hard wiring V3 Bias Tee (for Android use)

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bigbloke`
Posts: 2
Joined: Fri Aug 28, 2020 2:41 pm

hard wiring V3 Bias Tee (for Android use)

Post by bigbloke` » Fri Aug 28, 2020 3:04 pm

Hi All,

using the RTL-SDR with an android car stereo - for SDR touch and DVB-T2 applications

it seems that Martin M's android RTL SDR Driver does not support the bias tee sadly
so you cant use it directly with an LNA.

I therefore need to hard wire the Bias tee in the least intrusive manner.

looking at the PCB the control chip has no ID :-(

, but its a 3 pins over 2 device

I'll label it

| | |
A B C
D E
| |

looking at the board with a magnifying glass:

B looks to be ground plane
E looks to be voltage out to the bias tee via L13
C I suspect is bias tee supply in (i am assuming that RF2 is a resetable fuse ?)

That leaves A and D

A I suspect is VCC for the IC ?
Which leaves D as the GPIO control .

So the "dirty way" to hardwire would be to solder bridge C to E leaving RF2 inline for protection
but there must be a "polite" way - perhaps raising D positive ? but as I dont know the IC I dont know
where to take the logic feed from and at what voltage (5v ? 3.3V ?

Anyone got any clues please ?

Regards

BB

bigbloke`
Posts: 2
Joined: Fri Aug 28, 2020 2:41 pm

Re: hard wiring V3 Bias Tee (for Android use)

Post by bigbloke` » Fri Aug 28, 2020 3:26 pm

so on closer inspection (damn my old eyes) A is an R to ground not Vcc

alanzfq
Posts: 190
Joined: Thu Oct 04, 2018 11:18 am

Re: hard wiring V3 Bias Tee (for Android use)

Post by alanzfq » Sat Aug 29, 2020 11:33 am

I'd be inclined to use an external BiasT board as available on Ebay or the like.
Alan

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