Thinking about orthomode feedhorns

[Corrado]

What are the disadvantages of the orthomode feedhorns? After doing some reading, I'm not finding much negative other than availablility and price. I'm mainly thinking C band. From what I have read many people report gains using them in place of more common feeds such as polarotors or LNBFs on the BUDs.

I'm surprised that no one considers selling them with today's low priced switches and LNBs. The design is so simple someone could manufacture them easily, but the available commercial units are rather steeply priced. I think somone's missing the opportunity with this.

I have 3 commercial VSAT transmitter type orthomode tranducers from my Prodelin dishes and after studying the design, I was toying with the idea of refitting them to see if they could work with other LNBs. They have nice conical scalars built into the front. Now that I have a third setup to experiment with for the offset design feedhorns.

 

[Anole]

I've been talking to Stogie, and know he put one in recently.
Here's the best info I could find posted, though.
I recall that he found a C-only feed new, for a very attractive price.

When I was doing some follow-up, I located C-band LNBs for cheap, at Galaxy-Marketing.
Back then, Robby had some customer buy him out, but he's since restocked.

 

[crackt]

you can find a chaparal ortho mode feed for 60 bucks. the lnbs can get pricey though. they do perform very well.

crackt out,.

 

[stogie5150]

Somewhere is a huge writeup that we did on the issue. The problem for the average FTA'er is that you have to POWER those LNB's with 18V, BOTH of them. Which means you either mod a powered multiswitch ( which is what I did), or buy a power inserter or two and use that. The guys with more electronics training than me say the power inserter gives you more gain, because the multiswitch kills some. But both of my dishes are on orthos with the modded multiswitches and I don't want to go any other way, and I love the performance.

Here's the Horn on my Paraclipse:

Dual C-Band Feed :: C/Ku...

And these are the LNB's I used on the Paraclipse.

DMX211 C Band LNB Single Output for BUD Satellite Dish Antenna


The Birdview has a Chaparral Ortho with some old 35k LNB's I had in the junque box.

 

[stogie5150]

Here's the thread on my Paraclipse.

With all the links inside the thread that Lizard couldn't find.



http://www.satelliteguys.us/c-band-...06691-how-i-learned-love-bomb-paraclipse.html

 

[crackt]

your right stogie. my vertical lnb only recieves 13 volts and i can tell it doesnt perform as well as it should be. i modded a zinwell 4x8 but havent installed it yet.... i was gonna use some taps and a power supply instead as it would scale a little better in my farm. i think im off to tweak this feed horn as some wind the other day showed me how poorly aimed it is. for a few hours i had every s2 signal on the western side of my arc at 90 plus q's on my 10 footer. alot better than the 70 q's i have now.

crackt out,.

 

[pendragon]

A single ortho with good LNBs is nearly impossible to beat on C-band. I suppose the single polarity feeds with a motor that drives the entire feed might be a little better. I would suggest a Chap single for $57-65 as crackt points out. Modifying a transmitter feed is going to take some plumbing to adapt the LNBs - you will get small or large losses depending on how well this is executed, but you will get losses.

Power inserters or modded 4x8 switches should both work fine. I'd choose a good 4x8 most of the time over power inserters because of the simplification in wiring and the fact the switch can fan-out to multiple receivers. Power inserters are simple, but they still introduce very minor losses. A switch can make up for this.

 

[chapelrun]

A few questions

I really like this idea as it seems like a good way to go. Better C-Band (I doing my first big dish now)

I already have several 4x8 Zinwell's around - - - modifying them using pendragon's procedure should be fairly simple

If I purchase this

Dual C-Band Feed :: C/Ku...

as stogie5150 suggests do I put TWO Norsat LNB's (one for Vert and one for Hor)?

I guess I don't understand how the Zinwell is powered and then how the Norsat are powered from the modifed Zinwell.

Does someone have a diagram or picture of how your are setup? I do good with pictures.

 

[stogie5150]

I really like this idea as it seems like a good way to go. Better C-Band (I doing my first big dish now)

I already have several 4x8 Zinwell's around - - - modifying them using pendragon's procedure should be fairly simple

If I purchase this

Dual*C-Band*Feed*::*C/Ku...

as stogie5150 suggests do I put TWO Norsat LNB's (one for Vert and one for Hor)?

I guess I don't understand how the Zinwell is powered and then how the Norsat are powered from the modifed Zinwell.

Does someone have a diagram or picture of how your are setup? I do good with pictures.

Yes, you need two LNB's, one for vertical and one for horizontal. You run two coaxes (one from each LNB) to the inputs on the multiswitch, and then the modded multiswitch powers the LNB's. The Multiswitch gets its power from a 110V transformer, and the power goes from that transformer VIA regular coax to the multiswitch, where there is a regular coax connector for you to plug it into.

Look at this pic:

http://www.satelliteguys.us/attachment.php?attachmentid=50523&d=1272308812


The Multiswitches on either side are my two modded ones (have 18V written on them). Look on the RIGHT side of those switches, you will see a coax plugged in with two BLUE tape stripes on them. Thats the multiswitch power coming from the transformer. The top is the two coaxes coming in from the LNB's at the dish, and out the bottom are the coaxes going to all my receivers.

The middle multiswitch is an unmodded regular powered switch for my dual output 1m Primestar.

I hope some of that helped ya.

 

[crackt]

good to see pendragon commenting here ( a very respected opinion in my books ). i finally tweaked my ortho and i just have to say wow. i knew i could squeeze alot more outta of it and i have. i like 100% q readings from the azbox on s2 tps. next project is my new t90 toriodal. one thing to keep in mind is that an ortho with some heavy norsat lnbs is alot heavier than an lnbf so make sure your dish is equipped to handle the weight.

crackt out,.

 

[ikki]

crackt do you have pictures you could post?

 

[Vorg]

These wave guides sound like they might be the answer to adding some c-band to a small dish if they didn't charge so much for metal tubes. Even found one that seems to convert circular to linear without using inserts that adversely effect the linear. Waveguide Polariser | Feedhorns | Av-Comm

Seems the potential is here for a truly universal feed that does C and ku in both circular and linear on a single feed horn be it for prime or offset. Just need to find someone willing to make and sell them at a price more fitting the little cost of materials. Hundreds of dollars for a few inches of cast aluminum tube?

 

[Anole]

gotta walk, first ...

Before we get sidetracked with circular, let me draw your attention to another thread by Pendragon:
C-band Linear/Circular Orthomode Feed Modification

 

[Corrado]

Thanks for the input guys, plenty of interesting reading. All good and nothing negative. Good tips on suppliers, I didn't find those either.

I was thinking about looking at every remaining Bud I could find to see if one was available for feedhorn salvage locally. I already have a shelf full of assorted LNBs and a brand new Zinwell 4x8 in the box.

 

[madbull]

I just aquired a chaparral bulleye othro feed. I have a channel master 6904ifd 4x4 switch that That was used with dtv. I was thinking about putting a power inserter on the field side of the 13 volt outputs. Will this work. or is there a better arrangement . I also have a zinwell 4x8 around here, would it be better? looking for the best way with the smallest lost. I only have two coaxes going to the dish at present. need some guidance from one of you guru's as to the best arrangement.. If I posted this question in the wrong thread please excuse me.

 

[madbull]

I just did a search and found pendragon's mighty mod for the zinwell wb68 multiswitch. It looks like the simplest an best. Forgive me for not doing a search before the first post. He is "the" man.

 

[crackt]

I just did a search and found pendragon's mighty mod for the zinwell wb68 multiswitch. It looks like the simplest an best. Forgive me for not doing a search before the first post. He is "the" man.

your power inserter solution would also work.

crackt out,.

 

[1captain]

I use several orthos here, 3 dual C & Ku, and 3-dual single band ortho. now the problem by converting 1 of these switches to output 18-V on all 4-ports is their wimpy wall wart that they have for their power supply, pluss you are limited to the voltage output of it's regulator. now a lot depends on the lnb's that are going to be used, I have seen some lnb's draw around 400ma, and most of those wall warts are only 1Amp, so 4 lnb's will = 1.2amp. now I have also seen some lnb's only pull a little over 100ma so you will be well with in these wall wart limits, but I would still recomend to check you amp draw before you set it all in stone.

now 1 other thing that I have found threw out my years of dealing with satellite and ortho's, is the voltage that you are send out to a lnb, and I have shown this to my freinds here a few times and every one has been amazed, and that is most lnb's will work better and receiver more signal with a higher voltage. here I have a home built P.S. that I can turn volage up or down to the lnb's and you can watch signal and quality do the same when I do this too, now I run all of my lnb's here just a tap under 20-V which is well under a lnb's max voltage, and for me work very well.

once you have you're ortho install and tune in Corrado, you will wish that you did it a long long time ago, trust been their, done it, and seen the results.

 

[chapelrun]

OK - another question

I just ordered Chaparral Dual LNB feedhorn and two Norsat 8700 LNB's. (Got a pretty good deal)

I did this mainly because of this thread and I really like the idea of not having to worry about a servo motor - - - it just seems like a better solution.

Thus, I'm going C-Band only on my 10 foot Channel Master.

What I'm still a bit fuzzy on is the best way to wire this. I have read pendragon mod. thread several times and I think I understand. If you don't do the modification one of you LNB's will be under powered thus I should definitely do the mod.

I have a slightly newer, smaller Zinwell SAM-4803 4x8 Mulit-Switch - - - could I do the mod using the same procedure? Or I should I stick with the older proven Zinwell 6x8 Multi-Switch.

ACRadio uses a Spaun SMS5802 4x4 (5x4) multiswitch with power inserters on all LNB's - - - - but I would need to learn how that is wired.

I have at least 3 or 4 Zinwell 6x8 Multi-Switch's can someone who has done the mod. let me know if their are any gotcha.

And how would you wire both the pendragon way of doing it and how would you wire the ACRadio way of doing it?

Sorry so many questions.

 

[ACRadio]

ACRadio uses a Spaun SMS5802 4x4 (5x4) multiswitch with power inserters on all LNB's - - - - but I would need to learn how that is wired.

... and how would you wire the ACRadio way of doing it?

Sorry so many questions.

I build my own power inserters using bias tees and a 19 volt laptop power supply, so it would be simpler to use the standard Tru Spec dual power inserter for your purpose. I used these until I was powering a larger number of LNB's and I sold my last 2 yesterday. You would only need one of these for a single band as each supply can power 2 LNB's. They cost around $25-30 and the loss through the supply is negligible. I use the 5802's because I am using a C/KU band ortho, as well as a dual C band ortho. A 3402 or 3403 would work well if you don't have more than 4 receivers. I like the Spaun switches...they are built well and have some amplification and slope correction.

Separate coaxes from each LNB comes into the TO LNB ports (H and V) of the power inserter, then the H OUT goes into the Horizontal (18V) input of the switch and the V OUT goes into the Vertical (13V) input of the switch. Then each receiver connects to the switch outputs. The toggle switch on the power inserter should be in the UP position so that 18 volts is sent to both H and V LNB's.