Channel A for 100MHz, Channel B for 1090MHz, at same time,is that OK？

[hawkingyy]

I want to use channel A in GQRX to demode AM signal， and to use channel B in gr-air-modes to decode ADS-B, can LimeSDR work at same time?
How can I set the arguments in both softwares?

[mzs]

Short answer: you can’t

RX @ 100MHz and RX @ 1090MHz at the same time using one LimeSDR USB/PCI device is not possible. Because both RX channels share a common fractional-N PLL synthesised LO. The frequency difference between two similtanious RX channels is limited to being within the same 61.44 MHz of bandwidth. Even though there is a seprate analogue path for both RX signals you could still look at the extraction of the two RX channels as happening in the digital domain. Conceptually it might make it easier to understand.

Transmitter side specs

Yes, you got it right. If one of the TX is tuned to 2450 MHz the other should be within 61.44 Mhz, same for the RX if the one is tuned to 1545 MHz the other should be within the 61.44 Mhz. The gap from the TX and RX may be anything within the declared range 0.1. - 3800 Mhz

But you can RX at any frequency within the devices operational range and similtaniously TX at any frequency within the devices operational range (because there is a seperate, but still sharing a common clock, fractional-N PLL synthesised LO for TX).

EDIt: I’ll also point you at the Functional block diagram: LimeMicro:LMS7002M Datasheet - Myriad-RF Wiki

[texasyojimbo]

There is a hardware level work-around for this: use a mixer (and ideally, a filter or two) and make yourself an up/down converter.

For example:

Channel A – RX on 1100 MHz from IF output on a mixer, TX on 1000 MHz into mixer LO, connect antenna to mixer RF input
Channel B – RX on 1090 MHz

Mixers will have a little bit of conversion loss (5 dB or so).

You can get a used one for about $20 on eBay.

I was playing around last night with a Mini-Circuits ZLW-1 that I bought used. I was able to tune in pretty much the entire AM band with a stock RTL-SDR telescoping whip, by upconverting the AM band to VHF. With a little preamplification to compensate for mixer loss this could be a pretty decent setup for AM DXing (The stock LimeSDR is pretty deaf below about 1 MHz, even with the filter fix, but has really great receive on VHF).

[9a4db]

For that task you may consider to use this ->

moRFeus: A Low Cost Wideband Signal Generator and Frequency Mixer

Spec. sounds promising…
BRG
Djani

[ChuckM]

From the MoRFeus description: “Unfortunately one limitation is that moRFeus’ lowest input frequency is 30 MHz, so it can’t be used to upconvert HF signals.”

The ERASynth can do it (it goes down to 12.5Khz) with a mixer.

[9a4db]

Channel A for 100MHz, Channel B for 1090MHz, at same time

was my remark. so MoRFeus is fine for that.
BTW Here have ERASynth+ but not happy with web interface, only command line over serial,
works good enough.