ctelfer38
Well-Known Member
Can anyone tell me if a Decca aeriel and cabling will send a workable signal to a medium frequency radio? Thanks /forums/images/graemlins/grin.gif
Decca Aeriel/cabling
- Thread starter ctelfer38
- Start date
Bilgediver
Well-Known Member
Remember that most decca antennas were active. This means that the antenna was fed with a DC voltage to power the device in its base.
These arials were set for a particular frequency but may work on medium wave however you need to get the makers details and work out if the one you have was powered up the coax or by a third wire. You will then need to make a small interface to go between the antenna and radio so that the radio does not see this voltage.
O have no doubt an enthusiastic Googler will find such a set up /forums/images/graemlins/smile.gif
John
These arials were set for a particular frequency but may work on medium wave however you need to get the makers details and work out if the one you have was powered up the coax or by a third wire. You will then need to make a small interface to go between the antenna and radio so that the radio does not see this voltage.
O have no doubt an enthusiastic Googler will find such a set up /forums/images/graemlins/smile.gif
John
steve_cronin
N/A
Decca receivers.....
... received the signals from four transmitters, one master and three slaves. The frequencies varied between 70 kHz and 130kHz - lower than commercial long wave transmissions (BBC Radio 4 is on 198 kHz). This means that there would normally be a chance, but only a chance of the "tuned length" of a simple wire aerial hitting a multiple (harmonic) of the required length for a meduim wave transmission. However, since these tubular aerials tend to have a "Stacked array" connected to a simple amplifier, the whole suitability thing is skewed. It is probably down to a "suck it and see" approach. But as these aerials (The Navstar is the one I had) are fed by 5vdc to power the amplifier you would need to provide this but you would also need a capacitance interface to prevent this voltage going into the detector stage of your receiver. To NOT feed it would leave you with a very poor antenna for MW transmissions. Hardly worthwhile, surely?
If you have a NASA HF3 then these are supplied with an active aerial which is powered by the boat battery at 12vdc, same as the set, so no problems here. These aerials are available from NASA for not too many pounds.
We have our NASA Clipper Navtex and an HF3 running from the HF3's active antenna but because of the Navtex's own active being 5vdc, we have built in a simple capacitance isolating interface. The set-up works superbly. The SSB is unafected but the navtex reception is much improved. #1 son built the interface after having taken guidance from those nice people at NASA.
Steve Cronin
... received the signals from four transmitters, one master and three slaves. The frequencies varied between 70 kHz and 130kHz - lower than commercial long wave transmissions (BBC Radio 4 is on 198 kHz). This means that there would normally be a chance, but only a chance of the "tuned length" of a simple wire aerial hitting a multiple (harmonic) of the required length for a meduim wave transmission. However, since these tubular aerials tend to have a "Stacked array" connected to a simple amplifier, the whole suitability thing is skewed. It is probably down to a "suck it and see" approach. But as these aerials (The Navstar is the one I had) are fed by 5vdc to power the amplifier you would need to provide this but you would also need a capacitance interface to prevent this voltage going into the detector stage of your receiver. To NOT feed it would leave you with a very poor antenna for MW transmissions. Hardly worthwhile, surely?
If you have a NASA HF3 then these are supplied with an active aerial which is powered by the boat battery at 12vdc, same as the set, so no problems here. These aerials are available from NASA for not too many pounds.
We have our NASA Clipper Navtex and an HF3 running from the HF3's active antenna but because of the Navtex's own active being 5vdc, we have built in a simple capacitance isolating interface. The set-up works superbly. The SSB is unafected but the navtex reception is much improved. #1 son built the interface after having taken guidance from those nice people at NASA.
Steve Cronin
Bergman
Well-Known Member
I think the word Steve is groping for ....................................
Is no.
Sorry
Is no.
Sorry
ctelfer38
Well-Known Member
Many thanks guys for taking the time to advise on my query. I have been away hence my slow acknowledgement. I'll use the fixing atop for other purposes.