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Old 13-01-2013, 15:04   #16
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Re: Where to Mount Antenna For SSB DSC

OK, I was unaware you could do test messaging and actually when DSC first came out the USCG prohibitied it, at least doing test DSC calls to the USCG.

It seems that has all changed now...

I just found the USCG Notice indicating that all DSC radios built on or after March 25, 2011 must have additional features, including the ability to run a test with Rescue 21 (USCG).

Here is the link to the USCG DSC Page with instructions on how to run a test and everything you ever wanted to know about Digital Selective Calling.

Now I understand we can all keep using our radios produced before March 2011, but is there going to be software upgrades for the older ICOM 802 in paticular?
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Old 13-01-2013, 16:03   #17
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Re: Where to Mount Antenna For SSB DSC

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Originally Posted by jeremiason View Post
OK, I was unaware you could do test messaging and actually when DSC first came out the USCG prohibitied it, at least doing test DSC calls to the USCG.

It seems that has all changed now...

I just found the USCG Notice indicating that all DSC radios built on or after March 25, 2011 must have additional features, including the ability to run a test with Rescue 21 (USCG).

Here is the link to the USCG DSC Page with instructions on how to run a test and everything you ever wanted to know about Digital Selective Calling.

Now I understand we can all keep using our radios produced before March 2011, but is there going to be software upgrades for the older ICOM 802 in paticular?
My 802 from the 2008 vintage includes the 'test' DSC message. Check page 36 of the current manual.
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Old 13-01-2013, 17:52   #18
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Re: Where to Mount Antenna For SSB DSC

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Originally Posted by Dockhead View Post
Height is king only for line of sight propagation like VHF.

Whether or not the frequencies used by SSB DSC are line of sight or not, I don't know. That was kind of my question.

I do know that Navtex signals, which are also in the HF band somewhere, are not line of sight and actually work better if the antenna is closer to the water.
Absolutely right: height is important for VHF communications because that is primarily line-of-sight plus about 20%.

However, height is NOT of similar importance for HF radio transmissions. In fact, vertical antennas mounted close to the water typically have a lower vertical angle of radiation ("takeoff angle") and, thus, greater distance potential.

DSC signals to/from your 802 fall within the HF spectrum (3000 to 30000 kHz). They have long-distance potential because they use signals which are reflected off the ionosphere, and under the right propagation conditions and an appropriate frequency can cover many thousands of miles.

By the way, DSC signals are not SSB (single sideband); they are digital. In the marine world, the term, SSB, is typically used incorrectly to refer to a type of marine radio, when in fact SSB refers to a type of modulation of radio voice signals.

Ham radio operators also use SSB, as do aircraft, military, land-mobile, emergency, and other service users. SSB modulation has been in wide usage for over 60 years.

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Old 14-01-2013, 01:49   #19
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Re: Where to Mount Antenna For SSB DSC

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I had assumed the reply to the 'Test' message was automated. But you are right in that calling them would at least let me know if they received my request.

I dont know the ICOM radio, but the Furuno SSB with DSC which I am used to using, you can set up a routine DSC call to a individual vessel.
If you know someone with a MF/HF DSC radio, you could schedule a DSC call with them to establish if the set is working OK
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Old 14-01-2013, 01:58   #20
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Re: Where to Mount Antenna For SSB DSC

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Originally Posted by btrayfors View Post
Absolutely right: height is important for VHF communications because that is primarily line-of-sight plus about 20%.

However, height is NOT of similar importance for HF radio transmissions. In fact, vertical antennas mounted close to the water typically have a lower vertical angle of radiation ("takeoff angle") and, thus, greater distance potential.

DSC signals to/from your 802 fall within the HF spectrum (3000 to 30000 kHz). They have long-distance potential because they use signals which are reflected off the ionosphere, and under the right propagation conditions and an appropriate frequency can cover many thousands of miles.

By the way, DSC signals are not SSB (single sideband); they are digital. In the marine world, the term, SSB, is typically used incorrectly to refer to a type of marine radio, when in fact SSB refers to a type of modulation of radio voice signals.

Ham radio operators also use SSB, as do aircraft, military, land-mobile, emergency, and other service users. SSB modulation has been in wide usage for over 60 years.

Bill
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OK, and the conclusion is? OK to put this antenna on the pushpit, or should it be up the mast?
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Old 14-01-2013, 02:04   #21
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Re: Where to Mount Antenna For SSB DSC

By the way, I have a NASA freestanding Navtex receiver, inherited from the PO, which has a dedicated ICS antenna on the pushpit. Can I use the same antenna for both purposes? Through a splitter?
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Old 14-01-2013, 02:52   #22
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Re: Where to Mount Antenna For SSB DSC

I connected the DSC antenna from my Icom 802 to the aluminum toerail. Seems to work OK.
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Old 14-01-2013, 03:34   #23
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Re: Where to Mount Antenna For SSB DSC

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I connected the DSC antenna from my Icom 802 to the aluminum toerail. Seems to work OK.
My toerail is solid teak. Somehow don't think that will make a good antenna!
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Old 14-01-2013, 04:44   #24
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Re: Where to Mount Antenna For SSB DSC

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OK, and the conclusion is? OK to put this antenna on the pushpit, or should it be up the mast?
Put it on the pushpit, not up the mast.

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Old 14-01-2013, 06:12   #25
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Re: Where to Mount Antenna For SSB DSC

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Originally Posted by btrayfors View Post
Put it on the pushpit, not up the mast.

B
Thanks! The pushpit it is. I've got a spot for it and even an existing gland to run the cable through, from a previous Navtex antenna, since removed.

I now understand that I was confused about using a Navtex antenna. That's tuned for 490 -- 512 khz and will never work. I was confusing Navtex and Weatherfax, which operates on similar frequencies to HF DSC. So I guess the Metz antenna it will be.

A bit of thread drift -- do those with SSB installations nevertheless keep their separate Navtex receivers? I know you can pick up Navtex broadcasts using the M802, but I think you need to be tuned in with the computer set up to receive them at the right times -- bit of a PITA compared to having a dedicated receiver. What do you guys think?

I don't use Navtex all that much since around the coasts here I always have Internet access and pick up the messages online. But I do use it if I just need a quick look at the shipping forecast and don't feel like going on line. And it seems like it's something one would like to have for when you're out of sight of land.

Weatherfax I guess makes sense doing over the SSB -- it's a lot of data. This I guess will be really valuable on a longer passage.
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Old 14-01-2013, 07:00   #26
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Re: Where to Mount Antenna For SSB DSC

You can connect a wire coat hanger to the DSC receive on the Icom 802 and it will work, but the only ones who maybe listening are the big ships and base/land stations who are the ones you want to get your call anyway. Most cruisers, myself included only turn the HF on at certain times of the day, so really having the DSC receive function is a bit mute.
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Old 14-01-2013, 09:21   #27
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Re: Where to Mount Antenna For SSB DSC

There is obviously a few confused souls as to DSC on MF/HF

Quote:
Not key in an emergency? It is how you will receive your reply to a DSC SOS! Your SOS will still be broadcast using your SSB antenna but you will know it is received (DSC acknowledged) on the DSC antenna so it is my understanding that you will not get a reply to your DSC SOS if you do not have this working.
Do not take this as expert advice but I am not a dummy,
The radio does not need a DSC receiver in order to generate a DSC Distress Signal. SO yes in an emergency , where you have lost the DSC receiving antenna, you wil ( or may)l not get the DSC Distress Ack, Thats doesnt matter GMDSS requires that all DSC messages are followed by voice, SO you will be talking on voice. Of course I would humbly suggest that if you are in extremis, with antennas down, maybe you're not too worried about DSC Distress Ack.

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Old 14-01-2013, 09:24   #28
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Re: Where to Mount Antenna For SSB DSC

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A bit of thread drift -- do those with SSB installations nevertheless keep their separate Navtex receivers? I know you can pick up Navtex broadcasts using the M802, but I think you need to be tuned in with the computer set up to receive them at the right times -- bit of a PITA compared to having a dedicated receiver. What do you guys think?
why would you drop Navtex, Its the better of all the systems on board, especially around Europe.

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Old 14-01-2013, 09:31   #29
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Re: Where to Mount Antenna For SSB DSC

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why would you drop Navtex, Its the better of all the systems on board, especially around Europe.

dave
I never suggested dropping Navtex altogether. I was only musing about whether or not a standalone Navtex receiver is needed if you have an SSB connected to your computer, as I will soon (I already have all the gear including Pactor III, antenna tuner, and antenna, and all the cabling, just need to install it).

It seems to me, although the only thing I know about using SSB is from books, that it's somewhat inconvenient receiving Navtex messages over the SSB and thus better to leave the standalone receiver.

I have an el-cheapo NASA Target Navtex receiver. I kind of covet one of those panel-mounted ICS Navtex receivers with the built-in thermal printers. All you have to do is pull off the printed report -- cool.
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Old 14-01-2013, 09:47   #30
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Re: Where to Mount Antenna For SSB DSC

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I never suggested dropping Navtex altogether. I was only musing about whether or not a standalone Navtex receiver is needed if you have an SSB connected to your computer, as I will soon (I already have all the gear including Pactor III, antenna tuner, and antenna, and all the cabling, just need to install it).

It seems to me, although the only thing I know about using SSB is from books, that it's somewhat inconvenient receiving Navtex messages over the SSB and thus better to leave the standalone receiver.

I have an el-cheapo NASA Target Navtex receiver. I kind of covet one of those panel-mounted ICS Navtex receivers with the built-in thermal printers. All you have to do is pull off the printed report -- cool.
I had the ICS printing one on the last boat , fab piece of kit , interfaced to the GPS it switched stations automatically, The paper is a great energy saver. Pity they discontinued the model.

I think you may have confused things, To my knowledge real time Navtex is not available over the internet and therefore cannot be picked up using your Pactor modem. What you are comparing may be weather fax. That is available digitally and therefore I would question the need for standalone weather fax. ( though again the printer is great).

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