Digital Radio Central - Sponsored by TSS Radio
  DRC Home Page DRC Forums Contact Us  
 
SIRIUS Backstage Forum
 
 
 
  Sirius Satellite Radio XM Satellite Radio iTunes/iPod Slacker Pandora  
 
 
FAQ Members List Calendar Search Today's Posts Mark Forums Read  
Go Back   SIRIUS Backstage Forum > >
Visit Digital Radio Central

Notices

Install Garage & Help Desk You've got the radio, now which cable goes where? Got questions about factory installed radios in your car? Ask any installation or help questions here and someone will get to you soon.

 
 
Thread Tools Display Modes
 
 
Old 02-29-2004, 12:21 PM   #1
lincoln30
Just Tuned In
 
Join Date: Feb 29, 2004
Location: Dallas, Tx
Posts: 2
lincoln30 is on a distinguished road
Default Newbie: Home antenna question...can the antenna be converted

to run over RG6 or Cat5 for a home installation of a Kenwood ST-7000S. I know that I can get a 50ft extention for the antenna cable that already has the SMB connectors on it, but I have a situation where the house is prewired with lots of extra RG6 and Cat5, running a new wire to the tuner location will be almost impossible. So can this be converted to some other connector/wire type and then reconverted to SMB at the tuner??? All the extra RG6 and Cat 5 is unterminated, so any connector that works with each cable type could be used for this.

This is for a friend who already has the Kenwood tuner and the Kenwood home antenna. He will send all this stuff back if we can't use the house wiring for this...he considers it unacceptable to have an exposed wire running over a window sill in his new house and I don't blame him since he already spend an extra $20K over what the builder offered on wiring this house for audio/video/computer/security.
lincoln30 is offline  
 
 
Old 03-15-2004, 10:41 PM   #2
vo1one
Mixologist
 
Join Date: Dec 27, 2003
Location: Mount Pearl, Newfoundland, Canada
Posts: 336
vo1one is on a distinguished road
Default

Your question made me think for a bit. The 8-wire ethernet cable is not an option. It is not meant to carry RF at all. I think the TV cable is your best option, given the two choices. SMB connectors and RG-174 coax cable are 50 ohm impedance. Standard TV coax cable such as RG-6 or RG-59 is 75 ohm impedance. Using 75 ohm cable with a 50 ohm antenna and a 50 ohm receiver creates an impedance mismatch and introduces loss. However, RG-174 is awful thin cable and is super lossy at 2GHz anywas. I think the figure is around 39.5 db loss per 100 feet! RG-6 on the other hand loses about 10db per 100 ft @ 2GHz IIRC. You mentioned 50 feet in your post so we'll divide those figures in half giving us about 20 db loss with Sirius' extension cable, and about 5 db loss with TV cable. That's a difference of 15 db. I believe this would make up for the loss resulting from an impedance mismatch.

You still need to convert the SMB Sirius connector to the F connector used on TV cable. I've never seen such an adaptor, but I've seen SMB to BNC cables used in networking equipment, and there's a connector which converts BNC to F. These extra connectors insert losses as well, but once again I believe the amount you gain by using better cable will make up for it.

I've never tried this myself, but theoretically I'd say it would work.
vo1one is offline  
 
 
Old 03-16-2004, 09:02 AM   #3
lincoln30
Just Tuned In
 
Join Date: Feb 29, 2004
Location: Dallas, Tx
Posts: 2
lincoln30 is on a distinguished road
Default

I emailed my question directly to Sirius tech support and they responded that the RG6 would work fine, but offered no help with the adaptor. If an SMB to BMC is truly readily available (premade) then I can terminate the RG6 with a BMC connector and avoid the conversion to F. I appreciate your insight on this and it gives me a little confidence that it will really work. Hopefully, I can find the adaptor or make one in the next few weeks and see if I can make it work.
lincoln30 is offline  
 
 
Old 03-16-2004, 11:00 AM   #4
Icing
Rocket Scientist
 
Join Date: Jan 29, 2004
Location: the urban northeast
Posts: 577
Icing is on a distinguished road
Default

Quote:
Originally Posted by lincoln30
Hopefully, I can find the adaptor or make one in the next few weeks and see if I can make it work.
They certainly exist, but whether you can find them at a retail-friendly supplier is another question. www.pasternack.com is more geared toward industry than retail, but it shows that the adapters exist. I'm not sure which genders you want, but all combinations are there: part numbers PE9132, PE9135, PE9136, PE9137.

Quote:
Originally Posted by vo1one
Using 75 ohm cable with a 50 ohm antenna and a 50 ohm receiver creates an impedance mismatch and introduces loss
Is the loss the only issue with the mismatch? Having 50ohm components on either end of a 75ohm cable will make standing waves on the cable. Could this be a problem for the receiver? Passband ripple, etc?

Quote:
Originally Posted by vo1one
giving us about 20 db loss with Sirius' extension cable
The extension cable (at least the one from Terk) includes an in-line amplifier to get around this problem.


Quote:
Originally Posted by lincoln30
I emailed my question directly to Sirius tech support and they responded that the RG6 would work fine
I guess they don't think it's a problem. It would certainly be amusing to try. Let us know what happens.
Icing is offline  
 
 
Old 03-16-2004, 01:09 PM   #5
vo1one
Mixologist
 
Join Date: Dec 27, 2003
Location: Mount Pearl, Newfoundland, Canada
Posts: 336
vo1one is on a distinguished road
Default

Try on eBay for the adapters. I looked on there quickly and found some premade cables with SMB and BNC connectors on them for about $13.

Quote:
Is the loss the only issue with the mismatch? Having 50ohm components on either end of a 75ohm cable will make standing waves on the cable. Could this be a problem for the receiver? Passband ripple, etc?
Well I think SWR would only be an issue with transmitting rather than receiving. Still, I think that standing waves would only be an issue if the coax somehow became part of the antenna. I'd say that provided the antenna has a proper ground plane that this wouldn't be an issue. Of course I could be wrong; I'm by no means a professional ;-)

Quote:
The extension cable (at least the one from Terk) includes an in-line amplifier to get around this problem.
Aha, interesting. I also find it interesting though the length of cable which is included attached to the antennas by themselves. It doesn't take a very long run of that super thin stuff to make a big dent in the signal. It would be interesting to see if someone with an antenna with a messed up cable would try cutting the bulk length of the cable, hooking it up and trying it in fringe signal areas to see what kind of difference it would make. Also, since it is powered, I'd think that it would be impossible to insert any kind of balun to correct the impedance mismatch.

Quote:
Hopefully, I can find the adaptor or make one in the next few weeks and see if I can make it work.
Yes, please do let us all know how you make out with it. I, for one, would be interested in knowing the results. A friend of mine is getting Sirius, and they were quite concerned about hiding the antenna wires. The solution as is is a Ramsey FM transmitter to transmit Sirius on the FM band to the stereo systems, but I never thought about using the TV cable, since their house is prewired for it, but there is no TV using it in that room. I might have a better solution for them now!
vo1one is offline  
 
 
 

Go Back   SIRIUS Backstage Forum > >


Digitalradiocentral.com




Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump


All times are GMT -5. The time now is 02:39 PM.
Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2020, vBulletin Solutions Inc.
Search Engine Optimisation provided by DragonByte SEO v2.0.39 (Pro) - vBulletin Mods & Addons Copyright © 2020 DragonByte Technologies Ltd.
All Content Copyright SIRIUS Backstage. All Rights Reserved. SIRIUS and registered trademarks are the property of SIRIUS Satellite Radio, Inc. The opinions posted on SIRIUS Backstage website and forums are those of the individual posters and/or this website and are not necessarily the opinions or positions of SIRIUS Satellite Radio, Inc.