steve_cronin
N/A
If, like me you have a NASA Clipper Navtex and one of their excellent HP3 receivers you might well also have two stub antennas. One short for the navtex and the other approx twice as long for the radio.
Getting ready for the new gantry we are having made, a thought came to me. Why do I need two antennas when the reception frequencies of the navtex are covered by the radio's active antenna bandwidth? Can I use a splitter after the in-line aerial amplifier and run both off the longer stub?
So I rang NASA in Stevenage from the boat in Athens. Their technician thought about it and said "Why not, but you'll have to make up a lead in RG58 with a coax plug on one end and a phono on the other and ensure that the splitter is low loss and doesn't have a balans circuit inside it."
Not having access to our well equipped family "electronic workshop" I rang #1 son who was at home for a few days. He made up the lead but decided to have a second check with NASA before dispatching it via his mum to me in Athens. They advised that, after further consideration, to avoid excess battery consumption we isolate the two units by incorporating a capacitor in the feed to the navtex. So James (he's a good lad & will make a fine doctor in three years time) made up a little screened box with a piece of veroboard and a suitable circuit inside incorporating a 0.1mfd capacitor.
Duly installed, this gives perfect results and has improved the navtex reception beyond all expectations. We can receive Rome in Athens now (except that we've moved to Corfu) with nil drop-outs.
Hope that this may help someone else.
Steve Cronin
<hr width=100% size=1>The above is, like any other post here, only a personal opinion
Getting ready for the new gantry we are having made, a thought came to me. Why do I need two antennas when the reception frequencies of the navtex are covered by the radio's active antenna bandwidth? Can I use a splitter after the in-line aerial amplifier and run both off the longer stub?
So I rang NASA in Stevenage from the boat in Athens. Their technician thought about it and said "Why not, but you'll have to make up a lead in RG58 with a coax plug on one end and a phono on the other and ensure that the splitter is low loss and doesn't have a balans circuit inside it."
Not having access to our well equipped family "electronic workshop" I rang #1 son who was at home for a few days. He made up the lead but decided to have a second check with NASA before dispatching it via his mum to me in Athens. They advised that, after further consideration, to avoid excess battery consumption we isolate the two units by incorporating a capacitor in the feed to the navtex. So James (he's a good lad & will make a fine doctor in three years time) made up a little screened box with a piece of veroboard and a suitable circuit inside incorporating a 0.1mfd capacitor.
Duly installed, this gives perfect results and has improved the navtex reception beyond all expectations. We can receive Rome in Athens now (except that we've moved to Corfu) with nil drop-outs.
Hope that this may help someone else.
Steve Cronin
<hr width=100% size=1>The above is, like any other post here, only a personal opinion
