The Aero Thread..

[Lazarus]

I Ronsealed my Window Frames today. Maybe I'll go out and watch them dry.

 

[Vipersan]

I Ronsealed my Window Frames today. Maybe I'll go out and watch them dry.

R U suggesting this is boring you G ..
Sorry buddy ..
doh!

 

[Lazarus]

Not at all. It's very interesting indeed - but boy it seems to take a long time to come to fruition!

 

[Vipersan]

Not at all. It's very interesting indeed - but boy it seems to take a long time to come to fruition!

Indeed it has ..
and still not there yet ..imo
I rather fancy I am once again ..'fringe'
..and that does require a bit more effort sadly ..

 

[Vipersan]

Ok ..didn't wait till tomorrow ..cos this is Manchester ...and chances are it will be raining ..
Moved the Helical back to the 1 mtr ...without changing anything or even powering down Airspy ...
..and yes occasional data is possible ...but so many CRC errors and dropped frames ..
Another couple of DB gain would fix this I'm sure ...
Now Im wondering how I can squeeze those pips ?
I'm even considering sending the Helical when complete to L-Band to see if it can be tweaked ...
he has the gear for this ..

My initial observation is that there is enough signal ...but The noise floor keeps rising in bursts ..
and when it does ...the data peaks shorten ..
Thus the variation I'm seeing ..perhaps ..
I'll try and grab a couple of extremitities ..
rgds
VS

 

[Vipersan]

A couple of screen grabs ...moments apart ..
Good (Lower) and Bad (Upper)..
Bad actually gets worse than this ..but catching it aint easy ..

Its as though the agc floats ...but unlike before I'm not seeing a signal trigger....but there must be one ?

 

[Lazarus]

Nope. I'm saying nothing. Especially about extremities.

 

[Vipersan]

..Got a passband filter to try (made by L-band ) which I intend to try ..but need my second LNA4ALL for this ...which is currently on order..

 

[Vipersan]

Feeling a bit sorry for myself today ...having parted with about a beaker full of blood over the last 24 hours ..
Folling a visit to the dentist and 1x wisdom and one molar removed ..
Nonetheless I did manage to play out in the sun for an hour or so ...but still can't eat yet ..
doh ..
water or luke warm tea ..
Ok ..So I got my second LNA4ALL ...and already have a 1.5ghz filter from LB ...
also have one from Adam ...as he posted me one of his construction as well ..
So 2 filters to choose from ..
both are have the active path at DC ground ..so I needed to jump the 4.5v supply from the Bias T of LNA1 to power LNA 2
LNA1 being closest to Airspy ..
LNA2 being isolated somewhat and directly connected to the Helical element
LNA 2 is also screened inside a seperate metal box ..
LNA1 and the filter are exposed to the elements atm ...but will eventually be inside the diecast box ..as will all the RF elements ..
They wont fit in atm although close ...due to extra sma straight couplers needing to be employed..(taking up valuable space)
I have a dozen right angled Male to Male couplings on order but these will be at least 2 weeks arriving from China.
So ..a photo of the plumbing arrangenents as they currently are ...I have tried both filtes ...and so far LBs appears to have the edge ...
RFI appears lower ...vut the extra DB gain still makes for scrappy and occasional data received ..
Most of the time Jaero fills up with CRC or Souncard buffer errors ...but the three target peaks appear to be about 8db tall now ..
So I am at a loss to explain why this is so ..?
I still think this may be as a result of footprint and that I am indeed 'fringe'..

The phrase being ..you simply can't polish a turd ...
No amount of amplification will help if the signal is poor or corrupt at the point of reception ..
you simply amplify the errors along with the good stuff ..
(fingers crossed I am wrong about this)
Here are the pix..

Helical Element > LNA 2 > Filter > LNA 1 > Airspy

 

[Vipersan]

Looks like I have aquired some issues in windows since I either have allowed updates ...on the Optiplex 990 ...or installed something that caused more issues ..
Basically ..I disabled VB ..and actually listened to the signal ..
Hmmm ..every few seconds there was a silence and a pause ..
This was NOT happening when I first bought the SFF PC ..
Luckilly I had the sense to keep the original supplied HD ..so cloned it backwards onto the 990s hard drive .,.thus giving me a clean slate ...
The difference is substantial ..
There is still an occasional pause ...about every 30 seconds ...but is so much smaller ....thus is causing much less problems for the data ..
Not at all sure where this pause or hiccup is being generated ...or by what ...but is a real problem when other programs or updates have been installed...
but for now ..
this is Soooo much better ..


So atm ..there is data more than there isn't data ...and the tiny occasional pauses in the audio ...
I can maintain Quadrature lock for quite long uniterrupted periods ...and thats on the 1mtre dish..
I believe these may well be responsible for the lost frames ....which before the 'wind back' of win7 ...were much more frequent ..and lasted longer ..
Thus the data was unstable..

 

[Vipersan]

Just woke up and a quick check reveals the stream I was monitoring ...remained locked all night for at least 99% of the time ..
Interesting to monitor these channels ..but what a pity the streams dont contain positional data ..that could be used for PP ..
Afterall ..it may be expensive to build and setup ...but is do-able on a 1 mtre dish.
rgds
VS

 

[Vipersan]

Starting to lose lock now ...approx 50% of the time ..
presumably elevation variation of the satellite ...as I have changed nothing ...
will keep monitoring this same channel to see how long the outage lasts ..
Rising temperature ie increased background noise may also be playing a part..

 

[s-band]

A couple of degrees elevation change shouldn't matter. The beam width will be quite wide at 1.5G, about +/-6 degrees at -3dB points

 

[Vipersan]

In that case SB ..
I think I would blame background radiation levels ..which even as I type appear to be improving ...
lock is about 75% atm ..
This problem will hopefully lessen as I eventually get the 1m at height ..
rgds
VS

 

[Vipersan]

Well ...I have changed nothing ..but continued to monitor the data stream/quadrature channel lock on Jaeros constellation window ..
Absolutely no chance of signal lock at the moment ....not even occasional ..
Thus I have to blame something ..
It is a warm sunny day here so ..yes ..it could well be there is too much background radiation ...or it could be dish misalignment relative to the inclined Inmarsat bird ...
I dont want to go chasing it ..so will test again later to see if the signal returns.
rgds
VS

 

[Vipersan]

Still monitoring the signals from Inmarsat 15W L band ..
Totally unlockable atm ...with only occasional hints at lock QPSK ...
No changes have been made ..and the temperature has now dropped quite a bit ...so am inclined ..(pardon the pun) to think it is indeed down to the fact that Inmarsat is inclined..
Total and solid lock was achieved for most of last night ...so will be watching for the same tonight..
rgds

 

[Vipersan]

...The signal just went into solid lock again about 10 minutes ago ..
I'll need to perfotm this 24 hour test again ..whilst watching the elevation changes on N2Yo ..
rgds
VS

 

[Vipersan]

Once again this morning I woke to a locked signal ....and has remained locked as I suspect it will till around 4pm -ish
From what I have observed so far ...the worst time for lock is late afternoon till around 7pm-ish ..
Which coincides with the most elevated position (above equator) or Inmarsat 2-f3.
So ..If this is so ..then I suspect I have simply set up my test rig at the wrong time of daty ..
Centering I think needs to be done when the sat is roughly equatorial ..
rgds
VS
here is a snapshot of the current position of this bird ..and currently I have lock ..though occasional errors are creeping in ..
rgds
VS

 

[Vipersan]

Looks like my prediction was correct ..
Just nipped home to check ..
Inmarsat currently above the equatorial plane ...and no lock possible ...
missed the upper limit by about an hour ...
rgds
VS

 

[Confucian]

Mods to C1W-PLL (not-Lite)

Polarisation
As received this switched at 15V to H and 14.5 to V. Curiously, there is an intermediate state when dropping from 14.7 to 14.6V. The level dropped by ~10dB before switching fully. That may be yet another reason why random changes in performance are seen. I didn’t investigate but maybe it’s when both front ends are on at the same time? It’s probably not needed but I changed the switching voltages to 15.9/15.2V by changing the circled resistor to 8k2 (was 10k)

TCXO
This was fitted in a different way, compared to the lite, on another piece of PCB with track hacked to suit. The PCB is grounded via a copper strap with some Kapton tape to prevent shorting to the main PCB tracks. As per Osmocom, the level is not really that critical. When doing the lite I hadn’t noticed that the duty cycle of the Rakon output changes dramatically if loaded resistively. That must have messed up the bias in the downconverter. For this one I put a 47p in series and then a 100p to ground to form a capacitive divider to drop the level. The supply was fed from the 6V line via a 220R decoupled with 100n. The voltage is still a bit high but it works.

The point marked “TP” can be used to probe with a counter without upsetting the TCXO.

Sealing
I also put some screws in the empty fixing holes and the holes for which I didn’t have short enough screws, I filled with sealant.

I don’t know why I spent so long on this but once I started….

View attachment 92312

Just finished and installed a TCXO modified LNB , monitoring drift for the next 24hrs.
Thanks to S-Band for all the help and info that even an (old) novice like me could follow.