Ka B/C overlap (Hughes) Thread

[hvdh]

Oooh I thought this is the obvious way for a long time already, but assumed you didn't want to mess with the Hughes like this! Or did you need all this time to gather the courage?

 

[Vipersan]

I had it in mind for some time Hans ..but getting in my Hughes wasn't as obvious as Llews version ...
Plus we still need to make osc switch to gather the nessessary info ...and make those voltage checks.

There was always the fact that I didn't want to poke around too much in such a confined space with tiny SM devices ,,
My 57 year old eyes object these days ..
So yes gathering enough courage WAS important..

lol

..and that transistor ...or so I thought ...is actually a Shottky barrier diode ...

 

[Llew]

Looks like you're onto something there VS. Mine's definitely a 10393, checked a while ago when down for photos.
I'll do some circuit tracing around the chip when I open it up soon. BTW, just to add, that choke (black round component) near the input will no doubt be for the 27MHz filter network, but hopefuklly that won't concern us if your idea comes to fruition
Back later with my findings.

 

[hvdh]

BTW, just to add, that choke (black round component) near the input will no doubt be for the 27MHz filter network, but hopefuklly that won't concern us if your idea comes to fruition

Yes behind that filter (or maybe just that choke), it should be fine to put the 2-resistor voltage divider, towards the comparator.

 

[Llew]

Oooh I thought this is the obvious way for a long time already, but assumed you didn't want to mess with the Hughes like this! Or did you need all this time to gather the courage?

Vague ideas investigating further Hans, sidetracked by our ongoing and seemingly never- ending quest for the perfect 27MHz switch

 

[Vipersan]

..Now ..I cannot find any DC switched via the Diode having lifted the centre leg ,,,
So the 1.36v no longer appears at all ..thus ..I assume the Schotty simply provides a small DC voltage by half wave rectifying the 27mhz AC RF when present...presumably provide by a tune circuit or amplifier ..involving that Choke you mentioned Llew..
So we can ignore this ..remove the diode ..and simply apply our own 1.36v ...generated with a potential divider from the 13/18v line..
This all makes sense and is why the Hughes functions in VERTICAL mode when no 27mhz is present ..
ie zero volts on pins 3 and 6 of the comparator..
Time to give my old eyes a rest ..but were halfway home and hosed I think Llew ..
;)

 

[Vipersan]

Ok ..so a very rough addition ..
pins 3 and 6 isolated from the rectified 27mhz signal..
15k up to lnb input ..and 1.2k to ground ..the mid point to pins 3 & 6 of the comparator ..has pins 1 and 7 toggling between 0v and 4.8v ..on alternate H and V looped scans from the TBS card.
NOW my eyes hurt ..
lol
Tomorrow I'll fit the divider properly with some ferrite beads added..
In fact I might increase the resistors by a factor of 10 ..150k/12k ...so as not to load/damp the output signal too much.
rgds
VS

 

[Llew]

OK, my comparator circuitry is the same as yours VS. Thanks for investigating the voltage conditions - despite your tired peepers. I have a few years on you mate, and my eyes are objecting strongly today even looking at a soldering iron...

I'll do some similar experiments with resistive dividers tomorrow, so we can compare results.

Regarding my Hughes version, yes it has a neoprene seal, so easy to open. Version number? The only numbering I have is above the bar code - RNLNB0014617.

 

[Vipersan]

Go get 'em Llew ..
Here is the first near perfik scan ...
No gremlins ...
As you can see I have little patience and couldn't wait till tomorrow ..
The divider mounted directly onto the GND pin and the INPUT pin of the large 5v regulator ..
one ferrite bead at the junction ..and then coupled direcrtly to the isolated pins 3 and 6
We done it buddy ,,,

;)

Just hope it don't rain tonight ...as I still have to re-seal the Hughes

 

[Vipersan]

You will notice the Vertical scan is active which means the bottom port which is still blanked off is as we figured the Horizontal port..
rgds
VS

 

[Vipersan]

..and finally ...a scan with both ports open..
;)

 

[Llew]

Wahaay...

Well done VS, beat me to it! I'll see tomorrow how mine pans out with your mod.

Hughes a clever boy then

 

[Vipersan]

Wahaay...

Well done VS, beat me to it! I'll see tomorrow how mine pans out with your mod.

Hughes a clever boy then

I think we both deserve a pat on the back mate..
It was after all ...a joint effort from the beginning..
....but I am having a job reeling in my cheesy grin..

 

[Vipersan]

,,,and all this just to get a closer look at Sicral 1B ...
Still not enough for lock but positivly ID'd I think ..
It being the only linear signal I can get..ln Ka band C
20534 V

I'm amazed I get this much..
Well out of footprint it being centered on Italy

 

[Llew]

OK VS, done the Hughes mod. Needed to increase the top PD resistor to 22K from 15K to drop the comparator voltage input to below the ref. voltage.
Scanning H and V fine, bit raggedy carriers, put the LNB on the longest cable run I have for the test. Also, I don't think the dish is spot on at present.

And no gremlins

 

[Vipersan]

OK VS, done the Hughes mod. Needed to increase the top PD resistor to 22K from 15K to drop the comparator voltage input to below the ref. voltage.
Scanning H and V fine, bit raggedy carriers, put the LNB on the longest cable run I have for the test. Also, I don't think the dish is spot on at present.

And no gremlins

Nice one Llew ..
obviously a slight variation on your Hughes comparator internal voltages (ref voltage )..but job done ..
Nice ..
Looking at your scan I'm assuming you have the polariser set for either RHCP or LHCP ..not linear ..
I'm assuming this cos of the variation in peak heights at 9E on the 2 scans ..?
nonetheless...we should be real proud of ourselves.

Gremlins banished..
Case dismissed

rgds
VS

 

[Llew]

Do you mean turning the polariser to the new slot we made? No, it's on one of the original slots, so the polariser either RHCP or LHCP. Can't remember which one. Should it be in Linear mode?

 

[Vipersan]

Do you mean turning the polariser to the new slot we made? No, it's on one of the original slots, so the polariser either RHCP or LHCP. Can't remember which one. Should it be in Linear mode?

No mate ...we have choices now ..with the the extra slot...
I left mine in linear mode to test for H or V (sicral 1B )...but at 9E circular is required ..
I just assumed circular cos of the peaks on your 9E scan ..second series of 4 being the opposite of the first 4 height wise.
;)

 

[Llew]

Oh, right. Don't think I'll find the feed on Sicral 1B with my dishes, but it won't be for the want of trying.

Anyway, as you say, we can pat ourselves on the back now, considering we were working blind from the start

 

[Vipersan]

Now that we have both LNB ports functional it just remains to tidy up the polariser details ..
For this I shall be using Hylas 1 at 33.5W ...
because many of the signal SRs are known are is their polarities. (R or L circular)
Having both borts active and switchable means we now can see both RHCP and LHCP on successive scans ..as V and H successively....
providing the polariser is set correctly ..which is what I shall now do ..
The lower frequency peaks are predominantly RHCP ...and the higher frequency peaks LHCP ..according to Flysat ..so this is what I'm using as reference.

Scan and Photo with Polariser set incorrectly ..
Correctly set to follow
rgds
VS