Antenna thread

[Vipersan]

Never mind being 0.5° off, with a few tens degrees beamwidth!
Instead, no room left on your bigger dishes?

possibly I could mount it on the 1.5 temporarily ...tomorrow that is ..
but I wanted a permanent solution ..
Just so many variables atm ....
I could understand a weak signal ...but no signal at all ?
thats just frustrating ...
Is there such a thing as a footprint map for Inmarsat at 15W ..
It would be nice to know if I even have a shot at this ?
Data is hard to come by re- L band

 

[hvdh]

Indeed, I've not seen a better footprint maps than this:
Our coverage - Inmarsat
(click on map for slightly better readability)

 

[Vipersan]

Thanks Hans ..
hard to tell ...but looks at first glance that the coverage is even over the intended target area ...so theoretically ...a 90cm dish at Adams location should provide as much signal as one at my qth ?

 

[battenfan]

Where is focus on a spiral antenna?

 

[Vipersan]

Where is focus on a spiral antenna?

Good question BF ...
Not sure myself ...
Hopefully someone will know ..

As to this project ...
I have spent hours on it and a fair bit of cash ...but still no results ..
..and I'm getting frustrated to the max ..
Having been up the ladder again this morning ...and brought down the helical ...I did a straight swap for the C band LNB on Carl ..mounting it as best I could ..
The Cband lnb was previously picking up Aero C band ...so was definately in the right bit of arc ..
I attached an LNA to the helical to offset the long 75 ohm cable run ...and powered up AirSpy ..
Zip ...Nada ...Sod all ..
I am getting to the point where I guess I need confirmayion this is even possible in the MW of the UK ...and Aero His actually still running at 1.5ghz ..
Adam manages it on a 90cm dish behind glass with a linear antenna ..
Surely I should see _something_ ???

 

[Vipersan]

Is it possible to contact Jonti directly in order to at least confirm Aero-H is still viable ?
As said already ...I now have the helical on Carl ...and still nothing ..
In fact this area of spectrum is practically silent for me ..
Here is a photo and a spectrum scan with the LNA still in circuit..

Even if I totally fffed up designing the helical ...to be _that_ selectively deaf ...would be almost a miracle..
Help!!
rgds
VS

 

[s-band]

Is it possible to contact Jonti directly in order to at least confirm Aero-H is still viable ?
As said already ...I now have the helical on Carl ...and still nothing ..
In fact this area of spectrum is practically silent for me ..
Here is a photo and a spectrum scan with the LNA still in circuit..

With a wide sweep your bandwidth will be wide and you will not see narrow band signals at the kind of levels we get from Inmarsat. Set to 10MS/s, decimation = 4, centre freq circa 1545.5MHz.

I just tried waving the helical in front of the dish and got the following EbNo: 25E 15dB, 15W 13dB, 54W 13dB on the 10500 bps sigs. It said 50dB on the 600bps (must be the maximum, doesn't make sense). Being a PF dish I had it at about 10W to get 25E and 30W to get 15W & 54W i.e. using the dish as an offset and keeping myself out of the beam. It's abit difficult to hold in place for very long though! I view SDR# and JAERo via VNC on an Android tablet. It is just about possible to control it via the android but fiddly.

I'm using a 0.3dB NF LNA which I had left over from the S-band kit for Arabsat and re-tweaked for 1.5GHz

 

[Vipersan]

ATM I'm trying to get a laptop outside to be closer to the helical ..thus a shorter cable run ...
Problem is my lappy still has Vista on it ..
..and I'm having trouble getting SDR#/Airspy to run..
No plug n play ...
I think it needs a driver ..
Is there an Airspy driver for Vista x86 ..?
If there is I can't find it on the web ..
anyone ?

 

[Vipersan]

With a wide sweep your bandwidth will be wide and you will not see narrow band signals at the kind of levels we get from Inmarsat. Set to 10MS/s, decimation = 4, centre freq circa 1545.5MHz.

I just tried waving the helical in front of the dish and got the following EbNo: 25E 15dB, 15W 13dB, 54W 13dB on the 10500 bps sigs. It said 50dB on the 600bps (must be the maximum, doesn't make sense). Being a PF dish I had it at about 10W to get 25E and 30W to get 15W & 54W i.e. using the dish as an offset and keeping myself out of the beam. It's abit difficult to hold in place for very long though! I view SDR# and JAERo via VNC on an Android tablet. It is just about possible to control it via the android but fiddly.

I'm using a 0.3dB NF LNA which I had left over from the S-band kit for Arabsat and re-tweaked for 1.5GHz

Cheers SB ..
any chance of a photo of your Helical antenna ..to compare physically with mine ?
I'd appreciate it muchly..

 

[Vipersan]

Finally got this lappy to install a win usb driver ...automatically via windoze updates ...
now comlaining about .net not being suitable ..
This too I now need to update..
Better let sleeping lappies lie ..I think ..
This one hasn't been used for yonks..
lol

 

[s-band]

Cheers SB ..
any chance of a photo of your Helical antenna ..to compare physically with mine ?
I'd appreciate it muchly..

It's about 65mm dia and 30-35 pitch. The bit of wire close to the board is the matching. Although it looks like a bodge (it is), I have the advantage of being able to tweak it on an analyser.

I'm using a 40m cable run but it doesn't matter as there's plenty of gain at the front end. If you can get a VNC set up you could still use the main PC and any old thing as the viewer.

 

[Vipersan]

Thanks for the pics ..
yours too looks to twist clockwise viewed from the front ...so I am guessing I have the polarity right on mine..
diameter of one turn is 60 mm approx (3.5 turns in total)...and 49 mm seperating each turn ...
the first quarter turn running parallel to the reflector at a height of approx 3mm ..
Sound Ok ?

 

[Vipersan]

Have Microsoft thrown a hissy fit ?
Successfully installed win7 on this spare laptop..
Can't run SDR Sharp ....on account it needs Dot Net4 or later ..
Cannot download and install this on the lappy ...as first I need a later browser IE11..
cant install IE11 until I've installed win7service pack 1 x86 ..
Tried to download and install this ...but cant FFFing find it at MS ...
have they pulled the plug on Win7 as well in response to the hate shown for Win10 ?
wtf is going on ..
???

Found a link to KB976932 ...which I hope is the update I need ..
fingers crossed the link is still active..
Data is coming down but very slowly

 

[Analoguesat]

.
have they pulled the plug on Win7 as well in response to the hate shown for Win10 ?
wtf is going on ..
???

There more than slight suspicions MS have deliberately borked the win7 updates over the last few months - there have been reports of slow starting downloads from several members here & Ive seen no end of reports on computer sites as well

It will update on its own - eventually.

 

[Vipersan]

So took nearly all day to get this old lappy up to speed with win 7 ...
But once outside and connected with a short 1m length of 50 ohm cable ...I set off Airspy ..
Tis a very lumpy procedure ..on account the processor is maxed out ..but did manage to grab this image ..
Certainly looks promising I think ..
That being the case ...better cable is probably needed ...
non of this 50 to 70 ohm conversion ..and an LNA at the very least to help cover such distance and get the signal indoors,,
The image you see is Helical to Airspy direct ...through a metre of cable and 50 ohm connectors ..
rgds
VS

What do you think SB ...have I found AeroH ?
Can't run jaero on this lappy as well as Airspy ...
the load would be too much.

I feel another spend coming on ..
This time a 50 mtre reel of 50 ohm coax...

Adam A ...of course uses his downconvertor ...which makes data transfer over cable easier ..
but his MIX4ALL is not in the public domain as yet ..
Pity..

 

[s-band]

This is what I get on 25E with the same settings as you. The cursor is on one of the 10500 signals. Note that the loudest signal are the narrow band aero at 1545.120ish. The most obvious are the ~180kHz wide data sigs.

This is a close-up of the 10500 that's being decoded

This is the group of 2 1200bps and 1 600bps at 1545.120


I've got all sorts of mis-matches. Up to the output of the LNA it's 50R then it goes through 40m of CT125 (75R) then back to 50.

I thin that you need a decent LNA. The Airspy may have an NF of 4dB compared to my 0.3dB. That's going to make a big difference - cant work it out in my head!

 

[Vipersan]

100% sure now ..but can't try to decode ...that lappy is just too slow..
lol

 

[s-band]

100% sure now ..but can't try to decode ...that lappy is just too slow..
lol

s/n looks too low. I get some errors at 13dB on JAERO

 

[Vipersan]

s/n looks too low. I get some errors at 13dB on JAERO

Agreed ...
lots of tweaking to do ...but at least I've found my target ..

..and no LNA in the mix as yet..
;)

 

[Vipersan]

Ouch that hurt ..
couldn't get a 50mtr drum ..so had to opt for 100mtrs ..
RG58 Mil Spec ...
£38 delivered..
just hope Mil Spec means something ...and not just a label..
lol