[RFI] 40M QRM/RFI
w8bya at mchsi.com
Fri Jan 12 17:36:11 EST 2018
Yes most if not all will have a main PCB controller board with a uP or
at least a u-controller and all kinds of discrete and integrated drivers
and relays inside the main control panel box.
That unit is normally hidden downstairs and is central to the entire
security system. It is powered via a 117 VAC wall wart, etc which you
will need to unplug. Then inside the control panel (box) there will
usually be a 12 VDC gel-cell for emergency backup. You will need to
unplug the positive lead from that battery to totally deactivate the
alarm system. If connected to a traditional twisted pair telephone
system disconnect that as well. Just make sure the owner notifies any
monitoring company of what is going to be happening before you do any of
this. You also should double check to see if by doing this you will wipe
any stored settings of the alarm system.....owner would be real ticked
off if the entire house had to be re-programmed. And also take a look at
any remote control panels to see if they have any kind of hold up
batteries etc inside. These are the small panels in the hallway or
kitchen where you enter your code in to arm or disarm the system as you
come and go.
Gallery at http://w8bya.com
Light travels faster than sound....
This is why some people appear bright until you hear them speak.
On 1/12/2018 4:44 PM, Randall K Martin wrote:
> I am fairly certain that one of the houses has a security system
> installed. Do these generally have some kind of main control unit that
> I could have him unplug as an easy test, or is it more involved than
> that. I'll find out if that is the source, before asking what can be
> done do cut down on the RFI.
> Thanks Jim K9YC for your comments, too.
> On 1/12/2018 2:36 PM, Leonard Halvorsen wrote:
>> Are those 4 houses high-rent-district kind of places?
>> Sounds like maybe a memory or sensor refresh on a security or fire
>> detector system.
>> On Fri, Jan 12, 2018 at 3:24 PM, Randall K Martin
>> <rkmassoc at comcast.net <mailto:rkmassoc at comcast.net>> wrote:
>> I have recently noticed a 24-hour per day source of QRM on 40M CW.
>> On 7031.9 there is a steady stream of dashes, with the dash lasting
>> about 1.5 seconds and then a space of 0.5 seconds. What is
>> interesting is that there is a second signal which is much weaker on
>> 7041.9 which is the exact inverse of the first. When the first
>> signal is on, the second is off, and vice versa. Both sources peak
>> at the same heading, roughly 90 degrees from my main 40M yagi.
>> I have zeroed in on a spot about 2000 feet east of me where the main
>> signal is almost 40 dB over on a mobile rig (K-3 with hamstick).
>> I've ordered a DF loop antenna so I can try and pin it down further
>> before knocking on doors. There are four houses in the immediate
>> Just wondering if anybody in this group has ever come across
>> something like this. Google searches and archive search for this
>> reflector came up empty. The signals do not drift in frequency.
>> Speculation as to the source?
>> 73 Randy K0EU
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