C-band LNB.

[G4EWJ]

I understand that it's possible to use a C-band LNB with a Sky dish to receive 3.4GHz, but I can't find any information. Does anyone have any pointers, photos etc please.

Brian

[g8vpg]

Brian,
The C band LNB that I have (Titanium C1W-PLL) is physically much larger than a LNB for the usual 10-12GHz satellite bands with a large scalar feedhorn nearly 160mm in diameter. The waveguide input to the LNB is about 67mm diameter, whereas most of the Sky LNB's have a 40mm diameter fitting. I think you would need to fabricate a special mount for it. Obviously, the C band LNB's are bigger because the wavelength is longer.
73 Shaun.

[g8gtz]

I use a Titanium LNB on a sky mini dish. I placed the feed point of the C Band LNB at the same point as the Sky LNB on the basis that the focal point of a dish is the same regardless of frequency. I've done no scientific tests but it seems to work OK receiving GB3HV over a 15 Km obstructed path and seems fairly sharp on direction.

G8GTZ@home with Sky mini dish on 3.4 GHz

IMG_1910 (Mobile).JPG (42.83 KiB) Viewed 9508 times

73

Noel - G8GTZ

[G4EWJ]

Thanks both.

Would you expect better performance if the LNB arm was 're-worked' out of the way, so that the flat or conical scalar feedhorn could be used?

Brian

[M0DTS]

On my 23cm EME setup i found the choke ring only make a dB or two if difference when measuring sun noise.
The lnb choke ring is designed for a prime focus dish by the look of things.
Using the lnb with the oval sky dish is not optimum either so just optimise the position and you will not be far from optimum with the lnb alone.

Rob

[tonyaxn]

Here's a pic of the horn I made to fit one of these LNB's.. although I can get a pic from GB3NV the local DATV repeater 16 miles away just by pointing the LNB out of an upstairs window without any antenna.

73
Tony.
G4AXN

[G4EWJ]

Thanks both.

Brian

[M0DTS]

Nice job with the Horn Tony!

Is that riveted or welded at the join?

Rob

[tonyaxn]

Good question Rob

As is often the case the view from behind is not as attractive as the view from the front !
Slightly hidden is the jubilee clip which clamps the serrated narrow end of the horn to the circular waveguide on the LNB.
Important to slide the horn up and down the waveguide for max gain using a signal meter or spectrum analyser before tightening the jubilee clip.

Tony.

[G8DKC]

Will have to get Aes down soon to upgrade 70cms beam, I think a dish or horn at roof height is out of the question with the other antennas.
As a thought...with the C1W-PLL, there appears to be a progression in diameter from the feed tube block to the front.
The "extra" tube is approx. 9cm long and internal diameter at the front end of 6.3cm a label inside says 65dB Gain.
Is there a way to extend the progression in diameter to get a little more gain?

No great loss if no, could put up as is for local signals.

Pic attached of similar feed.

Peter