Length of Feed Line to Receiver

Discussions about low-noise blocks, waveguides, horns and other components used at the prime focus of your reflector dish.
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FN56XX-0
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Length of Feed Line to Receiver

Post by FN56XX-0 » Sat Jul 21, 2018 12:57 pm

Hello, this is my first post here other than the introduction I made.

My question is I'm planning on installing a C-Band dish system and I'm wondering as to the length of the feed line from the dish to the receiver. How long is too long before it starts to degrade the signal. Currently I'm planning to place the dish 80 feet from my house, plus another 10 feet extra to get to the head end equipment. Any info would be valuable. Thanks.

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Re: Length of Feed Line to Receiver

Post by jess76 » Sat Jul 21, 2018 4:18 pm

If I remember correctly my"Radio Shack" set-up came with 100' of ribbon cable and a warning NOT to cut it. You should be good with what you have. The "ribbon" came with wires for the dish mover, C and Ku cable,and wires for the polorotor control. Jess out in California.
9' mesh with c/ku feed horn,lnb's w/polorotor. Recievers hooked up: AZ prem hd., Pansat9500,and Manhattan. I have a few others in my colection including an old Satcruiser and a Captiveworks3000.

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Re: Length of Feed Line to Receiver

Post by dishcrank » Sat Jul 21, 2018 9:37 pm

Even 200 feet should not be a problem with standard coax. The main problem people encounter with longer runs is problems changing the signal polarity or communicating with a switch. Signal degradation also occurs, but of secondary importance. You can avoid these problems by using (low loss) solid copper coax (e.g. rg11).

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Re: Length of Feed Line to Receiver

Post by FN56XX-0 » Sun Jul 22, 2018 10:55 am

Thank you for the replies. I'll definitely look into the RG11.

Would upgrading to a larger dish size compensate for the mild signal degradation or is the extra cost not worth it?

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Re: Length of Feed Line to Receiver

Post by fatso » Sun Jul 22, 2018 11:53 pm

FN56XX-0 wrote:
Sun Jul 22, 2018 10:55 am
Would upgrading to a larger dish size compensate for the mild signal degradation or is the extra cost not worth it?
FN56XX-0 wrote:
Sun Jul 22, 2018 10:55 am
Would upgrading to a larger dish size compensate for the mild signal degradation or is the extra cost not worth it?
Bigger is always better when it comes to tvro...most serious c-band enthusiasts have a 10 ft dish. This dish size is large enough to receive all dvb-s2 (8PSK) signals over north America. It will also get you most of the latin American birds too. With a well tuned 10 footer, you will always have 1-2 dB of margin above the noise threshold when tuning most 8PSK transponders. This is enough to watch tv without any pixelation or other problems, even on a windy day.

A 12 footer on the other hand will give you better than 3-4 dB of margin. This is overkill for c-band enthusiasts in north America, but comes in handy if you are hunting low power transponders from Europe, Asia and South America. If you got a really long cable run (e.g. greater than 300ft), the 12 footer will make all the difference. Another reason for using a larger dish is terrestrial interference. Interference from the wireless providers enters via the dish side lobes. A larger dish by definition has a bigger main lobe and smaller side lobes. This means better performance in the presence of noise. If you are worried about the new fcc rules which will allow wireless providers to use part of the c-band spectrum, you may want to get a bigger dish to be safe. So far, fcc has not made a decision, but it is looking increasing likely that they may allow sharing of the 3.7 - 3.8 GHz spectrum beginning in 2020. If they do, and you are near a cell tower, a bigger dish will come in handy.

I consider an 8 foot dish a beginners :bigsmile antenna. It works, but when it comes to high fec rate 8psk signals, some of them will be right on the noise threshold. You need to do a super job of peaking a dish this size to get the most out of it. Also, you would use the most efficient c-band feed you can find and forget about adding ku support because it will degrade the c-band performance. Less than 75ft cable run is a must for this smaller dish. This dish size is best for the central USA where satellite EIRP levels are highest. It should be avoided on the east/west coasts and in Canada/Mexico where EIRP power levels start dropping.
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Re: Length of Feed Line to Receiver

Post by FN56XX-0 » Tue Jul 24, 2018 12:03 pm

Thank you fatso for all that info, this really helps me out a lot. I'm in far north Maine, rural area with no cell towers near by so it looks like I'll be going with a 10 footer. Do you have a preference as to where I should purchase the equipment?

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Re: Length of Feed Line to Receiver

Post by fatso » Tue Jul 24, 2018 10:58 pm

FN56XX-0 wrote:
Tue Jul 24, 2018 12:03 pm
Do you have a preference as to where I should purchase the equipment?
I would purchase from Tek2000.com

They upgraded all their antennas this year and I am told they are top notch. Also, they got the lowest prices!
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Re: Length of Feed Line to Receiver

Post by AlieLeite » Tue Sep 25, 2018 12:53 pm

Hi...as per my experience any decent receiver in the band of interest, preferably with an RF or IF gain control and switchable AVC, is exactly what you want. If it has an S meter that could possibly be helpful along with a directional antenna; but not as much as you might think for near-field work.

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