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Old 03-21-2008, 05:37 AM   #42 (permalink)
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Default diode & battery

quote from

Hi guys,

this discussion has gone the wrong direction as it's based on wrong assumptions not backuped by manufacturers' data.

99% of today's transmitters are perfectly happy when powered from any solid current source ranging from 9 to 12V. The key word is "solid" and voltage itself is of no importance as long as it stays within 9 to 12V.

Output RF power is constant and clean in that voltage range thanks to various stabilizer circuits implemented for simple reason: FCC rules conformity.

And there is a simple reason transmitter copes with 12V source with ease: It must accept primary cells (carbon-zinc and alkaline) in case rechargeable batteries are not at hand.

Sometimes, you can find in users manual manufacturers don't recommend using primary cells but this is not because of to high voltage expected. On contrary, this is because to low voltage can emerge from low quality carbon-zinc batteries due to their high internal impendance loaded at 200-250 mA transmitters usually draw.

Besides, to high battery internal resistance frequently cause transmitter output circuitry instability, interference and low output power. Sensitivity to high power supply impendance makes use of diodes connected in series with battery (as proposed by someone in this thread) a no-no since this raises the impendance to dangerous values.

Alll the above are based on manufacturers' service and users manuals as well on 30 years of radio gear repair experience.
So guys just relax and enjoy using 11V Lipoly TX packs. The only real problem you'll have is weight imballance due to much lower Lipoly pack weight.
I've solved the problem by using 2.4 GHz RF module which calls for taking out standard antenna.

Regards, Miljenko
Hi Denis,

Thank you for the additional info. I went to My Hobby City and read the reviews about the battery. There was a reference to a thread about the use a lipos in TX. The above quote is from there. My question is about using the diode because of the following statement "Sensitivity to high power supply impedance makes use of diodes connected in series with battery (as proposed by someone in this thread) a no-no since this raises the impedance to dangerous values." Do you have any thoughts on this?

Thank you for your reply with the additional info about your installation
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