Ka B/C overlap (Hughes) Thread

[Llew]

The 19E scans with the 27MHz setup in line. Two without the H/V ports switched (Horizontal port active) - 27MHz switch off. Other two with switch on (Vertical port active).

So I presume these are circular feeds? - both show before and after switching.

Having the switch assembly inserted between the LNB and receiver (pci card -> Crazyscan) seems to increase the noise floor when the 27MHz signal is switched on. I think maybe it's too strong a signal and the receiver (my pc card) can't filter it out sufficiently. No doubt the receiver that's normally used with the Hughes setup has efficient filtering. Will need to look into adding a HPF between the switch and card.

 

[Vipersan]

The 19E scans with the 27MHz setup in line. Two without the H/V ports switched (Horizontal port active) - 27MHz switch off. Other two with switch on (Vertical port active).

So I presume these are circular feeds? - both show before and after switching.

Having the switch assembly inserted between the LNB and receiver (pci card -> Crazyscan) degrades the signals unfortunately, need looking into.

Nicely done Llew..
I too suspected circular ..but couldn't confirm.
rgds
VS

 

[Vipersan]

Continuing my trip across the arc I've now reached Hylas 1 at 33.5W ..which I am fairly familiar with shown in the pic with multi humps ...but on my way there I found another hump I have not seen before at approx. 30W ie Hispasat territory..
freq 19720 sr 34000 fec 1/2 (private data) and a lowish but lockable signal around 2.5db..
Obviously commercial and not in the higher military band so what could it be and where is it originating from ?
I didn't think Hispasat carried any Ka transponders ..but maybe one of them does ?
rgds
VS

 

[hvdh]

I am happy you checked 30.0º West already!
Because according to sites like Gunter's or Weebau, XTAR-LANT (ex Spainsat) has one Ka-band transponder, in addition to the many X-band transponders. There is no mention of this on XTAR's site: http://xtar.com/xtar-lant/
So, that's another question mark I can get rid of!

 

[Vipersan]

Happy to have been useful buddy.....but sadly my arc trip has now completed ..so other than inclined birds there wont be much else to examine ...and even in winter after the leaves fall ..only another 15 or 20 degrees to the East.
Thanks for your help hvdh ..and if you have any inclined positions you wish me to check ..by all means list them in this thread.
Maybe I'll do it all again once I get the Hughes switching polarity
;)
rgds
VS

Final question ..you mentioned X band ..
from what frequency to what does X band cover?
I have seen lnbs for X band and they look very very pricey ..
no plans to buy one but ..ya never know ..
maybe I'll win the lottery ..
lol

 

[hvdh]

Sure there are still quite a few satellites you haven't tried, with 19.7...20.2...21.2 GHz downlink, also non-inclined.
For example the new Turksat 4A (19.7...20.2 GHz).

The trouble with the many inclined milsats is, the use of Ka-band 20.2...21.2 GHz is never clearly specified, all it says is SHF or EHF. When you want and have your setup in best shape, we should try these nevertheless!

X-band is 7250...7750 MHz. That is also specified on my web page (at the bottom).
Probably watching it, it causes information overload, and one sees nothing in the end.

 

[Vipersan]

Sure there are still quite a few satellites you haven't tried, with 19.7...20.2...21.2 GHz downlink, also non-inclined.
For example the new Turksat 4A (19.7...20.2 GHz).

The trouble with the many inclined milsats is, the use of Ka-band 20.2...21.2 GHz is never clearly specified, all it says is SHF or EHF. When you want and have your setup in best shape, we should try these nevertheless!

X-band is 7250...7750 MHz. That is also specified on my web page (at the bottom).
Probably watching it, it causes information overload, and one sees nothing in the end.

In actual fact I have already had a test transponder from Turksat 4A shortly after she moved to 42 East.
If I remember correctly 18600 ....
but nothing as yet from the higher Ka band transponder of which I believe she carries 1 in band A and 1 in band B..
I do periodically check this ..but all quiet as yet ..and 18600 also now quiet.
rgds
VS

Just found the capture so will attach it here though strictly not relevant to this thread.

 

[Vipersan]

Well Llew ..
I managed to get my hands on a HG2150CA osc device ..
But wanted to experiment with adapting the conventions of HV switching ..
To this end I sacrificed an old black inverto premium to have a look inside ..
Photos of this will follow at some point..
Once inside I reverse engineered some of the circuitry..
It uses a 16 oin quad pack device to switch between the 2 H V probes by providing bias voltages G1 D1 and G2 D2 for the 2 fets attached to those probes ..
The chip ZXNB4200 interprets the incoming 13/18v coming up the IF cable and switches the appropriate fets and probes..
It also decodes/detects 22khz on the IF line ..but we don't need this.
So ..using the V chip bias output at D1 (1.9v) I borrowed this to drive a BC184L NPN transistor (base bias through a 1K resistor) and thus ground the OE (output Enable) pin of the 27mhz osc package ..and the 5volt supply to the osc is derived from the control chip also..
At the moment I have it detecting if 13v or18v is present ..ie V or H and turning the osc off if it is 18v (H)
I've not tried re-injecting the 27mhz signal back into the IF line as yet ..but it does work ..
Ignore that the osc device says 35 MHz ....mine is a 27mhz version.
Diagram attached ..and done enough tonight ..
My eyes are tired..
More playtime tomorrow ..
rgds
VS

 

[Llew]

Yes, that's an elegant way of controlling the switching VS. Good design. The first version I made used an old MTI KU LNB, no fancy FET controller IC in that. Just used one of the comparator outputs in the quad IC (BA10339) to switch on/off the 27MHz oscillator depending on whether the comparator input was 13 or 18V. Next version used potential dividers into an op-amp to switch the oscillator. But ...
The problem with connecting the 13/18V output from the IF line to our circuits is that, being a straight DC connection, the 27MHz switching has also to be inserted to the line - with a simple on/off switching circuit and a splitter with power isolation for the 27MHz I'm using, there's no IF feed connection to the switch. With receiver controlled 13/18V circuits there's no isolation between the 14/18V feed and the circuit, and the attendant problems with lack of filtering.

 

[Vipersan]

Cheers Llew ..
Here are a couple of photos ..
Still in the lash up stage atm..
I'll try and tidy up a bit before I continue..
Single strand wires with no insulation are a nightmare ..
lol
rgds
VS

 

[Llew]

Cheers Llew ..
Here are a couple of photos ..
Still in the lash up stage atm..
I'll try and tidy up a bit before I continue..
Single strand wires with no insulation are a nightmare ..
lol
rgds
VS

Very good VS. By design, the 13/18V feed into the Inverto LNB circuitry will be sufficiently filtered, as was my MTI LNB, but I reckon that maybe radiation from the oscillator was getting into the feed line and causing problems for me. Maybe a screening can over the oscillator would have helped.

If you haven't already, don't forget to place a 100nF capacitor as close as possible between the oscillator's Vcc and ground.

 

[Vipersan]

A bit tidier now ..
Hopefully if I sort this out ..the components will be replaced with surface mount parts.
Not so easy for my old eyes tho'
;)

Certainly the inverto board is small enough to be mounted once complete inside a small die cast box ..with an F connector either end ..
Thus the signal will pass straight through and the voltage switch action will turn the 27mhz osc on or off ..
It drawing its power from the IF line.
I will de-populate the inverto board of anything not neccessary ..to reduce current consuption..
No point in having a DRO in there as well..
lol

 

[Vipersan]

Time for a break and some lunch..
The osc fets, probes and pucks have now been removed ..
No change to the 27mhz function ..as expected..
rgds
VS

 

[Vipersan]

So ..
at this point not going as well as I'd like ..
I can still see the large hump from 38E though there is considerable ringing on the trace ..
I am still generating 27mhz OK ..but this is currently only cap coupled back into the IF ..so may well be insufficient amplitude to switch the Hughes ..but gave it a go anyway ..
Covered the active H port with ally take and rescanned 38E ..
I heard the 27mhz switch kick in as I'm monitoring the frequency with my scanner ..but the scan didn't produce the large hump ?
conclusion ..the Hughes isn't responding/switching from H to V ..
So ..some info Llew..
How exactly do you have your switch coupled ? proximity to the lnb ..distance down the cable etc etc..
It may well be my signal is too weak over a 20mtre plus cable..
After all I'm using the 27mhz osc chip unbuffered ..and driven directly into the IF cable through an 18pf capacitor..
rgds
VS

 

[Vipersan]

..Answered my own question ..
Took the switch outside and linked it into the IF line with about 3 mtres of cable ....
Result a scan that's far from perfect ...
Much 'ringing' ..but functional ..
The red scan is a vertical switched scan 13V..
Still work to do ..but getting there I 'spose..
rgds
VS

 

[Vipersan]

Next stage is to deal with the 'ringing'..
First I need to isolate the cause..
Could respond to more decoupling on the inverto board ..but MAY be harmonics from the osc device radiating up into the IF range of the TBS card/receiver..
Some sort of filter needed to remove the harmonics allowing only 27mhz through if this proves to be the case.
My brain hurts..
Time for a break and a cuppa..
;)

 

[Vipersan]

Something like this may do the job ...but where to get one ?
C'mon you CBer types ..a little help here ..
lol
http://www.amtsaw.com/brochure/saw/A02502.pdf

 

[hvdh]

I'm not sure what you're complaining about VS.
When you say "ringing", do you mean the wavy Crazyscan pattern?
Because that is not ringing. What I see is standing waves, caused by a badly terminated 75 ohm transmission line.
Probably the way you insert the 27 MHz signal into the IF line.

 

[Vipersan]

I'm not sure what you're complaining about VS.
When you say "ringing", do you mean the wavy Crazyscan pattern?
Because that is not ringing. What I see is standing waves, caused by a badly terminated 75 ohm transmission line.
Probably the way you insert the 27 MHz signal into the IF line.

Sounds plausible buddy ..
I guess some eperimentation in termination neccessary then ..
Any suggestions other than simply dumping a 75ohm resistor accross the IF line ..
Not sure that would be the best idea ..on account it is carrying both signal and 13/18v ..plus it may well damp the 27mhz making it unuseable..
Happy to take any suggestions you might have..

Also a bit surprised that the inverto pcb taken from a pukka lnb isn't terminating the IF line by default.
rgds
VS

 

[hvdh]

Normally a simple diplexer should do, with a few coils and capacitors.
A bit like we once had to combine VHF and UHF antenna signals.
But you want DC pass as well, on the high freq. port.

My radio amateur skills haven't been maintained for about 20 years.
So I hope a more active radio amateur shows up soon!