[TowerTalk] 20 Meter

[Maurizio Panicara]

Everything is relative.
Conventional inductors are loading devices with appreciable losses if
compared to full size elements and this loss is more evident in yagi arrays
where the amount of the current in detuned parasitic elements is one of the
keys to keep gain.
Loading coils are definitely less lossy or even a better solution with
compact antennas when compared to unproper linear loading arrangements.
Back to the matching circuits, they may introduce losses when some of their
elements have losses, tipically a gamma capacitor with a lossy dielectric @
28 MHz is one of the the worst cases for HF, or when the mechanical
construction (i.e. with an hairpin) involves a number of different parts
with several joints and the impedances in those points is already rather
low.
Although nothing fails and noone notices the heath, or neither a signal
decrease is roughly appreciable, when discussing about marginal gains like
0.25 or 0.5 dB (a 5% or 10 % of the power) already a simple 0.5 Ohm series
resistance in a 20 OHm radiator adds an extra .22 dB loss.

73,
Mauri I4JMY

----- Original Message -----
From: "Tom Rauch" <w8ji@akorn.net>
To: <TOWERTALK@contesting.com>
Sent: Monday, March 05, 2001 8:40 PM
Subject: Re: [TowerTalk] 20 Meter


>
> > exceed 10 dBi , even with only 4 elements. Incidentally, any matching
> > system to rise a low feed point impedance (hairpin, gamma etc.) is a
> > bit lossy and those losses tend to increase when the fed impedance is
> > starts to be lower than 30 Ohm. Once again, nothing real is for free.
>
> While a 50 ohm dipole feedpoint is convenient, it seems like we
> place far too much importance on matching losses. Which are
> most often not even large enough to be measurable.
>
> This reminds me of sale talk for linear loading where it is compared
> to "lossy inductors".
>
>
> 73, Tom W8JI
> W8JI@contesting.com
>
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