youen
Well-Known Member
How can you link a coaxial wire to an isolated backstay to get an efficient antenna ?Thanks
Antenna
- Thread starter youen
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VicMallows
Well-Known Member
The very first question is: an antenna for what? What frequency?
youen
Well-Known Member
I want only to receive BBC or France inter on 198Khz AND 164 Khz in Galicia Spain
William_H
Well-Known Member
Do not use coaxial cable as such. However the centre of coaxial cable especially the RG8 (10mm) coax is excellent. The presence of the shield over the cable if it is earthed provides a very large capacitance to ground which may upset the tuning of your radio input circuits and tends to bypass the signals to ground. So just an insulated wire is best.
If the radio has a coax type input connector then just connect to the centre pin. The radio should however be earthed to the sea via the 12negative of the boat or by a wire from the outer shield of the aerial input. Coax cable is for 50 ohm characteristic impedance circuits but your antenna at those frequencies will be very high impedance. So large losses with coax.
The actual connection to the backstay is made by a clamp onto the SS wire or if it has copper swage then you can solder to that. good luck olewill
If the radio has a coax type input connector then just connect to the centre pin. The radio should however be earthed to the sea via the 12negative of the boat or by a wire from the outer shield of the aerial input. Coax cable is for 50 ohm characteristic impedance circuits but your antenna at those frequencies will be very high impedance. So large losses with coax.
The actual connection to the backstay is made by a clamp onto the SS wire or if it has copper swage then you can solder to that. good luck olewill
oldvarnish
Well-Known Member
Probably not best practice, but I used a jubilee clip to clamp the wire the the backstay.
Put a loop in it to prevent drips of water running down the wire and working their way through the deck.
Put a loop in it to prevent drips of water running down the wire and working their way through the deck.
Roberto
Well-Known Member
If it is just for reception, before all the hassle to thread the cable through the boat, up to the isolator, etc I would definitely make a few tries by simply connecting the radio for example to the internal metal reinforcing of a shroud, or to the base of a stanchion, etc
It just takes a few minutes, sometimes it's all you have to do for a good reception. Sometimes not, then you use the isolated backstay.
Sandyman
Well-Known Member
I use a bulk standard Earth Bonding strap. Works fine.
Billjratt
Well-Known Member
what receiver? - and will it ever be changed... If you use one that is meant to have an active aerial ( like a navtex ) then you need a capacitor in series to isolate the DC voltage from the rig ESPECIALLY if you don't have proper isolators in the backstay. If you bang DC up the rigging for a long period it will probably fall down. As for attaching - there are proper bronze clamps for the job, but as long as you protect the joint with self-amalgamating tape any decent clamp will do.
rob2
Well-Known Member
I'm ready to be shot down in flames here, but assuming there are no isolators in the backstay, wouldn't you expect acceptable conductivity for a receiving aerial from the chainplate? I'd try running a single core wire from the centre of the radio's socket to a ring connector on one of the chainplate bolts. If it works satisfactorily, then it has the advantage of all the extra bits being below deck and not subject to the weather. If it doesn't work all you have to do is snip it off the ring connector...
Rob.
Rob.
GHA
Well-Known Member
For wfax on ssb I've had decent reception just with the antenna of a portable reciever resting against a chainplate down below.
Whatever works works
Biscay 36
Well-Known Member
France Inter? thought that had been stood down.
Roberto
Well-Known Member
It's RFI Radio France Internationale that does not broadcast the weather bulletin any more, a pity because it was the only one to cover the whole of the E-W transatlantic; France Inter LW still broadcasts the Metarea II bulletin, if I am not wrong they just stopped broadcasting the western metarea III (west mediterranean).
