Normally, to power on a routerboard without an antenna, I would remove the radio so it wouldn't be damaged, and then install the radio when I'm ready to install the antenna.

On the RB411AR with the built-in radio, is there any safe way to power it on without an antenna? Or, do I always have to have an antenna connected?

Also, if the radio is disabled in the software, does it still require the antenna since it is still on the board and still receiving power?

This could also be an issue if someone ever upgraded to a better radio... what to do with the on-board radio without an antenna?

Thank you.

This is the first I've heard of the product. I would like if MT told more about it's radio's capabilities

Here is where I bought it:

https://www.roc-noc.com/product.php?pro ... age=2&js=n

The documentation is for the RB411 in general, not the radio part.

the radio is disabled at first boot. you dont need an antenna

http://www.routerboard.com/pdf/rb411ar.pdf

Low power cards usually do not burn out with no antennas plugged in.

I can't figure out from pdf the following: is the integrated radio supports 40Mhz, 10MHz and 5MHz bandwidth modes?

the radio is disabled at first boot. you dont need an antenna

True.

Plus, we always keep a 2.4/5GHZ N-connector rubber duck, and a 2.4/5GHZ Ufl-connector rubber duck antenna on the test bench for use in initial configurations and testing.

Use 50ohm terminator to test radio. Easy to use and don't transmit unwanted electromagnetic field.

I never knew that using the mini-pci card without a antenna was bad?

How does this cause damage?

if you are using high power card with out antenna (enable card and start to transmit something) you can blow out its power amplifier.

As mentioned before - radio by default is disabled - so you can use the unit as usual if radio is disabled. When you think of enabling it - better connect antenna.

Oh.

i just setup a system and tested it without antennas.

well i know for next time?

how do i test it then?

do i buy a small indoor antenna.

Taken from wikipedia in reference to standing wave ratio..(i.e. running a transmitter without proper loading)

Practical implications of SWR

The most common case for measuring and examining SWR is when installing and tuning transmitting antennas. When a transmitter is connected to an antenna by a feed line, the impedance of the antenna and feed line must match exactly for maximum energy transfer from the feed line to the antenna to be possible. The impedance of the antenna varies based on many factors including: the antenna's natural resonance at the frequency being transmitted, the antenna's height above the ground, and the size of the conductors used to construct the antenna.[1]

When an antenna and feedline do not have matching impedances, some of the electrical energy cannot be transferred from the feedline to the antenna.[2] Energy not transferred to the antenna is reflected back towards the transmitter.[3] It is the interaction of these reflected waves with forward waves which causes standing wave patterns.[2] Reflected power has three main implications in radio transmitters: Radio Frequency (RF) energy losses increase, distortion on transmitter due to reflected power from load[2] and damage to the transmitter can occur.[4]

Matching the impedance of the antenna to the impedance of the feed line is typically done using an antenna tuner. The tuner can be installed between the transmitter and the feed line, or between the feed line and the antenna. Both installation methods will allow the transmitter to operate at a low SWR, however if the tuner is installed at the transmitter, the feed line between the tuner and the antenna will still operate with a high SWR, causing additional RF energy to be lost through the feedline.

Many amateur radio operators believe any impedance mismatch is a serious matter.[1] However, this is not the case. Assuming the mismatch is within the operating limits of the transmitter, the radio operator needs only be concerned with the power loss in the transmission line. Power loss will increase as the SWR increases, however the increases are often less than many radio amateurs might assume. For example, a dipole antenna tuned to operate at 3.75MHz—the center of the 80 meter amateur radio band—will exhibit an SWR of about 6:1 at the edges of the band. However, if the antenna is fed with 250 feet of RG-8A coax, the loss due to standing waves is only 2.2dB.[2] Feed line loss typically increases with frequency, so VHF and above antennas must be matched closely to the feedline. The same 6:1 mismatch to 250 feet of RG-8A coax would incur 10.8dB of loss at 146MHz.[2]