# Attenuators vs Splitters



## Humble (Jul 21, 2010)

If I take a 4 way splitter and cap three of the outlets and use the fourth as a pass through to my Tivo Roamio Plus, what is the reduction in DB's compared to an attenuator?


----------



## hefe (Dec 5, 2000)

Humble said:


> If I take a 4 way splitter and cap three of the outlets and use the fourth as a pass through to my Tivo Roamio Plus, what is the reduction in DB's compared to an attenuator?


An attenuator will attenuate by its rating. They can be built for different values. Could be a 3 dB attenuator...6 dB, 10 dB...whatever the rating is.

A 4 way splitter will attenuate the signal because of 2 things. The splitting loss, actually dividing the power between the ports, and the insertion loss...the loss caused by the signal just passing through the device itself. A 4 way splitter will cause 6 dB of loss due to the splitting, and the insertion loss depends on the quality of the splitter. You can probably assume about 1 dB or so, although it may be less. So, around 7 dB is a good estimate.


----------



## Humble (Jul 21, 2010)

hefe: Thank you for the very clear explanation. It has been driving me nuts.


----------



## Marc (Jun 26, 1999)

If the splitter doesn't have anything else plugged into it, though, will it still provide the 6 dB attenuation?


----------



## JoeKustra (Dec 7, 2012)

Humble said:


> hefe: Thank you for the very clear explanation. It has been driving me nuts.


I like the brand "Extreme". They have the signal loss written on their splitters. 1 to 2 is 3.5dB, 1 to 4 is 7.5dB.


----------



## JoeKustra (Dec 7, 2012)

Marc said:


> If the splitter doesn't have anything else plugged into it, though, will it still provide the 6 dB attenuation?


Yes, and you should terminate unused ports.


----------



## hefe (Dec 5, 2000)

Marc said:


> If the splitter doesn't have anything else plugged into it, though, will it still provide the 6 dB attenuation?


It will, although in a perfect world and a perfect installation, any unused ports should be terminated. Not just "capped." A terminator matches the impedance that the port is expecting. Without a terminator, you can get signal reflecting back from the unterminated ports into the source and affect the isolation between the splitter ports. Possibly even cause interference on the original signal.

So if the intent is just to reduce the signal on a single cable, an attenuator is the device to use if possible. But I've used unterminated splitters myself in the house to split to a couple TVs. I wouldn't do it in a communication system where we need to recover every last bit of signal possible.


----------



## waynomo (Nov 9, 2002)

Do you want attenuation? 

If not, sounds like trying to use the splitter to to connect 2 shorter coax cables together. They make a simple female female coax connector. They are really inexpensive. Would that be a better solution?


----------



## hefe (Dec 5, 2000)

JoeKustra said:


> I like the brand "Extreme". They have the signal loss written on their splitters. 1 to 2 is 3.5dB, 1 to 4 is 7.5dB.


Yup...so that's 3 dB every time you halve the signal + 1.5 dB insertion loss.


----------



## Humble (Jul 21, 2010)

hefe: When I said the unused outlets were capped, I mean the cap is a silver cover with a pointy end. Does that "terminate" the outlet? To one of the other commentators, I was looking to attenuate, not split my signal.


----------



## hefe (Dec 5, 2000)

Humble said:


> hefe: When I said the unused outlets were capped, I mean the cap is a silver cover with a pointy end. Does that "terminate" the outlet? To one of the other commentators, I was looking to attenuate, not split my signal.


Does it have a center conductor? A terminator has a center conductor, like this.


----------



## Humble (Jul 21, 2010)

They do have the center conductor and look exactly like the ones on the right. Thanks again.


----------



## Humble (Jul 21, 2010)

hefe said:


> Yup...so that's 3 dB every time you halve the signal + 1.5 dB insertion loss.


Last question, hopefully. I ended up buying a 16db attenuator and putting it on the back of the Tivo Roamio Plus and hooking it up to the Frontier Fios cable (used to be Verizon Fios). When I started, my signal strength was 99-100% and my SNR was 38-41. After putting the 16db attenuator on, my signal strength is 93-98 and my SNR is 37-39. My picture is now fantastic and I get zero corrected and uncorrected errors.

Question? Why doesn't the signal strength fall 16db's and the SNR ratio fall slightly further? Thanks in advance and I will try not to become a pest.


----------



## unitron (Apr 28, 2006)

Humble said:


> They do have the center conductor and look exactly like the ones on the right. Thanks again.


If you check them with an ohmmeter and get a reading in the neighborhood of 75 Ohms, then you've got the right thing, because they're supposed to put a 75 Ohm load from the center wire to ground.


----------



## JoeKustra (Dec 7, 2012)

Humble said:


> Last question, hopefully. I ended up buying a 16db attenuator and putting it on the back of the Tivo Roamio Plus and hooking it up to the Frontier Fios cable (used to be Verizon Fios). When I started, my signal strength was 99-100% and my SNR was 38-41. After putting the 16db attenuator on, my signal strength is 93-98 and my SNR is 37-39. My picture is now fantastic and I get zero corrected and uncorrected errors.
> 
> Question? Why doesn't the signal strength fall 16db's and the SNR ratio fall slightly further? Thanks in advance and I will try not to become a pest.


Perhaps you shouldn't trust everything shown by the diagnostics? It has been demonstrated by many that the signal level never goes above 100. That's why a number in the low 90s is better than 100. The SNR seems pretty good though. My TiVo Roamio, Premiere, TV and cable modem all have a SNR of 35-36dB from one cable feed. Given that the premiere has a signal level of 75 and the Premiere is 90, I'm not sure if I trust the Roamio. Also, the error counters of the Premiere increment when I have noise, as does the cable modem. The Roamio displays the noise on the screen but the counters on all four tuners are stuck at zero.

You're not a pest.


----------



## hefe (Dec 5, 2000)

Humble said:


> Last question, hopefully. I ended up buying a 16db attenuator and putting it on the back of the Tivo Roamio Plus and hooking it up to the Frontier Fios cable (used to be Verizon Fios). When I started, my signal strength was 99-100% and my SNR was 38-41. After putting the 16db attenuator on, my signal strength is 93-98 and my SNR is 37-39. My picture is now fantastic and I get zero corrected and uncorrected errors.
> 
> Question? Why doesn't the signal strength fall 16db's and the SNR ratio fall slightly further? Thanks in advance and I will try not to become a pest.


That's because the number you are seeing on the screen is not an RF strength measurement. It is a quality number that the TiVo calculates internally, probably a combination of factors including strength and bit error rate on a scale that ends at 100.


----------



## Humble (Jul 21, 2010)

Thanks to the last two posters. I get it.


----------



## Humble (Jul 21, 2010)

unitron said:


> If you check them with an ohmmeter and get a reading in the neighborhood of 75 Ohms, then you've got the right thing, because they're supposed to put a 75 Ohm load from the center wire to ground.


unitron: If you saw my question re the "pointy end" on the terminator you can assume I probably don't own or know what an ohmmeter is. It did give me a great laugh and thank you for your guidance.


----------



## JoeKustra (Dec 7, 2012)

Humble said:


> unitron: If you saw my question re the "pointy end" on the terminator you can assume I probably don't own or know what an ohmmeter is. It did give me a great laugh and thank you for your guidance.


I guess if you were asked about the difference between resistance and impedance you would have busted a gut laughing too.


----------



## Humble (Jul 21, 2010)

JoeKustra said:


> I guess if you were asked about the difference between resistance and impedance you would have busted a gut laughing too.


I was a CPA for 35 years. I didn't say I was bright! If someone asked me the difference between resistance and impedance, they might have enjoyed the blank stare they would receive.


----------



## skid71 (Mar 20, 2013)

@Humble
Can you post a link (if purchased online) of the attenuator you purchased?
I'd like to ensure I'm purchasing the right thing.

I would have that blank stare as well if asked about resistance/impedence.


----------



## Humble (Jul 21, 2010)

skid71 said:


> @Humble
> Can you post a link (if purchased online) of the attenuator you purchased?
> I'd like to ensure I'm purchasing the right thing.
> 
> I would have that blank stare as well if asked about resistance/impedence.


Ordered on Amazon. Type in 16 db attenuator and it should take you to the site. I ordered a 10 db and it didn't do the trick. The 16 db did. It came in two days with free shipping but the shipping charge was built in to the price of the product. I think the brand was called Steren but I am not positive.

Shipment Details

http://www.amazon.com/s/ref=nb_sb_n...lectronics&field-keywords=16db attneuator pad

16dB InLine Attenuattor Pad 
Sold by CablesOnline 
Condition: New

Steren 10dB Inline Attenuator Pad 
Sold by CablesOnline 
Condition: New


----------



## break19 (May 21, 2015)

Marc said:


> If the splitter doesn't have anything else plugged into it, though, will it still provide the 6 dB attenuation?


Yes. Splitters are passive, not active, and the signal is still split inside the splitter, regardless of where it goes after the split..


----------



## mstrumpf (Jul 29, 2010)

Humble said:


> I was a CPA for 35 years. I didn't say I was bright! If someone asked me the difference between resistance and impedance, they might have enjoyed the blank stare they would receive.


Resistance is futile, Impedance is a season of Star Trek: The Next Generation.


----------



## aaronwt (Jan 31, 2002)

Humble said:


> Ordered on Amazon. Type in 16 db attenuator and it should take you to the site. I ordered a 10 db and it didn't do the trick. The 16 db did. It came in two days with free shipping but the shipping charge was built in to the price of the product. I think the brand was called Steren but I am not positive.
> 
> Shipment Details
> 
> ...


I just installed a 6dB attenuator I got from Amazon.

http://www.amazon.com/gp/product/B004C5P9MI?psc=1&redirect=true&ref_=oh_aui_detailpage_o00_s00

I did not realize I was having some uncorrected error issues with some channels on FiOS until I upgraded to a 5TB drive in my Roamio Pro. I had transferred a bunch of recordings to a PC before the drive upgrade. And when I went to transfer them back, some had issues transferring. And the ones that had issues were from the same channels. Which when I looked all had uncorrected errors on the Diagnostics page. And to fix I had to run them through VideoReDo and use the stream fix? option.

But since installing the 6dB attenuator a few days ago I have not seen any uncorrected errors show up on the diagnostics page from the channels that were having issues.


----------

