[UK-CONTEST] Strange signals on 28 MHz

[G3RAU at aol.com]

Hi folks.  I can't give you a definitive answer to the question of  legality 
but my thoughts are these. Clearly somebody has gone to the  trouble of 
assigning identification letters and frequencies to these devices, so  it is not a 
case of random pirate activity by a few individuals. Some  country with an 
interest in fishing vessels is involved here.  The  clue is in the bearings.
 
Now Dave is correct that 28MHz is amateur primary, but there is a sneaky  
little ITU rule that effectively says administrations can use any frequency for  
whatever they like if it can't be heard outside their own country.   Seeing as 
these things are obviously very QRP, well down in the milliwatt range  by the 
sound of it, an administration could claim that they are effectively  
inaudible outside their own fishing waters.  This is clearly going to  be  true for 
most of the time, and even when it isn't true they will claim  that they are 
very weak signals that should cause no harm to anybody.
 
Of course, just because an amateur band is "exclusive" does not mean that  
you will never hear low level spurious or harmonics from other services.   The 
ITU accept that principle and, for example, have set limits for spurii &  
harmonics that reduce interference  problems to a point where they are  not a 
serious issue, but on the other hand the limits do not set equipment mfrs  an 
impossible task or make eqpmnt prohibitively expensive.  
 
So the answer seems to me to be that they are almost certainly authorised  by 
some Administration or other, BUT, why have they chosen 28MHz?  That is  the 
avenue to explore if anybody feels motivated to chase this.  Drift net  
fishing takes place in many areas of the world, what frequencies are used  elsewhere 
for this purpose?  I don't know.  As the things are not  going to disrupt 
amateur communications in any meaningful way I doubt  anybody at the ITU would be 
overly concerned, but if anybody  is interested enough  a talk with DJ7KG may 
shed more light  on the subject. 
 
 As to Illegal CB FM from Spanish fishermen on 10M, a nice bit of  protracted 
linear tuning ---  and they will soon QSY! 
 
73 Derek G3RAU