Multiple DSC units

[suiramor]

Should I enable DSC operation on my new ICOM803 if I already have DSC on my Standard Horizon GX1600 HF transmitter? Does it add anything except redundancy? (my only possible, hopefully unneeded use would be for emergency comms).
If yes, do I need to install a new HF antenna on the top of my mast, like the one used by Std Horizon or could I share the existing one?

[PippaB]

Confused. The M803 is an HF radio and the GX1600 is VHF?

Different frequencies, different antenna lengths, and different use cases, so if I had both aboard I would have DSC configured on both. Even if they were both VHF, why would you not set both up? Silencing alarms on two devices is the only reason I can think of not to set them up.

[suiramor]

Originally Posted by PippaB

Confused. The M803 is an HF radio and the GX1600 is VHF?....

I think it's me who is confused. I presumed that the separate, additional antenna 803M needs for DSC operation is a VHF antenna (and the unit somehow operates on these frequencies as well). Just rechecked the docs and realize that it is a separate HF antenna that's needed. I assume therefore that 803 operates its DSC on HF while Horizon on VHF. Is that correct?

What kind of antenna would I then install for 803M? The one I have for SSB goes via AT-140 to my backstay.

[PippaB]

The main antenna should work with your 140 and backstay, you will need a switch or some other method of switching connections between two radios.

The DSC antenna connection is for receiving DSC emergency alerts from other vessels. The radio can listen on those six frequencies even while in other operation - if you have a separate antenna connected. This would typically be an HF whip or similar, although finding space on a small boat can be a challenge. Depends on how much you want to be a good neighbor.

[suiramor]

Thanks so much for your replies PippaB.

Originally Posted by PippaB

The main antenna should work with your 140 and backstay, you will need a switch or some other method of switching connections between two radios.

Which two radios? My Std Horizon already has its own VHF antenna on the top of the mast. ICOM is using the backstay for its normal SSB HF.

Originally Posted by PippaB

The DSC antenna connection is for receiving DSC emergency alerts from other vessels. The radio can listen on those six frequencies even while in other operation - if you have a separate antenna connected. This would typically be an HF whip or similar, although finding space on a small boat can be a challenge. Depends on how much you want to be a good neighbor.

I can see plenty marine VHF whip antennas on the internet but no HF. Do you know of one?

[PippaB]

I misinterpreted “the one I have for SSB” as being a separate existing radio. So the 140 and backstay for the 803 main, then https://seatech.systems/product/metz...icom-m802-ssb/

Or the Shakespeare 393 ( the standard HF whip, it is 23’ long - hence the space question).

On a bigger vessel you can get some separation between the antennae, harder to do on our size boats.

[ka4wja]

Suiramor,
1) NO, you do NOT need / want a "switch"!

2) All of this is explained up in the "stickies" above....please have a look see.


3) But, 'til then....a simple, small HF wire or whip, fed with inexpensive coax...and mounted/installed out on a stern rail, etc., will work okay for you, for an HF-DSC receive-only antenna. (I used one myself for a few months, before "upgrading" to a longer antenna --- a 22' long insulated aft-lower shroud)

Both GAM and Metz sell such an antenna....and it should have been included in with your HF-DSC-SSB installation.

https://defender.com/en_us/gam-elect...jRqW9xwKGzycxW

https://seatech.systems/product/gam-...20zshz0V9Xts2S

https://www.metzantennas.com/product/weather-fax/


4) Suiramor, please forgive my bluntness....I mean NO offense at all...
But, if you're confusing your VHF and HF radios, I recommend that you take a few minutes and learn a bit about them / about HF radio and HF radiowave propagation....otherwise, I think you'll be disappointed in your HF system!

Further, if I were you....I'd do 3 things:
a) Read the above stickies and watch the videos! (and learn the basics of radiowave propagation, noises, static, interferences, etc....it will only take a couple hours!)
b) Call the guy that sold / installed your M-803, and ask him why he didn't finish the installation....AND why he didn't explain all of this to you!
c) Be prepared to rid your boat of RFI (Radio-Frequency-Interference) producing devices! (lots of info about RFI in the stickies)


First step is to click here...
https://www.cruisersforum.com/forums...ml#post3932684

Watch those videos....and read thru those postings....
Then, come on back here and ask some more questions....and we'll get you going!


Fair winds.
John