Please enable / Bitte aktiviere JavaScript!
Veuillez desactiver vos / Por favor desactiva el Javascript![ ? ]
FSL ANTENNA DESIGN OPTIMIZATION ARTICLE | Radioaficion Ham Radio

FSL ANTENNA DESIGN OPTIMIZATION ARTICLE

Share

Hello All, As most of you know, FSL antenna design has been a somewhat controversial topic since Graham Maynard's original article in Medium Wave News a year ago. Differences of opinion about how to design and build the most effective FSL models have continued for the entire year, and efforts to bridge opinion gaps have been few and far between.  In an honest effort to resolve this situation and bring final clarity to the design factors influencing an FSL antenna's weak signal DXing performance, seven new FSL test models were constructed here,  purposely designed with diverse coil diameters and diverse ferrite  material (bars, and both short and long ferrite rods). The seven new  test models (plus one previously-designed 7" FSL model) were then  tested extensively for reception of weak-signal daytime DX stations in  the open-air back yard here, with MP3's recorded to document relative reception.  The first interesting fact was that two of the new  test models were equal in weak-signal performance, although they were radically different in design. The 7" bar model (25 of the 100mm x 20mm x 3mm) bars was deadlocking in performance with the 3.5" long-rod model (23  of the 200 mm x 10 mm rods), and both of these FSL antennas were also deadlocking with the 4' PVC air-core loop. Further experimentation showed that both of these new antennas also deadlocked with the 5" Mini-FSL antenna (45 of the 140 mm x 8 mm rods), providing a chance to sort out the design factors in play causing the three-way deadlock.  Other interesting facts were that the 5" bar model (17 of the 100 mm x 20 mm x 3 mm bars) was slightly outperforming the 5" short-rod model  (47 of the 65 mm x 8 mm rods), but was being outperformed by both the  3.5" long-rod model and the 5" Mini-FSL model (45 of the 140 mm x 8 mm  rods), which were the two new antennas involved in the deadlock with  the 4' PVC air core loop.  These facts together, when considered as a package, finally provided the evidence to clarify several FSL design-optimization principles:  1)  Assuming that Litz wire, coil design and ferrite permeability are equal, an FSL's weak-signal performance is related to both its coil diameter and the length (not the shape, or thickness) of the ferrite material in its sleeve.  2)  Smaller-diameter FSL models (rods or bars) can outperform larger diameter FSL models (rods or bars) if the length of their ferrite sleeve is significantly greater than that of the larger diameter FSL models (this was experimentally proven here a couple of times).  3) An accurate way to predict any FSL's weak-signal performance in relation to that of any other same-parameter (Litz wire, coil orientation and ferrite permeability) FSL is to multiply the coil diameter by the ferrite sleeve's length (regardless of whether it is constructed of bars or rods). For example, in the case of the three- way FSL deadlock mentioned above, we have the following equations:  3.5" Long-rod FSL          3.5 x 200 = 700 5" Mini-FSL                  5 x 140 = 700 7" Bar FSL                   7 x 100 = 700  Once this equation and design principle is accepted, it opens up a fascinating new perspective on FSL antenna design. The ferrite bar models can be constructed at a lower cost and lighter weight, with DXing performance equal to that of the heavier and more costly rod models. Placing several ferrite bars end-to-end to create a longer sleeve (on a longer supporting form, with a soft foam covering) should be an easy way to create very effective FSL antennas, with reasonable cost and weight.  Full information on this all-out FSL Design Optimization experimentation is contained in the article newly posted at 
http://www.mediafire.com/?6oyoldllrbiwf91 
 which I hope will help to bridge various opinion gaps on FSL antenna  design. 
73 and Thanks, 
(Gary DeBock (in Puyallup, WA, USA) NRC-AM via DXLD
 

 
 
Related Articles