Operation at 200kHz

I’m trying to set up a LimeSDR USB board to generate a tone at 200kHz using the LimeSuite GUI
I’ve successfully tuned the transmit frequency to 30MHz and then used the TxTSP NCO with a FCW of 10MHz to downconvert to produce an output of 20MHz but that seems to be about the limit of what the GUI will let me program. What do I need to set in the GUI to get the output into the 100s of kHz? I’ve seen some other posts but they talk about other tools and using settings that seem out of range of what the GUI will let me use.
I’m new to SDR and RF so apologies if I’m asking something that is pretty obvious


About the only feasible way to do this right now is to obtain the SDRAngel application and tune it to 200 kHz and then you can transmit about anything you want (AM, FM, SSB, CW). SDRAngel can tune to 100 kHz from what I remember and it, too, uses the NCO to subtract from 30 MHz - in this case you’ll want to apply a 29.800 MHz subtraction to get that 200 kHz transmit signal. Granted, this is asking a lot from a board that really doesn’t have the output power to transmit down that low - the output signal level could be rather small (I’m guessing less than -20dBm at 200kHz), but it’ll be there and you’ll hear it if you have a receiver tuned there. If you were to set up a PA to buffer up from -20dBm (and again, this is totally a guess) then you could operate in that frequency range for receive and transmit, voice, data or CW.

I should mention that at this time SDRAngel is the ONLY PC application for Windows or Linux (it works for either OS) that transmits properly and effectively for HF. Other apps, like SDRConsole, are only able to receive in HF right now but can only transmit above 30 MHz effectively (presumably 30 MHz to 3.8 GHz).

I’ll confirm this with my setup tonight and report back. I have the means to do this (I have two Limes and I have multiple receivers to choose from to tune to 200 kHz). So once I have the recipe I’ll let you know how to do that, too, using SDRAngel.

More to follow as I have that info - stay tuned…

73 de Marty, KN0CK

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Thanks for the reply - sorry its taken so long to get back to you
I’ve downloaded and installed SDRAngel v4.4.4 on my Windows PC and have had a go at setting up as you suggest. Some observations first off - I’ve been playing around with the main frequency dial (NCO off) and noticed that the signal dies when I tune below 30.56MHz, unlike the LimeSDR GUI which tunes down to 30MHz (checking this on a spectrum analyser)
The main problem I have is that the NCO is limited to +/- 20MHz so even if I get the main tuning down to 30MHz I can only downconvert to 10MHz; having said that, it doesnt seem to matter what I do with the NCO the output freq doesnt change - all that seems to happen is that the main freq dial in SDRAngel is adjusted by the amount of the NCO. Am I missing something here - by your suggestion, I was expecting a negative NCO freq to be subtracted from the main frequency. So I am in the position where I can’t follow your advice as the UI doesnt seem to let me. I’ve also played with the Delta Frequency by clicking on X - that does seem to do something but as soon as the combined main freq and delta add to less than 31MHz the output dies from the Lime
Any thoughts?

NCO offset is limited to the sampling rate/2. So to offset by 30 MHz your sampling rate needs to be at least 60Mhz, to achieve that in the LimeSuite GUI increase CGEN frequency.