VHF & AM/FM Radios

phwrd · Jul 13, 2010

I want to hook up both my mounted VHF and a AM/FM radio to the boat speakers.

But how can I have the noise from the AM/FM stop when the VHF sounds off.

Any ideas on how this is done?

Thanks in advance, you geniuses . . .

springhead · Jul 14, 2010

Re: VHF & AM/FM Radios

VHF / Stereo Switch
Am/fm/VHF separator
Automatic Band Separation

Item #: 251474
Manufacturer: SHAKESPEARE
Model #: 4357-S

Automatic AM/FM/VHF coaxial switch allows you to simultaneously use your VHF and AM/FM radios with a single VHF antenna.
Automatically switches off AM/FM channel during VHF transmission to prevent damage to your AM/FM radio.
Includes 10' rg-62 AM/FM cable, 3' rg-58 VHF cable, and connectors.

this might be what your looking for

Splat · Jul 14, 2010

Re: VHF & AM/FM Radios

There is no easy way to do what you want.

Why do you want to drive your vhf through your stereo? If its hard to hear while underway you'd better off hooking up a external speaker, they make a world of difference in clarity of sound compared to the speaker on the vhf. You can even daisy chain 2 or more, however you would want a amplified external speaker at that point.

Bill

phwrd · Jul 14, 2010

Re: VHF & AM/FM Radios

Mr. Springhead,

you sir, are a genius. This is exactly what i was looking for.

Thanks !

NYBo · Jul 14, 2010

Re: VHF & AM/FM Radios

phwrd said:
Mr. Springhead,

you sir, are a genius. This is exactly what i was looking for.

Thanks !

Um, that's for sharing an antenna. Your original post was about sharing the speakers. Which are you trying to do?

springhead · Jul 14, 2010

Re: VHF & AM/FM Radios

NYBo said:
Um, that's for sharing an antenna. Your original post was about sharing the speakers. Which are you trying to do?

And he is looking to have the noise from the AM/FM stop when the VHF sounds off.
Both VHF and boat stereo speakers have the same impedence (4ohms), so in fact he can use his boat speakers with his VHF radio with this automatic band separator.

phwrd use the vhf radio external speaker wires and hook them up to one of your boat speakers it works well, I also get better reception from my am/fm stereo.
Good Luck David

Bondo · Jul 15, 2010

Re: VHF & AM/FM Radios

springhead said:
And he is looking to have the noise from the AM/FM stop when the VHF sounds off.
Both VHF and boat stereo speakers have the same impedence (4ohms), so in fact he can use his boat speakers with his VHF radio with this automatic band separator.

phwrd use the vhf radio external speaker wires and hook them up to one of your boat speakers it works well, I also get better reception from my am/fm stereo.
Good Luck David

Ayuh,... I've got that on my barge,... It shares ONLY the antenna...
It will Not do what the OP wants...

NYBo · Jul 15, 2010

Re: VHF & AM/FM Radios

springhead said:
And he is looking to have the noise from the AM/FM stop when the VHF sounds off.
Both VHF and boat stereo speakers have the same impedence (4ohms), so in fact he can use his boat speakers with his VHF radio with this automatic band separator.

That gizmo will only isolate the AM/FM receiver from the VHF when the latter transmits (to protect the AM/FM receiver from damage). It has nothing to do with want the OP appears to want to do.

springhead · Jul 15, 2010

Re: VHF & AM/FM Radios

wow you guys dont get it it, stop bashing me and this thread, you hook up one of the boat speakers to your vhf radio and when the vhf radio recieves or transmits the am/fm radio stops working, the only other way to use a boat speaker with the vhf radio together with the boat speakers is to put in a manual switch, yes I know it shares the antenna and for 43 dollars it works well on my boat,

bruceb58 · Jul 15, 2010

Re: VHF & AM/FM Radios

springhead said:
wow you guys dont get it it, stop bashing me and this thread, you hook up one of the boat speakers to your vhf radio and when the vhf radio recieves or transmits the am/fm radio stops working, the only other way to use a boat speaker with the vhf radio together with the boat speakers is to put in a manual switch, yes I know it shares the antenna and for 43 dollars it works well on my boat,

So what happens when the VHF is receiving and both the VHF radio and the AM/FM radio are driving the same speakers? This device does nothing for this situation.

http://www.shakespeare-marine.com/images/main/4357-s.jpg

As seen in the photo, the device only hooks up to the antennas and does not hook up to either radio's power or speakers.

And here are the instructions. Again, nothing to do with speakers.
http://www.shakespeare-marine.com/pdf/4357-s.pdf

NYBo · Jul 15, 2010

Re: VHF & AM/FM Radios

springhead said:
wow you guys dont get it it, stop bashing me and this thread, you hook up one of the boat speakers to your vhf radio and when the vhf radio recieves or transmits the am/fm radio stops working

Absolutely not. It only blocks antenna signals to the AM/FM radio when the VHF transmits. When the VHF is receiving, it will be mixing its audio signal with the AM/FM radio, exactly what the OP is trying to prevent.

phwrd · Jul 16, 2010

Re: VHF & AM/FM Radios

David,
Thanks for your help. Sorry for the abuse your answer has caused you.

I will let everyone know what happens once I do get it hooked up. At best, it does what i want it to do. At the worse, i don't have to add another antena for the am/fm.

RickJ6956 · Jul 17, 2010

Re: VHF & AM/FM Radios

I built a device 20 years ago for my '86 Four Winns cuddy that used a transistor and relay to switch from the head unit to the VHF whenever it detected a signal from the VHF. If your soldering skills aren't up to snuff, find a teenager. There are probably 20 or more walking around the marina.

It's inserted between the head unit and amp, so it requires an amp. It could be made to work with speaker outputs, but if you have 4 speakers it may be too much load for the VHF.

The AM/FM plays until a signal is detected from the VHF. The potentiometer (volume pot) sets the sensitivity for the circuit to activate. When a signal is detected, the transistor turns on and energizes the relay coil. The diode prevents back voltage from causing audible pops.

Use the VHF's volume control to match the volume level with the AM/FM.

jhebert · Jul 17, 2010

Re: VHF & AM/FM Radios

I don't recommend connecting one speaker to two audio amplifiers simultaneously. Whether it will work or not depends a great deal on the circuitry used in the audio amplifiers. In the worst case, you could damage one or both of the amplifiers.

The antenna sharing device recommended does not perform the function required in the initial posting, even though the initial poster seems convinced it does, that is, it does nothing for the problem of combining the audio output of two amplifiers into one speaker. Even though several people have clearly pointed out this problem, the proffered advice has fallen on deaf ears and seems to be ignored.

RickJ6956 · Jul 20, 2010

Re: VHF & AM/FM Radios

I replaced the original drawing with one that has all the details.

I agree, jhebert. The output impedance of an amp is extremely low -- 2/10ths of an ohm or less. Connecting one to another would mean both would be operating into the equivalent of a direct short.

Hawk Eyes · Jul 20, 2010

Re: VHF & AM/FM Radios

Splat said:
There is no easy way to do what you want.

Why do you want to drive your vhf through your stereo? If its hard to hear while underway you'd better off hooking up a external speaker, they make a world of difference in clarity of sound compared to the speaker on the vhf. You can even daisy chain 2 or more, however you would want a amplified external speaker at that point.

Bill

Can I get that as a subwoofer....

VHF & AM/FM Radios

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