WiFi, External vs Internal Antennas...

Consider External WiFi Antennas or USB WiFi Adapters and here is why:

WiFi transmitter power is restricted to 100mw as mandated by the FCC in America (and other countries as well) ~ and that's not much power at all... 

Also the WiFi Band is shared with many other devices from smartphones to laptops and tablets to remote sensors, actuators televisions and many more ~ so every milliwatt counts!

First consider a kitchen microwave oven ~ designed and shielded to keep 'microwaves' inside the oven.  "Metal" computer cases are "grounded" and shielded too and this creates similar conditions, where significant WiFi signals are trapped inside cases and this of course impacts WiFi range and signal patterns too! 

Electrically grounded cases also reflect Router WiFi signals away... blocking parts of WiFi from your cards and the antennas deep inside cases.  While there is access and openings for cards and drives, etc, a grounded metal cover usually blocks that opening too ~ and quite well!  So actually, almost ALL of your computer interior is "RF shielded"  (read your WiFi too) by your grounded metal case ~ and what case surface is not? 

It is truly amazing that internal WiFi cards perform as well as they do!

Laptops also have lots of metal around most WiFi cards... things like hard frames, batteries, hard drives and perhaps motherboards, etc... all impact WiFi signals and antenna patterns. 

Some manufactures help overcome these 'shields and reflectors' by installing WiFi antennas around the display edges thus making Antennas elevated and more 'exposed' to the outside world.  But most LCD screens have grounded full metal backs too. ..   

The tan cable shown contains Display  and camera wires... maybe the Mic too?  Under that tan wrap a grounded copper or foil wrap is often used over wires for more shielding.  A path (for WiFi Antennas) as far away from 'grounds' as possible is desired and no clue why the antenna was placed so close to that shielded tan cable?

A (white) WiFi wire antenna is shown wrapped around a LCD display:

So how does your WiFi get out and in? 

One computer mentioned was "Tempest" in design?  Two tiny WiFi antennas are shown on top, but they appear to be almost entirely 'clamped in metal'?  Better if the Antennas were mounted in sturdy, non-conductive plastic clips to allow almost full unrestricted exposure to the outside world and perhaps longer Antennas too with more gain? 

Can't fathom why metal was used because the clips appear to be 'grounded'?  It seems that most of the "WiFi" signals would reflect UP and to the sides from the clips ~ and the clips may be acting much like a  reflector in a flashlight?

True "TEMPEST" includes extreme standards that demand as much heavy shielding as necessary  TO KEEP  ALL hints of system RF INSIDE the case!  This includes cables, displays and keyboards too...

It would not be unusual to see TWO shield cages around some items inside Tempest computers and displays because there are many frequencies operating inside and none may escape.  Three layers of heavy armor braid plus copper foil around cables are quite common too ~ just a few examples of some measures taken to 'Tempest qualify'. 

Obviously all showing the importance of external antennas! 

Satellite antennas are external too even though they have lots of elevation working for them... get the picture? (pun intended).  (Do try a Google photo search for all Tempest items mentioned here, it is interesting)... 

I know of one incidence where high-end "QUALIFIED" TEMPEST COMPUTERS suddenly FAILED on the test range because detected RF Radiation was "too high"?  After LOTS of INTENSE and EXTENSIVE testing it was found that a VENDOR substituted non-conductive screws in part of his shipment and THOSE SCREWS caused RF leakage ~ and a TEMPEST violation! 

This required a huge audit of every system built after that screw shipment date!  *EACH system* HAD to be found and re-worked  and retested to certify ALL components met Tempest requirements!

THIS is ONE EXAMPLE WHY the "Tempest Program" is monitored so closely.  

Systems are measured from the "noise-floor" up to the first microvolt detected and across the entire radio spectrum.  So when a "Tempest" computer radiates RF (at all) beyond it's case ~ it is (probably) not true "Tempest" and is very similar to putting a Rolls Royce emblem on a Cadillac...  it just ain't so.

So "Tempest" IS a true "standard" and qualification that should never be claimed lightly... and Tempest is not just another seven letter word. 

FYI, "Tempest computers and systems" are demanded by most 'sensitive' agencies like the Pentagon and most other alphabet entities.  Qualifying Tempest "systems" are CERTIFIED, critically tested and constantly verified to meet or exceed all Tempest Standards!  Not just by the companies building Tempest Systems, but "focused" and critical government verification too. 

I apologize if I appear to digress, but shielding and WiFi are both partners and foes.

______________________

***SIMILAR TOPIC... also found on the Internet today (7-3-19):

WiFi (802.11b/g) is in the 2.4GHz range. The power output of the cards and routers is ~ 100mW. If you wanted to, you could unencrypt your network, claim it as a ham station (by setting your SSID to broadcast your callsign) and run all the way up to 1.5kW since the 2.4 GHz spectrum is shared with the amateur bands.

(most of the BOLD is mine for emphasis)...  Search for:  "typical wifi transmit power"  And yes, that is 1,500 WATTS!  Want to "own" WiFi channel 5 in your city?

YIKES!

Anthony