bendyone
Well-Known Member
Is it possible to make a navtex aerial. I have looked on the web a seen a lot of discussions and designs for Loop aerials.
Navtex aerial
- Thread starter bendyone
- Start date
steverow
Well-Known Member
The navtex active antenna is made up on a long PCB with lots of "pcb coils" to make up the length.
This is followed by a high gain amplifier and narrow band RF filter tuned at 518 KHz.
The physical length of a half wave antenna for 518kHz is found from the formula:
length (ft) = 468/0.518
As you can see this is a bit long for the average boat.
However it is possible to make an antenna using the loop principle, or better still a ferrite rod antenna....but when the NASA active antenna is only about £38 is it really worth the hassle?
Some people also get good results from a random bit of wire either up the mast or on the backstay.
A lot depends on how good your receiver is as well.
Steve.
This is followed by a high gain amplifier and narrow band RF filter tuned at 518 KHz.
The physical length of a half wave antenna for 518kHz is found from the formula:
length (ft) = 468/0.518
As you can see this is a bit long for the average boat.
However it is possible to make an antenna using the loop principle, or better still a ferrite rod antenna....but when the NASA active antenna is only about £38 is it really worth the hassle?
Some people also get good results from a random bit of wire either up the mast or on the backstay.
A lot depends on how good your receiver is as well.
Steve.
steve_cronin
N/A
There is very little to the "active" aerials. I have a spare NASA one as we feed the Clipper Navtex from a splitter in the SSB receiver antenna which has higher gain.. The narrow band navtex aerial is just a folded loop on a pcb board with some simple tuning circuitry. I'll bring a photo in tomorrow and post it.
Steve Cronin
Steve Cronin
Halley
New Member
My active Navtex aerial failed after two years. A friend recommended connecting a small lead to a stanchion bolt and using the fortitoulsy connected stainless guard wire as the Navtex aerial. I find that I get far better reception than I ever got with the active aerial. Recommend you give this a go.
