Re: DIY CNC Router Uses Chains The Right Way
Cinty Bolner
Information on antenna chains has been difficult to find, (google seems to think I want to search for antenna gain). I found this IEEE article which defines what they are, but it doesn't explain how I'd use that information when configuring a device.
I installed DD-WRT on my TP-Link WDR3600 and it says I have two physical radio interfaces. Based on the options in the network mode dropdown menu, I assume that one is the 2.4Ghz radio and the other is the 5.0Ghz radio. However, both have the option to select the TX and RX antenna chains (either 1 or 1+2). What is an antenna chain, what does 1 / 1+2 mean, and how would I be able to figure out the correct setting for my device?
Short version: Using both radio chains is potentially twice as fast as just using one. You only want to limit yourself to a single radio chain if you're doing a long-distance outdoor link and trying to save money on antennas, or perhaps for certain troubleshooting situations.
Long version:
802.11n introduced the concept of MIMO (Multiple Ins, Multiple Outs) to Wi-Fi networking. MIMO radios use multiple radio chains working in parallel to transmit twice as much data at a time as a single radio could do.
You always want both chains in operation for the fastest rates. With just one chain, you're not doing MIMO, you just doing traditional SISO (Single In, Single Out), so you're not much better off than 802.11a or 802.11g. A and G used 20MHz wide channels and got a maximum PHY rate of 54Mbps. If you use those same 20MHz-wide channels with 802.11n and limit yourself to SISO (a single radio chain), your maximum PHY rate only goes up to 72.2Mbps. This increase is only because 802.11n added a couple new higher-rate modulation schemes than A/G had.
The only time you'd want to disable a radio chain is if you were trying to do a long-distance outdoor link, and didn't have an antenna rig that could provide enough separation between your two radio/antenna chains. If you didn't want to have to mount twice as many antennas on your antenna masts at each end of the link, and have them spaced far enough apart that they don't interfere with each other, then you might opt for a SISO link for cost/simplicity sake, even though it means only half the throughput (150 Mbps max PHY rate instead of 300).
MIMO* introduces a new paradigm in RF systems design. MIMO-capable radios actually perform better within a multipath-rich environment. A MIMO system has multiple radio chains each of which is a transceiver with its own antenna. A radio chain refers to the hardware necessary for transmit/ receive signal processing. A MIMO radio can then apply several techniques to enhance signal quality and deliver more throughput. It is this ability to add signal components from multiple antennas that differentiates MIMO access points from traditional access points that use antennas in a diversity configuration. An access point with antenna diversity selects signal components from the antenna that provides the best signal performance and ignores the other antenna.
For beam-forming (directing a transmission without moving the antenna), signals from multiple antennas are actually mixed in a special way to adjust for the angle the signal was received from. Since the antennas are at a known position, the antenna RF chains can be configured to mix the signals constructively or destructively depending on where the signal is expected to arrive from. In this case, the "chain" analogy kind of breaks down, because really it's an array of components connected both in series and in parallel.
If the antenna's at one end of a chain, what's at the other end? Well, once the signal is conditioned, there's often a second set of transformations to handle something called demodulation, and a third set of digital components for decoding - possibly (many) others. Often times the components for these things are sort of shared by other parts of the radio, so "chains" of signal sort of converge on them and merge / split. Note that some radios include analog-to-digital conversion in the antenna RF chain, but this was historically done after things like up/down converting, demodulation, and additional amplification/filtering.
Now that you (hopefully) understand what an RF chain is, you might soon be confused by the term "radio" (transceiver). A device like a wireless access point is part radio transceiver part router (among other things) - the parts attached to the antenna are the radio, and the farther you get from the antenna, the less likely it is to be part of the radio. Also, there are sometimes multiple radio transceivers (e.g. for 802.11a), and sometimes one transceiver does double-duty (e.g. 802.11n + 802.11ac).
Finally, the number associated with each chain doesn't seem to follow a convention, so just figuring out which antenna is "1" is difficult. Additionally, the set of chains used for tx (e.g. 1 + 2) are sometimes the same set used for rx (1 + 2), and sometimes they're a different set (e.g. rx 1+2 / tx 1+3).
There are a million and one ways to build your own CNC router, depending on your tastes, budget, and application, your design choices will differ accordingly. [Steve Tyng] was well aware of this when undertaking his project, and built the machine that made sense for him.
When it came time to build the axes, there was plenty of roller chain on hand. Chain is usually passed up for options such as timing belts or ballscrews in the CNC community, as it tends to stretch over time and offers poor accuracy. However, [Steve] took stock of the drawbacks of the method, and made efforts to overcome these weak points in the design. The Y and X axes were specially designed to keep the chain supported along its length. This helped avoid the problem of long drooping chains and poor tension.
Cool design but why is it so noisy?
Maybe your motor controllers?
Chains have typically frowned upon not due to jumping teeth but backlash generally there is a little play in chains and sprockets.
As a newbie to the CNC router community , I soon learned what happens when the router power cable gets caught on a high profile item. I decided to implement an extra drag chain assembley on the right Y axis, like the Shapeoko Pro.
And of course, drag chain which I got off of Amazon. I chose a larger size than is installed by Carbide3D as I wanted room for a router power cable and maybe other cables such as a long length shielded USB or USB-C cable to deliver signals to accessories via the Z axis.
On the outer side of the right Y axis, place the larger chain support bracket in place and mark with a pen, two bold holes through the bracket slots. You can either drill 4mm holes in the aluminium frame and tap, or use more double sided tape to hold the larger bracket in place.
A) cut the power cable to the router and replace the cut with some IEC power connectors. Male plug end on the router and female flag end from the drag chain. This makes it easy to remove the router from the collar and put in some other device.
I have read that I can connect a second router by turning off DHCP and NAT, but I want the second router to assign DNS (I'm using it as an access point for my kids, and will use OpenDNS family service to help prevent inappropriate web pages).
One of your routers will be connected to your ISP. This router needs to be assigned the internal LAN IP 192.168.1.1, and hand out DHCP addresses on something like 192.168.1.2 through 192.168.1.50. Call this router Router A.
Connect a cable from one of the LAN ports on router A to the WAN port on router B. Set Router B's WAN IP address to 192.168.1.51, and its internal LAN IP to 192.168.2.1. Tell it to hand out DHCP addresses on something like 192.168.2.2 through 192.168.2.50. Set the DNS settings on this router's DHCP to what you want for your kids.
Router A should work normally. If you have things you need accessible via the Internet, make sure it's connected to Router A and setup your port forwarding on Router A like you would on any normal router.
Set the DHCP ON for both routers. This is particularly nice for wireless connections when Router 1 is slow, you can flip the connection to Router 2. For hardwired connections, you can setup a batch file to flip the network settings to reflect the proper IP Address and default gateway. The method you've demonstrated forces everything to be routed through Router 1 unless you manually assign IPs.
a. Set IP to 192.168.0.2 (default gateway2)(keep it on same subnet 192.168.0.xxx if you want connections on both routers to see each other, if you want connections to be isolated on independent networks put it on 192.168.1.xxx or 192.168.2.xxx)
Short answer: no, you cannot bridge two DHCP servers together. Computers that join the network would get an address from whichever router that responded first, and the two routers would not check in on each other.
Longer answer: you could make one router a DHCP client of the other. This would make a network inside your network, and you could control what the inside subnet would see. Downside is the inner network would have NAT running twice, but you'd have a "private" network.
You can absolutely do this. I have a wireless AC router with the default gateway being 10.0.0.1 and this is my main or master router. I have another router that's connected from a powerline adapter wired into the second router. The second router has an IP address range of the standard 192.168.1.1 address block and although I assigned my second router a static IP from the master router it would work either way. I have router RIP enabled only because of other things I do behind the double NAT.That slave router model should be fine and you would have the second router allocating IP addresses and you shouldnt have a problem using DYNDNS or OpenDNS. Sometimes depending on Hardware its kind of trial and error. You could also have the second router in the same subnet as the master router by creating a different segment within that ip network. i.e.Master 192.168.1.2-192.168.1.100 and slave 192.168.1.101-192.168.1.200. Some routers may give you issues if you use a VPN to encapsulate your data and ive noticed the packet headers may contain some false data but everything should work ok with a little work and configuration.Following the answer given above will work but doing it with both routers dhcp enabled and segmenting the network will give you more security and better network minipulation.
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