Fairwaves XTRX - Page 1
Forum section: electronics / rf-microwave

author: nidlaX
author_rank: Frequent Contributor
timestamp: January 17, 2018, 02:37:27 am
content: https://www.crowdsupply.com/fairwaves/xtrxAny thoughts on this SDR? It's nearing the anticipated shipping date. I backed a LimeSDR Mini, and now I'm considering getting one of these when it comes out because the form factor is convenient for my purposes.

author: hagster
author_rank: Frequent Contributor
timestamp: January 17, 2018, 08:06:03 pm
content: It looks descent and in many ways better value than the full size LimeSDR.It has the GPSDO onboard which is rather cool.I guess there may be interference problems if you stick it inside a PC or Laptop and you also have the problems with antennas. The USB3 carrier board is probably the best option for most people. You can buy these cheaply elsewhere.You should get much higher bandwidth if you really need it and have the grunt to process it.Support is still a bit of an unknown at the momemnt. If obviously shares a lot with the Lime radios, but there is plenty different that could cause problems.

author: jgalak
author_rank: Regular Contributor
timestamp: April 15, 2018, 07:00:19 pm
content: I've been wanting something to use as an integrated "remote" VHF/UHF station to complement my Flex 6500, and this looks like it could form the heart of it.I love the ability, on the Flex, to have it located where it's convenient to the antenna, and only run cat6 from there. No need to route antenna cables through the house.I'm thinking some sort of micro PC holding one of these could do the trick. Run GNURadio or PowerSDR on it, and just remote in.Anyone know of a small PC (like, Intel NUC size) that has a mini PCIe slot like this? As far as I can tell, the NUC only has a single m.2 slot for the SSD.

author: radar_macgyver
author_rank: Frequent Contributor
timestamp: April 15, 2018, 08:40:38 pm
content: If you don't need an Intel compatible PC, many routers (that run OpenWRT and hence Linux) have mini PCIe slots for Wifi boards. Some older laptops have it as well, for the same purpose.You could also get an adapter for standard PCI express:https://www.amazon.com/Mini-PCIe-Express-Adapter-Antenna/dp/B0057UPNBEEdit: sorry, I just looked at the Crowd Supply page and realized they mention the adapters there.Question for folks who have studied the LMS7002 in greater detail: does it support multi-chip synchronization at the RF level? In other words, can the LO synthesizers be synchronized across chips? The similar products from ADI (AD9631 and AD9371) do not, since their synthesizers generate 2x the LO and they divide them down to get the 0 and 90 degree phase shifted versions. That divider introduces phase uncertainty between chips. The data sheet for the LMS7002 is low on detail in this regard.

author: jgalak
author_rank: Regular Contributor
timestamp: April 16, 2018, 12:09:52 am
content: Quote from: radar_macgyver on April 15, 2018, 08:40:38 pmI need to run Linux, but I also want a reasonably powerful device - I'm not sure the routers will be able to handle it (since things like PowerSDR take a fair amount of computer resources).I really don't want to use a laptop - too big, too power hungry. I want something small I can tuck away in a corner, headless, and just remote in.

author: jgalak
author_rank: Regular Contributor
timestamp: April 16, 2018, 12:11:19 am
content: Quote from: radar_macgyver on April 15, 2018, 08:40:38 pmIf you look at the Crowd Supply page, you'll find their 8-way set up. That appears to synchronize the clocks, but I don't know if it synchronizes them enough for your purposes.

author: radar_macgyver
author_rank: Frequent Contributor
timestamp: April 16, 2018, 05:16:24 am
content: I noticed that 8-way setup, that's what drove my question actually. The AD9631s also offer similar capability to sync the baseband part of multiple chips, even providing a SYNC_IN input for that purpose. However, there is no RF (strictly, LO) synchronization due to the dividers not being controlled by that SYNC_IN input. Here's an app note about it:https://wiki.analog.com/resources/eval/user-guides/ad-fmcomms5-ebz/multi-chip-syncHere, they provide RF switches that allow one to sample the TX of one chip with the RX of another, and null out the phase offsets. This may be do-able in a 2-chip case, but doesn't scale to larger arrays.Also, in an answer to your original question, what about something like this:https://www.newegg.com/Product/Product.aspx?Item=9SIABVR6PV1157Not quite as small as a NUC, but it might work when paired with a small mini-ITX case. 6W TDP CPU. There are several others that are intended to be turned into routers, these have beefier CPUs than your average home router.