TV antenna Splitter + 75 Ohms caps + 24V PSU ? - Page 1
Forum section: electronics / general

author: djococaud
author_rank: Regular Contributor
timestamp: January 18, 2014, 11:36:09 am
content: Hi boys and girls !what's up ?Here's a question for you (I know there is already a topic on this but I can't find it with the search option. I must be too tired for this) :A friend of mine has this TV antenna setup :ANT------>RF AMP------>RF 1 to 4 passive splitter|------------>Amp PSU(24V)--------->TV 1|------------->TV 2|------------->Open (for another possible TV in the future)|------------->Open (for another possible TV in the future)This works fine, but when the weather is very bad, the HD stream is "glitchy". To help keeping a good signal integrity, I would like to put 75 Ohms RF caps on the 2 open ouputs of the splitter. I measured a cap (which is 75 Ohms as expected) and I found that there is no capacitor in series with the resistor. I'm afraid that the two caps could overload the 24V amp PSU (I don't know how many mA it can deliver...).What do you think guys ?

author: SeanB
author_rank: Super Contributor
timestamp: January 18, 2014, 12:17:01 pm
content: The splitter will typically only have a single output ( input) with DC pass, and it will be marked as such. The others will already have a DC blocking capacitor on them. If not you need a better splitter, they are cheap enough. If you are getting low signal with bad weather either the antenna is waving around in the wind, the signal is marginal or there is a lo level of signal and the cable loss is killing it.If the signal is acceptable in good weather realign the antenna to get best signal, and brace the antenna to stop it waving around. If the antenna is damaged replace it. Make sure all connections are both clean and tight on the F connectors. Make sure the cable is not full of water or corroded inside. Same with the in line amplifier, it must be in a waterproof box close to the antenna. Basic antenna installation tips, just with digital it is fine with poor performance up to a point where it falls off the cliff.

author: djococaud
author_rank: Regular Contributor
timestamp: January 18, 2014, 02:08:11 pm
content: As far as I've seen, the cables and connexions are in an extremely good condition, the antenna is well braced and oriented. Just a bit far from the TV broadcast station I think...I don't remember exactly if there was only one DC passing ouput on the splitter or all the ports, but I think it's the kind of those with only ferrites beads inside (so DC passing through all ports)... I will check it the next time I have to fix something on my friend's installation.The general question is : How many mA can be pushed by a 24V amp PSU...(I think I will need to look at the PSU the next time I will be there...)By the way, The weather is rarely bad here and it works very good 99% of the time...But, as every engineer, the lasting 1% bothers me !

author: SeanB
author_rank: Super Contributor
timestamp: January 18, 2014, 02:49:29 pm
content: If it is the cheap and nasty one with no caps buy a new one with the single cap in it, or open it up and add a 1n small ceramic capacitor to the wires from the ferrite bead to the other outputs and then it will work. Chip capacitor or a small leaded one works well enough at TV frequencies, the splitter is poor enough that a very short extra lead will have little added loss.

author: firehopper
author_rank: Frequent Contributor
timestamp: January 18, 2014, 03:16:07 pm
content: why not put the rf amp supply between the rf amp and the splitter? instead of feeding tv1 feed the rf splitter instead.

author: djococaud
author_rank: Regular Contributor
timestamp: January 18, 2014, 07:01:07 pm
content: Hi,Simply because there is no 230V in the attic, where the amp and the splitter areAnd it won't fix the problem of putting several rf caps on 24V...Since It's not My own installation, I won't change anything now (hey, I works...). I was just thinking of a possibe impovement, but as you said, the open ports of the splitter are not necessarily causing a lot loss...

author: GreyWoolfe
author_rank: Unknown
timestamp: January 18, 2014, 07:28:36 pm
content: I know it isn't quite the same thing, but the cable company here will terminate unused outlets on a splitter. We aren't using an amplifier as it isn't necessary. I would think that even a small loss can make a difference when the signal becomes marginal.

author: NiHaoMike
author_rank: Super Contributor
timestamp: January 19, 2014, 12:29:12 am
content: If the splitter is easy to get to, swap it for a 1 to 2. Every time you split a signal in half, you get a bit more than 3dB of losses.

author: Strada916
author_rank: Frequent Contributor
timestamp: January 19, 2014, 02:42:10 am
content: Quote from: NiHaoMike on January 19, 2014, 12:29:12 amWhat he said ^^^^You may look into a better antenna, something like a log periodic antenna, If it is not one already. Is the antenna up high? ie on a mast? If so change out the 4 way to a 2 way as you will be loosing signal from a 4 way as they are about 6dB loss where as a 2 way is about 3 dB.