Low threshold receivers

[linuxman]

I have a question about low threshold receivers.

I currently own:

1 - Coolsat 5000
1 - Traxis 3500
2 - Pansat 3500

The Pansats will display with no pixelation channels even with high FEC numbers at around 30% SQ. On lower FEC like White Springs, they will display at 10% SQ.

The Coolsat has a threshold at around 65% SQ no matter what the FEC is.

The Traxis threshold is around 45% SQ, but it will vary with the FEC numbers.

I haven't ever been in love with the Coolsat for some reason which I can't figure out. Nothing wrong with it, does a good job, and has a pretty fast blind scan. I should have bought one of them first, but I didn't. I got a Pansat first and that may be part of the reason why.

What are some other brands, makes, models of FTA receivers that we don't hear about much, that have blind scan, handle motors well, handle multiple diseqc/22k switches well, have ac3 passthru, you get my drift.

I read the post about getting White Springs with 0% SQ by WEC4104 and he was using a Viewsat Ultra I believe.

I saw some of them being flushed on Ebay this morning. Brand new etc for ridiculously low prices.

The the VS ultra have the things I mentioned above?

If you have some answers or comments, please let me know.

Fred

 

[Anole]

beating around the bush

So, are you insisting the Pansat will recover the weaker (or noisier) signal?
If so , you weren't very clear.

The question I would ask, is this...
"for a given (weak) signal, how do the various receivers report it, and how do they display it?"
That is to say, regardless of SQ reported, do all the receivers get a given (weak/noisy) signal?


This discussion is going to get way too technical to stay in this part of the forum.

 

[linuxman]

Hey Anole,

Well, I don't exactly what I am asking for sure.

You might have phrased it best yourself.

I am in a quandary with the Unimesh dish that I just set up. I tried to use the Traxis at first for tuning in the dish, but found that it was detracting from my usual method of tuning in the weakest signals which the Traxis wouldn't even scan in the transponders.

I switched to the Pansat, and it did like it always does and scans in and displays the lowest signals on the meter which allowed me to ultimately finish that dish.

I then hooked the Traxis up, and compared a few numbers and was perplexed by some of the numbers being higher than the Pansat numbers and some being lower. I couldn't figure that out, and still can't.

For instance my weakest TP on G11 is the National Labs test card. 12060 V. On the Pansat I had a 45% SQ, and it displayed fine. On the Traxis, it shows at 45 - 50% right now, and as long as it doesn't drop below 45% the picture displays properly. Below that, and the picture becomes unwatchable.

So what makes one receiver able to display properly and some not on the lower signals?

So I am thinking about a change. I might even change out the co-rotor in favor of a voltage controlled LNBF. I would love to just buy another Pansat, but too many Pansats in the same room leads to remote controls problems etc.

If it gets technical, the mods can move it. Fine with me.

Fred

 

[Anole]

What makes the receivers impossible to compare, is that for any given signal, two receivers will give different SQ numbers.
Now, beyond that, just what SQ each will put up a good picture for, is different, too.

Let's say you have a very weak signal, or one that's hard to decode due to ... well, we don't know why - it's just weak.
Receiver A shows sq=10, and you are right on the threshold of picture/breakup.
Receiver B shows sq=60, and it is also on the threshold.
Is receiver B the better one, just because it shows a higher number?
No, both are the same, if both die on a slightly weaker signal.

And, due to the differences in FEC or adjacent-bird spillover , and in the absence of good test equipment, I think you are limited to using only one signal at a time when comparing two receivers.

That would mean you cannot make a chart of various birds using a single receiver, and get a clear view of how it performs.
Reason being, those signals will vary greatly in their FEC and other intangible qualities.

Now turning to signals everyone can get...
I received Whitesprings great on what I like to refer to a popsicle stick and a foil gum wrapper (on my cheapie Satpros 500).
Yet other folks across the country have trouble with much bigger dishes.
And presumably better receivers.
Well, maybe I live in a hot spot for that bird... that was my first thought.
But perhaps you have a good point that some receivers just do a better job with a crummy signal.

 

[linuxman]

But perhaps you have a good point that some receivers just do a better job with a crummy signal.

Different processors of course all perform their functions a little differently than others.

I have read where the processor for the Traxis was chosen specifically because it was very fast on blind scanning. The same processor might be great at one thing, and not so great at another.

I don't know about the Coolsat and the Pansat whether they have the same processor or not, but there is also circuitry involved, then the firmware/software engineers write the code that makes it all work.

This much I do know having worked on computers and networks for over 15 years is that poorly written code can slow down a processor until is crawls.

So there might be as you say a lot of variables as to why.

My question at the moment is which works better with a "crummy signal"?

 

[Anole]

I wonder if any of our member have a proper RF lab and could do some tests of various receivers?

Manufacturers publish noise figure specs on LNBs, to entice you to buy one model over another.
Sometimes they print the truth, only to ignore other contributing factors.
Phase-noise and stability can play a serious factor, too.
Receivers have stability, noise bandwidth, and other undocumented ratings.

Lacking good test equipment, one could rig up a test with an attenuator, I suppose.
You could lower the signal level, keeping the noise constant (well, reasonably so)
Is it even worth describing that idea?

 

[linuxman]

Lacking good test equipment, one could rig up a test with an attenuator, I suppose.
You could lower the signal level, keeping the noise constant (well, reasonably so)
Is it even worth describing that idea?

Sounds like a good experiment.

I wonder if any of our member have a proper RF lab and could do some tests of various receivers?

Another good idea if someone has the equipment.

Unfortunately we will probably just have to rely on the experience of members here and their equipment.

 

[updatelee]

how I compare irds is with my motor, I switch to v1.2 mode and move the dish off target one step at a time.

Ive got a multiswitch so one ird controls the motor and all irds have exactly the same signal coming into them, this is the only way you can get an accurate comparison imo.

my genpix skywalker-1 is the first to loose lock
satlook NIT spectrum analyzer is next to loose lock
dreambox 500 and 7000 loose it next
fortec mercury II holds on the longest

 

[linuxman]

Ive got a multiswitch so one ird controls the motor and all irds have exactly the same signal coming into them, this is the only way you can get an accurate comparison imo.

That certainly would give a decent comparison without all the expensive equipment.

my genpix skywalker-1 is the first to loose lock
satlook NIT spectrum analyzer is next to loose lock
dreambox 500 and 7000 loose it next
fortec mercury II holds on the longest

Now we are getting some actual experiential results.

So what is the threshold on the Fortec meter?

 

[Anole]

good input

That's a pretty valid test, as it gives all receivers the same signal and noise for a single test session.

Another member recently reported some sort of reception problem which he cured with a better LNB.
I think it may have been in the C-band section of the forum...
It would certainly be valid to retest all receivers with the same methodology, using different LNBs.

Doesn't the Genpix use a DBS front end?
It's intended for hot clear signals, and doesn't need to operate down in the noise.

I'm encouraged by the Mercury II results.

Will have to rethink my attenuator idea, and draw up a picture or schematic of a possible test fixture...
...but first, some lunch. - :up

 

[kymics]

Perhaps a little off topic, but I thought I'd post that my Pansat 3500 is pulling in the first set of Equity channels on G10R at 15% with spikes up to 20% and for the most part there is no breakup in sound or picture. Yet on other channels, the meter goes all the way up into the 80s and almost 100% on circular. That's quite the range, but I never really considered it to be related to the sensitivity of the IRD. I just assumed it's Pansats way of converting the signal strength into something arbitrary like a percentage.

Heard reports of other receivers having different standards for measuring the signal.

 

[linuxman]

Pansat 3500 is pulling in the first set of Equity channels at 15% with spikes up to 20% and for the most part there is no breakup in sound or picture.

That is what I would like to find out.

Are there other receivers makes and models that work similarly to the Pansat with a low threshold for viewing weak signals, yet with realistic numbers for the meter with numbers of what the signals really are?

 

[updatelee]

its hard to equate things into hard values, because numbers vary from system to sytem.

db vary from ird to ird, and uV vary from lnb to lnb.

using 123.0w 11800/V/26660 3/4fec as my first test, remember fec is a HUGE factor.

at 45uV the genpix, satlook, and mercury II all aquire a lock.
at 43uV the genpix and satlook will hold a lock, but will not aquire a lock
at 42uV the the satlook looses lock, the mercury is getting the odd pixelation, genpix is clear as a wistle.
at 41uV the mercury is still holding a lock, but pixelating pretty good, the genpix just lost it
at 40uV the mercury II looses its lock

the genpix is really good at holding a lock, it just seems to want a little higher signal to aquire the lock.

Is there a specific freq you'd like me to test ? different symbol rates will efect things differently, but FEC is a big one obv. a 7/8 fec will act much different then a 2/3

 

[linuxman]

Is there a specific freq you'd like me to test ?

Not necessarily a specific frequency. I am just looking for some others to answer with their experiences with their receivers and how the receivers handle low quality signal numbers.

The specific frequency that I am experiencing problems with is on G11 12060 V 26700. That is the National Labs test card and it is in the center of my arc.

That freq comes in at 45% SQ on the Pansat meter, the Pansat will find it at 10% and lock it at around 30% with no pixelation.

I had to manually enter the transponder into the Traxis, and it wouldn't even see it until it got up to around 20%. It is about 50% on the Traxis meter right now, but with gusting wind, it will drop to below 45%, and become unwatchable. On the Pansat, it never pixelates until below 30% which it doesn't ever get that low even on the Traxis meter.

So that is what I want to see. If there are other receivers which will act like the Pansat.

Pick up the signal at a very low rate, lock it at the low rate, and display it at the low rate.

 

[updatelee]

12060/V/26700 3/4fec

48uV satlook, genpix, and mercury II all aquire lock, and look good
47uV satlook will not aquire lock and looses exsisting lock, genpix and mercury II both aquire, and hold, but both are pixelated baddly
46uV none will hold a lock

so different irds handle different signal fine, here the genpix and the mercury II are on par, no difference. on other signals the mercury II has a slight advantage on aquiring a lock and holding onto the lock.

satlook looses lock at 47uV, signal must be 48uV to aquire lock.
genpix gets pretty bad pixelated at 47uV but maintains lock, picture is beutifull at 48uv, will aquire at 47uV

at 48uV my satlook sais the db is 4.4db and genpix sais the db is 8.6db, so its hard to compare numbers.

at 50.2uV (the highest I get for this tp) my satlook sais about 8.0db and genpix sais 13.0db. the fortec (which doesnt give me a db) sais 80% signal and 65% quality.

there doesnt seem to be any standard between ird's for the signal strength/quality, its just an arbitrary number the manufacturers deem is good. for example if I tune 119.0w I can accually get tsreader to tell me Ive got 105% signal strength, lol.

 

[Anole]

Whitesprings may (or may not) be worth watching, but it's an interesting test case.
The low symbol rate of 2920 might be a factor... or not...
The FEC is listed at a very generous 1/2 !
Now, that most likely is a factor!
So, I propose WS as one test case. Here's their NA signal power distribution map.
Now we need something with a higher Symbol Rate, and not-too-high an FEC (maybe 3/4?), for comparison.
If warranted, we might also add something with a really crappy FEC like 7/8.


Just got off the phone with my retired TV station engineer.
Wanted to get his input on my attenuator idea.

First, he was shocked to death that anything downstream of the LNB had any affect on reception!
But then, he's used to working with bigger dishes, even for Ku, and much better link-budgets.

The receivers we have are built for sale around the world.
In Europe, the satellite signal is often intended for consumer reception, and that's why there are a lot of 15..20" multi-LNB dishes over there.
Here in North America, we FTAers are not generally the intended viewers, so 36" dishes are the norm.
Even so, we encounter a much wider range of signal level, including weaker (noisier) ones.
A receiver that may work fine in Europe, may not be your best choice for Canada, USA, or Central America.

Well, anyway, back to how to test.

Scottie suggested a thumbscrew to adjust elevation would be best.
That way, you aren't moving your motorized dish toward something else that is an interfering signal.

Second choice would be to use a motorized dish and do as udLee suggested.
Everyone can do that, so it's probably a good choice.

My attenuator idea would require making or finding a surplus attenuator, and would still only result in relative data.
So, being harder to implement, it might be the least desirable.

Well, that's what I got for now.
Will be looking forward to other comments in this very interesting thread!

 

[linuxman]

there doesnt seem to be any standard between ird's for the signal strength/quality, its just an arbitrary number the manufacturers deem is good.

Well I guess it all boils down to personal likes and dislikes.

I like the way the Pansat does it. It finds it even if it is weak, and brings in the transponder even if it doesn't lock a channel, the tp still gets put into the menu allowing for tuning to bring the signal up. After tuning, a re-scan, and the channel comes in if there is one available FTA. The channel will display at a very low SQ, and the meter gives (at least to me) a realistic feel for whether the tp is strong or weak.

I like having the whole range of the meter from 10 - 99 with the threshold being at 10. Why have a meter if you get no indication of anything until 45 or 65 and a range of only that much for comparison or tuning?

I guess you could buy a satellite meter for finding weak tps and tune from that, just seems an extra expense of money and time unless you go pro.

 

[linuxman]

Scottie suggested a thumbscrew to adjust elevation would be best.
That way, you aren't moving your motorized dish toward something else that is an interfering signal.

That is exactly my point.

The elevation bolt is a large thumb screw and it is used to tune the signal to make it better. If the receiver won't even "see" the signal and bring in the tp, what good is it?

 

[Anole]

If the receiver won't even "see" the signal and bring in the tp, what good is it?

I realize you have a bone to pick (and rightly so) with receivers that won't show you anything until a signal is decent.
The idea of adjusting the elevation screw , was not to get/find that signal, but just to help determine which receiver was preferable to use for your "aiming receiver".

 

[linuxman]

The idea of adjusting the elevation screw , was not to get/find that signal, but just to help determine which receiver was preferable to use for your "aiming receiver".

I guess that is the proper way to put it.

I don't really have a bone to pick, but part of the reason I picked up the Traxis used from a fellow member because of it's reputation for fast blind scans and accurate meter. I was going to make it my main receiver for aiming and tuning dishes. I can't do that now.

After using it for a while, the blind scan is fast, but the dish must already be fine-tuned before using it, and even then it will miss the weaker signals. I would assume the same would be true for the Coolsat. I have never tried using it to aim or tune a dish. The motorized primestar it runs was tuned in and peaked with the Pansat.