radiators 10m, 12m, 15m, 17m and 20m,
* Reflectors 10m, 12m, 15m, 17m and 20m
* Directors 2x10m, 15m and 20m

The spiderbeam antenna conceived by
Con/DF4SA is an alternative of the G4ZU beam also called “Bird-yagi”, as Con/DF4SA had not found any available documentation about a multiband antenna design, in the similar type, he decided then to conceive one of them himself. In this project, during the development phase, several hamradios brought their invaluable assistance and particularly: DF4RD, DF9GR, DJ6LE, DL6LAU, HA1AG, HB9ABX, W4RNL, WA4VZQ.

Many thanks also to everybody who helped translating this document into other languages: G3SHF (& TEAM), 9A6C, BG7IGG, CT1IUA, CT3EE, EA2PA, F2LZ, F4ANJ, F5IJT, F6IIE, G3MRC, HB9ABX, I0SKK, IZ5DIY, JA1KJW, LX2AJ, OH6NT, OK1DMU, OZ8A, PB0P, PC2T, PE2RID, S51TA, S57XX, SM0ETT, SM0JZT, RA3TT, RV3DA, YC0CRA, YU1QT.

Photo2 - nice view of Spiderbeam antenna


Photo3 - Another view of the Spiderbeam


Assembly of the Spider center joint

Monday, 03rd of september 2007

The assembly of the spider center joint is the most delicate part of working, the French assembly handbook, is really explicit one could not better do (
I benefit from it to humbly thank our french translators who made us there, a work of excellence, I harnessed myself there one year ago, by being unaware of that our friends F2LZ, F4ANJ, F5IJT, and F6IIE had already opened us the way).

Below, in bulk, some pictures about this exciting operation.

Photo4 - My working area


Picture 4
All hardware parts take place on a small garden table,

An electrician pliers, a set of punt and eye spanners for tightening all 6x55mm stainless bolts.

Photo 5
The center joint is quickly assembled, it is composed of 2 aluminum square plates of 220mm by 2mm of thickness. One can notice the smoothness and the precision of the parts machining allowing to fix all aluminium tube pieces in place, as well as the tightening of the unit to the mast, by the mean of 2 stainless collars through 2 metal U-sections.

Photo5 - Assembly of center joint supporting the 4 fiberglass poles


Photo6 - Insertion of a small sleeve


Photo 6
Insertion of small aluminium tube spacers (35mm long by 10mm in diameter) inside the aluminium support tubes of 175mm length and 2mm of thickness.

Photo 7
The rollers on which all the conducting elements of Spiderbeam: radiators, reflectors and directors are joined together.

Photo7 - All wire elements fit on the winder


Mounting the symetrical transformer

The ferrite toroid type used is a FT-240-61 and with coax cable, after 6 windings on one side, cross over the other side and put on another 6 windings. This coax cable choke will prevent the current from flowing on the sleeve (external conductor), and will thus give in result, a good match of the balanced antenna to the unbalanced coax cable.

Photo 8
The Balun is hermetically be locked up inside the inclosure. Rolling up the coaxial cable, 6 windings on the left side, then 6 other windings on the other side, the whole is maintained tightened by the mean of electrician ribbon, or better, with plastic fasteners which one can easily get in any hardwarehouses.

Photo8 - Balun and its enclosure


Photo9 - No special tools required


Photo 9
No special tools are required for the construction of the transformer, it is important to maintain coax cable windings well tightened and distributed on the ferrite toroïd.

Photo 10
Here how the transformer will be presented, once weldings of cable lugs are finished. The feeding connections on the top are duplicated to allow feeding of the radiators elements for 10-15-20m.

At the bottom, on SO-239, the weldings of inner conductor and the braid, will have carefully to be realized.

Photo10 - Balun with all achieved welding


Photo11 - Close-up on 4 cable lugs


Photo 11
An increased sight of the connections shows the Balun enclosure, once cable lugs are welded they must firmly bolted inside the inclosure with use of seals inside and outside the enclosure in order to preserve the transformer of any water infiltration, to keep it in a good running condition.

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