FTA OMT Controller

Discussions about low-noise blocks, waveguides, horns and other components used at the prime focus of your reflector dish.
norman881
TVRO Guru
TVRO Guru
Articles: 0
Posts: 65
Joined: Thu Nov 27, 2014 8:55 am
Location: Eastern Washington
Has thanked: 39 times
Been thanked: 2 times

Re: FTA OMT Controller

Post by norman881 » Wed Jun 29, 2016 3:27 pm

Foxcreek

I was an EE major when I left school to join the Army. After I got out (and after the Desert Shield/Storm recall) I went back to school, but changed majors to Physics/Optics. I have been in a lab ever since.

The spread spectrum multiple access experimental machine we had was made by Magnavox (Magic Box)

We also had an ancient machine that did the same thing with far crappier performance. (I'd rather not say the name.)

Small world,
norman881
10 FT Winegard Pinnacle w/Venture 36" Maxie Heavy Duty Ball Screw Actuator 90 cm Fortec w/DG380 and Avenger PLL LNBF Amiko HD265 & Edision OS Mio 4K Titanium ASC1 Controller & C1 PLL LNBF

Foxcreek
TVRO Guru
TVRO Guru
Articles: 0
Posts: 233
Joined: Mon Dec 15, 2014 11:15 am
Been thanked: 1 time

Re: FTA OMT Controller

Post by Foxcreek » Sun Jul 03, 2016 4:19 pm

All,
Do you remember this post..... Well to date we haven't seen any response from Tek2000.

Talk is cheap !

foxcreek :?:






Postby Foxcreek » Thu Jun 16, 2016 2:47 pm
Tek2000,

Could you post a diagram / drawing for your adjustable feed set-up......
I can't quite picture it based on your description.

Thank you.

foxcreek

User avatar
tek2000
TVRO Salesman / Sponsor
TVRO Salesman / Sponsor
Articles: 0
Posts: 329
Joined: Fri Jun 20, 2014 4:38 am
Location: Canada
Been thanked: 11 times
Contact:

Re: FTA OMT Controller

Post by tek2000 » Thu Jul 07, 2016 7:16 pm

I will post pictures when I get a chance. The concept is similar to a telephoto lens.

We are re-engineering the whole feed system and hope to introduce the most efficient consumer grade c and ku band feed system available anywhere.

Now that we got the TVRO reflector designed properly, along with a strong frame and a variety of masts for proper ground and roof installations, we are focusing on the next most important thing: better quality feeds and controllers.

You will all thank us when 16APSK and 32APSK signals become common place. :wink
Owner
http://www.tek2000.com
#1 Supplier of TVRO Satellite Equipment in North America
[email protected]
(I am not on this forum often and don't check forum PMs, so please email me for faster service)

elko
TVRO Guru
TVRO Guru
Articles: 0
Posts: 213
Joined: Sat Aug 30, 2014 11:02 pm

Re: FTA OMT Controller

Post by elko » Fri Jul 08, 2016 1:01 am

Foxcreek wrote:elko,

Cryogenics is very extreme and cost prohibitive for all except giant
corporations, governments, military which of course have unlimited
budgets ! I believe Cryogenics is used at the Arecibo radio telescope
for example. It's really a neat phenomena however ........ by cooling
the first few amp stages in the LNA to just below absolute 0 ( -273 C )
All molecular activity stops hence the noise disappears. Science has
been working on combining certain materials to make super conductors
so the extremely low temps are not required !

Noise will always be a factor due to the Cosmic noise background from
the BB ( Big Bang ).

foxcreek :cool2
You are plain wrong about this. Nowadays, kids are using cryocoolers to liquify the the oxygen and nitrogen in the atmosphere. Have a look at this video



Get yourself a cryocooler and put your LNA in a thermos and those D/N channels should pop right in on your 7.5' bud. :wink

Why didn't you try this already? :doh :utterlyconfused

Foxcreek
TVRO Guru
TVRO Guru
Articles: 0
Posts: 233
Joined: Mon Dec 15, 2014 11:15 am
Been thanked: 1 time

Re: FTA OMT Controller

Post by Foxcreek » Fri Jul 08, 2016 2:12 pm

elko,

No comment !

foxcreek :cool2

Foxcreek
TVRO Guru
TVRO Guru
Articles: 0
Posts: 233
Joined: Mon Dec 15, 2014 11:15 am
Been thanked: 1 time

Re: FTA OMT Controller

Post by Foxcreek » Sun Jul 10, 2016 2:40 pm

tek2000,

Based on your response's to my inquiries you seem to be desiring
to design and build the "ultimate" satellite dish. So I have to ask
why aren't you considering an offset feed design ? As I'm sure
your aware offset designs are considerably more efficient than
a prime focus design.

foxcreek :cool2

User avatar
tek2000
TVRO Salesman / Sponsor
TVRO Salesman / Sponsor
Articles: 0
Posts: 329
Joined: Fri Jun 20, 2014 4:38 am
Location: Canada
Been thanked: 11 times
Contact:

Re: FTA OMT Controller

Post by tek2000 » Sun Jul 10, 2016 10:08 pm

Foxcreek wrote:tek2000,

Based on your response's to my inquiries you seem to be desiring
to design and build the "ultimate" satellite dish. So I have to ask
why aren't you considering an offset feed design ? As I'm sure
your aware offset designs are considerably more efficient than
a prime focus design.

foxcreek :cool2
Our goal is to produce the most efficient consumer grade TVRO systems at the most affordable prices so that they appeal to both enthusiasts and ordinary cord-cutters alike. We want to give the average 'Joe' the opportunity to experience pure HD programming and the thrill of finding wild feeds without the steep learning curve that often accompanies this (up until now) hobby.

Most c band enthusiasts on this board and others, almost certainly have a math/physics background or are engineering/technical professionals such as yourself. But even among this group, very few have the knowledge to fully understand the propagation of microwaves and what is needed to efficiently capture this energy for signal exploitation. Outside this group, it is entirely hopeless to expect anyone to have a realistic chance of successfully installing a fully functional TVRO system that will pick up all types of satellite signals in both bands.

This is why we are working on a custom feed system for our antennas. It will be plug-and-play (not unlike the feeds for dbs systems) whereby the end-user will simply point the dish south, adjust his elevation to his latitude and then allow a controller to do the rest.

As for your specific question about offset designs, I am not sure if you mean the reflector and feed are both off-axis or the feed is off-axis but uses a prime-focus reflector, but I will answer both.

If by offset you mean using a section of the parabola that is not symmetric about the axis, then although the efficiency of such an aperture is greater for smaller reflectors, it doesn't help much for larger ones. Consider a 120" (10ft) diameter prime-focus dish with an 8" diameter scalar ring. The power lost by the scalar ring blockage over the dish aperture is a mere 8^2/120^2 = 0.44%. It is even less for the 4 lnbs struts (even thick ones). Even with a 6ft prime focus dish, the power lost would only be 1.23%. It is hardly worthwhile to manufacture offset reflectors for TVRO unless the dish dimensions approach those of dbs, but then you won't capture enough c band energy to begin with. Besides feed blockage, an offset reflector will suffer less from terrestrial noise spill over interference. I will grant you this, but a properly illuminated prime-focus dish that is perfectly matched to its feed will also minimize terrestrial noise interference. Besides, an offset reflector destroys the symmetry we have with prime-focus reflectors when it comes to designing feed horns and circular waveguides and unnecessarily complicates the design of the feed. Turning a prime-focus dish into an offset dish is actually quite simple. For example, if you have an 8-panel 10ft prime-focus dish and you install only 4 of the panels, you will end up with the equivalent of a 7ft offset dish and your feed will be out of the way for the most part, but now your nightmare of designing a matched feed to your offset aperture begins!

If by offset you mean using a prime-focus dish with off-axis feeds (e.g. c band feed at prime-focus and ku feed off-axis), then yes, this will let you separate the different bands for better efficiency and in fact, we are pursuing this approach. Such off-axis feeds have been discussed in section 8 of our installation guide and it is nothing new (commerical solutions were available back in the 1980s), but people require a commercial solution for optimal results, rather than the cookie-cutter stuff you see people posting on various boards.

http://www.tvrosat.com/phpBB-3.0/phpBB3 ... 146&t=1252

When all is said in done, even the most efficient feed will not help if you don't also incorporate: off-axis band separation, automatic skew adjustment and automatic declination adjustment. Although consumer solutions exists for skew adjustment, nothing exists for these other problems. It turns out you can't track the Clarke Belt perfectly unless you are at the equator. Everywhere else, you will need a slight declination adjustment (1-2 degrees), but this will make all the difference for ku band reception, and to a lesser degree, c band reception.
Owner
http://www.tek2000.com
#1 Supplier of TVRO Satellite Equipment in North America
[email protected]
(I am not on this forum often and don't check forum PMs, so please email me for faster service)

Foxcreek
TVRO Guru
TVRO Guru
Articles: 0
Posts: 233
Joined: Mon Dec 15, 2014 11:15 am
Been thanked: 1 time

Re: FTA OMT Controller

Post by Foxcreek » Mon Jul 11, 2016 8:54 pm

tek2000,

https://www.google.com/search?q=Greenba ... oM%253A%25

Need I say more ?

foxcreek :cool2

elko
TVRO Guru
TVRO Guru
Articles: 0
Posts: 213
Joined: Sat Aug 30, 2014 11:02 pm

Re: FTA OMT Controller

Post by elko » Tue Jul 12, 2016 1:39 am

I believe an offset dish is only superior to a prime-focus dish when it is stationary (as regards ground noise). Think about it :thinking , as the offset dish tracks the arc from west to east, the LNB(F) will point up in the sky and then down into the ground (or vice-versa).

If you want to eliminate ground noise :underchair in a prime-focus dish, you can either design a very deep reflector or encapsulate the entire prime-focus dish in a cylindrical mesh cage to reflect away any terrestrial radiation. :biggrin

Foxcreek
TVRO Guru
TVRO Guru
Articles: 0
Posts: 233
Joined: Mon Dec 15, 2014 11:15 am
Been thanked: 1 time

Re: FTA OMT Controller

Post by Foxcreek » Tue Jul 12, 2016 4:24 pm

tek2000,

For those who seemed to have missed the point with my posting of the
Greenbank radio telescope. The statement made by tek2000 that offset
dish designs were only more efficient in smaller sizes is total bunk !

My suggestion to tek2000 is to seek out a qualified antenna engineer
if your indeed serious about designing this ultimate dish you've talked
about here.

foxcreek :cool2

Post Reply

Return to “Feed Systems”