----- Original Message -----
From: "g3ldo" <[email protected]>
To: <[email protected]>
Sent: Monday, March 31, 2003 9:17 PM
Subject: LF: Loading coils
> NEVER put your loading coil in a metal box, it totally destroys the
> efficiency. Consider it as part of the antenna from the radiation point
of
> view. You have never seen a loading coil on a Mobile encased in a metal
CAN,
> the coil contributes to the over all efficiency ie coil plus whip.
> I have seen reference to encasing the loading coil here on this
reflector
> that is why those signals are poor.
> My coil sits outside exposed to the elements and does not seem to be
> effected by changing wx, neither does the amps vary whether it be dry or
> wet. Recent info on here suggests heating the loading coil to increase
the
> amps consumed, if this is the case the coil wire, insulation etc is very
> suspect.
> I change my antenna wire and rewind a new coil at least once a year. I
also
> check the insulated radials and change if necessary.
> Try a turkey next Xmas without the FOIL, Foil is nether good for antenna
> coils or Turkeys
> 73 de Mal/G3KEV
The loading coil complex used by the Decca stations were located in a
small
concrete building. In the early days I understand that there were problems
until the whole building was lined with copper - in other words a screened
box.
This screened box was also electrically heated.
It is obvious that these Decca design engineers didn't know what they were
talking about.
Its a question of requirements.
1. These Decca coils were used only on TX and 10/15 db loss was acceptable
by putting these coils in a metal cage for environmental reasons.
2. Heated coils generate noise, in fact the coils should be kept cold, but
again in a TX only mode it does not matter.
Because the LF radio amateur also requires the antenna and associated coils
for receiving , heating the coils produces unnecessary noise and on Transmit
one cannot afford 10/15 db loss of radiated power.
For those using RF preamps try running them in a cold environment, in a cold
box at 0C and get a superior signal over noise at the RX front end.
The above info is old hat for those in the know, it would appear some have
led sheltered lives in the wireless world.
G3KEV
Regards,
Peter, G3LDO
e-mail <[email protected]>
Web <http://web.ukonline.co.uk/g3ldo>
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