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Roberto
Well-known member
Re: My turn now - split aerial advice needed
I do not know the furuno wfax in particular, but it must not be too different from a good hf receiver. I would use a different aerial just to make things simple and not having the need to remember on/off/on; especially as you want to keep it running all day long.
Either a long wire or a dipole (don t worry too much about length, longest would do) can be put in the inside of the boat, for example under the roof lining, and forever forgot. I used a length of coax to the roof, then 4/5m of wire going to the bow connected to the coax inside wire, +4/5m wire going towards the stern connected to the coax shield. No need for baluns. This setup worked very well for receiving most hf frequencies; I do not think it would with low freq as navtex.
Or, if you want to use a long wire as a receiving antenna, you could improve it with an impedance transformer to match it to the various frequencies you would listen to. It is *very* easy to build (even for me!), even easier to buy it and it definitely improves reception. I ll try to find a diagram and post it.
rob, m0ita
I do not know the furuno wfax in particular, but it must not be too different from a good hf receiver. I would use a different aerial just to make things simple and not having the need to remember on/off/on; especially as you want to keep it running all day long.
Either a long wire or a dipole (don t worry too much about length, longest would do) can be put in the inside of the boat, for example under the roof lining, and forever forgot. I used a length of coax to the roof, then 4/5m of wire going to the bow connected to the coax inside wire, +4/5m wire going towards the stern connected to the coax shield. No need for baluns. This setup worked very well for receiving most hf frequencies; I do not think it would with low freq as navtex.
Or, if you want to use a long wire as a receiving antenna, you could improve it with an impedance transformer to match it to the various frequencies you would listen to. It is *very* easy to build (even for me!), even easier to buy it and it definitely improves reception. I ll try to find a diagram and post it.
rob, m0ita
DMGibson
New member
Re: My turn now - split aerial advice needed
There are two main reasons why these two sets can't share the same aerial, even for receiving only (if you start the transmitter, you will literally melt the fax receiver).
One is that the tuned circuits at the input of both sets remove most of the signals they are not actually tuned to, so each set will be removing the signals the other is trying to receive.
The other is that the reciever passes a small amount of leakage of the internal oscillator frequency back to the aerial socket. This normally does not radiate very well from the aerial, but it would be picked up by the other set as a strong local signal and cause a fixed tone whistle on the communication receiver, and interfere with the operation of the fax receier as well. This signal is actually the one picked up by TV detector vans.
So, you need two aerials, preferably at least a couple of metres apart so you don't actually destroy the fax receiver when you transmit on the SSB, although the fax receiver will almost certainly stop receiving anything while the transmitter is working.
There are two main reasons why these two sets can't share the same aerial, even for receiving only (if you start the transmitter, you will literally melt the fax receiver).
One is that the tuned circuits at the input of both sets remove most of the signals they are not actually tuned to, so each set will be removing the signals the other is trying to receive.
The other is that the reciever passes a small amount of leakage of the internal oscillator frequency back to the aerial socket. This normally does not radiate very well from the aerial, but it would be picked up by the other set as a strong local signal and cause a fixed tone whistle on the communication receiver, and interfere with the operation of the fax receier as well. This signal is actually the one picked up by TV detector vans.
So, you need two aerials, preferably at least a couple of metres apart so you don't actually destroy the fax receiver when you transmit on the SSB, although the fax receiver will almost certainly stop receiving anything while the transmitter is working.
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Roberto
Well-known member
Re: My turn now - split aerial advice needed
Brian, this is the diagram for the impedance transformer you can use for your long wire antenna
http://www.hard-core-dx.com/nordicdx/antenna/feed/9_1balun.html
it decreases impedance by a factor of nine bringing it somewhat closer to the 50ohm needed by the receiver. I found it really makes a difference in signal strength and noise reduction.
there are commercial versions available at radio suppliers.
Brian, this is the diagram for the impedance transformer you can use for your long wire antenna
http://www.hard-core-dx.com/nordicdx/antenna/feed/9_1balun.html
it decreases impedance by a factor of nine bringing it somewhat closer to the 50ohm needed by the receiver. I found it really makes a difference in signal strength and noise reduction.
there are commercial versions available at radio suppliers.
Bergman
New member
Re: Final thought
Don't forget earthing.
Its important that both SSB and Furuno machine are connected to the same earth, don't rely on negative power lead only.
Also earth wire as short and fat as possible.
A cautious man would turn the weatherfax of while transmitting, or clamp a good earth to the aerial wire, particularly if both aerials run in same plane.
Don't forget earthing.
Its important that both SSB and Furuno machine are connected to the same earth, don't rely on negative power lead only.
Also earth wire as short and fat as possible.
A cautious man would turn the weatherfax of while transmitting, or clamp a good earth to the aerial wire, particularly if both aerials run in same plane.
