LimeSDR suitability as QRP Ham rig?

Marty, I am not so sure about that 160 m
all the rest is UFB

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@9a4db - Djani,

It receives real well below 160m, so I’m going to try to make transmit work there, too, if possible…Stay tuned on that…I know 80m and up are fair game.

73 de Marty, KN0CK

I see that the Latte Panda Alpha (and Beta) Kickstarter is about to end, fully funded. I’m trying to decide whether the best strategy is to buy in now, or wait to see whether this, the Udoo, or the Jetson (or something else) ends up being the platform of choice to power our unit. I know you’ve indicated that you’re working on the Latte Panda, Marty, and so I’m inclined that way.

Given what’s happening currently with SDR Angel re: Windows, and just generally with the overhead on Windows over Linux, I’m thinking I don’t need a W10 license. Whatever the final result is, I think the integration of a powerful Linux-capable SBC with Arduino/GPIO for switching and other aspects of rig control will be vital.

Any thoughts on whether to speculate on the Latte Panda, or wait to see how things shake out?

Thanks, all, especially Marty, Ed, Adim. I appreciate the work you’re all doing!

When I get into something, I happen to go all out.
I was looking at the Udoo Quad, as I already have one (Was developing an ECU for 24 valve Dodge diesel trucks).
Then, I looked at the Udoo X86 Ultra. Really nice.

Then, I did some digging & found the Jetpack TX2. A quad processor (Lighter multithreading), dual core Denver (High intensity apps), memory & the latest in Nvidia GPU are all connected through a matrix. No busses in the middle (Well, sort of, but insanely faster). The GPU controller distributes FFT into how many CUDA cores & CPU processors that are needed.

Benchmarks alone, the TX2 is by far the winner. FFT alone, the TX2 is the winner. 14 watts at full tilt boogie !!!

Don’t get me wrong, the Udoos are great products, but for the purpose of SDR, I think the Jetpack wins.


If your application supports CUDA acceleration and makes good use of this, yes. Otherwise a quad-core UDOO x86 is likely to far outperform a quad-core ARM. Note also that the UDOO x86 supports OpenCL on the Intel GPU, so this would give you another boost if your application supports OpenCL but not CUDA.

Well, just due to size, I went with the Udoo X86 Ultra. For this system, I need a small control board and with all of the GPIOs, I should be able to do HF-440 Mhz, with 3 different amp/LPF/BPF systems. I think I am going to give up the idea of using the TS-440 AT unit, as it just won’t fit my enclosure. I am scrounging for VHF & UHF amp modules from an older DC to daylight rig. I would like all modes, so the FM only units will not do.
I will still probably get the TX2 for a later project.


I’m not sure if they are still available, but for a period of time Nvidia was selling Jetson TX1 development board without the cameras for $199 USD. You may want to take a look and see if they are still available. I think they also offer education discounts as well.

The TX1 is an awesome board with USB3, Ethernet, Wifi, Bluetooth, PCI-E, SATA, and a myriad of GPIO and connectors. Not to mention it’s discrete graphics with 256 Maxwell Cuda Cores. It may be a bit overkill but there are also some other SBC’s that might have enough performance to drive the LimeSDR.

Edit: Just to note in case size is a concern. The carrier board that comes with the TX1/TX2 is Mini-ITX footprint. Apparently you can get custom carrier boards that are much smaller, but will likely lose out on many of those awesome ports that are available. Performance has been pretty solid on the TX1 and from what I’ve read performance on the TX2 is supposed to be even better.

I am stuffing all of this into a smallish mobile forklift computer. Size is of great concern. I will still get a TX-2 for future projects, with my friend’s .edu discount. I almost have my boss ready to buy a TX2 to dabble with at the shop.
The Udoo X86 Ultra will be the choice for this build. I have already interfaced the Lime USB, PC and an arduino controlled TS-440 SAT PA, LPFs, BPFs & AT. VHF & UHF are what I am looking at figuring out now.


hello Marty
when you plan to use that as a ham rig … will it do all modes?? (also television in analog/digital)?? base as software could be something like sdrangel
when using the lime … then please also add 13cm (in minimum) better also 9cm … (lime goes up to 3.8 gig)
13cm will be used as uplink on eshail (downlink on 10 gig can be solved with a modded lnb) … having a rig for also 13cm would be great …
9cm could be added as a “bonus” (maybe some spare room on pcb as option for the needed parts??)
2.4 gig is on receive and tx separate from the lower bands on the lime …
so maybe this band could be added with just a few parts (and not hurting your design in any case) … what do you think??
i was planning same thing … grin … lime as base for a multiband multimode rig (maybe together with a small single board pc and a display 7-10 inch?!?)
but i highly wanna also have wideband modes in the upper bands (tv in analog and digital in uhf, 23 and 13cm) if that is possible
what do you think?

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hello Ed
there are a few vhf uhf modules available that are linear modules (also good for an ssb rig) with a bit higher bias setting …
that could be ok for 2m 70cmand higher (several from mitsubishi and motorola)
70cm mhw2723 (just an example)
for 23cm RA18H12G (30w fm up to 5 w linear)
for 13cm am mw4ic2230 ??? (up to 20w in fm but lower for linear modes)

there are a lot of diferent modules available for vhf uhf and higher … and many of the high power modules can be used for lower power in linear modes … some are special build for this (with higher bias)

so the upper bands are more or less easy to solve

shortwave bands is also not that difficult

my guess is the most problematic thing is finding all parts needed , hacking that is a nice case … and then solve the software thingy

will it do all modes?? (also television in analog/digital)?? base as software could be something like sdrangel

Using the LimeSDR you can transmit and receive all types of signal, analog and digital, within the limits of the maximum sample rate.
That includes digital television, analog television, digital voice (Codec2, D-Star, System Fusion, DMR) and analog modes.
The best software for digital television is probably Evariste’s F5OEO D-ATV transmitter.


@dg9bfc - Sigi,

Yep - I had planned for all modes with SDRAngel and other apps to modulate SSTV, RTTY, FT-8, and other digital modes. There is no need to add those digital modes to the LimeSDR when the PC can provide those and pipe them using Virtual Audio Cables from the modulating app to SDRAngel.

Also, I am going to devise separate amplifier (PA and Preselector) strips for HF, VHF, UHF, and SHF such that optimal performance can be attained. More on that later -

73 de Marty, KN0CK

The TS-440 PA & LPFs are pretty compact. I am cutting up the RF board to get the band decoder & BPFs. I might do a wideband amp for VHF/UHF. Not really concerned with higher freqs at the moment.


i have a defective ft757 in my attic … cpu dead and its an obsolete part … so i could hack out the pa section from that rig … shortwave pa and lpf is solved (more or less)…
dg9bfc sigi

Hi Marty,

I know that this has been rehashed before, but the sensitivity of the receive channels on the Lime chip is horrible at lower HF frequencies. The sensitivity at 2 Mhz is at least 50 dB lower than at 100 MHz, apparently due to the design of the receiver front end. The noise figure is correspondingly much higher. So why would you choose this chip for a Ham transceiver? Are you planning to include an upconverter?

Not a criticism, just a question,

PS: Does anybody know WHY Lime decided to roll off the LF response this much?

With the RXLO mod, the figures are not that bad. It surely covers more ham bands than anything I know of. That’s why I am using it as a ham transceiver.

dg9bfc Download the schematics & figure out the bandswitching, too. I’ll look at them. Sometimes, with some “Creative dremeling”, you can get the bandpass filters, atenuators, pre-amps & the such.
Look on P. 39 (Adobe page) schematic of the RF unit, on the lower left, the MC14518. It controls the BPFs & probably more. There’s your start. THose signals will go to the LPFs & other things to control in the TX/RX chain.


It’s not optimized for HF because the design was originally aimed at IoT/LTE developers and so was optimized for500MHz - 2800MHz.
It was found that by doing the mods described in the HowTo on the wiki here that we could get it useable down to these frequencies.
It is great on VHF and UHF as is, but as you say it’s not optimal for HF.

I tend to use my HPSDR rig for HF and the Lime for anything above 50Mhz when at home and the LimeSDR when I am onsite at client locations, it does work but if you are looking for DXing it might not be the best choice. I am happy with it because it is tiny, gets the job done relatively well and covers every band I’d want to use.