Smallest EMWIN antenna

[outatyme]

Doubleoh,
Can you make me a baseband recording in sdr-console and upload it somewhere and provide me the link.
(using Display -> data recordings -> recorder) - This should allow me to possibly do some additional troubleshooting.

I would need about 2 minutes worth of recording.

 

[GOES 12 GVAR user]

That's an idea as well, But again the antenna element is still going to be short for 1.6 GHz. One thing good about that dish on ebay besides it's price and shipping...ouch is that the offset feed has pretty good efficiently at these frequencies due to the feed not blocking (shadowing) the dish.

Timothy KC0HWG

 

[GOES 12 GVAR user]

I am getting off here for the night got to go. I will be back tomorrow (today if you want to look at it that way) in the eve. Talk to ya later.

Timothy KC0HWG

 

[doubleohwhatever]

Can you make me a baseband recording i

Sure thing:
http://www.filedropper.com/28-mar-2016065838542139200mhz000

ebay besides it's price and shipping...ouch is that the offset feed has pretty good efficiently at these frequencies due to the feed not blocking (shadowing) the dish.

One of the only things I like about offset dishes.

I am getting off here for the night got to go. I will be back tomorrow (today if you want to look at it that way) in the eve.

I'm heading off for the night as well. Cheers and thanks for the help so far!

 

[outatyme]

http://www.satelliteguys.us/xen/posts/3491638/
http://www.satelliteguys.us/xen/posts/3492278/
http://www.dslreports.com/forum/r21216147-Converting-less-expensive-2-4-GHz-Grids-to-1-9-MHz-Grids

Posts from page 2 of this thread talk about optimizing these grid parabolic feeds. - I did *NOT* do anything other than raise my reflector.

 

[doubleohwhatever]

I did *NOT* do anything other than raise my reflector.

You extended it out from the feed housing?

Also, I noticed that your reflector is bent whereas mine is flat.

 

[outatyme]

All i did to my antenna was spaced out the sub reflector alittle bit more - I do think a V shaped sub reflector would help you. I am looking at your file now. I am unable to get any data from it holdon. I will edit this post momentarily


Observations:
0). I was able to use audacity to resample the file from 625Khz to 500Khz.

• Good news!

1). You are still running through an unnecessary downconverter which could be reducing signal-to-noise ratio and a remote possibility of it introducing noise.

• Take that thing out if/when you can.

2). You have a periodic noise problem like some strong signal source is periodically keying up for a few seconds and causing noise across the whole band / sample range of your SDR.

• (could be a strong signal source overloading the RF frontend of the receiver).
• This is only an intermittent problem - therefore, you should be able to get periodic sync with the demodulator if this interference was your only problem.

2a). you have a continuous noise problem (those pesky peaks beside the emwin signal that should not be there).

• Get a band pass filter for the 1650-1700 MHz Band.

3). your signal is relatively weak. it sounds faint. (the Bzzzzt sound that the packets make).

• The signal looks weak in audacity.
• You need to improve your signal by about 3-5db somehow.
• (check your gain settings in the airspy).
• Reduce coaxial cable length if you can (per-foot loss), re-peak your dish, improve your feed / reflector. get a hotter LNA.

Those are some things you can do to improve your signal.

Get me some more sample recording files to check out Maybe 2-3 minutes

Do not fret too much - you will get it in time - have Faith, Grasshopper!

 

[outatyme]

Have you set the skew of your dish? (it should be turned clockwise or counterclockwise so many degrees)
This could cost you 3-5 Db of gain if you have not performed this adjustment.

http://arachnoid.com/satfinderonline/

Go here to figure out your skew.
you will probably have to re-peak after skewing it.

 

[doubleohwhatever]

Alrighty, I've removed the downconverter and have used the following setup with today's testing:

Dish
N to SMA Adapter
Bandpass filter: https://www.minicircuits.com/pdfs/VBFZ-1690+.pdf
LNA
SMA to N Adapter
3ft of coax (short SMA)
N to SMA Adapter
SDR

I've peaked the dish and made the skew adjustment (thanks for that link BTW). One thing I did notice while messing around with the dish is that the grid spacing on my dish is a little over an inch. Outatyme, what's the grid spacing on your dish? I'm wondering if that may be a difference between the two dishes. I have one of the TP-Link dishes coming tomorrow so I can see if perhaps the feed is better suited to this use.

The main thing that took up my time today before it got dark was trying to figure out where the heck all the noise is coming from. It's worse than I realized. Take a look at the attached photos. The photo with the spikes was with the above setup. The photos without the spikes is the exact same setup with the dish disconnected from the filter. I just don't get it. This noise was absolutely not visible a couple of weeks ago. Do you think it could be outdoor AC units? I did a quick count via google maps and there's at least 40 withing 500' of the dish (I wish I was joking).

I've uploaded two recordings:
http://www.filedropper.com/29-mar-20160047486731692700mhz000
http://www.filedropper.com/29-mar-20160124268751692700mhz000

I think this is the best it's gonna get with my current hardware. It's also at the same 625Khz sample rate. The Airspy just can't do 500Khz it seems. I have an sdrplay arriving tomorrow to fix this issue.

 

[GOES 12 GVAR user]

outatyme I know you said that you have boradband noise problems with reception, how much data can you get off EMWIN before demod. loses sync?
Next you mentioned doubewhatsoever may need a hotter LNA, between the LNA and downconverter he gets a min of 55dB of gain. That's more then any of my systems give in gain terms. In other words with those two active blocks he has a hot setup.
I have been thinking and this might help some noise maybe get rid of some unwanted garbage. Due to that antenna being a grid it does allow signals to get through in the opposite polarization through the grid. Even if it's 3 dB less than GOES polarization the signals getting through could be overwelming the amp and SDR.
I simple and cheap way to help the front to back ratio of that antenna as a test would be to use aluminum foil to cover the grid to make it solid. This may help the noise figure a bit too. Just a suggestion

Timothy KC0HWG

 

[GOES 12 GVAR user]

doubleohwhatever I have a dish like you posted on ebay, I have extra feeds and lna's here from past setups. If you want it would take within the week unless weather goes bonkers here is SW IA, I could make an EMWIN setup with it and report back the results on here.

Timothy KC0HWG

 

[GOES 12 GVAR user]

doubleohwhatever that looks like 120hz noise, simple way to see if that is it.. Get an AM radio tune to unused part in between radio stations in the band and listen to see if you hear some type of oscillating noise( this would be coming through the RF antenna). OR your LNA power supply is not filtered or the filter is bad in it.

Timothy KC0HWG

 

[doubleohwhatever]

use aluminum foil to cover the grid to make it solid

Should I put the foil on the front or back of the dish (or does it matter)?

I could make an EMWIN setup with it and report back the results on here

If you have the time that would be great. If it turns out to be a rock solid setup I can just duplicate it here.

Get an AM radio tune to unused part in between radio stations in the band and listen to see if you hear some type of oscillating noise

I just took an old clock radio out near the dish and there's a distinct buzzing sound. It sounds like the noise a street light makes when the bulb is about to die.

 

[GOES 12 GVAR user]

On the side the RF is reflecting on, so inside of the dish, OK I should be able to get it up in the week, the biggest part I will have to slap a mount for the pole together quickly.
Streetlight, ya that very well could be the culprit. I had a noisy HV insulator on my pole that would cause some problems here some time ago. That's why there are a few hammer dents in the pole.

Timothy KC0HWG

 

[doubleohwhatever]

Well, the foil took care of some of the smaller noise spikes. One thing I did notice is that the noise varies in intensity based on the dish position. I pointed the dish at the ground and the noise virtually disappeared. So it definitely seems to be an environmental issue rather than an issue with my hardware.

I'm still leaning towards grabbing the dish off of ebay. I'm going to need a better dish eventually no matter what. EMWIN will eventually be combined with LRIT and the grid antenna just isn't going to work for that.

 

[GOES 12 GVAR user]

Even with the the foil you got no signal improvement? Again as the forum says Smallest EMWIN antenna. Outatyme seems to think it will work but I just don't know.
One thing about EMWIN if you are getting block errors often the files are most typ. lost and can't be recovered. If you have a system that is soo close to margin and the weather degrades the signal or conditions then the signal will drop below margin and the data may not be useful. I look at this data for forecast information so I want a reliable link. I always go for some margin when working with these things if possible.
Since your putting all this labor and time in this and your HOA may allow a 4' dish I would go that way. But that's me.
There are so many factors that can affect a weak signal, many that can't be controlled esp. in this RF device world we have now the can affect signals like this one. You will have to make that decision... I will continue to work on this here and keep you informed.
Here is a pic of the feed for the antenna.

Timothy KC0HWG

 

[outatyme]

Something still doesn't sound right about those recordings.
I can hear the bzzzzt noise of the packets but it does not sound right.

I'm betting there is something odd going on with your airspy settings.

The picture you posted of the wide sample rate with the noise spikes shows a good amount of signal when you think about it in terms of the noise floor VS the crest of the signal.

 

[outatyme]

Here is a current picture of my setup running.
I do not have a band pass filter installed.
I still have the periodic broadband noise issue.


Just got my first full disk image off emwin!

 

[GOES 12 GVAR user]

I'm still here outatyme just came from from outside.

Timothy KC0HWG

 

[GOES 12 GVAR user]

doubleohwhatever has a streetlight nearby that is thought to be causing that buzzing noise. Thanks, I wonder what you had there I was getting the impression that your signal too was come and go. Noticing how many blocks you have got with no errors that's doing great. That gives me a lot more confidence about the size of antenna doubleohwhatever is and you are using. It's seeming he may also have a higher noise issue that you are. Though It does seem he (as you said) has a decent amplitude signal there. I told him to try some tin foil on the reflector which did help reduce some of the noise. Otherwise I am setting up a 4' offset feed here as to demonstrate and confirm.

Timothy KC0HWG