Midland 77-861 power output lower on battery, Mod to high?

[DaveC]

To anyone familiar with this radio:
The Sam's guide lists the power output for this porta-pack 40 channel radio at 4W for 13.8V mobile (car battery) and only 3W for 12V AA battery power (The power jacks are different for car 13.8V and 12V AA) . Is the wattage difference because of the slightly lower voltage of the AA batteries or do they tone down the power so that AA batteries last longer? If so is there a way to mod the radio to output at least 4W when on AA power too and battery life be damned? I wouldn't think this impossible as many 12V AA battery walkie talkies output 4W.

 

[autotuner]

Yes, the lower output would be because of lower voltage, and honestly no-ones going to notice the difference between 3 Watts and 4 Watts. I wouldn't bother trying to up it. Much more gain to be had playing with antennas (pardon the pun).

 

[DaveC]

Yes, the lower output would be because of lower voltage, and honestly no-ones going to notice the difference between 3 Watts and 4 Watts. I wouldn't bother trying to up it. Much more gain to be had playing with antennas (pardon the pun).

It just didn't seem to make sense that a 1.8V difference, around 10% was going to create almost 25% loss in power. Wouldn't a full watt give more range? If it was an easy adjustment I would attempt the boost.

 

[bob85]

The lower voltage on AA batteries is not only a drop to the final transistors output,
All stages in the tx drop in power & it adds up to less drive reaching the undervolted final.

 

[nomadradio]

The wattage difference comes from the lower operating voltage the battery pack delivers. Add to this that your 13.8 Volt supply probably doesn't drop voltage as much under load as the batteries will do. It takes only a small drop of a Volt or two to reduce RF power by a Watt or large fraction.

Full power life-be-damned on batteries is simple. More cells in series. Eight of them get you 12 Volts. Ten of them gets you 15 Volts. Odds are it won't drop much below 13.8 Volts under load while transmitting.

The bonus is that the current draw on the batteries will now be higher, causing them to empty out even faster.

I'll skip the lecture about how impossible it will be to see your small power increase on the receiving S-meter at the other end of the conversation.

If what you're seeking is more transmit range, this won't affect it enough to matter. And if what you want is a higher meter reading? Hey, it's only money.

73

 

[autotuner]

The wattage difference comes from the lower operating voltage the battery pack delivers. Add to this that your 13.8 Volt supply probably doesn't drop voltage as much under load as the batteries will do. It takes only a small drop of a Volt or two to reduce RF power by a Watt or large fraction.

Full power life-be-damned on batteries is simple. More cells in series. Eight of them get you 12 Volts. Ten of them gets you 15 Volts. Odds are it won't drop much below 13.8 Volts under load while transmitting.

The bonus is that the current draw on the batteries will now be higher, causing them to empty out even faster.

I'll skip the lecture about how impossible it will be to see your small power increase on the receiving S-meter at the other end of the conversation.

If what you're seeking is more transmit range, this won't affect it enough to matter. And if what you want is a higher meter reading? Hey, it's only money.

73

Nomad has it in a nutshell.