In article ,
(Larry) wrote:

Look in the owners manual for a section on receiver tuning. Not sure
about the R21, but newer Raymarines have a digital control of the
tuning right from the display. It sounds like your receiver tuning
has drifted off the transmitter.



On 06 Aug 2003 22:44:03 GMT, (Capt Lou) wrote:

My radar screen still reads the echoes, but the screen gradually became full
of
snow. Also, when the set is first turned on and warming up, it stops my VHF
from scanning and the squelch cannot filter it out on any channel. As soon
as
the radar is "ready," my VHF starts scanning again. My open array antenna
spins, and even with the screen full of snow, I can still read the echoes.
Anyone know what's wrong and is it worth fixing. It a 12 year old Raytheon
R21.


"Listen to the live broadcast of 'Nautical Talk Radio' with Captain Lou
every
Sunday afternoon from 4 - 5 (Eastern Standard Time) on the web at
www.959watd.com or if you are in Boston or Cape Cod set your radio dial to
95.9FM.

Larry

Extremely intelligent life must exist in the universe.
You can tell because they never tried to contact us.


I suspect that the receiver hasn't moved at all but the Magnitron
(Transmitter) has aged to the point that it has changed frequency
and is transmitting on a different frequency than the receiver can tune.
This is a very common ageing failure for Magnitorn Powered Radars.
The easy fix is to retune the receiver to match the Magnitron drift.
This will do for a while, but as the Magnitron ages, it will drift more
and faster untill it dies completely. The long term fix is to replace
the Magnitron, and then retune the reciver to the new Mag. Magnitrons
are expensive, and have a fixed Service Life usually in the neighborhood
of 1000 Hours or so. figure $350US for a new one and an hour of Techtime
to do the rteplacement and retuning.

Been there, done that, hundreds of times as a Marine Electronics Tech.

Bruce in Alaska