Radio Question

[vontresc]

Well I have a question about the radio in my glider.

I have a Terra TX-720 in the panel, and notice that when I transmit that the power draw is sufficient to lower the voltage on my panel mounted voltmeter significantly. I am currently running all of my electrics off of a 7.2 AH 12V gel cell.

I realize that the radio draws significant current in transmit mode, but was wondering if wiring in a large capacitor would help at all?

Opinions????

 

[SCCutler]

No, it would not.

 

[wanttaja]

Well I have a question about the radio in my glider.

I have a Terra TX-720 in the panel, and notice that when I transmit that the power draw is sufficient to lower the voltage on my panel mounted voltmeter significantly. I am currently running all of my electrics off of a 7.2 AH 12V gel cell.

I realize that the radio draws significant current in transmit mode, but was wondering if wiring in a large capacitor would help at all?

Opinions????

Well, a battery is a large capacitor, after all, and the one you have isn't holding the voltage. I think any "ordinary" capacitor would probably discharge nearly instantaneously until it matched the battery voltage.

This may be a case where too much knowledge is a dangerous thing; does anybody report having trouble hearing you? If not, I wouldn't sweat it.

How old is the battery? Is it possibly just getting tired?

Ron Wanttaja

 

[gismo]

Well I have a question about the radio in my glider.

I have a Terra TX-720 in the panel, and notice that when I transmit that the power draw is sufficient to lower the voltage on my panel mounted voltmeter significantly. I am currently running all of my electrics off of a 7.2 AH 12V gel cell.

I realize that the radio draws significant current in transmit mode, but was wondering if wiring in a large capacitor would help at all?

Opinions????

Let's just say you couldn't afford such a capacitor. One Farad has the capacity to deliver one amp for one second with a one volt drop. To limit the voltage drop to half a volt during a 10 second transmission when the radio is drawing 5 amps, you'd need 10*5/0.5=100 Farads (at 15 or more volts).

A much better solution (assuming you're actually having a problem) would be to use a 14v battery instead of a 12v one. You might also confirm that the battery's internal resistance is where the voltage drop is coming from as it could be in the wiring. Just put a multimeter on the battery terminals and see if that agrees with the panel gauge'd measurment of the drop when you transmit. Your battery could also need replacing or "desulphating" as a 7AH battery should be able to deliver 5A with less than half a volt decrease.

 

[flyingcheesehead]

Let's just say you couldn't afford such a capacitor. One Farad has the capacity to deliver one amp for one second with a one volt drop. To limit the voltage drop to half a volt during a 10 second transmission when the radio is drawing 5 amps, you'd need 10*5/0.5=100 Farads (at 15 or more volts).

Wow... I was just reading about this. I think I still have a textbook showing the "largest" capacitor ever at 164 Farads. Now, I see they've gotten upwards of 5,000 Farads:

http://en.wikipedia.org/wiki/Supercapacitor

 

[BillTIZ]

Well I have a question about the radio in my glider.

I have a Terra TX-720 in the panel, and notice that when I transmit that the power draw is sufficient to lower the voltage on my panel mounted voltmeter significantly. I am currently running all of my electrics off of a 7.2 AH 12V gel cell.

I realize that the radio draws significant current in transmit mode, but was wondering if wiring in a large capacitor would help at all?

Opinions????

It sounds like an old battery. Borrow a new one and see if there is an improvement.