California Amplifier CF-50 feedhorn

[paulvr]

Dear folks,

I'm having big problems getting my C-band reception streightened out. More of that later in some other thread. But my first question refers to a brand new feed that has been laying around in my shack for ages. It's the CF-50 feedhorn made by California Amplifier (or at least sold by them under that name). I can't find any information about it, but it has two peculiarities:
1. A much bigger diameter: the outer scalar ring of a chapparal feed is the smallest of the only two rings of the CA. There's one more ring but spaced outside of this other one. It throws therefore a much bigger shadow over the dish which at the time was a reason for me not to pursue the matter as far as I remember. Both inner rings that are normal for Chapparal and other C-Band feeds are lacking so you see a very empty space between feedhole and first ring. (Let me know if you require a photograph).
2. Equally unusual is the fact that in the semi-trapeze-formed piece that all C-band feeds have in order to put the LNB lenghtwise under the hood of the dish lacks the typical little pin that I assule has some function to transport the signal towards the LNB opening.

Which also brings me to the question if there is any advantage to leave that peace off a feed (I have a rather flat Gardiner 25 degrees K LNB which would easily fit without bending the signal lengthwise. But I never saw a system without that extra piece, perhaps it does have a function???

btw: I remember reading somewhere that such a bigger scalar ring thingy would reduce terrestrial interference. But then why no inner rings?

 

[phlatwound]

I don't have any input on your questions but yes, please post some pics of this. That should help generate some conversation.

 

[Anole]

The "elbow" is waveguide, and I didn't think it was anything but smooth and hollow.
It was used to re-route the signal out of the side of your feed, to the long C-band LNB of the day.
Today, we have short ones which wouldn't need the elbow to fit under your LNB cover.
There is some signal loss in the elbow, so if you were looking for that last tiny bit, you'd be better off without it.

Can't say for the rings of the scalar.
Sounds like an old one.
Many were bigger back then.
We do have quite a number of people who were practicing the black art 30 years ago, so I'm sure you'll get a good answer.

 

[tvropro]

Cal Amp back in the day used National ADL dual hybrid mode feeds. These were the RP1C and RP1C-KU. The were and still are excellent feed's. The large scaler actually blocks TI and the dual modeing chambers (in place of a choke plate) take out of phase energy and turns it into extra signal. I have been running the ADL RP1C since 89 and love it. Much better than any Chaparrel or choke plate scaler feed.

 

[paulvr]

pictures

Hi,

Hereby some pictures of the beasty, I hope it works (never tried sending pics before)
Note besides the lacking inner scalar rings the strange carvings on the right-bottom side of the scalar rings. If this is indeed a very good feedhorn I do wonder why it left out the two inner scalar rings that are commonly used. "Something we can do without?"

 

[FaT Air]

Looks like an RP1 - Commercial and residential satellite reception systems by ADL Feeds, Inc

 

[paulvr]

Thank you, yes once I heard this I checked the forum on it. Interesting to see that the extraterrestrial looking drawing appears to be a little block for C/Ku Band versions.
The biggest disadvantage seems to be the fact that I won''t be able to use my Unimesh hood that so nicely weather protected LNB and polarizer.

But talking about this, what about the even bigger Seavey feed type ESR-124H-1 #115 (on the sticker). Embossed on the body is written SEA 8539-01 ESR-124-H.
In Europe it was marketed with Drake receivers and the very deep dish Winegard 8 and 10 ft dishes.

But after my 10 ft Winegard literally closed like a clam in a big storm I obtained a less deep dish and a Chapparal Corotor that was recommanded with it leaving the Seavey in a still fairly like-new condition in a cardboard box from then on.

Also at that time we merely used the range from 10.95-11.75 GHz for Ku band, now the much wider 10.7 - 12.75 GHz range so perhaps the feed would give certain losses,

Which brings up the questions:
- Does anyone know this feed?
- As it has a larger diameter than the ADL RP1C would it be better against ti?
- It seems that it is then also a dual hybrid mode feed ??? (I don't know what the term means but the feed also has such an open chamber without a stick in it as described above)
- would anyone recommand the use of it or is it only suitable for these relatively rare deep dish types?
- As the wind moves the dish back and forth too much on it's AJAK mount Ku band reception is not very reliable on such a large dish. So I''d use it more for C-Band only. Would the presence of the Ku Band branch off cause so much loss compared to a pure C-Band feed that it''s better not to use it?

I won''t ask if the Ku-feed would give many losses outside the rather restricted range indicated as I understand that in North America the Ku band still is rather limited so no one could know?

PS: sorry for not really cleaning the feed before taking the picture

 

[paulvr]

By the way, Anole, thanks for your advice about the waveguide. I already wanted to remove that thing, only to find out that it was all cast as one piece (see attached photograph). By the way, I used to live in the L.A. area, have still friends there. But that was before there was sat tv or internet...

 

[Anole]

Sorry 'bout the bad info.
Hadn't seen the picture when I posted.
Had envisioned something totally different.
Just another reason I ask for folks to show us photographs... so everyone knows what we're talking about.

 

[paulvr]

oops - I just checked the hood of my Unimesh dish. I was talking gibberish. It's big enough to hold any feed no matter how big the scalar rings!

 

[paulvr]

Don''t say sorry: this is useful knowledge that I will be able to apply in other situations.
In the old days waveguides were necessary because of the shape of the LNB's so the question wheather or not I could do without it never came top my mind. Now I know

Happy Easter, we have glorious weather for it here in Holland.

Paul.

 

[tvropro]

ADL made the Dual Hybrid Mode feed, Cal Amp slapped their name on them. I will try to explain it's operation. A normal feed (Chaparral) with the multiple scaler rings uses those rings to choke off out of phase energy. The ADL DHMF takes that out of phase energy and puts it back in phase then channels it into the waveguide throat, thus adding gain to your signal. The choke plate (multi scaler) feed chokes off that information and it is lost giving less performance than the DHMF. So you get extra DB gain with the ADL installed and set up right. Second the large outer scaler shrouds the throat preventing TI from entering.

 

[Anole]

Stogie5150 has/had two orthomode feeds for sale. (see pictures)
I was thinking about them when I posted.
Note the older long LNBs are on the Chaparral feed, which is set up to bolt the LNBs on from the rear.
The other feedhorn has a side port and end port, and works great with the small LNBs.

This picture shows an elbow on the Ku port, and another larger one which can fit the C-band port.
Both appear removable.
More like what I was thinking of.

 

[paulvr]

Thank you, I know, I have that Corotor II as well. I assumed that it was the best I had until I went to single C-band reception only and from that moment on I went to a regular Chapparal C-Band only feed. However, this thread has taught me to give this ADL feed a try. I only used it briefly because in one of the holes a small array for S-Band was fitted which I experimentally used for the at that time active S-Band transponders on Arabsat. I had no idea that the feed had such good C-Band properties.