warwicksail
Well-Known Member
Is this any differnt to the FM splitters used for TV/CABLE and SKY Satalite ?
VHF/FM Band Splitter.
- Thread starter warwicksail
- Start date
rob2
Well-Known Member
In principle, probably not. But the VHF/FM splitters are set to split the frequencies involved which are different from those between FM/TV.
Rob.
Rob.
VicMallows
Well-Known Member
You need to bear in mind that ideally the antenna should be resonant at the frequency in question, so one designed for marine VHF will be just like a random bit of wire to the FM radio. If you only want to RECEIVE the FM signal is usually so strong that almost any odd piece of wire will work. You could use a simple two-way resistive splitter from the marine VHF antenna, but why bother.
If you also want to TRANSMIT from the VHF things become much more complicated (you need to prevent the transmit signal getting into the FM receiver and destroying it) and frankly would not be worth the bother/expense ... far easier to provide a second antenna...not too close to the transmitting one!
Vic
If you also want to TRANSMIT from the VHF things become much more complicated (you need to prevent the transmit signal getting into the FM receiver and destroying it) and frankly would not be worth the bother/expense ... far easier to provide a second antenna...not too close to the transmitting one!
Vic
st599
Well-Known Member
In principle, they are completely different.
The FM/TV splitters are just resistive splitters - port 1 split equally to 2 and 3 (2 split equally to 3 and 1 etc.)
If you transmit 25W into this, you'll get 12.5 W to the Aerial and 12.5W to the FM radio - which will cease to be an FM radio.
You need a proper filtered system or diplexer.
lw395
Well-Known Member
pedant Actually the resistive splitters are 6dB loss /pedant
But some splitters are transformers not resistive, so theoretically a 50:50 split, but using them out of their intended band, anything could happen. They may also blow up when presented with 25W, maybe damaging the VHF transmitter.
So, Yes it's completely unsuitable, you need a 'diplexer' which is basically two filters to isolate the VHF marine band from the FM band. The two arms have to be tuned to the right frequencies. A good one may be more expensive than a decent FM aerial. And still not give that much isolation. The damage level of the FM radio may be quite low in relation to the power out of the VHF, maybe as low as 25mW vs 25W.
