Sirius Radio Antenna

Spire_Jeff

Has anyone had any luck with using the Sirius antennas on longer cable runs? I have an antenna on about 80-90 feet of wire. This is about as close as we can get the antenna to the unit. We have tried adding the Terk Amp, but still don't get a signal. We are using rg58 wire spliced with BNC connectors. The Kenwood DT7000S recognizes the presence of the antenna, we just don't get any signal.

Any info would be appreciated.

Thanks,
Jeff

Reese Jacobs

Sirius Radio Antenna

Jeff,

I have one Sirius installation that uses a 25' RG58U cable connected to the 50' Terk extension cable with appropriate BNC to SMA/SMB connectors on either end since we are connecting to an Antex SRX-3 tuner. We are also using the antenna supplied by Antex which is similar if not identical to the Terk SIR-6 antenna. In this configuration, we have excellent signal - generally between good and excellent. The good signal strength is during the 3 times a day when the satellites are positioned at the point furthest from the antenna. Otherwise, signal strength has been excellent. It did take a considerable amount of tweaking to get the antenna locked onto the signal in an optimal manner.

Reese

Spire_Jeff

thanks for the info, I'll try to play with the aiming.

Thanks,
Jeff

DHawthorne

On that bandwidth, a good cable with solid terminations is critical. I had a manufacturer-supplied cable termination fall apart in my hands one day while working with a 900MHz device - not quite as finicky a bandwidth, but I still shudder at the thought of the standing wave interference. Back in the day when I did a lot of RF work, I made it a point to test every cable and every connection; when possible, I would retune the antenna itself to the cable run for optimal signal strength. I don't even own those meters anymore, though I often wish I did. The thing is, the cable is part of the antenna system, and the "sloppier" (for want of a better term) the cable, the more detrimental to your signal. You can't always just add cable length or take it away, without messing up the tuning of the antenna. I knew a fellow who was an RF engineer, and he referred to working with it as dealing with "black magic and voodoo." I think he had a point.

TurnipTruck

I'm not sure what the impedance of the antenna line is. If it is 75 ohm, try using RG-8 coaxial cable, if it is 50 use RG-8. Both cables are about a 1/2 inch diameter and will have less than 6 dB loss per 100' at 1GHz. The quality of your terminations must also be good. No solder and splicing. All of your connectors and connections must maintain the impedance of the line.

Jill

The quality of the cable at that distance is important. As Turnip Truck mentioned the RG-6 and RG-8 is much better than regular RG-58. I would consider even a quad shield RG-6/8. Use the correct connector and terminate them as per spec. Also a signal level meter comes in handy to fine tune the antenna.

Spire_Jeff

I'm not sure on using the RG6 Quad shield as the only RG6QUAD I've seen is 75ohm and the RG58 is 50 ohm. Altho, I did see a device that is externally powered and combines/uncombines Sirius signals with DISH or DirecTV signals across a single RG6. If I get desperate, I might try out that piece since it has an external power supply and I think it amps the signals.

As for a meter, does anyone know if a standard DirecTV/DISH will indicate the signal level of Sirius? We haven't tried it because I can't really find a lot of info on the signal specs for Sirius.

Thanks,
Jeff

P.S.
We might just wind up moving the receiver to a different building and sending the audio back to the rack instead

Jill

Salut Jeff
I asked a friend who is in sat communications about this and he mentioned a couple of things. The unit does require 50 ohm cable and specs RG-58 as okay. He suggested a RG-8 duel shielded cable. He also mentrioned that he read somewhere that the recommended cable run not to exceed 30' from the head.(He's not sure about this because he normally works on uplinks). I would try and move the reciever within 30' of the antenna and try it to see if it works, then you can proceed from there with solution.

TurnipTruck

A quad shield will not be any better than a dual shield in this application. Quad shield is used to minimize ingress/egress in CATV distribution. If a signal path would perform unacceptably with dual shield, but acceptably with quad, it's a sign of a greater problem.

If the satellite radio cable impedance is 50 ohms as someone stated previously, the RG8 with good quality adapters would be the way to go. The only thing better would be a hardline coax which would be totally unnecessary.

If the signal from the antenna could make it through the 25 feet or so of the skinny little cable they give you with the antenna, I'd be willing to bet it would make it through hundreds of feet of RG8. The best trick would be to cut off the majority of the skinny wire and properly install some sort of connector to terminate to the RG8.

The moral of the story is that thinner cables attenuate higher frequencies more per given length than they do lower frequncies. For example:

At 50 MHz (slightly below channel 2 on your TV, RG6 loses about 1.4 dB per 100 feet, but loses 5.1 dB per hundred feet at 650 MHz, approx ch 94 on cable. The 7/8 inch hardline coax your cable company runs from pole to pole loses about .3 dB per 100 feet but only loses 1.1 dB per 100' at 650MHz. I would suspect that the signal from the satellite radio antenna is somewhere between 950-2150 MHz, which is the typical intemediate frequency range used in satellite reception, thus a thick wire is your friend.

As far as using an inline signal meter, like those a DirecTV installer would have, I can't see what great piece of information it would give you. Satellite radio antennas are omnidirectional, so if it is in its proper orientation and has a clear view of most of the sky, you should be good to go. The signal meters just give you a relative reading of signal level. Even if you knew an actual signal level you were shooting for, the signal meter would have no way of reading it. You would need a fancier device like a spectrum analyzer for that.

Satellite radio sounds like shi_ anyway.

Jill

True Turnip Truck, I only suggested the quad shiel before I realized the unit was 50 ohms.(Guess I should of looked more closely at the manual,morel-never assume anything.) You could use the signal meter (I haven't tried to see if it work) to give an indication of the signal level at the attenna and at the reciever.There would be some drop but you should still have some signal.

mstc

Sirius and XM antenna extension and distribution solution

Hi;

Check out www.sandsationalsound.com and look at the antenna adapters we have. They are designed tro allow use of 75 ohm coax for extension of both Sirius and XM antennas. We also have a line of amplifiers and distribution equipment for XM, some of it also works with Sirius althouge we have not had much demand for the Sirius applications.

For those of you who are worried about 50 ohms vs 75 ohms please bear in mind that in this application we are doing interstage coupling of voltage amplifiers, not coupling a final amp to a transmission line and antenna.

I have had these tested at TB in New Jersey as well as at Russound and at Steren, where they showed an insertion loss of less than 1 dB for the set( pretty awesome number, I was stoked).

The botom line is these really work well, with cable, connectors and tooling that the average installer is familiar with and carries on their truck. Solid copper core cable is best, especialy if it is swept to 3GHz like some of the new DBS and or Digital Video cable. Feel free to contact me directly if you wish, I prefer to do application specific recommendations for amplification and distribution.

Kol

shr00m-dew

I can recommend Kol and his equipment. He was able to work out a single RG6 cable, single antenna solution for a job with both XM and Sirius!

Thanks again,

Kevin D.

Chip Moody

I can't say anything about the equipment, (haven't had a use for it yet) but I can say having Kol here is a great addition to the forum!

- Chip

tom goez

Coax cable

I think TurnipTruck meant to say if it's 75 ohm, use RG11 coax which is 1/2" cable.

All those 1/4" and 3/8" cables are not acceptable for long runs approaching 100', no matter what their impedance is.

Too lossy!

Tom

TurnipTruck

For 75 ohm RG11, for 50 ohm RG8.

As far as skinny cables like 59 and 6, they may very well have acceptable loss characteristics at 100 feet, especially if you remove the majority of the real skinny stuff that comes with the antenna.

Someone stated earlier that the impedance match from a 75 ohm cable to 50 ohm devices may not be that big of a deal. This is a good point. Often times the loss at the mismatch is made up by the fact that you are using a cable with substantially minimized cable loss. The use of RG59 on wireless microphone antennas in pro audio is very common, even though the receivers are 50 ohm devices, the antennas are supposedly 50 ohms, but vary in practice.

Precise impedance matching is mandatory in transmitter to antenna connections, preventing signal from reflecting back to the trans from the mismatch.

By the way, does anyone know what the "RG" in RG6 means? I'll give you a hint that it goes way back to early military comm. It has nothing to do with cable size.

tom goez

Coax cable

RG stands for Radio Guide. All RG cables also meet MIL-C-17 to be called RG.

Tom

Thomas Hayes

Radio Guide?

tom goez

RG Radio Guide

Yes, it's Radio Guide. It was a designation for coaxial cable determined before you or I were born.

It's not something I'm making up, I'm just the messenger!

Tom

Thomas Hayes

Yes, I believe it. I asked my dad(not always a good thing because you get a 2 hour talk about the old days and tube transmitters, the DEW line or someother thing) It neat to see where some of these terms come from. Like cold enough to freeze the nuts of a brass monkey.(Military saying also).

Spire_Jeff

Doesn't RG stand for Radio Guide.... and the number refer to the page of the guide that specified the cable? As I recall

Jeff

Jeff Lockyear

Er, at our shop (always the fastest installations) we have a cheapo Sirius receiver connected to it's antenna via 150' of Quad-shielded RG-6. Oh, and the connections are B-spliced. We just cut the antenna wire and stripped it and spliced it.

Of course we'd never do this in the field, but it'll work in a pinch, and it shows that they're probably not too finicky. I'm doing something similar at home (always the second fastest installations) with about 50' of Quad RG-6.

Jeff