EuropaSat/Hellas Sat 3 & GSat 17 VA-238,

[Llew]

OK John. Horizontal just now, Will try Vertical.

 

[John]

OK John. Horizontal just now, Will try Vertical.

Ok, thanks Llew, with my 1.25 Gibby being a roof mounted thing it's a bit of a pain getting up on the roof crawler to change the lnb around. Must get my finger out now and get another polarity motor built for it now that it looks like we will have a choice of polarities to look at from this bird and 19.2° E for the Newsnet stuff etc.

 

[John]

... This things going to explode soon lol..

 

[Llew]

 

[Llew]

Vertical beacon same magnitude/frequency as Horizontal John. LH or RH polarisation? No reason to upload a screenshot.

 

[John]

Vertical beacon same magnitude/frequency as Horizontal John. LH or RH polarisation? No reason to upload a screenshot.

Ok Llew, i must have missed it on Vertical. There is a carrier doing very quick sporadic bursts around the 19144 H area that i'm trying to catch. It's eased off at the moment and gone to ground lol.
Looks like i'll have to get some card out to make a polorising slab for the XMW cone feed to see if we can get a fix on the polorisation .

 

[Llew]

Ok Llew, i must have missed it on Vertical. There is a carrier doing very quick sporadic bursts around the 19144 H area that i'm trying to catch. It's eased off at the moment and gone to ground lol.
Looks like i'll have to get some card out to make a polorising slab for the XMW cone feed to see if we can get a fix on the polorisation .

Beacon disappeared last night, John. No sign this morning. Will keep an eye on the band V and H.

 

[John]

Ok Llew thanks, iv'e got an unmodded SL3 on the changer which i think will see these circular Ka beacon frequencies so i'll rotate that into position and see what it produces. Btw, there is still the very very occasionally burst appearing on 19144 to keep an eye out for.

 

[Llew]

Btw, there is still the very very occasionally burst appearing on 19144 to keep an eye out for.

OK, I'll do that, and anything else that pops up. It's easy enough for me to rotate the LNB on the ground-level Triax to check for any V linear activity.

 

[Llew]

OK, Back again. V Pol check (same as H).

 

[John]

OK, Back again. V Pol check (same as H).

View attachment 108686

.. Tried the un-modded SL3 this morning, hard work and confusing driving one of those things so gave up on it . Iv'e got two options to try now ... either make a plate up for the xmw cone feed or use a Hughes OMT with their polariser and drop one of my XMW 18GHz lnb's on the end of it ... filthy weather at the moment though for messing about outside so will have to carry on using the fixed Hor position for a while longer.

 

[Llew]

Weather OK as I speak John. I'll try a plate in the Norsat's XMW cone feed myself, ISTR doing that a while back on another test somewhere, still got the dielectric somewhere.

 

[John]

.

 

[John]

Excellent, might need to copy the shape off you then Llew . ;)

Just checked for any other carriers on Cband / Ka / & Ku and can only see the beacons on all of the bands .... thought there might have been a few TP frequencies up by now.

 

[Llew]

Let's see if I have this right. I inserted a plate in the XMW feed and tried V and H pols. signal goes down by approx. half when in H mode, V mode stays as without plate inserted.

My plate was made for tests with feeds from old Sorsat LNBFs, all I have at the moment.

The Promax reads 1.4dB in V mode, and 0.8db in H mode. Given that the signal seems generally weak this morning (cloud thickening, some spots of rain), I don't think it's the best time to do any worthwhile tests at present.

As the signal is best in V mode, does this indicate a RH circular polarised beacon? Some time since I did any tests for TP polarity.

 

[John]

Let's see if I have this right. I inserted a plate in the XMW feed and tried V and H pols. signal goes down by approx. half when in H mode, V mode stays as without plate inserted.

My plate was made for tests with feeds from old Sorsat LNBFs, all I have at the moment.

The Promax reads 1.4dB in V mode, and 0.8db in H mode. Given that the signal seems generally weak this morning (cloud thickening, some spots of rain), I don't think it's the best time to do any worthwhile tests at present.

As the signal is best in V mode, does this indicate a RH circular polarised beacon? Some time since I did any tests for TP polarity.

.. Iv'e not done a lot of messing about with plates myself Llew but when i did have a play with another SL3 a while back i found it to be really critical to get the angle just correct to obtain correct polarisation. I think there are some Ka beacons out there on different sats that do use RHCP so you could be right.

 

[hvdh]

As the signal is best in V mode, does this indicate a RH circular polarised beacon? Some time since I did any tests for TP polarity.

It depends on the orientation of the dielectric relative to the probes. IIRC, if the plate is oriented "between the probes" so to speak, L becomes H, and R becomes V.

 

[Llew]

It depends on the orientation of the dielectric relative to the probes. IIRC, if the plate is oriented "between the probes" so to speak, L becomes H, and R becomes V.

Yes, I need to check the position of the plate when I check again. Thanks.

 

[hvdh]

Although it is convention to convert L to H, and R to V, I'm not sure "between the probes" applies to all LNB designs... and how about when there is only one probe (single pol)?
Maybe check some other satellites as well for confirmation! Satellites Community - 17.3-19.2 GHz band E/A

 

[Llew]

The only polarity switchable Ka band LNB I have is the Inverto Ka/Ku LNB (both bands switchable).
The one I'm using in this test is a Norsat Band A, which has one probe only. So presumably the orientation of the dielectric plate is not critical?