Does size matter? AM/FM Antenna options

[Bycrick]

I’m with continuouswave. I can’t think of a single case of FM modulation being used in what’s normally defined as HF, ie below 30MHz. FM requires a lot of spectrum space relative to other modulation techniques. A commercial FM broadcast station has a channel 200KHz wide, with 150KHz potentially used by the modulation. That doesn’t make room for many stations at 500-1500 KHz.

The mathematics rules against FM on HF and lower frequencies. The modulation side bands in FM occur at harmonics of the modulation frequency. So even a maximally filtered FM voice transmission (300-3000 Hz, requires the bandwidth of an AM broadcast station and certainly wouldn’t be much use for broadcasting. Even marine VHF has 25khz wide channels.

I’d love to see a reference to stations using FM for voice communications on frequencies below 30 MHz.

[Jammer]

Originally Posted by S/V Illusion

Just to be clear, not all FM is in the VHF/UHF spectrum; some are in the HF spectrum similar to broadcast AM station signals.

I must admit that I've never encountered this even though I've done a fair amount of shortwave listening. I understand that there are some areas that use VHF low band for FM broadcast, notably the 65.8-74 MHz band in Eastern Europe and the 76-95 MHz band in Japan. But these are not HF.

Having said that, a longer, higher antenna will always out perform a small, low one.

I don't think that is universally true for AM broadcast reception, because such reception is often noise limited. For FM, of course, there are particular lengths and shapes that work better.

[Kelkara]

Originally Posted by Bycrick

I’m with continuouswave. I can’t think of a single case of FM modulation being used in what’s normally defined as HF, ie below 30MHz.

I don't know if anyone uses it, but the top end of the 10m amateur band in Canada is allocated for FM use (29.52 - 29.7 MHz).

[Bycrick]

I can remember when hams used to take FM mobile equipment, often old police or fire FM radios and convert them for 10-meter ham rigs. But my assumption was that this discussion was about broadcasting.

I also remember about 50-years ago a company that measured the frequencies of AM broadcast stations all over the US from a site in Kansas City. They had tens of acres of various antennas pointed in different directions. But I don’t think that logic applies to anything you’re going to put on a boat.

[continuouswave]

Originally Posted by S/V Illusion

And if/when I do, will you respectfully apologize for the implication I was incorrect?

Since you have been spectacularly incorrect in prior posts, no, I cannot make any promises. You seem to be playing this awfully coy. If you are holding any cards, time to lay down.

In any case, your comments were hardly making "clear" anything related to the original question about antennas. Clearly not your area of expertise.

[Lake-Effect]

Only CF can turn a thread about relays into a p1ssing contest. Nothing like a forum full of bored boaters

[continuouswave]

Originally Posted by Lake-Effect

Only CF can turn a thread about relays into a p1ssing contest. Nothing like a forum full of bored boaters

There are several informative and useful replies in this thread about antennas for reception of AM Broadcast Band and FM Broadcast radio stations on a boat.

There is nothing in this thread about relays.

People who join discussions for the purpose of changing the topic of the discussion to the the discussion itself or change the topic of the discussion to the participants of the discussion are DOING MORE HARM than anyone else.

If you do not like this forum, you should stop reading it. It hardly matters to me if you read it and you think your opinion about it is crucial for others to know. It is not important to me.

If this website or this forum wanted to DISCUSS ITSELF, then it would have a special topic area where you could go, and in that special topic area you could contribute your opinion about the website or the forum. As far as I can tell, the focus of this website is to discuss boating as related for cruising or sailing. This website does not try to discuss itself.

As general rule, forums that start to discuss themselves are not particularly useful and are headed for extinction.

I read this forum to learn useful information about electronics related to boats. I really don't care what others think of the forum, or this discussion, or of the participants in the forum or in this discussion. Those are not topics I have any interest in.

[Jammer]

Originally Posted by continuouswave

There is nothing in this thread about relays.

There's a separate relay thread that has also, well, exhibited a nonlinear decline in the signal-to-noise ratio.

[Lake-Effect]

Originally Posted by Jammer

There's a separate relay thread that has also, well, exhibited a nonlinear decline in the signal-to-noise ratio.

Yes, I conflated the two. My bad, Sorry. But yes... similar.

[PegasusPete]

What should I use as as an antenna for AM FM reception via Fusion stereo?
Old one died so have just upgraded boat stereo system.
I have a length of coax with a motorola plug on one end that plugs into stereo.
coax would live in electrics cabinet and when reception was dodgy I'd pull it out along cabin to improve reception.

What would be the best place to connect the other end of the coax?
No I'd prefer no to install a dedicated antenna.

Options I see are;
HF antenna being insulated stay
Stainless Chain plate attached to rigging
Stanchion base attached to S/S life lines
Then the next question is what the inner conductor and the shield/ ground should/should not be connected to?
Suggestions would much appreciated.

[CaptTom]

Originally Posted by Jammer

...exhibited a nonlinear decline in the signal-to-noise ratio.

Not only did I learn a bit about AM and FM radio from this thread, but I also learned a great turn of phrase which I fully intend to plagiarize some day.

[Spot]

Originally Posted by PegasusPete

What should I use as as an antenna for AM FM reception via Fusion stereo?
Old one died so have just upgraded boat stereo system.
I have a length of coax with a motorola plug on one end that plugs into stereo.
coax would live in electrics cabinet and when reception was dodgy I'd pull it out along cabin to improve reception.

What would be the best place to connect the other end of the coax?
No I'd prefer no to install a dedicated antenna.

Options I see are;
HF antenna being insulated stay
Stainless Chain plate attached to rigging
Stanchion base attached to S/S life lines
Then the next question is what the inner conductor and the shield/ ground should/should not be connected to?
Suggestions would much appreciated.

Hi Pete,
The coaxial cable is a method of shielding the antenna conductor until it reaches 'free air'. The center conductor is what is bringing the RF signal to the radio.

The only rules would be not to hook the center to the shield and not to hook either to a wire that is lit up with any other sort of power including the HF back stay.

Personally I'd spend a little more and get something discrete and modern (rubber duck, shark fin) to pair with the Fusion unit, wire it, forget about it, and go boating. This will remove the homemade clip and random wire/cable antenna as a potential downfall from the signal chain.

[PegasusPete]

Thanks Spot,
Now I have a better understanding.
After I posted the question I thought attaching to HF aerial might be a good way to cook the stereo.
I forgot to mention, I'm trying to avoid drilling a hole through to topside.
Think I might try a rubber duck or shark fin inside the cabin to start with.
I note you can get amplified shark fins.
Another power connection, I wonder if it's worth it?

[Jim Cate]

for a reasonable antenna for broadcast band MF reception, simply connect the antenna terminal on the receiver to one of your chain plates. It will work fairly well, cost nothing and require no holes to be drilled.

The simplest way to do the FM is to buy a cheap automotive antenna from your local car parts emporium. Try it below decks in a vertical orientation. If not good enough, try on deck or suspended higher. Not optimal, but how much effort are you willing to expend on this project?

Jim

[goboatingnow]

There are still people listening to broadcast radio , via the airwaves I’ll be dammed.

Next you’ll be telling me you ride a horse to work

My AM/FM radio on the boat went into the recycle skip 4 years ago.