Radio power supply

[ericmark]

I have a radio which required a voltage of 10.8VDC (maximum 13V) with a current consumption of between 20mA (RX squelched) and 700mA. The recommended power supply is quite complex for what it does seen here.

Radio charger

• ericmark
• 16 Sep 2011
• 1

I would like to include a dropper inside the cig lighter plug and I have a number of simple ideas.
One is a 7812 chip the other is three diodes with 0.6 threshold voltage that should drop the max voltage from 14.2 to 12.4 volt.
But two things worry me.
1) If it's so simple why did Yaesu use such a complex method?
2) Will it overheat?
Radio is very old so unlikely to get correct adaptor it's a FT208R so what do other think as to way to reduce car batteries voltage. The ideal would be a switched mode unit that would isolate from car battery and so I could then use a booster from same battery to lift output from 2.5W to 30W I have therefore considered a mains driven unit which I could then plug into my inverter so I have isolation as well as stable voltage.
Again any thoughts?
Considering this from Maplin but wonder about the RF and if it will affect its operation? Any thoughts please.

 

[bernardgreen]

The input voltage for that circuit can drop to be 0.5 volts above the required output voltage and it will still provide a regulated output.

The 78xx series require a minimum input voltage 2 or 3 volts higher than the output voltage to ensure stable regulation. They also required capacitors to prevent oscillation.

 

[Gees]

I have a radio which required a voltage of 10.8VDC (maximum 13V) with a current consumption of between 20mA (RX squelched) and 700mA. The recommended power supply is quite complex for what it does seen here.

Radio charger

• ericmark
• 16 Sep 2011
• 1

I would like to include a dropper inside the cig lighter plug and I have a number of simple ideas.
One is a 7812 chip the other is three diodes with 0.6 threshold voltage that should drop the max voltage from 14.2 to 12.4 volt.
But two things worry me.
1) If it's so simple why did Yaesu use such a complex method?
2) Will it overheat?
Radio is very old so unlikely to get correct adaptor it's a FT208R so what do other think as to way to reduce car batteries voltage. The ideal would be a switched mode unit that would isolate from car battery and so I could then use a booster from same battery to lift output from 2.5W to 30W I have therefore considered a mains driven unit which I could then plug into my inverter so I have isolation as well as stable voltage.
Again any thoughts?
Considering this from Maplin but wonder about the RF and if it will affect its operation? Any thoughts please.

Its a standard series regulator typical circuit for a rig accessory of that age. It will get a bit warm when the rig is on transmit as there is a 3 volt drop ( at the transmit current ) so a watt or so will need to be dissapated.

I do have a callsign but am not very active these days.

 

[ericmark]

It is a nostalgia radio same as I had when VP8XBHZ before I became VP8BKM saw for sale for £5 and could not resist it. However battery pack has been stripped of cells seem to remember shorter than standard AA so 9 cells were fitted giving 10.8 volt.
The microwave module linear got for the FT290R also now without batteries should work well with the old FT209R and since I also have a IC290 no real need to use FT290R for side band.
As VR2ZEP I did get modern set FT50R but the on/off button has failed and can't now get a replacement so have to stick a screwdriver in hole to start it off.
So it seemed a good idea to get the old FT208R up and running.
73 GW7MGW