External antenna voltage drop idea

I've had a trimble 16248-50 sitting on the shelf for a while. Voltage
specs are in this document:
http://www.rdrelectronics.com/skip/feb/tans.pdf
Basically 3.5V to 4.5V. [If you google this part, you will find my
post I did a while ago when I thought it might make sense to attach
this to an emap. With my GPS60, I can't see using any external
antenna.]

I acquired a Trimble Thunderbolt 10MHz reference box which provides 5V
for the external antenna. It seems to me I could just insert a diode
in the path and get the voltage to be compatible.

Any idea if this would work and what diode would be best?

On Tue, 2 Jun 2009 14:11:35 -0700 (PDT), miso@sushi.com wrote:


Yep - any silicon diode will knock off .7 volts and put you within spec.
--
Mike Russell - http://www.curvemeister.com

But I was wondering about how to get the least loss. I was thinking
maybe a power rectifier, which would have more capacitance. Then
again, a 1n914 would have less stray capacitance due to the glass
package.

I guess I need to hack and just try it.

In article


You want to avoid one large enough to have any significant leakage;
that'll swamp the whole forward conduction drop thing...

Isaac

On Wed, 3 Jun 2009 14:39:11 -0700 (PDT), miso@sushi.com wrote:

[re using a diode to reduce voltage to antenna circuit]

This might be worth it if you had something heftier that also needed the
lower voltage. My calculation is about 5 mw dissipated by the diode in
series with the antenna. Not much power, even on batteries. A switching
regulator would save that power, but would cost significantly more, be more
of a failure point, and generate RF noise for the antenna to deal with.

I don't see that capacitance is an issue for a constant DC voltage.
--
Mike Russell - http://www.curvemeister.com