Baby alarms

Post by **richardlowis** » 06 Feb 2005, 16:42

Baby alarms around top of the 49 mcs band, some left on all day, how far do these things transmit - pick up signals from more than the room they are placed in.

YouTube · Post by **Transmission1** » 06 Feb 2005, 20:36

I've seen them travel over a couple of miles before today! It's hard to believe this considering the very low power output but given height and a decent scanner these can propagate over a large area of town.

The main problem with baby alarms is that there are only a few channels that they operate on meaning that if you were to walk around with a scanner you will get interference from other beighbouring alarms. The same goes for the old type analogue cordless phones - they are also difficult to measure in terms of distance as one phone call often "keys" over the top of the other signal. Have a search for my article on monitoring cordless phones on this site, it will give you some further ideas for low power device monitoring.

Regards
Simon

Andrew · Post by **Andrew** » 07 Feb 2005, 09:32

I may be wrong, not sure, but I've been told plug in the wall ones have a habit of using the mains as a transmitting system. I have read of a couple who plugged the receiving unit in their living room, then the transmitting one in the baby's room, then found out it wasn't their child who was on the other end!

They could hear friends along the street in their house talking! I don't know if it was down to the make and model they were using. It was a few years ago I read it in a paper.

The furthest I know I've heard is about 400 yards, as the house was at a bus stop, and I could hear the engine ticking over as it was parked.

Post by **richardlowis** » 09 Feb 2005, 19:04

Thanks for the info, I'm lucky only have one dominant signal and still working on possible location/distance, also strange that this signal if far better on a 40 metre end fed longwire (horizontal of course) than it is on the dedicated scanner ant.

Rich

Website · Post by **Dragon Man** » 14 May 2005, 23:46

LOL here is a tip dont buy a baby moni from germany!! thay use the PMR446 band and i picked them up all over when i used my 5 Km radios on channel 5 also ppl are using them radios as baby monis
hey and a bout using the mains as a ariel thay are doing that with the clock for your heating timer
i dono if we had a baby moni that went through the mains... when i broke (with my help) i had a look inside and the airelwas the earth pin so i dono if thay use the earth to transmot on but it i could pick the moni up in the shed right down the bottom when i pluged the reciver in, but when i used the hand held one one there was no signal also i think its funni that uf i used channel 3 i could here music thow i didnt know what it was on
fun tryin to find it on scanner thow, i had no luck

Post by **jack_sparrow** » 14 Mar 2007, 17:12

what frequency are these on?

Website · Post by **Dragon Man** » 08 May 2007, 23:18

49Mhz.. but with them going swimming a few times (eg. knocked in the bath) it knocked some of the channels off frequancy, fun..
also i have found out that you can buy addapters that enable you to use your mains wiring as a computer network system.. i have no idea how that works... intresting thow and i wonder how far that would go... hmmm.. anyone got any info on that?

Post by **Andy** » 09 May 2007, 06:12

Be very wary of those 'home networking' thingies that work through the mains. A friend of mine has some neighbours who use them and the noise they make on parts of the SW band is chronic!

Website · Post by **Dragon Man** » 09 Jun 2007, 15:39

ferite rings? mabe they can filter some of the cr@p out... Allso.. STAY AWAY FROM THOSE MINI FRIDGES!!
damn the noise they make on the CB bands are insane i was getting a good 20+dB of hash

Post by **Andy** » 09 Jun 2007, 19:04

I think those old 'through the mains' wireless intercoms used LW, about 150 KHz. Someone had one around here and it was good n' strong.

Post by **nordhavn** » 18 Mar 2008, 19:32

When i lived in kent , i could pick up a couple of baby monitors from the house . I used to take my scanner with me on walks . Im one area i could clearly pick up 5-6 of them , but no houses for a couple of miles . So im not sure how that one worked .
cheers