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Old 14-01-2022, 05:29   #16
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Re: What are these things on my mast?

The primary difficulty (other than the loss of efficiency due to a mis-matched antenna), is when the VHF is transmitting, for example, the large power surge is presented to the SSB receiver. There are relays available to prevent this problem, but the loss of power in the relay and the increased complexity makes them less likely to be used.

I like the word gizmo in this case - it seems exactly right to me.
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Old 14-01-2022, 09:52   #17
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Re: What are these things on my mast?

Quote:
Originally Posted by alctel View Post
1 is half a wind indicator
2 is your VHF antenna
3 looks like a backstay insulator
I agree but would add that numbers 1 and 2 are probably an VHF antenna (usually the one with what's left of a windex on it) and the other is either an FM radio antenna or a separate AIS antenna. He said he has an FM radio, but did not mention whether he had AIS as well. Older VHF/FM splitters worked reasonably well but not so well with VHF/AIS. If this is an older setup it's quite likely to be a separate AIS antenna. You can now get active splitters that allow you to have all three fed by one antenna without any signal loss on any of them. I have a Quark-Elec active splitter that works a treat with all three input/outputs. (VHF transceiver, Class B AIS and FM radio)
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Old 16-01-2022, 10:55   #18
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Re: What are these things on my mast?

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Originally Posted by captstu View Post
The primary difficulty (other than the loss of efficiency due to a mis-matched antenna), is when the VHF is transmitting, for example, the large power surge is presented to the SSB receiver.

Hmm... not sure I understand the issue here, if any. When the VHF transmits at all of 25 watts through its whip antenna on top of the mast, entirely above the SSB's backstay antenna, the SSB receiver isn't likely to notice, nor is its front end tuned anywhere close to VHF, topping out around 30 MHz (vs 150+ for VHF).



Transmitting on the SSB at ~100W peak levels may well affect other ship systems, though infrequently on voice peaks.


It's also less likely for someone to be using both radios simultaneously.



The only interaction I've ever noticed on my boat (Standard Horizon GX2200 VHF, Icom M-802 SSB with AT-140 tuner on a ~42' long wire from the stern arch to near the masthead) is that the refrigeration compressor puts an intolerable whine into the M802 headphones, though not the speaker. Still working on filtering that out.
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Old 21-01-2022, 08:00   #19
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Re: What are these things on my mast?

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Originally Posted by suiramor View Post
What are these three gizmos attached to the top of my mast (see picture)? I assume they are related to my VHF transceiver. I also have a regular FM receiver onboard. If I install a ham radio for HF/SSB comms, can I re-use any of these wires?
By their apparent length, they seem to be VHF antennae. But that is only by rough reckoning. You need to climb up and look for manufacturer data on them. Should be a model number at the base that you can look up. If it is weathered off, you might bring them to a technician who has seen every antenna on the market. Might be able to identify. You definitely need to identify them before connecting a radio to avoid damaging the radio by frequency mismatch. As a general observation, an antenna for ham bands useful for long range coms will be quite long like a marine single side band antenna, due the long wave length. Such an antenna might have a tuner box at its base, or if one had been there, you should find mounting brackets or bolt holes.
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Old 21-01-2022, 08:10   #20
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Re: What are these things on my mast?

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Originally Posted by MicHughV View Post
#1 is just a piece of wire attached to your wind indicator to prevent birds from sitting there.
#2 is a vhf antenna
# 3 is an " insulator".....you'll probably find another one lower down. The lenght of the stay between insulators is your " antenna" for SSB/Ham radio. This stay will have to "tuned" , usually done by an automatic antenna tuner which will be part of your SSB/Ham setup.
I think #1 is a winded.
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Old 21-01-2022, 10:27   #21
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Re: What are these things on my mast?

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Originally Posted by alctel View Post
1 is half a wind indicator
2 is your VHF antenna
3 looks like a backstay insulator
Not a radio person, but could this be referred to better as an ISOLATOR as opposed to insulator?
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Old 21-01-2022, 11:28   #22
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Re: What are these things on my mast?

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Originally Posted by billdomb View Post
Not a radio person, but could this be referred to better as an ISOLATOR as opposed to insulator?
Insulators are used on backstay. An isolator generally refers to a device that separates signals based on frequency. Insulator is a simpler device that stops DC or if big enough it will stop RF also.
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Old 21-01-2022, 11:57   #23
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What are these things on my mast?

Quote:
Originally Posted by AlanR View Post
”IMO, I would now bother with SSB.”


A good example of posting the opposite to what you meant?



"I would not bother with SSB."



It pays to read before you post.



Best wishes,



Alan


Autocorrect issue as well as not double checking.
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Old 21-01-2022, 12:05   #24
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Re: What are these things on my mast?

The reason the VHF antenna can’t be used for SSB is that it is the wrong length and visa versa.

The physical dimensions of an antenna need to be somewhat closely related to the wavelength of the frequency being transmitted.

There are ways to make antennas much shorter than the wavelength being used work but there are significant tradeoffs in power and efficiency.
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Old 21-01-2022, 12:07   #25
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Re: What are these things on my mast?

Thanks again. I already have a Std Horizon 1600 and an em-trak AIS unit installed and working fine so clearly the VHF antenna is working. I also have an FM radio so perhaps it is using one of these 'gizmos' as its antenna. My main objective is not to change any of that - its working great - but whether adding an SSB radio will require another trip to the top of the mast or whether I can re-use what I have. Seems like the right backstay setup is an option. The backstay does not have any wires coming from it from above the bottom insulator so either the previous owner did not complete the SSB installation or removed that part before selling the boat. I will check with an antenna expert before installing a new SSB radio connection onto that backstay. Thanks all.
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Old 22-01-2022, 19:21   #26
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Re: What are these things on my mast?

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Originally Posted by suiramor View Post
This was the most agreement I have ever seen on this forum Thanks for your replies. Yes, there is another insulator at the bottom of the backstay - I will check for wires when next on the boat. I am still not clear whether this antenna can be shared by both the existing VHF transceiver and a new HF/SSB ham radio? Thanks again.



(I was just experimenting with my English with 'gizmo' - did not mean any offence).
Nope can't be shared, use the isolated back stay/tuner.
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Old 23-01-2022, 16:13   #27
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Re: What are these things on my mast?

#1 is the windwane as others have identified. The good news is that it is super easy to fix once you get to the top. I've just done mine. Go to WestMarine and pickup Davis Instruments 3150 Windex 15 for $40. This is an exact replacement for your unit and swapping is as easy as unscrewing old one and screwing in the new one. 5 minutes aloft.
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Old 23-01-2022, 21:10   #28
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Re: What are these things on my mast?

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Originally Posted by George_SD View Post
#1 is the windwane as others have identified. The good news is that it is super easy to fix once you get to the top. I've just done mine. Go to WestMarine and pickup Davis Instruments 3150 Windex 15 for $40. This is an exact replacement for your unit and swapping is as easy as unscrewing old one and screwing in the new one. 5 minutes aloft.
Thanks. My next to do. Plus finding someone who will hoist me to the top. The drone won't do it
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