What is SmartSignal, and how does it improve my transmitted signal?
SmartSignal™ is FlexRadio’s implementation of dynamic adaptive predistortion (APD), a technology that actively improves the linearity of your transmitted RF signal in real time.
When you're transmitting, especially at higher power levels, amplifiers and even transceivers can introduce distortion; those unwanted splatter or intermodulation products that occur outside your intended signal bandwidth. SmartSignal dynamically reduces unwanted splatter or intermodulation products.
It works by analyzing your outgoing signal, detecting the distortion it would create, and then pre-correcting the waveform before being transmitted by your radio. The result? A much cleaner, more defined signal on the air, with minimal TX filter bleed through and fewer artifacts that might otherwise interfere with adjacent frequencies.
- Lower IMD (intermodulation distortion)
- Cleaner signal reports from other stations
- Better spectral purity
- More efficient use of your amp’s power
The initial release of APD will be a Beta release. Feedback will be welcome in the FlexRadio community: https://community.flexradio.com/
Which FLEX radios support SmartSignal?
The FLEX-8400, FLEX-8400M, FLEX-8600 and FLEX-8600M.
Do I need any additional hardware to use SmartSignal?
No, not when using the FLEX-8000 series without an external amplifier.
Does SmartSignal require a specific firmware or SmartSDR version to work?
Yes, SmartSDR v3.9.18 or greater. Note that the version of SmartSignal released in v3.9.18 is designated as a "beta". Below are some key points and details about SmartSignal beta functionality and expected behavior:
• APD Generation: The Automatic Adaptive Pre-Distortion is generated from the transmitting slice. In a multislice scenario, this can become more complicated but typically follows the LocalPTT TX slice.
• Internal Sampler Requirement: Currently, SmartSignal can only be utilized with the internal sampler in the FLEX-8000.
• Works Best with Default RF Gain Settings: SmartSignal operates optimally when the RF gain settings are kept at their default values.
• Best Performance with Voice Signals: The feature achieves the highest success rate when employed with voice transmissions.
• Challenges with 6M Band: Generating an equalizer on the 6-meter band can be more complicated and less reliable.
• Challenges with AM Signals: Similar to the 6M band, creating an equalizer with AM signals is also more challenging.
• Limited Performance in MultiFlex Scenarios: The feature exhibits quirks in Multiflex scenarios and may not deliver the desired results.
• Occasional APD Stuck in "Calibrating Mode": There are instances where the APD may become stuck in "calibrating mode." This can happen if it cannot identify a better solution than a previously stored one. If this occurs, rebooting the radio may be necessary to resolve the issue and enable the APD to reattempt the calibration.
As a beta release, SmartSignal is intended for early adopters and "tinkerers" who are eager to explore its capabilities. This version is not intended to be perfect, and it is being released to gather feedback and generate data for future improvements to the underlying algorithm. We look forward to your feedback and suggestions for further development.
How do I enable SmartSignal on my FLEX radio?
Using SmartSDR for Windows, the APD enable control is located on the TX panel located on the right side os the screen.
Will SmartSignal work with third-party amplifiers?
Yes, but not yet (as of SmartSDR v3.9). For SmartSignal to function correctly, the software needs to be able to sample the RF from the output of the amplifier. Some Amplifiers, such as the Power Genius XL, have a -60 dB tap used to sample the RF output. A coax cable would be connected from this output to one of the RX or XVT ports. SmartSDR v3.9 uses an internal tap for ADP. Additional options to use external ports with amplifier samplers are features that will come in future software releases. Note that the improvement to the 100W PA in the radio will improve the overall signal even when used with an amplifier.
Can SmartSignal damage my equipment if set up incorrectly?
No,
How do I know if SmartSignal is working correctly?
The APD control panel will indicate Active when SmartSignal is applying predistortion correction.
Does SmartSignal automatically adapt over time or need manual calibration?
Manual calibration is not needed. When SmartSignal is enabled, anytime you transmit a phone mode signal when a recalibration is required, SmartSignal will automatically train on the transmitted signal and apply the appropriate signal corrections.
Can I disable SmartSignal?
Yes, you can turn it on and off for comparison
Is SmartSignal useful for both SSB and digital modes like FT8 or RTTY?
SmartSignal works best with signals that have varying amplitudes. Its effectiveness with fixed-amplitude signals such as FT8, RTTY, or CW is limited.
What happens if my operating conditions change—does SmartSignal adapt in real-time?
SmartSignal continuously tries to generate the best possible signal correction.
Does SmartSignal require calibration every time I change bands or antennas?
Yes. The distortion characteristics change with frequency and antenna load. So SmartSignal automatically recalibrates when you change bands, frequency, and power level.
Is SmartSignal FCC compliant? Will it help me meet spectral purity standards?
FlexRadios are already FCC compliant, even with SmartSignal disabled. SmartSignal will improve the spectral purity of your transmitted signal.
How much latency or processing overhead does SmartSignal introduce?
There is some additional latency incurred, but it is insignificant.
Will SmartSignal interfere with my contesting or DXpedition setup?
No.
How does SmartSignal interact with my tuner or antenna matching system?
SmartSignal does not interact or interfere with your antenna tuner or antenna matching system. However, it should recalculate if the external tuner changes settings.
Can I use SmartSignal with multiple transmit profiles or antennas?
Yes
Does SmartSignal work across the full power range of my radio?
Yes
Does SmartSignal work on the Transverter port?
No. It is only applicable when the radio power amplifier is utilized.
Is there a way to fine-tune or customize SmartSignal’s behavior?
No, it isn't necessary. SmartSignal is fully automatic.
How does SmartSignal work with multiFLEX?
SmartSignal stores a signal correction for a given antenna and frequency, which is used for all SmartSDR clients.
I operate remotely using my Maestro. Can SmartSignal be enabled using my Maestro?
Yes. The control is in the TX MENU.