Testing Transmit

I was trying to setup to transmit using SDRAngel before I had any antenna plugged into it… so I’m thinking I might have damaged the LimeSDR-USB (Hw v1.4s, Fw4, Gw2.21)…

  1. How can I connect the TX to the RX and run a self-test? i.e. How do the (4) TX1_1/2 and TX2_1/2 map to the (6) RX1_H/L/W and RX2_H/L/W connectors?

  2. Do I need to first enable the transmitter(s) in LimeSuite before running SdrAngel? SdrAngel detects LimeSdr[0:0] and [0:1], which I assume correspond to TX1_1/2 and TX2_1/2, but when I transmit NFM Morse at 467Mhz, neither an RTL-SDR, nor walkie-talkie detects any activity.

RTL-SDR RxSetup (works at decoding fm 106.7mhz and walkie takie squelch 467mhz):

LimeSDR TxSetup (setup and “transmitting” nfm at 467mhz) :

LimeSDR TxConfig (better screenshot of the Tx settings):


There’s no real way to destroy your LimeSDR-UISB other than if you overpower it from the external DC voltage connection - it’s a pretty resilient device. What I really need to see are clear (not fuzzy), static pictures of the SDRAngel screen so I can see the settings and the applied modulator that you have selected to make transmit work. I also have to see what settings you have for antenna, ect. So if you post those, then I can let you know where you’re deficient.

Let us all know - thanks,

73 de Marty, KN0CK

Thanks I posted an imgur link, basically I kept all the defaults, except for the Frequency (467,562khz), Sink Device (LimeSDR[0.0]), and the NFM Modulator (runs continuously).

As far as antenna settings, I haven’t (knowingly) set any… does something have to be configured/enabled in LimeSuite before opening SdrAngel? In terms of physical connections, I assume only 1 is needed but I have 2 antennas on the TX1_1 and TX1_2 connectors just in case.

Okay - here are the problems with your setup:

1.) LP should be adjusted to 130,000 to open it all the way up (no lowpass filtering)
2.) Gain control should be at least 75% if not 100% of the adjustable scale
3.) The most glaring issue…You have no antenna port selected (shows ‘NO’ right next to the antenna symbol)
4.) You may want to adjust the H? to 32, and the S? to 16 but always play with it with S? being half or less than H?
5.) Your sampling rate (SR) should really be 7,000,000 but 5,000,000 (and even 6,000,000) is acceptable

#3 is really your issue why you’re not transmitting anything…If you don’t select an antenna for the transmitter output, then nothing happens. Just select something and attach an antenna to it - then you’ll see a difference - - Just use the TX1_1 for now…

Hope this helps, 73 de Marty, KN0CK

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Thank you, thank you, thank you!! That WORKED!! There are so many things I want to try with SDR, so this was a HUGE first step and also verified that the hardware works. Much appreciate the help!

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Looks like @martywittrock has got you up and running :slight_smile: But just to note also that, if you ever want to do a loopack test, run LimeQuickTest.

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Thanks, good to know! I’m not seeing much in terms of instructions on the webpage… does it verify the the output of the tx antennas using a loopback to the rx antennas?

It verifies a number of things as described in its output when you run it, including transmit/receive capability and levels. Note that no antennas must be connected when you run this.