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Old 28-06-2022, 06:57   #1
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Sailor 7222 or Sailor 6222-VHF DSC channel 70

Is anybody able to help me?

I'm designing a system with Sailor 7222. I'm going to install two Antennas on the roof of the building (one antenna for receiving VHF DSC channel 70 signal from a device next to Jetty and one Antenna to acknowledge the signal). Both antennas will be connected to the transceiver 7226 inside the building. The problem that I have is:
There is only one existing coaxial cable from the rooftop of the building to the transceiver inside the building and I'm not able to run another coaxial cable due to the huge cost. I'm curious if I can use a combiner like RF hybrid coupler or similar to combine both antennas, so I'd be able to use only one cable?

If it's not gonna work what would be the reason?
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Old 29-06-2022, 19:10   #2
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Re: Sailor 7222 or Sailor 6222-VHF DSC channel 70

Mark,
If your requirement is a Class A VHF-DSC-FM Radiotelephone, then you cannot do what you desire without running additional cabling....(either an additional coax for the DSC receive antenna.....or a network cable to allow you to install a 7222 transceiver unit in a weather-proof case outdoors and use a network cable to allow the 7226 control inside).

The "main" antenna, called the Tx/Rx antenna by Sailor, is the transmit and receive antenna, and hence you cannot simply combine this with/into the VHF-DSC receive antenna....as this would instantly damage (blow-up) the DSC receiver, upon the first transmission made by the radio.

And, btw, you'd also need to keep these two antennas separated by significant distance to keep the radio's transmit signal from damaging the DSC receiver and/or to keep the transmitter from de-sensitizing the DSC receiver....(fyi, I'm pretty sure this is explained in the 7222 manual? at least it was, as far as I can recall, in the 6222 manual)


So, I'd recommend using a Class D VHF-DSC-FM Radiotelephone.....such as the Sailor 6215, etc...


Quote:
Originally Posted by Mark_Telecom View Post
Is anybody able to help me?

I'm designing a system with Sailor 7222. I'm going to install two Antennas on the roof of the building (one antenna for receiving VHF DSC channel 70 signal from a device next to Jetty and one Antenna to acknowledge the signal). Both antennas will be connected to the transceiver 7226 inside the building. The problem that I have is:
There is only one existing coaxial cable from the rooftop of the building to the transceiver inside the building and I'm not able to run another coaxial cable due to the huge cost. I'm curious if I can use a combiner like RF hybrid coupler or similar to combine both antennas, so I'd be able to use only one cable?

If it's not gonna work what would be the reason?
FYI, some might say you could use a duplexer and design your system as a you would a VHF repeater, using one side of the duplexer for your VHF transmit and receive (at some freq at least 500khz / .5mhz away from the DSC freq of 156.525mhz) and the other side for DSC receive (156.525mhz).....but, this isn't really practical, as most of the VHF maritime simplex / working channels are VERY close to ch. 70 / 156.525mhz....and, since you'd obviously need to transmit on ch. 70 as well as ch. 16 (156.800mhz), it just ain't going to work! (sorry!)

Oh, btw, in case someone wishes to argue the absurdity of the possibility of "what-if's"....even if you had the ability to use channels/freqs significantly separated in frequency of say one megahertz or more (which you do not), and if you still had a requirement to use two antennas (although, I cannot see why), you'd need a second duplexer outside (in a weather-proof cabinet) to connect your 2 antennas to still allow the transmit / receive signals in-and-out, and the DSC signals in....

Bottom-line here....if you must use a Class A radio, you must use two antennas with two feedlines.....and, these antennas should be kept at least 5m _(~ 16') apart, and preferably one-above-the-other....
[this is something I have a great deal of experience with, btw...]
BUT....

But, the real bottom-line is:
What you desire to do is not going to work without two coaxes...and, your simple, easy, and inexpensive solution is to use a Class D VHF-DSC-FM Radiotelephone!




Mark, I hope this helps?

Fair winds.

John



P.S. Anyone required to install a Class A system, should have the training and expertise to know all the above, so I assume the "requirement" for a Class A radio is not really a requirement?
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Old 02-07-2022, 06:53   #3
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Re: Sailor 7222 or Sailor 6222-VHF DSC channel 70

Quote:
Originally Posted by ka4wja View Post
Mark,
If your requirement is a Class A VHF-DSC-FM Radiotelephone, then you cannot do what you desire without running additional cabling....(either an additional coax for the DSC receive antenna.....or a network cable to allow you to install a 7222 transceiver unit in a weather-proof case outdoors and use a network cable to allow the 7226 control inside).

The "main" antenna, called the Tx/Rx antenna by Sailor, is the transmit and receive antenna, and hence you cannot simply combine this with/into the VHF-DSC receive antenna....as this would instantly damage (blow-up) the DSC receiver, upon the first transmission made by the radio.

And, btw, you'd also need to keep these two antennas separated by significant distance to keep the radio's transmit signal from damaging the DSC receiver and/or to keep the transmitter from de-sensitizing the DSC receiver....(fyi, I'm pretty sure this is explained in the 7222 manual? at least it was, as far as I can recall, in the 6222 manual)


So, I'd recommend using a Class D VHF-DSC-FM Radiotelephone.....such as the Sailor 6215, etc...




FYI, some might say you could use a duplexer and design your system as a you would a VHF repeater, using one side of the duplexer for your VHF transmit and receive (at some freq at least 500khz / .5mhz away from the DSC freq of 156.525mhz) and the other side for DSC receive (156.525mhz).....but, this isn't really practical, as most of the VHF maritime simplex / working channels are VERY close to ch. 70 / 156.525mhz....and, since you'd obviously need to transmit on ch. 70 as well as ch. 16 (156.800mhz), it just ain't going to work! (sorry!)

Oh, btw, in case someone wishes to argue the absurdity of the possibility of "what-if's"....even if you had the ability to use channels/freqs significantly separated in frequency of say one megahertz or more (which you do not), and if you still had a requirement to use two antennas (although, I cannot see why), you'd need a second duplexer outside (in a weather-proof cabinet) to connect your 2 antennas to still allow the transmit / receive signals in-and-out, and the DSC signals in....

Bottom-line here....if you must use a Class A radio, you must use two antennas with two feedlines.....and, these antennas should be kept at least 5m _(~ 16') apart, and preferably one-above-the-other....
[this is something I have a great deal of experience with, btw...]
BUT....

But, the real bottom-line is:
What you desire to do is not going to work without two coaxes...and, your simple, easy, and inexpensive solution is to use a Class D VHF-DSC-FM Radiotelephone!




Mark, I hope this helps?

Fair winds.

John



P.S. Anyone required to install a Class A system, should have the training and expertise to know all the above, so I assume the "requirement" for a Class A radio is not really a requirement?
Thank you so much, John. You really explained the reason and the recommendation well and were understandable.

Mark
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