75 ohm TV cable to BNC ??? - Page 1
Forum section: electronics / beginners

author: KM4FER
author_rank: Regular Contributor
timestamp: February 18, 2015, 12:31:17 am
content: My wife likes her TV. She likes it a lot! So much so that she sprung for one of these satellite antennas for when we go "camping".I have to admit it's a pretty cool device. Just set it on the ground or a table with the connectors facing approximately North, connect a coax between the antenna and the set-top box and it will rotate and tilt and fine tune in three different satellites in about 5 minutes.Only problem is it uses those crappy TV connectors ( type F?) which can be a pain to get aligned and screwed on without cross threading.So, what would be the issues with changing the connectors to BNC? Can I just replace the panel mount connectors with BNC and buy a new cable? Or is there more to it?The 25ft cable that came with the antenna is unmarked but I have a 50ft RG59 that works just great so I assume we are talking 75 ohm impedance here. They do use the coax to supply DC to the antenna for motors so any kind of matching transformer is out.Thanks...earl...

author: dave_k
author_rank: Frequent Contributor
timestamp: February 18, 2015, 05:14:45 am
content: You can buy F to BNC adapters which would make the job about 1000 times quicker and simpler

author: AG6QR
author_rank: Frequent Contributor
timestamp: February 18, 2015, 05:41:55 am
content: Be aware that there are two varieties of BNC connectors. They come in 50 ohm and 75 ohm flavors. For TV, you probably want the 75 ohm ones, along with 75 ohm cable. That will give you the best impedance match, best power transfer, and lowest reflections. The 50 ohm ones are much more common on test equipment and ham radio gear.http://en.wikipedia.org/wiki/BNC_connector#mediaviewer/File:BNC_50_75_Ohm.jpgI assume the satellite antenna has a downconverter and amplifier in the box, so maybe things would work without being super careful about impedance matching, but...I agree that BNC is so much nicer than F connectors, especially for camping, where you set up and take down somewhat frequently.

author: babysitter
author_rank: Frequent Contributor
timestamp: February 18, 2015, 05:55:29 am
content: Be more aware of the Quick-F Connectors... basically, a spring-loaded F without a thread.Be even more aware that RG59 (Radio guide from WWII) is crappy, use a modern made-for-satellite cable with mesh and foil sheath.

author: vk6zgo
author_rank: Super Contributor
timestamp: February 18, 2015, 09:10:57 am
content: Quote from: babysitter on February 18, 2015, 05:55:29 amReaL RG59 isn't crappy---only the rubbish they sell these days masquerading as the real stuff!

author: macboy
author_rank: Super Contributor
timestamp: February 18, 2015, 02:36:25 pm
content: I had a quick look for F Male to BNC Female adapters and all of the ones I found seem to have a 50 Ohm BNC, which is utterly inexplicable since F connectors are only and always 75 Ohm.You will probably get better signal transfer with a press-fit F connector than by putting one of those improper 50 Ohm adapters in between. For a temporary installation, the press-fit type will work fine. Also, consider using good quality RG-6 rather than RG-59 which tends to be quite poorly made by comparison.

author: ConKbot
author_rank: Super Contributor
timestamp: February 18, 2015, 03:32:36 pm
content: Compression 75 ohm bnc to rg6 or rg6 quad shield connectors are available on Amazonhttp://www.amazon.com/200088-RG6-Compression-Connector-quadshield/dp/B000JKSKTEthose ones are for rg6q, but ones for normal rg6 or rg59 are available. Search YouTube and you can find videos showing you how to use a compression connector installation tool.Not the cheapest tool, but not bad as far as connector related tools go. Plus good compression connectors are waterproof, though not so much the bnc connectors.

author: KM4FER
author_rank: Regular Contributor
timestamp: February 18, 2015, 05:32:43 pm
content: OK, I went for the easy approach and ordered up some F to F quickconnect adapters. Don't know why I didn't think of those earlier.Thanks everybody.earl...