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Old 03-04-2015, 06:12   #1
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Antenna switch to use the backstay with a Sony portable?

I've got an Icom 802 with an tuner and backstay antenna. I also have a little Sony portable SSB receiver. I would like to use the Sony to get weatherfaxes, to leave it on 24/7 plugged into my pc, which is on 24/7 anyway. The aim of this is for convenience, to always have the latest faxes without any effort and to save power. The Icom uses about 3A. The Sony uses close to zero. It's not quite as good as the Icom, but is OK.

The Icom transmitter box is located at the nav station, next to where I hope to install the Sony. From the Icom there is a coax cable to the 140 tuner in the lazarette. I was planning to install an antenna switch to the output of the Icom with a small lead to the Sony antenna jack from the second output of the switch.

Would this work, does anyone see any problems?

Should the wire from the Sony to the switch be a coax and if so should the screen be connected at both ends?

I am worried I might forget to change the switch and transmit from the Icom with the Sony connected and blow up the unconnected output stage of the Icom. Is the Icom output not protected?

If I use the Icom to tune the 140 tuner and then switch over to the Sony will the tuner hold its tune setting?

As an alternative I could rig a second antenna. I haven't tried this. The backstay I think will give better reception than a length of horizontal wire in the overhead, or a wire to the shroud won't it?
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Old 03-04-2015, 07:11   #2
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Re: Antenna switch to use the backstay with a Sony portable?

Quote:
Originally Posted by poiu View Post
The Icom transmitter box is located at the nav station, next to where I hope to install the Sony. From the Icom there is a coax cable to the 140 tuner in the lazarette. I was planning to install an antenna switch to the output of the Icom with a small lead to the Sony antenna jack from the second output of the switch.

Would this work, does anyone see any problems?

Yes, I can see some problems. The tuner will not be tuned once you turn off the 802 because the tuner will power itself down.

Should the wire from the Sony to the switch be a coax and if so should the screen be connected at both ends?

The Sony will work with just a wire antenna. I would first just rig another thin wire. Run it around the boat to see how it works. You might be able to hide it behind some cabinetry.

I am worried I might forget to change the switch and transmit from the Icom with the Sony connected and blow up the unconnected output stage of the Icom. Is the Icom output not protected?

In theory the 802 is protected. But it's not the best idea to rely on this.

If I use the Icom to tune the 140 tuner and then switch over to the Sony will the tuner hold its tune setting?

No, but the reality is that tuning isn't that important for receive. Tuning is more important for transmit than receive. The reasons are somewhat complex but basically the receiver presents a good match to the antenna so tuning doesn't do that much.

As an alternative I could rig a second antenna. I haven't tried this. The backstay I think will give better reception than a length of horizontal wire in the overhead, or a wire to the shroud won't it?
I would try this last idea before giving up. You may be surprised to find that a long wire hidden above the head liner will work just fine. Be aware that LED lights often interfere with HF reception. If you have LEDs then check whether they cause any issues by turning them all on and off.
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Old 03-04-2015, 08:27   #3
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Re: Antenna switch to use the backstay with a Sony portable?

I have had good results using an uninsulated shroud as a receive only antenna for the DSC function on my SSB. Just make sure your backstay transmit antenna is properly insulated from the rest of your rig.
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Old 03-04-2015, 10:29   #4
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Re: Antenna switch to use the backstay with a Sony portable?

poiu,
1) First off, I could recommend a switch for you....but, as transmitterdan pointed out there will be some issues trying to do things the way you desire!!!


2) Secondly, Gary H has hit on a great approach, and I've been using a similar approach for > 10 years!
{I actually insulated on starboard, aft lower shroud, and feed it from the chainplate, with just a piece of RG-8x coax (with the shield connected to a keel bolt, and center to the shroud chainplate)....
This ~ 22' long vertical stay is my HF-DSC receive antenna and my WeFax receive antenna....
I did NOT design/install any sophisticated splitter, etc., as I found absolutely no LO ingress, nor any image issues at all just using a coaxial "Tee" fitting at the Nav Station to connect BOTH the Icom M-802's "DSC Receive" antenna jack and my Furuno FAX-408 WeFax receiver, to this shroud antenna...
This has worked perfectly for me for > 10 years, > 15,000 miles offshore, multiple Atlantic crossings, multiple full Gales, 3 days sailing thru a Tropical Storm, all at sea....as well as 3 direct hits from three Cat 3 hurricanes (while at anchor)....}

Since you need an HF-DSC receive antenna anyway, why not multi-task that one antenna for double-duty!!

Over the past 20 years, many folks have simply (temporarily) clipped a wire from their portable SW/SSB receiver to a shroud / stay, and used that for an effective HF receive antenna...
If you simply do a more permanent installation, using coax and a coaxial "Tee" connector, you can have both an HF-DSC receive antenna AND a WeFax receive antenna, all-in-one!!


And, yes....you CAN use the M-802 radio AT THE SAME TIME as receiving a WeFax....I do it all the time....and I even transmit while receiving a WeFax....
If you look at some of my videos regarding offshore weather, you can see some of my Wefax'es where I point out a few dark lines across the image, that are caused by my transmitting on the M-802, while receiving a WeFax...
https://www.youtube.com/playlist?lis...zdjTJjHlChruyY



3) FYI, the actual current draw of the M-802 in receive is between 2.0 and 2.1amps (depending on speaker use / volume)....
But, I understand that even that 2 amps x 24 hours, adds up to 48 A/H's per day!!!


4) Finally if you, or anyone else, is interested in what coaxial switch to use for some applications such as you describe...
I've been using Diawa CS-201's for decades (both on-shore and on-board....I use one to switch between my backstay and some vertical dipoles)!!
There are great little switches....and will last years and years, even on-board a cruising boat!!
Daiwa CS-201A Coax Switches CS-201A - Free Shipping on Orders Over $99 at DX Engineering

DAIWA CS-201A | DAIWA 2 POST GOOD TO 600MHZ SW

Daiwa CS-201: Ham & Amateur Radios - Equipment, Parts and Supply | AES

Daiwa CS-201 coax switch Product Reviews


Oh, and all of the above companies are good to deal with....but, I prefer DX Engineering....you can get the coax, and "Tee" connectors anywhere, but remember BUY good quality and you'll never regret it!!
With so much being sold on-line being "no-name" junk, I'd say buy only name-brand (Amphenol, Kings, etc. connectors)...





To sum up....
Dan gave you the direct answers....but...
Gary H gave you the best idea!!
Go with Gary's idea!!


If you have further questions, please ask away....but I might not be too available tonight...

Fair winds..

John
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Old 03-04-2015, 11:10   #5
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Re: Antenna switch to use the backstay with a Sony portable?

Fantastic info guys. Thanks.

So here it looks like simplest is best.

Amazing how well John's faxes work from the shroud.

My shrouds are attached to the mast and the mast is earthed to the keel bolts, so I suppose it might not work so well if the connection between the shroud and mast is good?

If the screen doesn't work perhaps I could attach the screen to the SSB ground?

I guess it doesn't take much to try. If it doesn't work well, I can try the ssb antenna.

Good suggestion on the DSC receive. It is not connected.
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Old 03-04-2015, 19:45   #6
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Re: Antenna switch to use the backstay with a Sony portable?

Poiu,

The shroud is connected to the mast but the mast isn't really "ground" at HF frequencies. Don't worry about that too much. Try what John said and I'll bet it will work.
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