The number of wavelengths the focal point of a dish is from the surface means absolutely nothing. The only thing that matters is that at the focal point the distance all of the reflected waves are traveling before they reach the focal point is as close to exactly the same as possible such that all the signal arriving at the focal point will be in-phase with respect to each other. A parabolic dish is different in this regard than other antennas that have reflectors, such as yagis. For antennas like Yagis it matters because the driven element is receiving energy from both the incoming signal (and any director elements) in front of it and reflected energy from the reflector behind it at the same time. therefore it must be spaced a certain multiple of a wavelength to assure these signals are in phase and add together. With a parabolic dish this isn't necessary as all the energy arriving at the focal point is reflected. All that's necessary is that the reflector is as near a perfect parabola as possible.
Primestar 84E/BSC621-2 LNBF Experiment
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The number of wavelengths the focal point of a dish is from the surface means absolutely nothing. The only thing that matters is that at the focal point the distance all of the reflected waves are traveling before they reach the focal point is as close to exactly the same as possible such that all the signal arriving at the focal point will be in-phase with respect to each other. A parabolic dish is different in this regard than other antennas that have reflectors, such as yagis. For antennas like Yagis it matters because the driven element is receiving energy from both the incoming signal (and any director elements) in front of it and reflected energy from the reflector behind it at the same time. therefore it must be spaced a certain multiple of a wavelength to assure these signals are in phase and add together. With a parabolic dish this isn't necessary as all the energy arriving at the focal point is reflected. All that's necessary is that the reflector is as near a perfect parabola as possible.
Since the scalar ring is just a mount .... why not eliminate the scalar ring and mount the lnbf another way so the offset isn't so much compared to the lnb? I have to say the modifications you all made do look awesome though.
Wavelength,phase and focal point are all related that is why skew is so important.
Interesting "opinion" do you have anything to back it up with?
Yeah, it's called "Physics". Don't try to play "RF engineer" unless you understand it.
Skew has nothing to do with the distance to the focal point of a dish. Lots of people have different kinds of dishes and those different kind of dishes will have different focal points. Skew is totally unrelated to this. Skew is determined by your location on the earths surface and the satellite your aiming at and nothing else. For example I have a small primestar dish and I have an 8.5' birdview. Obviously the focal point of these 2 is very different but if they're both aimed at the same satellite and they're both in my backyard then the skew will be exactly the same.
I don't see how it would function beside being used for a mount and to make minor focal distance adjustments for signal strength. The rings actually have a function in the collection of the signal? If so how does the lnbf collect the signal if its caught in the rings? Look at C band multifeed adapters... there is no scalar ring only a tube to set focal distance for best performance to its application. So anyhow.. if that's true then wouldn't you expect a significant loss of performance by cutting a chunk out of the ring to make it fit next to a lnb? Don't get me wrong it looks pretty awesome modified like that I am just always full of questions.
Still works with chunk missing.
Can a short metal tube in front of the lnbf work better then using the scalar ring?
Can a short metal tube in front of the lnbf work better then using the scalar ring?
You make generalizations that you don't support with any documentation just opinion. Your examples just prove the point of inter-relationship between frequency, wavlength , focal distance, phase and skew.
Yes, I worked as an RF Engineer for 30 years.
I think you have found a topic and interesting project to explore for yourself. Please post your results.
DREAMFOX1-
Got my Panorama 13 Degree K LNBF yesterday from Ebay. Looking forward to testing it with the others.
Thanks for all the information you have posted, it's been a big help and target for others to achieve.
Findings and last post.
The Fabricated arm for the BSC-621-2 LNBF produced the highest SQ of 49%.
The P* arm and BSC-621-2 produced a SQ 8% lower.
The dish to lens was 22" for both arms.
The Fabricated arm for the BSC-621-2 LNBF produced the highest SQ of 49%.
The P* arm and BSC-621-2 produced a SQ 8% lower.
The dish to lens was 22" for both arms.
Attachments
Sunday Dinner At Anoles House
I understand that Anole invited Stogie over for Sunday Dinner.
It seems that they have both developed a taste for "EATING CROW".
http://www.satelliteguys.us/free-ai...-one-meter-primestar-mini-bud-experiment.html
Here is the link to Linuxmans C/ku mini-BUD Experiment.
I understand that Anole invited Stogie over for Sunday Dinner.
It seems that they have both developed a taste for "EATING CROW".
http://www.satelliteguys.us/free-ai...-one-meter-primestar-mini-bud-experiment.html
Here is the link to Linuxmans C/ku mini-BUD Experiment.
Satcom1, what was the cost of that Yuri C-Band / Universal LNBF you found on E Bay?
actually you will. I've tried it and got pretty decent results on G4. Lost a few points on the quality meter but it worked
But a scaler ring is the better option
Has anybody experimented using C-Band eqipment on a Dish Network or DirecTV dish yet?
I'm missing some of the Canadian programming that I used to watch on C-Band where I used to live and since the CANAM site is down and I can't have an extra dish pole at the public housing I'm at, some of the neighbors have "stacked" Dish Network systems, (one dish on top of another).
I have a Dish 1000 dish, a VIP 211 receiver and a 311 receiver and I have heard that you can use Bell TV-Express Vu system on a Dish Network system.
I was going to buy a Ku-FTA system, but was told "one pole only" and "that size of dish was too big for "stacking". Got any ideas?
I'm missing some of the Canadian programming that I used to watch on C-Band where I used to live and since the CANAM site is down and I can't have an extra dish pole at the public housing I'm at, some of the neighbors have "stacked" Dish Network systems, (one dish on top of another).
I have a Dish 1000 dish, a VIP 211 receiver and a 311 receiver and I have heard that you can use Bell TV-Express Vu system on a Dish Network system.
I was going to buy a Ku-FTA system, but was told "one pole only" and "that size of dish was too big for "stacking". Got any ideas?
EbaY lnbf
It was expensive, about $149.95 plus shipping "Buy it Now". Not an auction item.
It was expensive, about $149.95 plus shipping "Buy it Now". Not an auction item.
Yes you will
Depends very much on the dish and lnbf setup. Since my first negative test without a Scalar ring, I too was able to get C-Band signal on a small dish without Scalar ring at a reduced SQ by 4%.
Theroy has it that it does two things:
1- Reduces the noise coming from around the edge of the dish. Improves SQ.
2- Better 'Illuminates" the dish. Again improves SQ.
It is not just an LNBF holder.
actually you will. I've tried it and got pretty decent results on G4. Lost a few points on the quality meter but it worked
But a scaler ring is the better option
Depends very much on the dish and lnbf setup. Since my first negative test without a Scalar ring, I too was able to get C-Band signal on a small dish without Scalar ring at a reduced SQ by 4%.
Theroy has it that it does two things:
1- Reduces the noise coming from around the edge of the dish. Improves SQ.
2- Better 'Illuminates" the dish. Again improves SQ.
It is not just an LNBF holder.
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