29-12-2023, 12:19 PM
Recently I posted a question on RCG about dynamic power jumps that occurred in 2 flights. The resulting discussion cleared up a number of fuzzy understandings I carried about the RC signal. Now we have elrs, not only are there no control signal problems but the RC signal can be understood in much greater clarity.
You can read the long version on RCG #2431 and following:
https://www.rcgroups.com/forums/showthre...em/page163
Here is a summary of the discussion. The question was about dynamic power: why do we occasionally see a TPWR jump while the RQly remains normal? (see plots attached, where Edge plot 2 is a zoom view of plot 1).
I was perplexed because I did not have a clear understanding of my radio signal. In the discussion it became clear there are 2 sorts of packets in the radio signal, control packets going from the tx to rx, and simultaneously telemetry packets going from the rx to the tx (I kinda knew it but not the key details... a bit fuzzy).
A telemetry packet is 10 ms and a control packet is the same duration. The following calculations are for a typical airplane elrs setup of frequency 100Hz, telemetry ratio 1:32.
We can convert frequency units from hertz to millisecond (period), given that 100 Hz is 1000 ms or 1 second. If all the signal comprised telemetry packets, then telemetry would arrive at the tx at a rate of 1000/10 or 100 packets per second. But telemetry is only 1/32 of the signal. While the control packets are arriving at the rx at almost 100/sec, the telemetry packets are arriving at the tx at a rate 100/32 or 3.12 per sec.
Jumps may be triggered by drops in RQly, OR by falls in TQly (also by falls in RSSI and RSNR). See
https://www.expresslrs.org/software/...ransmit-power/
for a full discussion.
TQly is the percentage of missed or faulty telemetry packets arriving at the tx.
When Landru did a plot of TQLY and TPWR on data from the plotted Edge flight
the cause of the jumps was revealed (plot attached). The TPWR jumps correspond exactly to drops in TQly. The drop in TQly percentage is 4% (to 96%) for the 50mw TPWR jumps, and 8% for the 1000mw jump (attached) - in the Edge 16 plots the TPWR is divided by 2. This explains how dynamic power jumps occur with normal RQly.
Until now I had no idea I should be checking on TQly in my write logs.
When reading about packet rate, or watching online gurus, it is essential that we always be clear which packets are being discussed, rates are different for the control packets going from the tx to rx, and the simultaneously transmitted telemetry packets going from the rx to the tx.
You can read the long version on RCG #2431 and following:
https://www.rcgroups.com/forums/showthre...em/page163
Here is a summary of the discussion. The question was about dynamic power: why do we occasionally see a TPWR jump while the RQly remains normal? (see plots attached, where Edge plot 2 is a zoom view of plot 1).
I was perplexed because I did not have a clear understanding of my radio signal. In the discussion it became clear there are 2 sorts of packets in the radio signal, control packets going from the tx to rx, and simultaneously telemetry packets going from the rx to the tx (I kinda knew it but not the key details... a bit fuzzy).
A telemetry packet is 10 ms and a control packet is the same duration. The following calculations are for a typical airplane elrs setup of frequency 100Hz, telemetry ratio 1:32.
We can convert frequency units from hertz to millisecond (period), given that 100 Hz is 1000 ms or 1 second. If all the signal comprised telemetry packets, then telemetry would arrive at the tx at a rate of 1000/10 or 100 packets per second. But telemetry is only 1/32 of the signal. While the control packets are arriving at the rx at almost 100/sec, the telemetry packets are arriving at the tx at a rate 100/32 or 3.12 per sec.
Jumps may be triggered by drops in RQly, OR by falls in TQly (also by falls in RSSI and RSNR). See
https://www.expresslrs.org/software/...ransmit-power/
for a full discussion.
TQly is the percentage of missed or faulty telemetry packets arriving at the tx.
When Landru did a plot of TQLY and TPWR on data from the plotted Edge flight
the cause of the jumps was revealed (plot attached). The TPWR jumps correspond exactly to drops in TQly. The drop in TQly percentage is 4% (to 96%) for the 50mw TPWR jumps, and 8% for the 1000mw jump (attached) - in the Edge 16 plots the TPWR is divided by 2. This explains how dynamic power jumps occur with normal RQly.
Until now I had no idea I should be checking on TQly in my write logs.
When reading about packet rate, or watching online gurus, it is essential that we always be clear which packets are being discussed, rates are different for the control packets going from the tx to rx, and the simultaneously transmitted telemetry packets going from the rx to the tx.