Although the API returns a list of available antenna choices for both RX and TX, only one antenna from the lists can be applied. When connecting to a pluto, the RX antenna is set to A_BALANCED and the TX antenna is set to A. If a future revision of the Pluto hardware supports more than one antenna then this logic will be updated.
The hardware attributes of the development unit:
hw_model = Analog Devices PlutoSDR Rev.B (Z7010-AD9363)
hw_model_variant = 0
hw_serial = 104473dc59930019edff1100d8cd2918d7
fw_version = v0.29
ad9361-phy,xo_correction = 39999965
ad9361-phy,model = ad9363a
local,kernel = 4.9.0-10475-g2398d50
usb,idVendor = 0456
usb,idProduct = b673
usb,release = 2.0
usb,vendor = Analog Devices Inc.
usb,product = PlutoSDR (ADALM-PLUTO)
usb,serial = 104473dc59930019edff1100d8cd2918d7
From the device driver notes the minimum bandwidth is 2.083 MSPS unless FIR Decimation / Interpolation is set, so in this software the lowest bandwidth is 2.1 MHz, the maximum sustained throughput without packet loss is 6MHz.
The sum of the receive and transmit bandwidths cannot exceed 6MHz, so transmit is only enabled for bandwidths of 3 MHz and lower as the Pluto implementation runs in full duplex (simultaneous receive and transmit).
This text is from Analog Devices [link].
Manual: In MGC mode, the BBP controls the gain index pointer(s). In its simplest form, the BBP evaluates the digital signal level at the I/O port and then adjusts the gain appropriately. The BBP can control manual gain in one of two ways. The default method uses SPI writes (writing in_voltage[0,1]_hardwaregain) the total gain in dB. This results in different gain indices depending on the gain table loaded. Alternatively, the BBP can pulse the Control Input pins to move the gain indices.
Slow attack: Slow Attack Mode is intended for slowly changing signals such as those found in some FDD applications such as WCDMA and FDD LTE. The Slow Attack AGC uses a 2nd order control loop with hysteresis that changes the gain in order to keep the average signal power within a programmable window.
Hybrid: The AGC hybrid mode is the same as the slow AGC mode with the exception that the gain update counter is not used. Instead, gain updates occur when the BBP pulls the CTRL_IN2 signal high. The “hybrid” term arises because the BBP has taken some control of the algorithm away from the AD9361 so gain control is no longer completely automatic.
Fast attack: Fast Attack Mode is intended for waveforms that “burst” on and off, such as those found in TDD applications or GSM/EDGE FDD applications. The AGC responds very quickly to overloads at the start of a burst so that the AGC can settle to an optimum gain index by the time the data portion of the signal arrives.
The radio runs in full duplex (receiver runs while transmitting). This is required for transponders such as Es'Hail 2 (a geostationary satellite). There is a menu option RX Mute which is used to disable the waterfall and audio while in transmit mode.
If you monitor your transmission with the Pluto you will experience a delay; this is due to the buffer sizes used in the Libiio API. The buffer sizes will be customisable in a future version of this software.
For maximum drive make sure the band-specific Master Gain levels are set to 100 [Link].
Pluto has four general purpose output (GPO) pins. Direct support of these pins is planned.
Due to the design of the AD9364/AD9363, if both, the TX and RX Local Oscillators (LO) are set to the same frequency or very close to each other the TX LO may leak into the RX path. Monitoring your own signal with Pluto in full duplex mode is not recommended; use a second receiver instead.
There is a spur approximately 50dB below peak output at the transmit frequency. This is generated by the AD9363 / AD9364 chip in Pluto, the cause and possible mitigation are being investigated. It is probably DC leakage from an internal mixer [link].
To achieve the maximum sample rate of 6 MSPS (6 MHz bandwidth) a good, powered USB port must be used. USB3 is not necessarily better than USB2; so if there are breaks in the received data try a different USB port. Pluto's USB is USB 2.0 High-Speed.
Pluto has a second USB connector for additional power - don't be afraid to use it!
Here's a screenshot of a 'hacked' Pluto - the frequency range has been extended to 70 MHz to 6 GHz using the instructions on this page [link].
It's not quite as good as an Airspy but still very acceptable. The antenna is an 8 element yagi, so probably providing too much input, also picking up two very stong 2.4 GHz Wi-Fi signals.
More information about transmit support in this program is available here [link].
Beware: as supplied the development PLUTO generated an unholy amount of noise across the HF spectrum. A short USB cable wrapped around a high quality ferrite core reduced this noise.
So the rule for PLUTO is the same as for all USB SDRs - use a high quality cable, if you still have noise then get a ferrite!