[amsat-bb] Re: Interference from repeaters

Trevor . m5aka at yahoo.co.uk
Mon May 23 17:21:43 PDT 2011

As I recall IARU Region 1 (Europe&Africa) approved the use of 145.7875 MHz for repeaters over a decade ago. 

You're right it's unworkable with the ISS operating on 145.800 MHz +/- 3kHz doppler shift and with 5kHz deviation. 

Unfortunately that was what IARU Region 1 decided despite having agreed earlier to 145.800MHz being used for ISS. 

That decision means there are a large numnber of FM and D-STAR repeaters using 145.7875MHz. Anyone near to a 145.7875 MHz repeater will suffer considerable interference when listening to the ISS downlink. 

73 Trevor M5AKA

--- On Tue, 24/5/11, Richard Ferryman <g4bbh at btinternet.com> wrote:
> I have for some time wondered what
> was causing a considerable amount or QRM (S9+60dB) to the
> ISS downlink on 145.800. It took a while to identify as
> there is no CW ident etc. but I have now discovered this is
> a new D-Star repeater on our repeater channel RV63 
> which is 145.7875 MHz, only a couple of kHz from ISS and
> inside the doppler shift range.  It seems very poor
> planning to place high this powered high sited repeaters so
> near to the satellite allocation. Is this becoming a common
> problem and are repeaters also causing any problems to
> uplinks?
> Dick G4BBH
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