Groups > sci.electronics.design > #446472

Re: Blocking RF from intentional radiators

From	Don Y <blockedofcourse@foo.invalid>
Newsgroups	sci.electronics.design
Subject	Re: Blocking RF from intentional radiators
Date	2017-02-06 14:39 -0700
Organization	A noiseless patient Spider
Message-ID	<o7aqbi$p5n$1@dont-email.me> (permalink)
References	(1 earlier) <o79o8s$lq9$1@dont-email.me> <o79v02$dig$1@dont-email.me> <jg3h9cl6qf0931uujhcc27n481ekj8rvh1@4ax.com> <o7aj8t$s67$1@dont-email.me> <JtGdndyW17ljRAXFnZ2dnUU7-fednZ2d@giganews.com>

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On 2/6/2017 1:18 PM, Tim Wescott wrote:
> On Mon, 06 Feb 2017 12:38:47 -0700, Don Y wrote:
>
>> On 2/6/2017 7:55 AM, Jim Thompson wrote:
>>> On Mon, 6 Feb 2017 06:52:45 -0700, Don Y <blockedofcourse@foo.invalid>
>>> wrote:
>>>
>>>> On 2/6/2017 4:57 AM, piglet wrote:
>>>>> On 06/02/2017 07:40, Don Y wrote:
>>>>>> How can I economically, simply and reversibly inhibit the RF link to
>>>>>> a GDO?  Short the antenna?  Slip it in a grounded copper tube?  etc.
>>>>>
>>>>> Isn't the whole point of grid dip oscillators that they are mild
>>>>> radiators.
>>>>> What is the desired action?
>>>>
>>>> Garage Door Opener
>>>
>>> My garage door opener has a slide switch at the inside wall control
>>> that locks the opener from RF operation.
>>
>> That would be ideal.  But, if the receiver is in the power head, then
>> you'd not be able to purchase such a switch as an aftermarket item to
>> achieve the desired functionality -- you'd need another control lead or
>> other means of encoding the switch's position onto the signal pair that
>> normally actuates the opener.
>>
>> As the Rx antenna is typically just a short length of wire protruding
>> from a hole in the case, its hard with JUST access to it to ensure NO RF
>> makes it into the receiver (e.g., if the user stood directly below the
>> opener and activated his remote).
>
> If it's got a plastic case, then you probably need to wrap the whole
> thing in metal.
>
> Maybe put a tin can over the antenna, grounded to the power head casing?
> I give you no guarantees, but it may work.  If you're lucky you'll find
> something that telescopes well enough to make nice contact so you can
> just reach up and slip it over.
>
> My experience with RF and cheap devices is that it doesn't work when you
> want it do, but it _will_ reliably work when you'd really rather it
> didn't.

That's exactly the problem I've been facing with my experiments.
The things that you *think* would work all seem to fall down
in unpredictable ways.

Tuck the antenna into the case so none of it is "exposed".  Nope.
Too much of the case (cover) is plastic.

Ground the (loose end of the) antenna.  Nope.

Slip a narrow dia copper pipe (like a soda straw) over the antenna,
threading it carefully into the hole in the case through which it
protrudes, then ground that.  Nope.  (too much of a "service loop"
within that can't be adequately shielded).

Encase the opener in a metal shield.  Nope.  Chain/screw drive needs
a means of getting out of the enclosure along with power cord
and *wired* connections (wall mounted pushbutton, infrared detector)
getting in.  (also, looks like shit!  This was just an exercise to see
how extreme I would have to get to block the signal)

Discipline yourself NEVER to use the remote (i.e., HIDE it) still
leaves that function active.

[Our old opener had a 12 or 14b code -- DIP switch.  When we moved in, I
set it to something "random" -- for certain interpretations of "random".
Neighbor replaced their opener in roughly the same timeframe.  And,
wondered why *his* garage door kept acting of its own accord.  Until,
one day, he watched us pulling into our driveway and HIS door CLOSING
coincident with ours OPENING!]

[A *really* old opener we had some 40 years ago would trip when we
vacuumed the bedroom floor -- located immediately ABOVE the opener]

Unfortunately, the "wireless remote" is considered such an ESSENTIAL aspect
of a garage door opener that it never occurs to the folks designing the
receiver(s) to include a provision that disables the remote.  E.g., set
code to "INVALID".

This is true of many wireless devices -- that also have valid functionality
with the wireless aspect disabled.  Try to give a stranger directions on
how to turn off the WiFi on their router:  what make/model?  what is the
downstream IP address of the router?  does it have a web-enabled management
console?  do you know the password?  etc.  At least many laptops have discrete
SWITCHES to enable/disable the wireless without resorting to BIOS settings
and "apps"!  (of course, these aren't standardized so its still a challenge
to come up with generic instructions...)

Thread

Blocking RF from intentional radiators Don Y <blockedofcourse@foo.invalid> - 2017-02-06 00:40 -0700
  Re: Blocking RF from intentional radiators whit3rd <whit3rd@gmail.com> - 2017-02-06 00:56 -0800
    Re: Blocking RF from intentional radiators Don Y <blockedofcourse@foo.invalid> - 2017-02-06 02:19 -0700
      Re: Blocking RF from intentional radiators Robert Baer <robertbaer@localnet.com> - 2017-02-08 20:22 -0800
  Re: Blocking RF from intentional radiators piglet <erichpwagner@hotmail.com> - 2017-02-06 11:57 +0000
    Re: Blocking RF from intentional radiators "Tim Williams" <tiwill@seventransistorlabs.com> - 2017-02-06 06:51 -0600
    Re: Blocking RF from intentional radiators Don Y <blockedofcourse@foo.invalid> - 2017-02-06 06:52 -0700
      Re: Blocking RF from intentional radiators Jim Thompson <To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> - 2017-02-06 07:55 -0700
        Re: Blocking RF from intentional radiators Don Y <blockedofcourse@foo.invalid> - 2017-02-06 12:38 -0700
          Re: Blocking RF from intentional radiators Tim Wescott <seemywebsite@myfooter.really> - 2017-02-06 14:18 -0600
            Re: Blocking RF from intentional radiators Don Y <blockedofcourse@foo.invalid> - 2017-02-06 14:39 -0700
              Re: Blocking RF from intentional radiators Jon Elson <jmelson@wustl.edu> - 2017-02-06 17:10 -0600
                Re: Blocking RF from intentional radiators Don Y <blockedofcourse@foo.invalid> - 2017-02-06 17:06 -0700
                Re: Blocking RF from intentional radiators Jasen Betts <jasen@xnet.co.nz> - 2017-02-07 04:12 +0000
              Re: Blocking RF from intentional radiators Jasen Betts <jasen@xnet.co.nz> - 2017-02-07 04:05 +0000
          Re: Blocking RF from intentional radiators Jim Thompson <To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> - 2017-02-06 14:56 -0700
            Re: Blocking RF from intentional radiators Don Y <blockedofcourse@foo.invalid> - 2017-02-06 15:18 -0700
        Re: Blocking RF from intentional radiators Robert Baer <robertbaer@localnet.com> - 2017-02-08 20:41 -0800
      Re: Blocking RF from intentional radiators Robert Baer <robertbaer@localnet.com> - 2017-02-08 20:32 -0800
    Re: Blocking RF from intentional radiators Phil Allison <pallison49@gmail.com> - 2017-02-06 06:39 -0800
  Re: Blocking RF from intentional radiators John Larkin <jjlarkin@highlandtechnology.com> - 2017-02-06 08:28 -0800
  Re: Blocking RF from intentional radiators Jeff Liebermann <jeffl@cruzio.com> - 2017-02-06 09:23 -0800
    Re: Blocking RF from intentional radiators Lasse Langwadt Christensen <langwadt@fonz.dk> - 2017-02-06 09:30 -0800
    Re: Blocking RF from intentional radiators Don Y <blockedofcourse@foo.invalid> - 2017-02-06 11:52 -0700
      Re: Blocking RF from intentional radiators Jeff Liebermann <jeffl@cruzio.com> - 2017-02-06 11:31 -0800
        Re: Blocking RF from intentional radiators Don Y <blockedofcourse@foo.invalid> - 2017-02-06 12:49 -0700
          Re: Blocking RF from intentional radiators John S <Sophi.2@invalid.org> - 2017-02-06 14:07 -0600
          Re: Blocking RF from intentional radiators "nuny@bid.nes" <Alien8752@gmail.com> - 2017-02-06 12:09 -0800
            Re: Blocking RF from intentional radiators Don Y <blockedofcourse@foo.invalid> - 2017-02-06 13:37 -0700
              Re: Blocking RF from intentional radiators "nuny@bid.nes" <Alien8752@gmail.com> - 2017-02-06 14:35 -0800
                Re: Blocking RF from intentional radiators Don Y <blockedofcourse@foo.invalid> - 2017-02-06 15:59 -0700
          Re: Blocking RF from intentional radiators Jeff Liebermann <jeffl@cruzio.com> - 2017-02-06 17:56 -0800
      Re: Blocking RF from intentional radiators George Herold <gherold@teachspin.com> - 2017-02-06 12:03 -0800
        Re: Blocking RF from intentional radiators Don Y <blockedofcourse@foo.invalid> - 2017-02-06 13:31 -0700
          Re: Blocking RF from intentional radiators George Herold <gherold@teachspin.com> - 2017-02-06 13:29 -0800
            Re: Blocking RF from intentional radiators Lasse Langwadt Christensen <langwadt@fonz.dk> - 2017-02-06 13:32 -0800
            Re: Blocking RF from intentional radiators Don Y <blockedofcourse@foo.invalid> - 2017-02-06 15:01 -0700
              Re: Blocking RF from intentional radiators Jim Thompson <To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> - 2017-02-06 15:07 -0700
                Re: Blocking RF from intentional radiators Don Y <blockedofcourse@foo.invalid> - 2017-02-06 15:13 -0700
                Re: Blocking RF from intentional radiators Lasse Langwadt Christensen <langwadt@fonz.dk> - 2017-02-06 14:28 -0800
                Re: Blocking RF from intentional radiators Don Y <blockedofcourse@foo.invalid> - 2017-02-06 15:31 -0700
                Re: Blocking RF from intentional radiators Jim Thompson <To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> - 2017-02-06 15:59 -0700
                Re: Blocking RF from intentional radiators Don Y <blockedofcourse@foo.invalid> - 2017-02-06 17:08 -0700
                Re: Blocking RF from intentional radiators pcdhobbs@gmail.com - 2017-02-08 16:36 -0800
                Re: Blocking RF from intentional radiators Clifford Heath <no.spam@please.net> - 2017-02-07 10:26 +1100
      Re: Blocking RF from intentional radiators whit3rd <whit3rd@gmail.com> - 2017-02-06 13:05 -0800
        Re: Blocking RF from intentional radiators Don Y <blockedofcourse@foo.invalid> - 2017-02-06 14:22 -0700
          Re: Blocking RF from intentional radiators kevin93 <kevin@whitedigs.com> - 2017-02-06 13:39 -0800
            Re: Blocking RF from intentional radiators Don Y <blockedofcourse@foo.invalid> - 2017-02-06 15:12 -0700
          Re: Blocking RF from intentional radiators whit3rd <whit3rd@gmail.com> - 2017-02-06 14:43 -0800
            Re: Blocking RF from intentional radiators "nuny@bid.nes" <Alien8752@gmail.com> - 2017-02-06 16:29 -0800
      Re: Blocking RF from intentional radiators Jasen Betts <jasen@xnet.co.nz> - 2017-02-07 04:19 +0000

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