Smallest EMWIN antenna

[outatyme]

Just seeing these fabrication posts now! I hope they yield good results!!!

 

[outatyme]

UPDATE: Yesterday I did some work with the RTL-SDR dongles and managed to get a dongle with the e4000 tuner working with the demodulator!!!!!
I still need to see if I can iron some kinks out but have encountered a minor setback.

 

[usa-satcom]

For those that want a test signal, i am making this recording available: https://www.dropbox.com/s/an5d3uwbaggqbfk/20160331_034952_500000.zip?dl=0

From 1.2m dish. This decodes from start to finish without a single error and should results in viterbi corrections of < 35 with RS always equal to 0.

Hope this helps.

Joe

 

[doubleohwhatever]

managed to get a dongle with the e4000 tuner working

I tried that yesterday but couldn't set the e4000 to the 500khz sample rate in sdr-console.

 

[outatyme]

I am using sdr# to make a baseband recording then using audacity and exporting the wav file at 500000 (500khz).

 

[usa-satcom]

I am using sdr# to make a baseband recording then using audacity and exporting the wav file at 500000 (500khz).

What is the normal sample rate for that dongle? Just curious as i can add in support for different sample rates, depending on how far off of 500K they are....

Joe

 

[doubleohwhatever]

What is the normal sample rate for that dongle? Just curious as i can add in support for different sample rates, depending on how far off of 500K they are....

Joe

The closest airplay sample rate offered by sdr-console is 625

 

[outatyme]

Will post this here as well:

rtl-sdr (E4000) sample rates:
------------------------------
0.25 MSPS
0.900001 MSPS
1.024 MSPS
1.4 MSPS
1.8 MSPS
1.92 MSPS
2.048 MSPS
2.4 MSPS
2.56 MSPS
2.8 MSPS
3.2 MSPS
------------------------------

SDRPlay RSP Sample rates:
------------------------------
Zero IF:
200 Khz
300 Khz
600 Khz
1.536 Mhz
5.000 Mhz
6.000 Mhz
7.000 Mhz
8.000 Mhz

Low IF:
200 Khz
300 Khz
600 Khz
1.536 Mhz
------------------------------

R820T (not R820T2) radios that I have tested are completely deaf at the emwin frequency (1692.7mhz) so they would need a downconverter in order to work.

 

[doubleohwhatever]

Alright, I now have the new computer setup. Definitely makes a difference with sdr-console. It was running at 45% CPU usage and now it's at 3%. I also have the parts to make the feed for the new dish that should be arriving next week.

The good news is that everything seems to be a lot more stable now. I can actually see the data packets in the waterfall (screenshot attached).

The bad news is that I still appear to have signal issues. Hopefully the new dish will resolve this.

I've also uploaded a recording here: http://www.filedropper.com/02-apr-20160327239371692600mhz000

Something seems a little off with this recording. If anyone has the time, could you please upload a recording made with sdr-console so I can compare?

 

[GOES 12 GVAR user]

The results of the 1.2M offset fed dish. It seems to have about 6 up to 7 dB above noise.The EMWIN signal is solid as Joe said. Easy to aim and peak.
doubleohwhatever I will need to know how the feed brackets are on your dish, If they are like mine in the pictures the side ones need no modification. The bottom bracket that supports the feed will need a change if it's like mine. The feed should be in the center of the dish as looking from the front (see pic). I will send dimensions for feed placement. Also feed as looking from the front (not shown) the connector should be in the 1 to 2:00 position for proper polarity.
The last picture shows the scope's view of the EMWIN Signal with the antenna.
Parts used: Homemade aluminum feed horn, DEMI UTRA LNA, Wilmanco downcoverter @ 70 MHz output, 1.2 M Channel master offset fed dish.
I have been under the weather so it will take a little more time to get numbers for feed placement up here.

 

[outatyme]

Nice feed there Tim! I am eager to see what a recorded signal from that looks like.

Doubleoh, I took a look at your recording and you still have lots of noise spikes in there but plenty of gain.
Perhaps try lowering the sample rate of the SDR and recording again with the signal offset some from center.
Also try to lower the gain slightly to see if that has any affect on the noise spikes.

Here is an emwin IQ signal recording made using my SDRPlay SDR at 500Khz sample rate in sdr-console.

The recording was made with a severe thunderstorm overhead and heavy rain and extreme lightning were also ongoing - the Vit error was lower than 200 on my grid parabolic and I still had solid reception despite the thunderstorm. The decoder did eventually loose lock later but probably because of my periodic noise problem.

There should be at least one image file in the recording and several text files.

https://www.dropbox.com/s/e9ujokylhygj18t/02-Apr-2016 064401.065 1692.639MHz 000.wav?dl=0

 

[usa-satcom]

Nice feed there Tim! I am eager to see what a recorded signal from that looks like.

Doubleoh, I took a look at your recording and you still have lots of noise spikes in there but plenty of gain.
Perhaps try lowering the sample rate of the SDR and recording again with the signal offset some from center.
Also try to lower the gain slightly to see if that has any affect on the noise spikes.

Here is an emwin IQ signal recording made using my SDRPlay SDR at 500Khz sample rate in sdr-console.

The recording was made with a severe thunderstorm overhead and heavy rain and extreme lightning were also ongoing - the Vit error was lower than 200 on my grid parabolic and I still had solid reception despite the thunderstorm. The decoder did eventually loose lock later but probably because of my periodic noise problem.

There should be at least one image file in the recording and several text files.

https://www.dropbox.com/s/e9ujokylhygj18t/02-Apr-2016 064401.065 1692.639MHz 000.wav?dl=0

Have you played this file back and it works for you? I tried it and although the signal level is good, SR seems OK, i can't lock to it. Let me know if you can play it back in SDR-Console and feed decoder via UDP successfully and I will look at it again.

 

[usa-satcom]

Nice feed there Tim! I am eager to see what a recorded signal from that looks like.

Doubleoh, I took a look at your recording and you still have lots of noise spikes in there but plenty of gain.
Perhaps try lowering the sample rate of the SDR and recording again with the signal offset some from center.
Also try to lower the gain slightly to see if that has any affect on the noise spikes.

Here is an emwin IQ signal recording made using my SDRPlay SDR at 500Khz sample rate in sdr-console.

The recording was made with a severe thunderstorm overhead and heavy rain and extreme lightning were also ongoing - the Vit error was lower than 200 on my grid parabolic and I still had solid reception despite the thunderstorm. The decoder did eventually loose lock later but probably because of my periodic noise problem.

There should be at least one image file in the recording and several text files.

https://www.dropbox.com/s/e9ujokylhygj18t/02-Apr-2016 064401.065 1692.639MHz 000.wav?dl=0

Also, i have off-pointed my 1.2m dish to see how things work with less signal. Viterbi corrections > 200 will result in loss of lock at a rate that is not very workable. < 200 seems to give pretty good results. Due to the nature of the FEC/differential coding when lock is lost, re-lock is not always quick - if SYNC is not detected within a few frames it will reverse the IQ streams and try again. When signal level is low and viterbi errors are > 200 the re-lock process will be extended. This is not ideal but from a DSP perspective it was a bad decision NOAA made to deferentially encode and then do FEC, there is a penalty (~2dB).

 

[doubleohwhatever]

Does anyone have a recommendation for a LNA? I'm concerned that some or all of my problems might be coming from my LNA and I'd like to get another for comparison. The one I have now is from mini-circuits.

I found this one:
http://www.pasternack.com/1.4-db-3-ghz-low-noise-amplifier-34-db-gain-sma-pe15a1009-p.aspx

Has anyone used this brand before?

I have been under the weather

Thanks for the help! I hope you get better soon!

 

[GOES 12 GVAR user]

doubleohwhatever You can find one here, It's the same one I am using for the 1.2M dish project for $150 from Down east microwave. The noise figure is lower and gain is about the same. Gain #'s are nominal.

http://www.downeastmicrowave.com/product-p/1691lnah.htm

Here are some screenshots of the 1.2M dish with HSDSR. There are set of 2. First is of the downconverted 70 MHz band of EMWIN then LRIT. The screenshots show a very good signal for bolth.

This set show the output on 1690 MHz band. The EMWIN and LRIT are still very readable.

The SDR is the 100KHz-1.7GHz Full Band RTL-SDR USB Tuner Receiver R820T+2832U Radio doing the work. There is no audio files due to this software doesn't output the I/Q channels directly.
So I can't record the output unless I an using the Warner labs EMWIN II receiver.
Here are the Numbers for the feed placement on that dish.
Focal length is near 44 1/2" to 44 3/4"
All measurements are at lip of horn.
Distance for the side edges at center is: 46 1/2"
Distance from the center bottom is: 39"
Distance from the center top is: 55"
The next project will be the improved grid antenna.

 

[outatyme]

Here is the LNA I am using with excellent results:
http://www.ebay.com/itm/Ultra-Low-N...480555?hash=item41a758ac2b:g:-CIAAOSwKIpWDJuF

 

[outatyme]

Thanks for your testing Tim! - you just prooved that the RTL-SDR dongles can be used for this project.

R820t needs a downconverter to shift the IF from 1692.7 to something within it's hearing range - I have 2 of these tuners and can confirm BOTH are deaf at the GOES frequencies.
Folks with E4000 (e4k) based rtl-sdr's may get away without a downconverter.

 

[outatyme]

Also for informational purposes, I live close to down east microwave - my original unit was one of theirs apparently and it didn't do so hot but might have been damaged by someone before me.

Their gear is really well built for the price.
Weatherproof and good and shielded.

I got mine secondhand off ebay but it just didn't have enough gain.

 

[doubleohwhatever]

Thanks for the suggestions. I remembered that I have a LNA4ALL in my parts bin. So I'm going to give that a try tomorrow and see what difference it makes with my noise problem. If it's cleaner then I'm going to get a new LNA.

Here are the Numbers for the feed placement on that dish

Thanks for this. I'm going to work on my feed tomorrow if I have time.

Folks with E4000 (e4k) based rtl-sdr's may get away without a downconverter.

I have several of the e4000 units and they can definitely see the signal.

 

[doubleohwhatever]

Well, the LNA4ALL provided very similar (noisy) results. So I guess I'm just going to have to wait for the new dish to arrive and go from there.