Disqus - Latest Comments for HighdefJeff

Re: Satellite TVRO Part 5

Highdefjeff — Mon, 19 Oct 2009 15:40:50 -0000

Thank you for this series. Your articles are insightful and informative. I appreciate your writing these.

I would like to add a little regarding the offset dishes commonly installed at the home for receiving satellite services, if I may.

Site Survey

When considering look angles involved with the offset, or reflector satellite dish, it is important to understand what the dish "sees". With the reflector dish, objects that would cause obstruction are higher than one might first think. The satellite signals have a bounce angle from the reflector to the LNB. While the average individual usually trims the branches that look to be straight forward of the dish, these branches are not the cause of the obstruction. The offending branches are higher than what it would appear. This is difficult to explain in words so I have included a link to pictures that will show this offset angle more clearly.

http://www.wowvision.tv/wha...

Feed horn, polarity and LNB

Reflector dishes typically have no polarity adjustment at the LNB. Transponder and polarity of a satellite is selected by the voltages that are sent to the LNB from the receiver or signal meter.

To select and view even transponders, send 18 volts to the LNB and the signal received will be from even transponders.

To select odd transponders, use 13 volts and when using a satellite that has circular polarity, a 22khz tone is generated to accompany the voltages sent.

With the heightened sensitivity of these dishes, and the increasing demands of today's feature rich, bit hungry HD receivers, only a slight alignment error can produce many heartaches. It is more important than ever to achieve the true peak of these dishes for hassle free operation and awesome picture quality.

Thanks again!

Re: Satellite TVRO Part 3

Highdefjeff — Sun, 20 Sep 2009 15:29:22 -0000

Awesome articles! I am enjoying them very much. I would like to add a little, though.

When you say, "There are very few analog signals to look for, which means you need specialized equipment to monitor the satellite signals and to identify them." I would expound regarding direct-to-home dishes.

If by specialized you mean digital, then specialized meters are not needed for the small direct-to-home satellite dishes. Analog meters work quite well. If by specialized you mean dual meters, then I quite agree.

The problem with alignment comes from the addition of multiple satellites that are being received by a single dish. As you get to three and four satellites, this is where the difficulty lies.

Most dish antennas we work with now, have receive 2 or more satellite signals. One dish = 2,3,4, or more satellite signals.

Every time you adjust the dish antenna to increase a signal from one satellite, YOU ARE CHANGING SIGNAL RECEPTION for ALL the remaining satellites that the dish is supposed to receive!

Each time you adjust the dish for the satellite that you are "watching", you are simultaneously VARYING the signal for THREE more that you are NOT "watching"!

Every time you make an adjustment for one satellite, you should then go back and check all the remaining satellites to make sure you didn't lower their signal. It is a "blind" adjustment with regards to the remaining satellites. With so many variables to check, doesn't it make sense to move to "even the odds"?

The solution here is to better the odds by the use of Simultaneous Multi-Signal Metering. Using a dual meter and simultaneously viewing two (of the 3 or 4) satellites provides much more information and greater accuracy.

While a dual digital meter is some help, in my experience, the best tool for this is the dual analog meter. With a digital dual meter you can view two satellites at a time, but not simultaneously. Digital meters require you to wait while the signal is processed, and you must switch between the two. Some require you to still interpolate the peak, as they will show 100% throughout a small movement of the dish in either direction.

With a dual analog meter you get INSTANTANEOUS results on two meters (and tone), that is very easy to understand. The analog meters don't "top out" requiring any interpolation. Peak is when the needle is at its highest point on the scale.

Further, measurements using digital meters don't give the "big picture", but a very specific (tiny bit of the whole) reading - even down to a single transponder. You may have that single transponder pegged, but there are many more transponders on that satellite, let alone the other satellites.

I think of it as a railroad. The cars are the digital packets in the bit stream, and the track is the analog carrier wave. We can zero in on the train cars and check the payload (digital), or we can make sure that the tracks are solid (analog). Surely if the tracks are corrupted or weak, they won't deliver the cars without some derailment.

Lastly, offset dishes used for direct-to-home use have an elevation scale printed on the dish that compensates for the 21.5 degree offset so that when you want 40 degrees, you set it by the scale on the polar plate.

Thanks again and keep up the good worK!

Re: Satellite TVRO Part 1

Highdefjeff — Thu, 20 Aug 2009 13:18:22 -0000

Excellent article! Keep up the good work!