The Aero Thread..

[s-band]

Does it still recieve RHCP ? or is the signal direction of polarisation reversed upon reflection from the dish surface ..
ie Do I now have to modify that same antenna to receive LHCP ?

Yes, you need to reverse the sense of the polarisation for each reflection. A Gregorian's polarisation is the same sense as the feed.

 

[Vipersan]

Yes, you need to reverse the sense of the polarisation for each reflection. A Gregorian's polarisation is the same sense as the feed.

Thanks SB ..
thought as much ..
The patch Antenna I made is free standing ..for Aero H ..but my intention was to try and dish mount it ...so I now know I need to reverse the polarisation ..
cheers..

 

[Confucian]

System getting tidier. One or two issues to tinker with but overall it seems to be working well. Running three different dongles to try and find which works best. Strange thing I noticed, the one with the worst spec has the lowest noise floor (have tried all combinations of dish and dongle).

 

[spacedish]

Bit OT , but I decided to try my 90cm Greg on C Band AERO , but fell at the first fence. We had a power cut last week and the mains surge that followed fried my LT8700 which I used as a remote positioner :O(
This is the third LT I have lost to mains surges following power cuts.

/QUOTE]

Quick update on this....

Ordered a few new resistors, replaced R16 and R17 on the board.... Bingo its working again.
Did the same to my even older / dead LT , that's resurrected too :O)

 

[Vipersan]

Still persuing that 10500 data at 1.5ghz ...
I can lock the narrower band data streams most of the time but not the wideband stuff with my homebrew Helical and LNA4ALL ...
This has tied up Carl at 15W for long periods ...so having already tried already with a mismatched coax and connectors on a 60cm I got no useable results ..so contacted my friend Digi247 regarding gattting a larger dish to dedicate to Inmarsat at 15W.
Previously He has got for me Dishes branded Orbital ..but His supplier no longer stocks them ..so went on Ebay ..
Non on there either ..
Have they gone out of business ?
I did get a 1.1m branded Maxx ...for about£30 delivered ...
Is this Orbital re-badged perhaps ?
Now this dish will be much closer to the house ..just the other side of the playroom outside wall ...so a shorter run of RG58 ..
..which hopefully will help with signal levels /losses ..
And since the helical was getting _some_ results on Carl ...the 1.5m ...and offset several degrees from focus ...I'm hopefull that the helical on shorter cable run (probably 5mtrs as opposed to 15 >20 mtrs ...and at the focus rather than offset will yield results ..
fingers crossed.

 

[Analoguesat]

Bit OT , but I decided to try my 90cm Greg on C Band AERO , but fell at the first fence. We had a power cut last week and the mains surge that followed fried my LT8700 which I used as a remote positioner :O(
This is the third LT I have lost to mains surges following power cuts.

Get yourself a UPS - Uniterruptable Power Supply - they condition the incoming power supply to remove the damaging sags & surges. For sat receivers you would get away with the smallest ones going.

 

[scopus]

Get yourself a UPS - Uniterruptable Power Supply - they condition the incoming power supply to remove the damaging sags & surges. For sat receivers you would get away with the smallest ones going.

I use mains conditioners, well worth it where we live in the sticks, surges, all sorts of nasties....

 

[Vipersan]

Still after these elusive signals in L band ..
The rain has stopped this morning so ..was able to re-fit the Helical ..modded with a square of Brass under the bottom of the Element ...and a temporary screened and waterproof enclosure for the LNA ..
Made from an old cut down empty single colour ink cartridge... and ally tape ..
The signals from the narrower data channels has improved a fraction ...but still no hope of 10500 BW channels ..
But at least I dont have to bring in the LNA when it rains now..

rgds

 

[s-band]

Still after these elusive signals in L band ..

Looking at the feed again, I wonder if it is too close to the dish face to be at the focus. Can you take it off the dish and wave it about to find the best position? Another thing may be to turn the dish a bit further and try the feed more offset just to give more room to move it around.
The narrow sigs from 25E are much louder than 15W which may make it easier to align.

 

[Vipersan]

Looking at the feed again, I wonder if it is too close to the dish face to be at the focus. Can you take it off the dish and wave it about to find the best position? Another thing may be to turn the dish a bit further and try the feed more offset just to give more room to move it around.
The narrow sigs from 25E are much louder than 15W which may make it easier to align.

Fun stuff to dry over the w'end ...assuming it stays dry ..
good suggestions SB ..
I think the question was asked already in one of the threads ..
Where exactly IS the focus on a dish with Helical mounted ..
tricky indeed ..

 

[Lazarus]

The very thought of VS waving it about in his back yard is giving me nightmares.

 

[Vipersan]

The very thought of VS waving it about in his back yard is giving me nightmares.

Yes ..and I have new Neighbours who dont speak much English ...
So they certainly wont be used to my eccentricities..
;)

 

[Vipersan]

So ..maybe I can put this to good use ...
I contacted AT800 today regarding possible 4G interference ..

I hope to use the filter on my 1.5ghz project ..
;)
This is their reply :-

Hi Evan,

Thank you for getting in touch. I am sorry to hear that you have been experiencing Picture freeze and or picture loss with your Freeview service.

Using the address details you have provided, I can confirm the recent activation of 4G at 800 MHz masts in your local area.

As requested I have sent you an at800 filter. This should be with you in 3-5 working days and comes with full instructions. If the filter doesn’t resolve your reception issues, I would recommend calling us to complete a short diagnostics consultation so we can determine what further support we may be able to provide.

This can be completed by calling our contact centre on 0808 13 13 800*. Our opening hours are Monday to Saturday, 8.00 am to 6.00 pm. We are closed Sundays and Bank Holidays.

Alternatively, if you would prefer that we call you directly using the number you have provided us with, please reply to this email with a suitable date and time. We can then arrange for one of our advisors to contact you.

I hope this information is helpful in restoring your Freeview reception.


Kind regards,

Stuart
at800 Support Team

 

[hvdh]

So you'll have a filter to remove stuff above 800 MHz... what's the use of that at 1.5 GHz?

 

[Vipersan]

So you'll have a filter to remove stuff above 800 MHz... what's the use of that at 1.5 GHz?

Non I guess ...
No real use unless it's local high power RF bleeding over and affecting the Airspy AGC ..
usually tho ' that would be from a lower frequency source and its harmonics ..
but ..IF nothing else I can open it up to see what components have been used and in what config ...allowing me to improvise a copy that works at a different frequency ...
..and of course provides a screened case with connectors ..
Free is Free afterall..

 

[Lazarus]

Take 10 Honorary Yorkshireman points.

 

[s-band]

I was clearing out some junk and found a duff thermocouple from the gas boiler. What would any normal person do with it? Make a helical antenna. I wound it on an old SMW Ku LNB and attached it to the L-Band plate. It was a bit low in frequency so I tightened it (SMW X-Line aren’t good for L band).

EbNo with different amps on 25E 600bps using the Airspy with antenna on window sill:

No pre-amp and 3dB cable loss: 6dB
MGA 30889 (2dB NF 15dB gain) at antenna: 15dB
2 ATF 10136 GaAs (<.4dB NF 25dB gain) at antenna: 25dB

25E & 15W 10500 with GaAs LNA give about 5-7dB EbNo and not many “bad CRC”. That’s about the same as I got with the 2 turn feed & a GaAs LNA on an old 35cm BSB dish probably indicating that I was not illuminating the dish very well (it should have about 13dB gain at 1.5G).

25E signals are still visible when pointing at 15W and vice versa and it’s much more susceptible to interference. This pic 15W_helical_10500_gaas_lna, shows 25E sigs to the left of the 15W ones.

Calculated gain, for a 4.5t helical, is around 11.5dBi. My messy one? 9-10dB? A 20 turn should give ~6dB more i.e. a decent margin. The front to back ratio might be better on a dish though.

 

[Vipersan]

fwiw I went in earch of the Aero signals on 25E ....
I found em I think ...but they are at lower levels to those at 15W so wont produce lockable Data on 10500 ....
At first I did head East ..and on the way found some huge signals (non Aero) coming from something ...and in the same part of the spectrum frequency wise (L band) ...
any Idea what I might be looking at ..
Too dark to go out and get rough bearings ..but I'd guess about 4E
I'll try and grab a Spectrum spy pic ...as some are constant and wide enough to show up ..
rgds
VS

 

[Channel Hopper]

Still persuing that 10500 data at 1.5ghz ...
I can lock the narrower band data streams most of the time but not the wideband stuff with my homebrew Helical and LNA4ALL ...
This has tied up Carl at 15W for long periods ...so having already tried already with a mismatched coax and connectors on a 60cm I got no useable results ..so contacted my friend Digi247 regarding gattting a larger dish to dedicate to Inmarsat at 15W.
Previously He has got for me Dishes branded Orbital ..but His supplier no longer stocks them ..so went on Ebay ..
Non on there either ..

I have a couple of Orbital 1metre dishes here, but if you are something bulletproof then I still have one of the original 1m Triax dishes in the shed. At such a frequency though you reaally should be looking at a horn antenna - ooooerr ! .

Easily made and even easier to mount - oooooerr!

Horn Antenna calculator | converters and calculators

802.11b Horn Antenna Designer calculator.Frequency: i1wqrlinkradio.com

Simply scale up the following image onto a piece of tin for the correct frequency.

 

[Vipersan]

I have a couple of Orbital 1metre dishes here, but if you are something bulletproof then I still have one of the original 1m Triax dishes in the shed. At such a frequency though you reaally should be looking at a horn antenna - ooooerr ! .

Easily made and even easier to mount - oooooerr!

Horn Antenna calculator | converters and calculators

802.11b Horn Antenna Designer calculator.Frequency: i1wqrlinkradio.com

Simply scale up the following image onto a piece of tin for the correct frequency.
View attachment 93758

Another project for another day CH ...
Gonna try the 20 mtr usb repeater cable idea first..