Tx Power & Antenna Gain Advice/Suggestions

[dubstir]

I recently flashed my router to DD-WRT and now have the option to play with all the settings that cannot be change using stock firmware. Anyway, I have been searching for simple explanations regarding "standard" settings for the Tx Power (dBm) and Antenna Gain (dBi). I know that buying a higher gain antenna should produce longer/stronger signal, but I wish to the stock Linksys antennas and play around with the settings.

For my WRT1200AC, DD-WRT had the preset Tx Power to 30 and Gain to 0. Again, I am not sure if these values are poor, standard, or good. Any knowledgeable users out there, I'd appreciate the advice.

 

[Gabriel Pike]

The gain is dBm transmit power from the radio. You have the option of setting this between 0 and 30 for your router hardware chip. Depending on the gain of the antenna you use you add the transmit power of the radio to the added gain of the antenna and the additional gain on the firmware. Just remember louder is not always better. High gain can actually degrade connections close to the AP because it would be like someone screaming next to your ear. Do some testing by running speedtests from various places around your AP. If you have a PC there are several programs that will show power levels. I have used Xirrus WiFi Inspector in the past for PC. Android has several okay WiFi scanning apps. I use WiFi Analyzer. Physical obstructions and other WiFi can destroy your transmit and receive modulation. Play with the settings to see what works best overall in your location.

 

[DelJo63]

Background FYI: Power vs Gain

• Power, specifically RF Power is the Current x Voltage at the last RF amp. Firmware can manipulate it in various ways.
• GAIN applies to the antenna attached to the RF amp. Typically it is somewhat smallish and fixed per the make & model you purchase.

As we are using Ghz frequencies, RF radiation can be bounced or reflected to create directional gain w/o any direct connection to the radio. One example is two surfaces at right angles (can be manipulated) coated with aluminum foil placed so the external antenna is between the surfaces.

 

[dubstir]

Thank you both for the detailed information. I am still trying to understand this, for my best scenario. The DD-WRT has the TX at 30 and gain at 0. Linksys lists this for the antennas:

Antenna Gain (listed per Antenna if multiple):
2.4GHz: 2.5dBi (peak)
5GHz: 3.8dBi (peak)

If 30 is the max and the 2.4 band operates at 2.5dBi, should I not make the TX 27.5 instead of 30??? Considering here (and elsewhere) states these numbers get "added", or in my case subtracted.

 

[Gabriel Pike]

What are you trying to accomplish? If you set tx to 30 and internal gain to 0 then output is 32.5 dBm RSSI with 2.5dBi external gain.

 

[DelJo63]

Don't worry about matching things up - - use what works. Due to power consumption and heat, using the LEAST power will make the equipment last longer. GOOD designers use something called Power Factor and never use a PF=100%, but that means better components and heat control.

 

[dubstir]

What are you trying to accomplish? If you set tx to 30 and internal gain to 0 then output is 32.5 dBm RSSI with 2.5dBi external gain.

I am trying to gain knowledge and accomplish optimal settings within my house. As I've said, the default TX was 30. It's working pretty well most of the time, not accounting for other factors. Am I curious as to what others have their TX setting at.

 

[dubstir]

Don't worry about matching things up - - use what works. Due to power consumption and heat, using the LEAST power will make the equipment last longer. GOOD designers use something called Power Factor and never use a PF=100%, but that means better components and heat control.

Since the default was 30 and the range is 0-30, should I reduce down to 25 based on the longevity you mentioned?

 

[Gabriel Pike]

I am trying to gain knowledge and accomplish optimal settings within my house. As I've said, the default TX was 30. It's working pretty well most of the time, not accounting for other factors. Am I curious as to what others have their TX setting at.

So if you are working good leave it where it is. I have set several to 30 tx that have been running for years. On a few installations I have used larger antenna 9 - 12 dBi when longer range is required at a greater distance from the AP. You will have to test this physically though at your AP with a WiFi analyzer to get absolute results on the edge of your network. Other factors like interference and physical obstructions can have an effect on results. One way around this is to make sure your channel is set to where there is the least interference detected through a WiFi analyzer.

 

[Jollyriffic]

Optimal settings, you'll need monitoring tool to see what the "noise" on the wireless is.
There isn't a specific db that is perfect for any 1 user, but there are standards that the routers come with.
one easy way to test this stuff is by having an app on your cell that monitors all this. I cant name one off the top of my head because I've stopped using junk routers that perform like trash (most walmart/bestbuy if not all of them).
I got tired of buying every last router and having to adjust every last little thing to still have a mediocre router. I've bought everything from $500 and down from the top two stores.
wasn't till I finally did the smart thing and bought this https://www.amazon.com/dp/B01BMMK4HI/?tag=httpwwwtechsp-20 (actually have the previous generation) till I stopped having to do so much tinkering to try and get the routers I've bought to stop being worthless trash.
The first step in the best connection is the device you use. RouterOS makes ddwrt and tomato look like vtech for ages 4+
There are a ridiculous amount of settings you can fiddle with, but there's the basic settings that'll let you get up and running. Honestly don't even need to touch anything after that because of how rock solid RouterOS is.
Their routers look so basic, but they destroy everything on the market.

 

[Gabriel Pike]

Optimal settings, you'll need monitoring tool to see what the "noise" on the wireless is.
There isn't a specific db that is perfect for any 1 user, but there are standards that the routers come with.
one easy way to test this stuff is by having an app on your cell that monitors all this. I cant name one off the top of my head because I've stopped using junk routers that perform like trash (most walmart/bestbuy if not all of them).
I got tired of buying every last router and having to adjust every last little thing to still have a mediocre router. I've bought everything from $500 and down from the top two stores.
wasn't till I finally did the smart thing and bought this https://www.amazon.com/dp/B01BMMK4HI/?tag=httpwwwtechsp-20 (actually have the previous generation) till I stopped having to do so much tinkering to try and get the routers I've bought to stop being worthless trash.
The first step in the best connection is the device you use. RouterOS makes ddwrt and tomato look like vtech for ages 4+
There are a ridiculous amount of settings you can fiddle with, but there's the basic settings that'll let you get up and running. Honestly don't even need to touch anything after that because of how rock solid RouterOS is.
Their routers look so basic, but they destroy everything on the market.

I agree Mikrotik Router OS is the best there is but keep in mind it is not easy to use for beginners in networking. I use the MT 2011 with Unifi AC-LR but none of this is what I would call easy to setup by the average user.

 

[DelJo63]

There's a good explanation of dbm and db in the wiki

 

[dubstir]

I am toying around. The Settings are TX 30 and dBi 2. The attached screenshot shows the current output from DD-WRT at 60 ft away and outside my house with 2 walls in the way. The first client is my iPhone.

I have been using the SpeedSmart on my iPhone for many years. It's tough to decipher if the app is measuring the internet connection coming to the router or measuring bandwidth to my iPhone. I say this because the closer I get to the physical router, the faster the MBps get and vice versa. I was under the impression for all these years that these "apps" strictly measure internet speed from your ISP.