[LAU] MIDI over wifi on Linux, revisited

[Gene Heskett]

On Monday 04 January 2016 19:49:44 Jonathan E. Brickman wrote:

> On 01/04/2016 01:14 PM, Chris Caudle wrote:
> > I used to have problems with the WiFi to my wife's laptop slowing
> > greatly if we were heating anything in the kitchen microwave. I
> > can't conceive of using something that fragile in a concert
> > environment.
>
> I'll have to think that there are lots of factors; we used to have an
> early 1980's microwave, huge and powerful, about six feet away from
> our WAP and there was never a problem.  Maybe the laptop's chipset was
> sensitive in unusual ways, or something.

If your microwave interferes with the wifi. there is no way in hell it 
will pass an rf leakage test. If the door is sprung a teeny bit, or 
isn't closing because of cooked on spilled food, it can leak, a lot.

I am a retired television engineer, and one of the things we have to do 
every 5 years is rent a Holiday (sp?) certified broadband leakage 
measureing meter and survey all around our transmitters to show the FCC 
that its safe for humans to work around.  The field strength allowed is 
equ to 10 milliwatts per cubic centimeter of flesh for continuous 
exposure a 90MHz.  That is actually quite strong, but in the range of 
wifi or a microwave oven, both of which are adjacent in the 2.4 and 2.5 
GHz bands ISTR its dropped to 1 milliwatt per cubic centimeter.  Our 
elderly GE transmitter on channel 5 passed, no problem.

The engineer at WOAY is where I sent the meter that we have to use, also 
had to do his renewal. So when he unpacked it, checked the batteries and 
turned it on, then walked into the lunch room for a warmer cup of 
coffee, leaving it on the table 10+ feet from the microwave still turned 
on.  Putting the cup in the oven and setting it for one minute, as soon 
as the magnetron reached operating temps, typically not more than 1 
second, the alarm on the meter went off.  Scrambling back to the table, 
it was offscale and didn't come back to zero until the microwave timed 
out & shut off.  He looked at the door, and one hinge was bent so one 
edge had a gap of about 5 sheets of copy paper width.  Since it was a 
vendors unit, you can guess where the next phone call was to, and he had 
a brand new one an hour later, which was invisible to the meter.

Moral is, it doesn't take much to make one leak rf like a fire hose.

That was far enough down in the used calendar pile that we had no wifi, 
else I expect we would have been alerted sooner.  Now almost everyone is 
using it, so we've all a built in to the house alarm when the wifi dies 
when the coffee is cold and being warmed up.

> And I have to agree, 2.4GHz wifi is dangerous right now...but not
> really with directional antennas, banks are still using 2.4GHz for
> ATMs across quite a lot of space outdoors, with directionals.  And
> there's always 5GHz...IR...UV...visible...:-)
>
> The motivation for me is simple.  I have worn out too many USB ports
> to be happy about it!!!  I have thought of trying to throw USB over
> three 1/4" phone jack cables (using the _extremely_ __durable
> traditional Switchcraft hardware), but have thought that I would
> probably run into impedance, isolation, or something else hidden in
> USB.  I have also spent quite a lot of time looking for adapter combos
> which would let me use microUSB for the common detachments, but it
> seems that the parts builders just haven't had me in mind.


Cheers, Gene Heskett
-- 
"There are four boxes to be used in defense of liberty:
 soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author)
Genes Web page <http://geneslinuxbox.net:6309/gene>