On Jun 2, 8:40 pm, craigm wrote:
From
http://groups.google.com/group/rec.r...dfd16b3dca3750
b3?dmode =source

1.- The ext. antenna socket is "hot", i.e. powered through a 470 ohm
resistence + 100 uH coil. This means that it will deliver approx. 10
mA DC current to the external antenna circuit. The coil is to
prevent "polluting" the power circuit of the radio with radio
frequency signal. Evidently, the purpose of this arrangement is to
"inform" the accessory antenna when the radio is turned on. In case
of the Sony AN-LP1 it turns on the antenna without need to use the
antenna power switch. However, the 7600G will NOT power the antenna,
the 10 mA are not enough to power the amplifier circuit. The power
for the AN-LP1 comes from its own batteries. You can use this
feature with any active antenna by including a proper power-up
circuit - a nice feature if your active antenna is located far away
from the radio and you want it to turn on and off automatically when
you use your radio.

This does not sound right to me. A power detect circuit would only need
micro-amps not 10 ma. 10 ma is respectable power for a simple amplifier.

According to the schematic for the antenna, only 6.4 mA is drawn from the
batteries ( 3 volts) when turned on.

The sense circuit to turn on the antenna from a radio has a 100 kohm
resistor in it. This would draw 30-60 uA from the radio.

Also, the antenna schematic indicates that it is not possible to power the
antenna from the radio connection. (Although there could be different
versions of the antenna....)

FWIW the antenna's LED is powered with less than 1 mA.

The Sony radio schematics I looked at all have enough series resistance so
that shorting the antenna connection will not damage the radio. There is no
issue to settle.

craigm- Hide quoted text -

- Show quoted text -

Thanks, folks, for taking the time to delve into this a bit more
deeply. One question, though, even if the radio itself is in no risk
of any damage, could there possibly be any risk of damage to a non-
Sony amplified antenna that might be hooked up to this jack? i.e.
could this low-level current flowing out to the coax cable damage the
amplification unit of an active antenna?