RSP2 operating and/or Bias-T supply on over a long time

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AussieSusan
Posts: 30
Joined: Wed Aug 16, 2017 6:50 am

RSP2 operating and/or Bias-T supply on over a long time

Post by AussieSusan » Wed Feb 21, 2018 2:12 am

At this stage it is only a suspicion that I have but....

I have an RSP2 that is being driven by a RPi3. The RSP2 is connected to two antenna: a discone on Port A and a QFH with LNA on Port B. (The goal is to capture the weather images from the NOAA and METEOR satellites - the discone when they are at a low angle and the QFH as they get above about 30 degrees).

The software in the RPi calculates the visibility of the satellites and then selects the appropriate antenna based on there being a single satellite visible and the angle above the horizon, or just the QFH if more than one satellite is visible. (I sample the frequencies from 137MHz to 138MHz, and then decode the specific satellite frequencies in software to allow for multiple visible satellites).
Originally I had the LNA powered all the time through the Bias-T and later I turned it on and off only when the QFH was in use.

Now to the problem: I was getting reasonable images most of the time (it was either good or nothing - not sure what conditions determined which outcome) when I started the program running but after a time (days?? week+??) it was as though the LNA was not working at all. This was the reason I tried to switch from the LNA on all the time to switching it on when required in case it was related to how long the LNA was running.

If I disconnected the RSP2 and then reconnected and restarted everything, the 'good' (i.e.with LNA apparently working) images came back.... for a while.

I need to do more testing to monitor the Bias-T voltage over a long period of time to make sure that it is actually being delivered and/or the LNA is actually working over a long period of time. I'm not getting any error codes back from the API as I interact with the RSP2.

Has anyone else seen this type of behaviour when the Bias-T has been running for a while and/or the RSP2 has been powered up for a number of days?

I would assume that this (powered up for days at a time) is a 'supported' operational mode.

Susan

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RSP2user
Posts: 108
Joined: Mon Oct 09, 2017 7:11 am

Re: RSP2 operating and/or Bias-T supply on over a long time

Post by RSP2user » Wed Feb 21, 2018 3:12 am

Hi Susan,

Within the recommended operating temperature range and within the current-drive range of the Bias-T port of the RSP2, running a low noise preamplifier with filter (70mA at 5VDC) continuously for weeks at a time, I have not seen the Bias-T problem that you are describing. This has been done using SDRuno v1.22 and the prior version v1.13 and WXtoIMG application software. If you have not yet considered it, you may want to verify that you are not operating the RSP2 outside of its recommended ambient temperature range or beyond the recommended operating current for the Bias-T port or some combination thereof. For your reference, the APT image reception setup is described here: https://www.sdrplay.com/community/viewt ... f=5&t=2529

Additional information: APT images at the above link are within a few degrees of horizon-to-horizon using the QFH and preamplifier described. If you are setting up the RSP2 with either SDRuno or your own software, the SDRplay team has the IF AGC working very well in the latest v1.22 SDRuno version and driver, so instead of manually setting the IF gain, for optimization, the IF AGC now works very well and can be applied with excellent results for receiving NOAA satellite APT images. If you are trying to receive NOAA satellites and are occasionally having reception issues, check to see if Meteor MN2 was within reception range at the time as its LRPT signal will adversely affect APT image reception from NOAA satellites operating within the frequency range of the LRPT signal.

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Mike2459
Posts: 318
Joined: Mon Jul 24, 2017 8:24 pm

Re: RSP2 operating and/or Bias-T supply on over a long time

Post by Mike2459 » Wed Feb 21, 2018 2:56 pm

Susan, I was curious about your issue with the RSP2. I have an RSP2 that I use for satellite reception also. I use SDR Sharp to take advantage of it's QPSK Meteor plugin. The EXTio interface is required to communicate between SDRSharp and the RSP2. My LNA is inline powered and does not require the Bias-T.

I decided to check the operation of the Bias-T. I connected a 600 ohm load to the B-port and monitored the voltage across the load with a DC voltmeter. I discovered a problem with the operation of the ExtIO device controller software. If I select the Bias-T in the EXTIO panel it will enable the Bias-T one time and one time only. It will not be enabled the next time Sharp is started, (the program does not need to be closed). The check box in the ExtIO panel will still be ticked but there will be no voltage at the B-port. I've confirmed the same EXTIO bug when using the HDRSDRplay software. I'm suspecting you are facing this same issue with the RPI2.
SDRUno does not use ExtIO and the Bias-T works as it should.

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AussieSusan
Posts: 30
Joined: Wed Aug 16, 2017 6:50 am

Re: RSP2 operating and/or Bias-T supply on over a long time

Post by AussieSusan » Thu Feb 22, 2018 1:44 am

@Mike - I'm not using ExtIO. My program runs on an RPI3 (latest Rasbpbian OS) and communicates directly with the RSP2 via the API.
However I might try making the same sort of measurements to see what happens.

@RSP2user - your post made me think (a dangerous thing I'm told so I try to avoid it) and it could well be that the LNA I'm using is running very close to the current limit. I'll check that out when I have a bit of time.
As for the operating temperature range, the RSP2 (and RPi) are sitting on my desk in the house. While I do admit that living in Melbourne (Australia) does mean that we get days of over 40C, the inside rarely gets about the low 30's.
I was expecting the QFH to work down to lower angles but I'm a bit limited to how high I can put up antenna - basically I have to have it under a tile roof in the ceiling cavity. It was only through experimenting with the SDRuno program and switching antenna at 'strategic' times that I found the discone gave me a better signal at low angles than the QFH + LNA combination. I ended up going with the flow and putting off finding out why to a later date - which may have now come!

Susan

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RSP2user
Posts: 108
Joined: Mon Oct 09, 2017 7:11 am

Re: RSP2 operating and/or Bias-T supply on over a long time

Post by RSP2user » Thu Feb 22, 2018 3:08 am

Hi Susan,

Having sidewalk hot enough to cook an egg on in the summer is not unusual here either. If you are using the RSP2 on a really hot summer day outdoors in direct sunlight, you will likely notice that the black case absorbs radiant energy pretty well and the internal temperature gets a bit toasty. Just wasn't originally sure where you were operating the RSP2. Perhaps also consider the location of your low noise preamplifier and the ambient temperature it is operating in and how it might be affected (e.g., gain variation, filter frequency drift, etc.). I am making an assumption that it is located inside the attic space (ceiling cavity) along with your antenna where, at least here, temperatures may exceed 60C in the summer. In case it is helpful and as an additional data point for you, the antenna in the article is 214m MSL and about 8m AGL on a hill surrounded by otherwise relatively flat scenic terrain that extends hundreds of miles in all directions, subject to the curvature of the earth. From where the antenna is located, you essentially have a line of site to the horizon in all directions. So the images obtained are, in part, a result of that advantage. Best of luck on your project. I am sure you will track down whatever is causing your loss of signal issue and get it all going just the way you want it - and perhaps even post a nice APT or LRPT image of Australia (the limitation for posting images on this site is around 225kB).

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Mike2459
Posts: 318
Joined: Mon Jul 24, 2017 8:24 pm

Re: RSP2 operating and/or Bias-T supply on over a long time

Post by Mike2459 » Thu Feb 22, 2018 5:35 am

That crossed my mind as I was writing my reply. The problem may be as simple as a bad connection in the feedline. A common and sometimes difficult to find problem when it is intermittent. Good luck.

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