Re: 5" Mini-FSL Antenna- "Heathkit" Construction Article


d4g7johnson
 

After doing some computations with the one of the inductance values
that Everett came up with (385uH tuning with 10-381pf, tunes 400KHz to 1715KHz), I see that my idea is not going to be much good for
just 1 MW-sized coil, because the more fixed capacitance is added
the less tuning range you get. For example to start at 400KHz and
tune down you could add about 371pf fixed capacitance, but then the
lower range is then only about 293KHz. Adding more fixed capacitance
to make that the highest frequency then lets you tune down only to
about 242KHz, etc. A much-larger variable capacitor would alleviate
this problem but then its physical size would cause other problems.

--- In ultralightdx@..., D1028Gary@... wrote:

Hello,

Thanks for your interest in the 5" FSL antenna.

<<< Since Litz wire cost is significant, has anybody experimented with
a dual-use sleeve antenna using only one coil, but with switchable
fixed capacitor(s)? The idea is to use the MW coil plus 1 or 2
fixed capacitors to tune LW without the expense of more Litz wire.
How much would that degrade performance relative to building a full
LW coil instead? >>>

To my knowledge, this method has been tried by Steve, Kevin and Everett
to create dual-band (AM & LW) FSL systems with ferrite bar models,
although not with the 140mm x 8mm ferrite rods used in the 5" FSL. As
for performance relative to a fully resonant 660/46 Litz wire Longwave
coil 5" FSL (which has already been built here), nobody has ever
compared the two systems, to my knowledge. A fully resonant LW coil
uses a lot of the expensive 660/46 Litz wire, so I'm sure that less
expensive alternatives will become popular for those interested in
economy Longwave FSL models (less expensive Litz wire, higher tuning
capacitance, etc.). For my own objectives in creating the AM-only
Mini-FSL models, following the "KISS" principle (simple, effective and
inexpensive) was most important.

73, Gary DeBock (in Puyallup, WA, USA)





-----Original Message-----
From: d4g7johnson <d4g7johnson@...>
To: ultralightdx <ultralightdx@...>
Sent: Sun, Feb 19, 2012 10:14 pm
Subject: [ultralightdx] Re: 5" Mini-FSL Antenna- "Heathkit"
Construction Article







Since Litz wire cost is significant, has anybody experimented with
a dual-use sleeve antenna using only one coil, but with switchable
fixed capacitor(s)? The idea is to use the MW coil plus 1 or 2
fixed capacitors to tune LW without the expense of more Litz wire.
How much would that degrade performance relative to building a full
LW coil instead?

--- In ultralightdx@..., D1028Gary@ wrote:

Hello All,

The 5" Mini-FSL was the first of several compact, AM-only antennas
that
were developed for those DXers who thought that FSL models were
either
too expensive, too complicated, or both. It was designed to be
simple,
effective, easy to build-- and cost only about $90 in part purchases
(photo attached). After having been tested against various air core
loops in an outdoor environment, the tiny model really exceeded
expectations-- deadlocking in weak-signal performance with a
full-sized
4-foot air core box loop (the antenna of the August 2010 Oregon coast
DXpedition).

In an effort to make assembly of the tiny FSL antenna as simple as
possible, a special, 10-page construction manual has been prepared,
patterned after the famous Heathkit assembly manuals of the last
century. In a step going beyond the Heathkit manuals, multiple
Photoshop-enhanced assembly pictures are included in the article,
showing each assembly step in a clear way. Assembly of the model has
also been made as simple as possible-- all of the parts are readily
available on the open market, and most of them have been stockpiled
here. Pre-cut kits of the PVC frame parts have been prepared, which
are
available at cost (along with the other parts, as long as supplies
last). The tiny FSL was designed to be a DXing thriller, and for
those
still "on the fence" about giving new antenna design a try, the
perfect
introduction to a exciting new DXing experience
http://www.mediafire.com/?9ze98h293s85p86

Thanks very much to Rob Ross of London, Ontario for his generous gift
of 140mm x 8mm ferrite rods to develop this (and other) mini-FSL
models, and to Dave Kellmer of Portland, OR, for providing a generous
supply of the Funnoodle (soft) inner core material. Hopefully this
compact new antenna will provide a major boost in each builder's
hobby
excitement!

73 and Good DX,
Gary DeBock (in Puyallup, WA, USA)

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