I branch use in direct sampling?

Main forum to discuss RTL-SDR related topics.
Post Reply
tustinfarm
Posts: 8
Joined: Wed Jan 29, 2020 12:18 am

I branch use in direct sampling?

Post by tustinfarm » Wed Dec 16, 2020 9:16 pm

Curious to know whether there is any use for the I branch in the direct sampling mode - as far as I can tell there are no usable HF signals to be had from it...I assume because it would be behind the diplexer that splits HF away from VHF/UHF signals detected via the quadrature mode. If that is true, then I wonder if it might be possible to attach a second HF antenna after the diplexer, to be sampled via the I branch? In other words, sacrifice the VHF/UHF quadrature mode, and dedicate the dongle to direct sampling from either of two HF antennas.

rtlsdrblog
Site Admin
Posts: 2913
Joined: Mon Nov 19, 2012 11:54 pm

Re: I branch use in direct sampling?

Post by rtlsdrblog » Thu Dec 17, 2020 1:43 am

The I-branch is connected to the R820T2 tuner, so it can't be used for HF direct sampling.

tustinfarm
Posts: 8
Joined: Wed Jan 29, 2020 12:18 am

Re: I branch use in direct sampling?

Post by tustinfarm » Fri Dec 18, 2020 3:55 pm

rtlsdrblog wrote:
Thu Dec 17, 2020 1:43 am
The I-branch is connected to the R820T2 tuner, so it can't be used for HF direct sampling.
What I am wondering is whether there might be a pad on the board where a second HF antenna could be attached to that connection somewhere between the tuner and the ADC chips Might need to cut the connection to the tuner, of course.

rtlsdrblog
Site Admin
Posts: 2913
Joined: Mon Nov 19, 2012 11:54 pm

Re: I branch use in direct sampling?

Post by rtlsdrblog » Wed Dec 23, 2020 10:18 am

There are two test pads next to C33 and L5 (to the left of the LDO) which connect to the I-branch. But you will indeed need to disconnect the tuner by removing the two resistors next to the pads R13 and R12.

Post Reply