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mitigating_interference [2014/11/28 15:01]
dbrooke [Investigation]
mitigating_interference [2015/01/18 12:45] (current)
dbrooke [Investigation]
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 This did not completely cure the problem and on further investigation I realised that some local interference was triggering the start of reception about every 4 seconds. Similar interference was subsequently observed at Elsworth and is shown in James' report of the [[balloon_nodes:​ah3|AH3]] launch. Note that at this time my home nodes already incorporated some of the improvements described below. This did not completely cure the problem and on further investigation I realised that some local interference was triggering the start of reception about every 4 seconds. Similar interference was subsequently observed at Elsworth and is shown in James' report of the [[balloon_nodes:​ah3|AH3]] launch. Note that at this time my home nodes already incorporated some of the improvements described below.
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 +More recently I've used an RTL-SDR to look at the spectrum. The image shows what it can hear on the provided short mag-mount whip. The interference appears to be from a number of synchronised transmitters at different frequencies. A couple of my UKHASnet node transmissions are also visible.
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 +{{ :​radio:​interferer.png?​direct&​200 |}}
  
 Consequently I decided to restart the receive process a short time after the RxReady flag was set. This seemed to give a noticeable improvement but there was still a short period where the receiver was effectively disabled. I noticed that the radio module itself could generate an interrupt if RxReady was not followed by PayloadReady within a programmable time so implemented a receive restart using this. Consequently I decided to restart the receive process a short time after the RxReady flag was set. This seemed to give a noticeable improvement but there was still a short period where the receiver was effectively disabled. I noticed that the radio module itself could generate an interrupt if RxReady was not followed by PayloadReady within a programmable time so implemented a receive restart using this.
mitigating_interference.txt ยท Last modified: 2015/01/18 12:45 by dbrooke