Feedhorn ident

[archive10]

Chanced across these on ebay today.
They look like Prodelin to me, but could be some Chinese clones, I suppose. Or for some non-Ku band??
It will be interesting to see what opening angle they have, and what the flange interface is. (Seems to be six screws, not eight). And the neck seems a tad short...
Will post more pics when they arrive.
Any suggestions as to what make they might be?

 

[RimaNTSS]

Nice ones! How much did you pay?
Lets use proper terminology: Dish has opening angle, LNB (feedhorn) has illumination angle.
I think those feedhorns have ~80* illumination angle.

 

[archive10]

Nice ones! How much did you pay?
Lets use proper terminology: Dish has opening angle, LNB (feedhorn) has illumination angle.
I think those feedhorns have ~80* illumination angle.

About 65 GBP including shipping to Denmark.
Posted as "microwave feed horns, unknown make and model, sold as-is".
From browsing the Internet, I'm fairly sure they are Prodelin so-called 39 degree horns.
Illumination angle, then.
Remind me again: exactly how the illumination angle match an f/D?

 

[RimaNTSS]

Remind me again: exactly how the illumination angle match an f/D?

TBH I do not know that. But I know another thing- illumination angle of feedhorn should be equal to opening angle of the antenna, only then you get maximum performance of SAT-system.
I've measured 1,8m Prodelins I have and found out that opening angle is almost 80*, so I suspect that original feedhorn for those antennas should have about 80* illumination angle.

Add: And another thing I do not know, is how to find out exact position of phase center of the feedhorn

 

[archive10]

TBH I do not know that. But I know another thing- illumination angle of feedhorn should be equal to opening angle of the antenna, only then you get maximum performance of SAT-system.
I've measured 1,8m Prodelins I have and found out that opening angle is almost 80*, so I suspect that original feedhorn for those antennas should have about 80* illumination angle.

Add: And another thing I do not know, is how to find out exact position of phase center of the feedhorn

Hmm. Found the following in the Prodelin type 1132 installation manual:

"The General Dynamics 1.2 meter has an f/d ratio of .8 and an offset angle of 17.30°. This system is commonly used with a General Dynamics 39° feed horn."

Hmm. This would mean that the Prodelins feed looks at a smaller portion of the dish than, say, a Channel Master which has an f/D of 0.6 (according to documentation I seem to remember). This also means that a 0.6 f/D LNB would be looking "over the edge" of the reflector if seated in the LNB holder...

Does this correspond to your experience with the Prodelins?

 

[RimaNTSS]

TBH I do not really understand what F/D parameter of the offset dish really give to us
2 offset dishes with exactly same F/D can have completely different opening angle. Therefor, I see F/d of the offset dish as useless parameter. Only what matters is antenna's opening angle.

 

[Channel Hopper]

Prodelin made two dish designs, 0.6 and 0.8 f/d and with two horns of 39 and 51 degree illumination.

 

[RimaNTSS]

I do not know how to measure feedhorn illumination angle, but know for sure that my 1,8m Prodelins have opening angle ~80*. I also have one original feedhorn, by using it I get quiet good performance. I suspect that feedhorn can not have 51* or 39*illumination angle!
I just made small picture where Pink is prime-focus dish with 128* opening angle and F/D ratio about 0,6.
If we make Blue offset dish out of it than it also has F/D 0,6 and opening angle about 63*.
Lets make another cut of parabola- Green offset dish. This dish will also has F/D ratio 0,6, but only 56* opening angle.
Therefore, F/D ratio gives us nothing when we are in offset setup.

 

[Channel Hopper]

I do not know how to measure feedhorn illumination angle, but know for sure that my 1,8m Prodelins have opening angle ~80*. I also have one original feedhorn, by using it I get quiet good performance. I suspect that feedhorn can not have 51* or 39*illumination angle!

Take a picture of the back of your Prodelin dish and I'll let you know what model of feed it is supposed to have.

The dish designs of the 1.2 and 1.8 m antennas (and others) are matched to a particular feed at Ku band frequencies and the 0.8 f/d model with 39 degree feed ( part number 0800-1375) is certified for uplinking use (upward of 13GHz). If they were in any way underperforming they would have the ETSI approvals revoked.

http://www.satcomnow.com/satcom/pdf/1194geo.pdf

http://www.servsat.com/_pdfs/Prodelin Ku Band feed 39DegreeHornOMT_TRF.pdf

Measurements of the two feed designs

Model 0800-1375 39 deg . Outside diameter of the feed is 14.6 cm (5.76 inches). Feed opening diameter 12.75 cm. Length 10.9 cm. Intended for use with f/d=0.8 ETSI antenna approval

Model 0800-309 - 51 degree feed. Outside diameter 13.3 cm.(5.23 inches). Feed opening diameter 11.2cm. Length 9.1 cm. Intended for f/d=0.6 antennas such as 1123, 1124, 1125, 1183, 1184, 1251, 1255, 1381, 1383.

There is also a 50 degree antenna feed for older design antennas. 0800-1290 but I doubt you have this version.

 

[archive10]

I'm awaiting the feeds NeXT week. I'll know by then the actual Measurements.

 

[RimaNTSS]

Take a picture of the back of your Prodelin dish and I'll let you know what model of feed it is supposed to have.

First one is 0179-189 model and second one I do not know.

 

[archive10]

First one is 0179-189 model and second one I do not know.
View attachment 69852 View attachment 69853

I'm fairly certain the second one is a type 3180 Ka-band dish.

Looking at feed-horn info at Prodelin (gdsatcom.com), this also means that the second dish has a f/D of 0.8, not 0.6 as the series 1183 (which the first one is most likely). As you got this with an Inverto Black Ultra mounted, this means that the dish was underperforming since the LNB is looking at a bigger area than the dish (wider illumination angle of LNB than dish opening angle).

If I got this righ, you can't use standard LNBs with that (3180) dish for optimal performance, instead you need a 39 degree feedhorn and a flange LNB...

 

[RimaNTSS]

As you got this with an Inverto Black Ultra mounted, this means that the dish was underperforming since the LNB is looking at a bigger area than the dish (wider illumination angle of LNB than dish opening angle).

Where did you see IBU on my picture? That was original feedhorn which came with the dish.

 

[RimaNTSS]

If I got this righ, you can't use standard LNBs with that (3180) dish for optimal performance, instead you need a 39 degree feedhorn and a flange LNB...

I did not measure second dish, so do not know what is opening angle of it. Cold you shed the light on what 39 degree feedhorn means? What digit 39 represents?

 

[archive10]

Where did you see IBU on my picture? That was original feedhorn which came with the dish.
View attachment 69857

In the "Bargain second hand big dishes for sale" your wrote

There is polar-mount, actuator, IBU. No ground stand, just a piece of 100mm pipe. Also, seems, I will need lots of shampoo to make dish nice looking.

So I took IBU to mean Inverto Black Ultra??

 

[archive10]

I did not measure second dish, so do not know what is opening angle of it. Cold you shed the light on what 39 degree feedhorn means? What digit 39 represents?

As CH is saying:

Model 0800-1375 39 deg . Outside diameter of the feed is 14.6 cm (5.76 inches). Feed opening diameter 12.75 cm. Length 10.9 cm. Intended for use with f/d=0.8 ETSI antenna approval

Model 0800-309 - 51 degree feed. Outside diameter 13.3 cm.(5.23 inches). Feed opening diameter 11.2cm. Length 9.1 cm. Intended for f/d=0.6 antennas such as 1123, 1124, 1125, 1183, 1184, 1251, 1255, 1381, 1383.

There is also a 50 degree antenna feed for older design antennas. 0800-1290 but I doubt you have this version.

So you need a 39 degree feedhorn, probably. (But I am just speculating. Don't have a 3180 to hand!)

 

[RimaNTSS]

a, I am sorry, I thought you speak about picture I posted. Yes, second dish was used with IBU, and as we now know IBU has 84* illumination angle. But I do not know opening angle of second dish, if. lets say it is 70* than IBU is overiluminating dish, you are right.

 

[RimaNTSS]

39 degree feedhorn

I suspect that 39* does not represent illumination angle!

 

[archive10]

I suspect that 39* does not represent illumination angle!

It's probably half the illumination angle...

 

[RimaNTSS]

If this is drawing and not just picture than opening angle of this antenna is about 70*.

It's probably half the illumination angle...

I do not think so. Perhaps here we coming again to the issue "Where is phase center of feedhorn?"