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[Mel99]

I'm sure i'll get it eventually, but this RF stuff is mysterious to me.

For what it's worth ... (I'm over simplifying - feel free to correct/clarify anything) (And I'm not trying to sound 'preachy')

RF (Radio Frequency) is part of a wave continuum called the electromagnetic sprectum.  The major divisions (from longer wavelength to shorter) are:

• Radio frequency, including (in no particular order)

         Radio
         Television
         Mobile phones
         Wireless networking
         Amateur radio

• Microwaves
• Terahertz radiation
• Infrared radiation
• Visible radiation (light we see)
• Ultraviolet light
• X-rays
• Gamma rays

Wavelength and frequency are inversely proportional.  RF with its longer wavelengths has lower frequencies than do Gamma rays with extremely high frequencies and extremely short wavelengths.

Think of RF as being analagous to light -
   
Signal intensity is dependent on the power of the source - usually measured in watts.  A 100 watt light bulb gives off much more light that a 25 watt bulb.  And you can see things further away when using a 100 watt bulb.  In the CB radio world, a 5 watt transmitter will permit communications at a greater distance than a 1 watt transmitter.

Light will penetrate some substances better than others.  You can see things through glass but not through a fireplace.  Similarly, RF waves will penetrate some substances better than others, sheetrock (drywall) offers less resistance than real rock.

Light bounces off of surfaces to create shadows behind opaque objects.  So does RF waves.

Both light and RF require an antenna and a mechanism to transmit the signal to a processor.  For light, the eye is the antenna and the brain is the processor.

Some differences between light and RF.

Light, generally, travels in a straight line giving rise to the phrase "line of sight".

RF, with its longer wavelength, can bend around some objects.  This property is more pronounced as the frequency decreases.  The Navy, prior to satellite communications, used very powerful ELF (Extremely Low Frequency) transmitters to send messages to ships at sea.  The signal followed the curvature of the earth for great distances.

The human eye can adapt to varying light levels allowing us to see over a wide range of 'transmitter power' conditions. 

An RF antenna/processor system generally cannot adapt to transmission power levels. A number of conditions can cause an RF signal to degrade/decay/change such that the X10 receiver is unable to receive/interpret the signal -

• Signal strength
• Radio-opaque objects in the signal path
• Metal objects that can alter the signal frequency
• Etc.

Hope this helps remove some of the mystery.

Mel

[HA Dave]

.... The DS10a is on the far side of the chimney so I wonder if the bricks absorb some signal or block it not sure. Anyway I guess I'm going to try the passive radiator with copper foil tape trick, or maybe relocate the ds10a transmitter.

Between the heavy brick work and a big metal [garage] door your garage could be an unfriendly area for the tiny DS10A RF units. I've extended the wire to the magnetic reed switches on some of my DS10A units... by more than 30 feet. Moving the units can make a world of difference.

I'm sure i'll get it eventually, but this RF stuff is mysterious to me.

Mel99 certainly presented as nice a writeup about RF as I've seen in a while.

[Mel99]

Mel99 certainly presented as nice a writeup about RF as I've seen in a while.

Thanks - I was a Communications Tech in the Navy in the 60's.  Chief Petty Officers and senior First Class Petty Officers can be very persuasive when it comes to ensuring that a rookie Seaman (me) learned what they taught.

[dave w]

I'd say everything works pretty good right now except the one DS10a heartbeat so I guess I can live with that,

Well, maybe not. If you are not reliably receiving the DS10 heartbeat at your receiver (CM15A?), then you may not always pick up the actual alarm signal. since from an RF propagation stand point, the two signals are identical, other than duration.

Chimney brick shouldn't be a problem, but metal in the path between the DS10 and your CM15A, such as  a sleeved chimney or foil backed insulation could be causing your headaches. The passive repeater antenna or relocating the DS10 transmitter may help.

RF travels in waves, with peaks and valleys (nulls). If you have mounted the DS10 so the CM15A is at a null point of the signal from the DS10, moving the DS10 about a few inches closer to the CM15A or a few inches farther away from the CM15A may put the CM15A out of the null of the wave and fix your problem.

Yeah I know, it sounds weird. But have you ever been in your car listening to a weak FM station, pulled up to a stop light and had the station fade out?  You could bring back the station by allowing the car to roll a foot or so? If you have ever seen this, it is perfect example of your cars antenna being in the signal null at your initial stop. and moving a small amount gets it out of the null point.

That may be all you have to do here.

[Brandt]

Mel99 certainly presented as nice a writeup about RF as I've seen in a while.

Thanks - I was a Communications Tech in the Navy in the 60's.  Chief Petty Officers and senior First Class Petty Officers can be very persuasive when it comes to ensuring that a rookie Seaman (me) learned what they taught.

I was a Cryptologic Technician Communications (CTO3) in the Navy in the 2000's!  

I only really learned what I had to know to do my job on the ship (USS Nimitz), but I didn't really understand it in depth. We used encrypted HF LOS and SATCOM for voice. Other then that is was mostly encrypted computer networking for data.

[Mel99]

I was a Cryptologic Technician Communications (CTO3) in the Navy in the 2000's!  

I got out as a CT2.  Any relationship with the folks at ONI or NSA?

[Brandt]

I was a Cryptologic Technician Communications (CTO3) in the Navy in the 2000's!  

I got out as a CT2.  Any relationship with the folks at ONI or NSA?

There is No Such Agency 

[Brandt]

Chimney brick shouldn't be a problem, but metal in the path between the DS10 and your CM15A, such as  a sleeved chimney or foil backed insulation could be causing your headaches. The passive repeater antenna or relocating the DS10 transmitter may help.

RF travels in waves, with peaks and valleys (nulls). If you have mounted the DS10 so the CM15A is at a null point of the signal from the DS10, moving the DS10 about a few inches closer to the CM15A or a few inches farther away from the CM15A may put the CM15A out of the null of the wave and fix your problem.

Cool! I moved the ds10a kinda temporarily to allow it to peek around the corner of the wall that houses the chimney so it has a more direct shot to the attic and it worked! Not a single inactive sensor email in the middle of the night!!

I was not aware the the chimney was wrapped in foil insulation (house was built in '77)...That might have been the problem with this.

[Brandt]

Chimney brick shouldn't be a problem, but metal in the path between the DS10 and your CM15A, such as  a sleeved chimney or foil backed insulation could be causing your headaches. The passive repeater antenna or relocating the DS10 transmitter may help.

RF travels in waves, with peaks and valleys (nulls). If you have mounted the DS10 so the CM15A is at a null point of the signal from the DS10, moving the DS10 about a few inches closer to the CM15A or a few inches farther away from the CM15A may put the CM15A out of the null of the wave and fix your problem.

Cool! I moved the ds10a kinda temporarily to allow it to peek around the corner of the wall that houses the chimney so it has a more direct shot to the attic and it worked! Not a single inactive sensor email in the middle of the night!!

I was not aware the the chimney was wrapped in foil insulation (house was built in '77)...That might have been the problem with this.

I ended up putting the ds10a back were it was for a couple nights for one last test before attaching a longer wire to it in order to relocate it. The problem seems to have gone away...that is no more inactive sensor emails...after resetting the ds10a with a new code. I wonder how a new code could affect it's transmissions...

[Charles Sullivan]

Brandt,
Put the directive "DISPLAY_SENSOR_INTV  YES" in your config file.   This will append to each DS10A sensor signal displayed in the monitor/logfile the time elapsed from the previous transmission.  With the DS10A heartbeat interval of approx 70 minutes, and the default INACTIVE_TIMEOUT of 4 hours, two out of every three heartbeat signals could be lost without triggering the "inactive" indication.