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Old 24-02-2013, 13:46   #1
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SSB weatherfax receive only antenna

Hi Everyone,

I'm looking to obtain advice on setting up a fixed SSB recieve-only weather fax antenna. Currently, I have a masthead VHF antenna with splitter for my AIS that works quite well for that purpose. It also has an AM/FM BNC antenna connector on it that seems like it should work for my Kaito SSB reciever if I make a converting cable for it. My other option I think is to use my backstay as an antenna. SSB antennas that utilize the backstay must use an isolator so I hear, however I'm not sure if the reason for that is to improve transmitting only or to improve receive as well.

So, if anyone has any advice on what my best options are it would be much appreciated.

Thank you,

Cameron
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Old 25-02-2013, 15:38   #2
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Re: SSB weatherfax receive only antenna

Cameron,
Depending on how much you wish to spend ($$$) and how robust yiu wish to make the antenna, etc. the advice will vary....
And, of course WHERE you are sailing/cruising/voyaging, and WHAT STATIONS you'll be receiving weFax from.....
(I'm not sure is a "best option"!)
Quote:
Originally Posted by csmithers View Post
I'm looking to obtain advice on setting up a fixed SSB recieve-only weather fax antenna. Currently, I have a masthead VHF antenna with splitter for my AIS that works quite well for that purpose. It also has an AM/FM BNC antenna connector on it that seems like it should work for my Kaito SSB reciever if I make a converting cable for it. My other option I think is to use my backstay as an antenna. SSB antennas that utilize the backstay must use an isolator so I hear, however I'm not sure if the reason for that is to improve transmitting only or to improve receive as well.
So, if anyone has any advice on what my best options are it would be much appreciated.
1) First off, NO, your VHF whip is NOT going to work, no matter what the "splitter" output says....
So, you can remove that from your consideration.....
(BTW, on a side note, even thought the FM broadcast band isn't too far from VHF marine band, I've found VHF marine antennas to be fairly poor (mediocre, at best) FM broadcast rec antennas, and have found small vhf/uhf/tv/fm antennas to be far superior....)



2) For simple receive-only antennas, rigging insulators are not a necessity...(although I use them...)
The simplest/easiest HF receive antenna (for WeFax, etc.) to use on-board is:
a) clip a short wire to the chain plate of the stay/shroud CLOSEST to your radio, and attach this short wire to your radio's antenna terminal....
---- Or ----
b) If you do not have access to a chain plate / stay, that is close to your radio (a few feet or less), then use a short piece of coax cable from the radio's antenna jack to the shroud/stay chainplate, and attach ONLY the center conductor of the coax to the chainplate....
(if the chain plate is grounded, you can remove the green/ground wire and see if that improves reception / lowers the noise....but, since the rest of the rig is probably DC grounded, it's doubtful that this will make much difference...)



3) If you wish for better performance (probably, but not necessarily, better), you can rig any vertical wire antenna.....
a) A 20' - 35' long vertical wire strung up on a halyard / flag halyard, plugged-into your radio (Wefax receiver) will work well.....this costs little (even free, if grab some scrap wire out of a dumptser...
b) You could also rig an "alternative stay" antenna, using SS wire / SS lifeline wire, strung by halyard or permanently mounted, whether backstay or shroud....


4) Most WeFax reception will be from 6mhz to 12mhz (almost all between 4mhz to 17mhz), so an antenna optimized for the lower/middle of the HF spectrum is best....
This means an antenna of at least 20' long.....and as much as 40' - 45' long....(usually going longer than 45' is a detrimental, unless you will not be using freqs above 12mhz...)

So, use an antenna between 20' and 40' long....and you should be fine....



5) For more details on a WeFax receive antenna, have a read over the recent thread on HF-DSC receive antennas, as these are VERY similar uses and the needs/functionalities are almost the same....
ICOM M802 DSC antenna?




Cameron, I do hope this helps...

John
s/v Annie Laurie
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Old 25-02-2013, 15:57   #3
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Re: SSB weatherfax receive only antenna

I use my uninsulated backstay as a HF DSC receive antenna. When setting it up I briefly experimented by comparing it's receive performance with the 23 foot SSB whip that I primarily use. I found that even without insulators, it pulled in stations as well as the whip. Your backstay should work fine as a receive antenna for WxFax. Mine is wired with coax to the chainplate in the manner that John describes.

Best of luck,
Gary W9GJH
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Old 25-02-2013, 16:48   #4
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Re: SSB weatherfax receive only antenna

Thanks guys, this is exactly the answer I was looking for. My backstay is connected electrically to my boomkin and all the other stays except the lower shrouds and the inner forestay, so that may violate the 45' rule. I have a 40' mast. My inner forestay might be the logical choice. Failing that i'll use a piece of wire run up one of the spare blocks up at my masthead.

Sorry for not providing enough info there, I'm very impressed with the detailed response, ka4wja. I'm going to Mexico on the pacific side so i'll be interested in receiving faxes from Hawaii and California.

Thanks!
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