I am using an insulated backstay.
I used to feed the navtex-receiver with it.
Now I connected it to my ssb transceiver and I am looking for an
alternative antenna for the navtex.

I am told not to place the navtex antenna too close to the ssb antenna
cause the tx-power could destroy the navtex receiver.
I am now thinking about a switch that gives power a) to the ssb OR b)
to the navtex so there will be no possibility to send with the navtex
receiving.

My question: I am assuming the navtex will suffer no damage from the
radiated energy when the 12v-power to the navtex is off. Am I right?


TIA and fair winds,
Len.

Len wrote:


My question: I am assuming the navtex will suffer no damage from the
radiated energy when the 12v-power to the navtex is off. Am I right?


Short answer: wrong.

The navtex receiver can be destroyed
whether it is turned on or not. In
theory, the 12 volt wiring could provide
a convenient path for the radiated
energy to enter the unit and that
sometimes happens with all kinds of
electronics: hi-fi's, computers, battery
chargers, voltage regulators, etc. It is
usually curable.

The good news is that damage to the
navtex is very unlikely. On a sailboat,
it is almost impossible to locate a
navtex antenna far enough away from the
ssb antenna to avoid strong
electromagnetic fields.

I wouldn't worry about it, Len. Your VHF
and any AM/FM radio or TV you have on
board would be as likely to suffer
damage as the navtex.

You might consider one of the active
navtex antennas that uses a short whip.

Good luck.

Chuck

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"Len" wrote in message
oups.com...
I am using an insulated backstay.
I used to feed the navtex-receiver with it.
Now I connected it to my ssb transceiver and I am looking for an
alternative antenna for the navtex.

I am told not to place the navtex antenna too close to the ssb antenna
cause the tx-power could destroy the navtex receiver.
I am now thinking about a switch that gives power a) to the ssb OR b)
to the navtex so there will be no possibility to send with the navtex
receiving.

My question: I am assuming the navtex will suffer no damage from the
radiated energy when the 12v-power to the navtex is off. Am I right?


TIA and fair winds,
Len.

As Chuck says, I don't think it makes any difference whether the unit is ON
or OFF. The front end of the receiver is still going to get whatever comes
down the antenna lead. Your best bet would be to disconnect the Navtex
antenna when you want to use the SSB. I imagine you could use a fairly
simple switch for this purpose.
Having said that I doubt you would pick up enough radiated energy to damage
the Navtex if it's antenna is a couple of feet away. If you had a bare wire
whip and it touched the backstay that would be another matter...

Ok, thanks for the responses.
I'll install an active antenna for the navtex via a switch
and disconnect it when I use the transceiver.

Regards, Len.

Len ha scritto:
Ok, thanks for the responses.
I'll install an active antenna for the navtex via a switch
and disconnect it when I use the transceiver.

Regards, Len.


Just to be safe I would recommend putting also two parallelled
criss-crossed fast diodes (possibly germanium) from the navtex antenna
input to ground. Any spurious signal greater than 0.2 V would be safely
grounded. Just be sure that you put the diodes in a point where the DC
power to the active antenna is no more present - i.e. on the right side
of a condenser along the antenna circuit.

Regards
Daniel