vhf ch 28

[christhefish]

has anyone in the newhaven brighton area noticed when scanning vhf channels they stop on ch 28 is this something to do with the greenwich light vessel automatic ??????

 

[lenseman]

No is has nothing to do with Greenwich Light Vessel.

It is historic as the band plan for marine VHF was laid down just after WW2 and the channel spacing was 50kHz (or 50kc/s in those days).

When the bands became overloaded and technology advanced, the channel spacing was reduced to 25kHz and the new channels were inter-leaved within the old band plan. Channel 28 was at the top of the old band plan and channel 29 starts further down the original band plan continuing up to channel 66.

Hope this information helps?

 

[christhefish]

thanks for the reply at least I know now

 

[earlybird]

I once had a Navico RT6500 vhf, which I initially set up with the aerial fairly close to the set. When scanning, it always stopped at ch. 28. Eventually I found that increasing the separation from the aerial avoided this. I concluded that the set emitted RFI on this frequency from an internal circuit .
Don't know if there is any connection with your observation.

 

[ProDave]

I was going t ask what you meant by "stops at channel 28"

Whenever I set my radio to scan, it ALWAYS stops at channel 28. There seems to be a permanent unmodulated carrier there. I know it's being received by the aerial as it goes if you unplug it, and it's weak and varying in signal strength.

But I'm a LONG way from the OP so it can't be the same thing.

This is with the boat at home, It will be interesting to see if it's the same when back on the water.

 

[Bilgediver]

No is has nothing to do with Greenwich Light Vessel.

It is historic as the band plan for marine VHF was laid down just after WW2 and the channel spacing was 50kHz (or 50kc/s in those days).

When the bands became overloaded and technology advanced, the channel spacing was reduced to 25kHz and the new channels were inter-leaved within the old band plan. Channel 28 was at the top of the old band plan and channel 29 starts further down the original band plan continuing up to channel 66.

Hope this information helps?

I wasn t aware that the squelch circuit was choosy regarding whether the signal perceived was one end of the frequency band or the other. It hears a signal and stops the scan!!!!!

Here in the Forth Estuary all sorts of mysterious things are heard on the unused frequencies previously used for calls to coast stations including packet radio and taxi companies!!!! Could be anything.

 

[Twister_Ken]

I can't see that Ch28 is specifically allocated to anything specific, although it is a working channel for a very few CG and VTS stations. Maybe someone locally is using it because it seems to be vacant?

 

[mlines]

Channel 28 is a nice whole number in terms of RX frequency (162.00Mhz)

Therefore it could be in line for harmonics of other oscillators. e.g 81Mhz, 54Mhz