Building a Drain Pipe FSL Antenna
by Pavel Kraus
Hi, I greet all DX fans and the entire SWLing Post community! I enjoy reading reading this blog and the diversity of contributions from our authors and contributors; many thanks from me for so much useful information.
The following are the construction notes of my FSL antenna, which I designed thanks to the suggestions of GaryDeBock, and other FSL designers.
The antenna is a classic design featuring 60 ferrite rods 200x 10 mm, which are placed on a plastic sewage pipe.
In addition, sewer pipe sections are used for the entire antenna cover. I assume that this material can be obtained in other countries as well.
This solution ensures the robustness and durability of the antenna during transport by car as well as resistance to weather conditions. The cover consists of three pipe parts and two plugs.
A spacer ring is glued and screwed to the plugs on the inside, which ensures that the inner tube with the ferrite rods are centered so that it does not come into contact with the antenna cover and prevents possible damage to the ferrites.
The advantage of this construction is the watertightness of the cover and resistance to damage to ferrite rods.
The tuning and coupling windings are led out of the cover through rubber bushings.
The disadvantage is the greater weight, dimensions and appearance reminiscent of an anti-submarine mine. The whole cylindrical monster is loosely seated on a pedestal consisting of chipboard side panels and an electrical installation box with electronics.
The box contains a switchable preamplifier with gain control, tuning capacitor, tuned frequency indication, battery status switch and a scale illumination button.
The tuning winding and the coupling winding are connected via gold-plated cinch connectors on the rear panel. The cylindrical part of the ferrite rod antenna can be easily disconnected and the entire antenna disassembled into two parts – the control electronics and the ferrite rod antenna itself.
The output for the receiver is then realized by a BNC connector.
The tuning winding consists of 19 turns of Litz 1162/46 wire (approx. 300 microHenry), the coupling winding has 1 turn. The coupling winding is connected to the preamplifier. The tuning capacitor is from an old receiver and is mechanically coupled to a potentiometer, which is used to indicate the frequency with a voltmeter.
The preamplifier is switchable, which also allows passive operation by approaching the receiver with a built-in ferrite antenna. On the back there is a case for a 9V battery and a trimmer for calibration of the scale, because due to the gradual reduction of the supply voltage, the indicator may show different values.
The whole monster is placed on a Lazy Susan turntable and sprayed in black:
This antenna does not represent anything revolutionary in terms of construction and connection, I just wanted to point out the possibility of using sewer pipes as a construction material. (If we use a shorter ferrite rod for the construction, the length of the cylindrical cover can be shortened only to the middle part with plugs.)
The antenna is currently being tested in an urban environment (Prague – Czech Republic), however, the results are very good. Tested on Malahit SDR receivers, Eton E1, Kenwood R5000 – direct connection with preamplifier. Passively then Sony ICF 2010, ICF SW 100, ICF SW 77.
Project 2: Active Ferrite Antenna
The second design of the active ferrite antenna is more portable and is suitable for travel with a receiver that does not have a ferrite antenna (Malahit SDR, Eton E1, etc.). The antenna construction is housed in a plastic housing originally intended for a removable car radio panel. All electronics and controls will then fit in this case. There are glued two ferrite rods 200mm x 10mm covered with a plastic tube. Tuning winding connected to a variable capacitor, Coupling winding then to a preamplifier with gain control, powered by a 9V battery.
This antenna is then removably attached to the base (originally an industrial camera holder).
The antenna is surprisingly powerful and allows listening on MW and weaker stations.
I don’t have results and records of remote stations yet, I’m not an orthodox DXer in this sense (and now I’m cold on the balcony). I rather enjoy just tuning the band, listening and going back to my young years, when the jingle of Radio Luxembourg was heard from the air.
I wish everyone a lot of nice DX catches per MW with ferrite and other antennas.
Pavel Kraus, Prague, Czech Republic