Channel Master 120 for 28.2E in rural southern Sweden

[archive10]

Summer cottage installation. Was thinking of a CM180 installation, but after 2E and 2F, a CM120 was the obvious choice.

Dish is second-hand (proably fourth hand) CM120, with Inverto Black Ultra Quad LNB. Arms taken from another CM120 (as they were not too bent).

Main challenge was to find spot in garden that had a clear view of 28.2E. Lots of trees to the south made the task difficult. So first mount was to check if any reception at all...

So, first exploratory spring installation: Mount is Channel Master roof/wall mount, screwed to the wall of wooden Cabin. Don't think it would survive a November storm. But for PoC it was just the thing needed. Sky news and other were received, but no 2E/2F transponders. Cause not clear, but trees suspected. Not sure if 28.2E was above the tree-line here...

Decided to explore where to place the dish next; this needs more equipment etc.

(continued)

 

[archive10]

Then a survey of the garden using the TD64 showed that good reception was tricky - too many trees on the southern side of the plot (and in the neighbour's field) . Luckily, an october storm last year took our a large patch of trees on the east side of the house, and the forestry people took out everything else. This left the odd tree or two, between which 28.2E can bee seen . Good, secluded spot (but with a substantial cable run ), not too much visibility - time to pour the concrete...

First dug a hole to about 85-90 cm depth, then hit (bed)rock. In went a 75mm pipe with a rebar made from a threaded bar with two nuts to keep it in place. Drilled hole easily in pipe. Mounted the thing in the hole using toolmate bench (but any make will do) to keep it upright, and regular checking with spirit levels to keep it that way. My first poured concrete pipe - I am fairly pleased with the result (although constant checking with spirit levels was required!).

Next visit - time to mount the dish.

(continued)

 

[archive10]

So the concrete has now set for two months - should be stable by now. On went the dish, and alignment made with TBS USB tuner and laptop. Instant gratification! Sky news booming in, all seems well. Fine tune, and tighten the bolts.

Dish is situated 30m from house, so I laid some ersatz overground cables to see the thing work. Had to extend cables to reach in through window to FoxSat receiver. As can bee seen from pics, signal is coming in nice a strong,

Judging from how much the undergrowth has grown since July, I foresee that some bush-clearing action is soon required to keep reception clean. Also, in 20 years the forest may block everything again. Luckily, I have my trusty Husqvarna chain-saw...

I Also need to dig down the cabling to the dish - but it'll be 30 metres of mostly pristine forest ground (with roots and all!), so we'll see what can be done.

 

[Lazarus]

I like the fact it hasn't been cleaned - Blends in better with the surroundings.

 

[archive10]

I like the fact it hasn't been cleaned - Blends in better with the surroundings.

But, my friend, it *has* been cleaned.
You are looking at the results of a 20 minutes of action with a scouring sponge and soapy water...
Should have seen it before it got cleaneed - blended even better with the surroundings!

 

[archive10]

And here's the proof in the pudding: Reception is pretty good!

 

[skomedal]

Well done st1
Similar procedure that I followed with the modified 2 piece alloy lnb holder on the gibby 125.
Aimed the dish for sky news on astra 2a then tightened all the fastenings enough to fine tweak the dish, loaded pick tv 11914h into my technomate 5402 then tweaked that tp until it peaked ( 90% ), then loaded bbc tp 10818v and tweaked to max ( 67% ).
Unfortunately the bbc signal drops out ~2000 cet but is there again next morning.
Hope the 1 piece holder rectifies this when it arrives.

Regards

 

[RimaNTSS]

2st1:
In one month look for Sun Outage if you are lucky enough to get some sun one of those days.
And, just a friendly reminder for everybody to check where LNB has it's aiming point on the surface of antenna. Sometimes, even factory made antennas with factory made feedarms do not have properly pointed LNBs.

 

[archive10]

2st1:
In one month look for Sun Outage if you are lucky enough to get some sun one of those days.

Not sure I'll be in the summer cottage then. (It is after all not summer anymore?!?)

And, just a friendly reminder for everybody to check where LNB has it's aiming point on the surface of antenna. Sometimes, even factory made antennas with factory made feedarms do not have properly pointed LNBs.

I am happy to say that the LNB does indeed point to the very center of the CM120. Nothing bent here.

Some time ago, I had one particular Telesystem P57, IIRC, which was oval. But in contrast to similar looking Sky Minidishes, no special LNBs with oval feedhorns were required / supplied. In fact, when using the (non-adjustable) integrated plastic LNB arm+holder, the LNB was clearly pointing to somewhere two thirds up the reflector. Loosening the LNB, and pointing towards the center (downward tilt) gave another 1.5dB of signal strength, which is not insubtantial when you are looking at a dish with a gain of 34 dB!

After much head-scratching, I checked the Telesystems web-page, and shure enough, the P57 has a bigger brother with a *round* reflector (well, as in circle projected onto parabolic surface), using the same LNB arm+holder. On this dish, the LNB *did* point to the center of the reflector. To create the oval version, they simply designed a smaller reflector, but kept everything else...

 

[RimaNTSS]

I am happy to say that the LNB does indeed point to the very center of the CM120. Nothing bent here.

Aha, gotha I am sorry to say, but LNB should not point to the very center of offset antenna! With LNB pointed to the very center you will never get maximum possible signal levels.

 

[archive10]

And here's the proof in the pudding: Reception is pretty good!

But it is now even better!

Lately, I've been using a TBS-5922 connected to a PC as a sat-meter (at least a strength meter). I use the app that comes with it (fail to remember the name, but it's OEM and wants me to upgrade all the time).
But the readings are indicated as a perecentage, no indication of a percentage of what, or if there is a AGC or similar in operation. The readings when setting up this dish peaked at 96%, and 87% or somthing similar. You get the picture.

Not quite satisfied with this process, and wanting to get it spot-on, I borrowed the ProMax meter again, brought it to Sweden to optimize adjustment.
And shure enough, fine-tuning the alignment gave me an increase in power by about 1.2 dB, and that + skew adjustment gave me an increase in C/N (S/N) of just shy of 1.7 dB!

I now have better reception on 10773 (BBC) here in Sweden than I measured in Denmark in springtime using the exact same LNB on a CM120 (admittedly a different one, but this one is more battered than the one in DK!):

Eastern DK: avg 10.0 dB C/N
Sweden: avg 11.3 dB C/N

The swedish location is about 100 km further east then the DK one, but it is still a remarkable increase in C/N ratio.

Lessons confirmed/learned:
- Skew is super important for fringe
- Can't beat using a proper meter

 

[RimaNTSS]

Lessons confirmed/learned:
- Skew is super important for fringe
- Can't beat using a proper meter

Can not disagree about first one. Even more, skew is important all the times!
Second: do not see much difference between adjusting system with proper meter and same system adjustment with decent meter.
If antenna is not properly adjusted (elevation, azimuth, LNB in focus, LNB pointing, using of proper LNB and maybe some others) it does not really matter what kind of meter are you using- professional or very simple one.
In Brussels, I am getting 10773 on 120m dish quiet good. It is just FYI. %% taken from DM8k, and could be different from taken from another devices.

 

[skomedal]

In Brussels, I am getting 10773 on 120m dish quiet good.

Sorry for asking is Brussels designated as a fringe astra 2E reception area?

Regards

 

[RimaNTSS]

Not at all, that was just for information, as I've said FYI. Everything else I mentioned apples to all areas, including fringe. In fringe areas you should be very cautious about LNB placing and adjusting, that was my main message. If focus of antenna is "one big unknown place" than it does not really matter what kind of meter you are using to adjust LNB.

 

[skomedal]

Not at all, that was just for information, as I've said FYI. Everything else I mentioned apples to all areas, including fringe. In fringe areas you should be very cautious about LNB placing and adjusting, that was my main message. If focus of antenna is "one big unknown place" than it does not really matter what kind of meter you are using to adjust LNB.

Think you should make a sticky post with a detailed FYI for the correct procedure and instructions for setting up and fine tuning various lnbs to various dishes. With and without meters
Your knowledge will surly be very welcome to members and others on this forum:

Regards

 

[archive10]

Second: do not see much difference between adjusting system with proper meter and same system adjustment with decent meter.
If antenna is not properly adjusted (elevation, azimuth, LNB in focus, LNB pointing, using of proper LNB and maybe some others) it does not really matter what kind of meter are you using- professional or very simple one.
In Brussels, I am getting 10773 on 120m dish quiet good. It is just FYI. %% taken from DM8k, and could be different from taken from another devices. View attachment 67993

I meant comparing a meter (or a box that has absolute read-outs as your dm8K evidently has) with something that just states a percentage with AGC in full swing, and a "quality" measure that could mean anything...

The thing is, that fiddling with skew and aligment with a very coarse-grained means of measuring does not ensure optimal reception. If I can gain 1.5 dB in signal quality by using a good (not necessarily a ProMax level, but just a real meter, e.g. something costing EUR 200-250), then general reception and rain-fade resistance, and derived overall satisfaction can be improved using the existing reception equipment.

Probably, it also means that you should either beg, borrow or steal a meter for the final 10%, or get an installer to validate your installation (if you're not a driven enthusiast) to ensure optimal performance...

 

[RimaNTSS]

Your knowledge will surly be very welcome to members and others on this forum:

If this is not a joke, than you can create new thread, something like " How to find focus of offset antenna and place LNB properly". I will participate in discussions with pleasure.
To facilitate this I would like to make couple of statements:
- Not all users know where focus of their dish is located;
- Not all users, ever checked weather their LNB is located in focus of antenna and pointing to the right spot on surface of antenna;
- Not all users can say for sure they have got maximum out of their antenna;
- getting some signals, does not mean you are getting maximum possible.
- I doubt it is possible to tune simple system (as majority of us are using) better by using very professional meter and, as contrary, simple E2 receiver software.

Add: - Not all antennas with original feedarms hold LNB in focus and especially point LNB to "le G point"

 

[skomedal]

Does 8 hours of trial and error with various lnbs, and finally peaking "" fringe reception "" only to suffer evening signal lock a failure in you eyes?

"" It is also sounds like reception of Nordic beam from 4,8*E at my place. In the evenings signal level drops considerably up to no reception at all. ""

Regards

Sorry st1 for going off your topic

 

[RimaNTSS]

Completely out of topic: Sorry folks if I was rude in my previous postings. I am not so bad in real life, as it can seem in cyber space. Nothing personal. If some of you decide to make sticky post about LNB placement. I do not feel I know everything about this topic (nobody is perfect) but would certainly be happy to participate in discussions.
I also found out that any Sat-forum needs some agitation from time to time to not become just forum of transponder news. Perhaps this is the case.
However, my statements in post #17 are still valid.

 

[Captain Jack]

I'd also like to know how to find the focal point. I am guessing with the laser pen attached to the side of the LNB and rotate it to see if the laser draws a line around the very edges of the dish?