RF efficiency: an interesting observation - Printable Version
+- WeatherDuino Forum (https://www.meteocercal.info/forum)
+-- Forum: Weather Stations - WeatherDuino Pro2 Line (https://www.meteocercal.info/forum/forum-4.html)
+--- Forum: General Talking (https://www.meteocercal.info/forum/forum-23.html)
+--- Thread: RF efficiency: an interesting observation (/thread-1151.html)
+- WeatherDuino Forum (https://www.meteocercal.info/forum)
+-- Forum: Weather Stations - WeatherDuino Pro2 Line (https://www.meteocercal.info/forum/forum-4.html)
+--- Forum: General Talking (https://www.meteocercal.info/forum/forum-23.html)
+--- Thread: RF efficiency: an interesting observation (/thread-1151.html)
RE: RF efficiency: an interesting observation - danner - 26-06-2017
Watching both waterfalls at the same time, it appears that when it transmits the noise stops. Those breaks you see on spectran appear to happen when it is transmitting.
To be completely fair my 144MHz antenna is likely much longer than anything anyone else will be using. The gain of my yagi is high enough that I can bounce my signal off the moon, so this may not be an issue for the average person, but it is a slight concern to me. If I have to I will move it to a completely shielded enclosure. I knew that this sort of thing may be a possibility when I decided to build one.
RE: RF efficiency: an interesting observation - werk_ag - 26-06-2017
(26-06-2017, 00:33)danner Wrote: Watching both waterfalls at the same time, it appears that when it transmits the noise stops. Those breaks you see on spectran appear to happen when it is transmitting.
If the noise appears to stop when there is a transmission, maybe the source of the noise isn't the transmitter, as it is only powered during the time required to send each data packet.
In any case you are having a remarkable value for the RF Efficiency, I never achieved a value such high (my installation is not in an urban environment too), and I never expected to reach it too, mainly because it I'm using three TX units and some other RF devices, all transmitting to the receiver unit, so some collisions are expected which end in the lost of some data packets, which affect the RF Efficiency math.
RE: RF efficiency: an interesting observation - danner - 26-06-2017
(26-06-2017, 02:02)Werk_AG Wrote: If the noise appears to stop when there is a transmission, maybe the source of the noise isn't the transmitter, as it is only powered during the time required to send each data packet.
In any case you are having a remarkable value for the RF Efficiency, I never achieved a value such high (my installation is not in an urban environment too), and I never expected to reach it too, mainly because it I'm using three TX units and some other RF devices, all transmitting to the receiver unit, so some collisions are expected which end in the lost of some data packets, which affect the RF Efficiency math.
It'll be interesting to see what will "fix" it. The band pass filter should take care of any out of band energy coming from the transmitter by at least 50dB, and that's a lot. If the band pass filter doesn't fix it then I will still be more comfortable knowing the TX is safe from the 10,000 watt ERP at 144MHz I send in that exact direction. :-) I've blown up TV's, amplifiers, and even one of my old weather stations with RF.
Eventually the 144MHz antenna will be on the top of that tower so it should be enough in a null for it to not be a problem.
RE: RF efficiency: an interesting observation - uncle_bob - 26-06-2017
(26-06-2017, 02:29)danner Wrote: 10,000 watt
That's hell of a foot warmer
RE: RF efficiency: an interesting observation - danner - 26-06-2017
10KW ERP = 400W amplifier plus antenna gain. The yagi has over 16dBi free space gain and is 9.144m long. It's replacement that I designed is just over 11m long with over 17dBi free space gain.
RE: RF efficiency: an interesting observation - danner - 28-06-2017
I'm still waiting on the band-pass filter so I've been messing around and trying to understand what is going on with the interference I am getting on 144MHz. While listening to the TX0 transmitter using my RTL SDR dongle I noticed something strange. There is a little "tail" that can audibly be heard and it can be seen on the waterfall. I took a screen video of this and shared a link to the video. Can anyone else confirm that their transmitter has this tailing off signal? Or maybe it's just a strange artifact with my SDR dongle?
The video is in 1080P so you can make it full screen to see better.
https://youtu.be/XjLgn9PgQ9M
RE: RF efficiency: an interesting observation - danner - 29-06-2017
I think it's an anomaly from the signal being in the center of the passband. First time I've noticed something like that.
RE: RF efficiency: an interesting observation - danner - 30-06-2017
I kind of have an update, but on the RF efficiency thing.
Since I don't have any wires laying around other than UTP 4-pair CAT3 I used it to bring the power from the battery/charge controller to TX0 and I doubled up the wires so they could carry more current and have less voltage drop. I found one of the wires going from the battery to ground at TX0 was loose. I secured the ground and checked the other wires to make sure they were good. I also removed the ferrite cores from the wires of TX0. When I checked 144MHz the interfering signal was stronger with the ferrite cores removed. When I have time I will put the larger #61 UHF ferrite cores that I ordered on the wires and recheck.
Around the same time as fixing the loose ground wire, the new and larger UHF ferrite cores arrived. The new UHF ferrite cores were placed on the coax in the receiver box and I was pleased to find the RF efficiency went up a little. I've been watching it on and off throughout the day and now it seems to hover around 97-ish %. The idea of placing the ferrite cores on the coax is to act as a common mode choke. This is something I use with just about all of my antennas, but is possibly overkill on a weather station. I just wanted to see if it would help.
Since I don't yet have a WD the relay function is turned off.
Vid I made with my phone earlier.
https://youtu.be/AUDVW4DNPkw
I wish I had an extra rubber ducky to dissect. If it's not a vertical dipole then it still seems to work surprisingly well for a simple vertical with no counterpoise.
RE: RF efficiency: an interesting observation - Palmyweather - 07-07-2017
I gave adding ferrite cores to my transmitter a go as well. I added one around the power wires between the TX board and the settable voltage regulator I am using. My efficiency has gone from 75% - 80% before the ferrite cores to 92% - 97% after adding them. This is possibly worth doing for better data results.
PalmyWeather
RE: RF efficiency: an interesting observation - danner - 07-07-2017
That's fantastic, Palmy.
A quick update. My band pass filter arrived and I placed it on the transmitter, unfortunately the birdie I am receiving on 144MHz did not go away. My VNA cannot measure as high as 433MHz so I have no way to verify if the band pass filter does indeed have 50+dB of attenuation at 144MHz. I will assume it does so we can conclude that the birdie is not being transmitted via the antenna.
Not quite sure what to do at this point. It wouldn't hurt to add some ferrite cores to the solar panel leads. The charge controller is supposed to be RFI free, but who knows? Will have to do things one step at a time until I find the offending device. Eventually the 144MHz yagi will be far above the weather station so it wont be in the near field and likely the birdie will be attenuated by a significant amount. Until then I will have to live with it until I can figure it out.