LimeSDR suitability as QRP Ham rig?

Hi - the tl:dr version is How suitable would the LimeSDR (probably the original, not mini) be as the basis of a QRP ham rig, now or in the foreseeable future?

I’ve been interested in ham radio for ages - bought a Bencher paddle in the 1970s while in high school, never got to the completion of the requirements for my amateur license. Do a lot of listening to SW, have numerous consumer SWL radios and have in the past had high-end shack general coverage receivers. Added SDR capabilities last year via a couple of dongles, a couple of the dongle-based boxes, now also an Airspy HF+. Considering the LimeSDR, but mostly interested in whether the LimeSDR is likely to as the core of a Flex-like rig. Yes, I searched and found the thread on “Ham HF 6m…” and have added myself to the interest list. Asking to see if those with much more knowledge than I have some insights for me…

Thank you!
waldemar

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Hi Waldemar,

@martywittrock has been working towards this goal. You can find some of his videos floating around here and maybe he will reply to you. I can’t comment re. ham rig, but I can tell you the LimeSDR mini is great for low power, short distance ISM band applications, as long as you can deal with the learning curve (it’s a pretty complex beast).

Adrian

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@waldemar - Waldmar,

Adrian is right, I have been pursuing the LimeSDR effort since the very beginning (going on 2 years now) as the core element to a QRP, or for that matter, standard Amateur Radio equipment with 100W output capability (once you add the driver PAs and the Lowpass Filtering required for that). From all the time I’ve been associated with this LimeSDR effort I’ve had a fair amount of time to evaluate it for how feasible it is to make this a foundation piece for the Amateur Radio service, and I’m here to say this: It is feasible to implement the LimeSDR to be a wideband radio for Hams (160m to 23cm).

Having said that, it isn’t without some work that it can make such a transceiver. There’s a fair amount of filtering for the PA, preselection for the front end and some preamplification that’s necessary to make this a workable rig, but that’s not a very vaunted task to achieve, and for what it’s worth I’m working on that as I type this. I would hope that by sometime this summer I’ll have a companion board to do all the PA filtering, receive preamp and preselection as well as I/O for controlling external antenna switching employed over the whole range (160m to 23cm).

Continue to express your thoughts here, Waldmar, because that’s the end-game for me…Making the LimeSDR a very important part of a great wideband rig.

73 de Marty, KN0CK

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Hi @martywittrock on the topic of RF switching etc., have you seen this?

You probably have, but putting it out there for those that have not.
/ Gerry

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@gerryk - Gerry,

Yep - I’m aware of it, but I’m going to include the LPFs, preselection, and the RF switching to the design I have in mind so it’s a complete board for wideband use…Stay tuned…

73 de Marty, KN0CK

Marty, haven’t been on here since the whole debacle where posts “got lost”…but I’ve been following your work closely. Looking forward to seeing what you come up with, man. Take care, and thanks!

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@Ramsin,

Thanks so much and do stay tuned…I have a lot on my platter at the moment, but I am committed to making this happen because I want it…

73 de Marty, KN0CK

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That’s an interesting board Gerry, thanks for sharing. I wonder what type of switches are those and, more importantly, how fast can they switch. I recently started working on a TDMA mode for DMR and I need very low latency.

SV1AFN also manufactures some SPDT RF switches with fast switching time: https://www.sv1afn.com/hmc784_trswitch.html

I suspect for TDMA, switching latency is critical… mechanical relays are probably not a good fit.
40nS (as per SV1AFN unit) is pretty damn fast!

Thank you all, especially Marty, for the encouragement. I think it would be worth taking a flyer on the LimeSDR. Marty’s comments, comparing it with the Flex system, make this a fairly easy decision.

I have been reading through the threads, witnessing the agony and the ecstasy, and it’s great to see that at this juncture there seems to be a lot of hope. Marty, I’ll definitely be interested in that board or set of boards. I have some filters on their way for use with the Airspy HF+, but an integrated purpose-built solution sounds excellent.

I’ll be lurking here, waiting eagerly for the pieces to fall into place. Hope I can contribute in some way to the effort.

cheers,
Waldemar

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Indeed. Fast enough to run a GSM mobile station using the OsmocomBB software stack.

To the OP: regarding the suitability as a ham rig, you should be aware that the device needs a good frontend with band-pass and low-pass filters for the desired bands, and a power amplifier which can be controlled via GPIO. One of my wishes is to see the LMS7002 paired with an embedded Linux platform in one product, suitable for everything between land mobile radio and advanced telephony stuff. I have been toying with the idea of writing an open source Digital Mobile Radio stack (ETSI TS 102 361) that could run on a low power ARM platform, but having an open SDR radio terminal is currently outside the possibilities of an amateur.

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So far, I have pillaged the PA, LPF board, BPF board/band decoder and tuner from a Kenwood TS-440SAT. I have the signals to the decoder happening from my laptop & will need to interface it with the Udoo X86, when I get it. Also, I have the Ebay 1mw to 3W 1-700 Mhz amp (Not sure if it will be a final use with the lime, till tested). I also have BPFs for 6M, 2m, 1.25m, 440 that will be on the output & input.
I have not gotten SDRconsole to want to transmit yet, but think it’s in the settings, or the computer is not good enough.(Older laptop).
With some alterations, I plan to fit this all in a LXE VX9 mobile computer with a 12.1" touchscreen.(LimeSDRUSB, TS-440 TX/RX chain, 1-700 Mhz amp, V/U BPFs & Udoo Ultra [Dang, that Jetson TX2 looks nice, but pricy !!!]).
I will also have SMA ports for all connections on the limeSDR.

Ed

@adim - Thanks - I had figured that out, but am delighted that others are making sure it all works. I’m not expecting something in the FT-817/857/897 class in terms of integration and ease of use.

It’d be great if someone figured out how to do the McHF (I prefer the old case over the 0.7 variant, personally) using the LimeSDR as its basis. We’ll see…

In any case, I’ve pulled the trigger and have a LimeSDR on its way, or at least preordered.

Thanks, all - will keep reading and following.
waldemar

Ideally you should use LPFs on the output. BPFs won’t have the required rejection of harmonics.

If you replace the core of mcHF with a LimeSDR, you’ll end up replacing almost everything else and finally get something more like the Flex radio series :slight_smile:

That’s an interesting suggestion… using the mcHF RF deck with the LimeSDR. I have an mcHF, so will take a look at schematic to see where might be an appropriate place to splice in tx/rx signals.

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@gerryk - Gerry,

Or even better just get the cards for the RF deck and augment those to the LimeSDR…! I’m still going to design mine because I want full coverage (160m to 23cm) and that board will DEFINITELY be different…

73 de Marty, KN0CK

The VHF/UHF bandpass filters are mainly there for recieve, but will be in the 3W transmit path. That signal will go to amplifiers, that have input filtering.
Running out of room in this enclosure.
The BPFs for the HF recieve are from the TS-440SAT, as well as the HF amp, LPF board & tuner for the HF transmit.
Now wavering between the Udoo & the Jetson TX2 Dev kit for a computer. I have a friend that can order the Jetson for $299 with his colledge creds.

Ed

I share the same interests to use the LimeSDR as a QRP rig first then maybe as a fully 100W station second. As a QRP some of the filtering can be forgiven to simply the project. I am a novice at LimeSDR at the moment at the bottom of the learning curve. But, motivated to better understand the technology and what it can be made to perform for communications.

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@MA02129 - Don,

Eventually, the LimeSDR I have will be the core piece to a 20W portable and 100W self contained station that’s capable of 160m to 23cm for receive and transmit. While on the surface this would appear impossible, it’s actually real easy if the bands are split up as HF (160m to 6m), VHF (2m, 220MHz), UHF (440MHz), and SHF (23cm). PAs and receive front ends are just switched into the defined signal paths of the the LimeSDR and then SDRAngel takes care of the rest for controlling the rig for receive and transmit. Some of this will be relayed through the Arduino hooks that are present in the LattePanda PC (Win10 and has a built-in Arduino capability as well) to perform a lot of that handshaking.

More as I have it, stay tuned…

73 de Marty, KN0CK

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