Agreed but not that or as relevant with k band mw

I lile the 7xxx range from honeywell. For pure stability but slow detection then napco dt's

Fill us in on k band then.

non penetrating, a bit like safe sex for DT's

from the manufacturer

Superb Detection Through K-Band Technology

K-Band microwave technology delivers sharp detection without holes or weak spots. The custom-made source offers Pattern Shaping to fill the protected area with a broad, balloon-shaped pattern which matches the PIR pattern. It also offers Pattern Containment to reduce the penetration of microwave energy through walls.

Translation

from wikipedia

X band8 to 12 GHz

K band18 to 26.5 GHz

As k band is a higher freq it doesnt penetrate things as well. Still penetrates but if you think of it in sound terms. Low freq bass travels through walls well, ie the 'thud thud thud' but the treble doesnt. same basic principle.

Also the same for radio waves. Long wave (Low freq, the radio guys will know this a lot better than me) ie radio 4 comes from Droitwich (midlands) and covers most of the country. By comparison how far does fm (higher freq)?

198BBC Radio 4United KingdomDroitwich (SFN)T-aerial on 2 guyed steel lattice masts insulated against ground with a height of 213 metres50052°17′46.9″N 2°6′24.32″W ; 52°17′40.4″N 2°6′20.62″WAll three transmitters carry Radio teleswitchPSK data. Droitwich relays BBC World Service after the end of Radio 4 programmes.Burghead (SFN)Omnidirectional aerial, guyed steel lattice mast5057°41′57.9″N 3°28′4.78″WWesterglen (SFN)Omnidirectional aerial, guyed steel lattice mast, height 152 m5055°58′33″N 3°48′58.8″W

above from wikipedia for radio 4 transmitter.

Some think that k band doesnt have to be as accuratly setup as x band based devices. I suppose on a tech level its sort of true. But real world applications are non square rooms (eg 12m x 3m room). ie you need to wind the mic up to cover the 12m part of the room but then the mw is penertrating through the 3m wall.

There is also a problem with back pentetration with mics, ie directly behind the detector. That is why dt's are so heavy when not using a horn in an effort to remove the reverse bubble. Horns still suffer from it a bit but not as much. Also as the freq is higher on kband the pentration is lower by default.

But the radio ham guys will know far more about this sort of transmission

non penetrating, a bit like safe sex for DT's

lol

from the manufacturer

Translation

from wikipedia

X band8 to 12 GHz

K band18 to 26.5 GHz

As k band is a higher freq it doesnt penetrate things as well. Still penetrates but if you think of it in sound terms. Low freq bass travels through walls well, ie the 'thud thud thud' but the treble doesnt. same basic principle.

Also the same for radio waves. Long wave (Low freq, the radio guys will know this a lot better than me) ie radio 4 comes from Droitwich (midlands) and covers most of the country. By comparison how far does fm (higher freq)?

above from wikipedia for radio 4 transmitter.

Some think that k band doesnt have to be as accuratly setup as x band based devices. I suppose on a tech level its sort of true. But real world applications are non square rooms (eg 12m x 3m room). ie you need to wind the mic up to cover the 12m part of the room but then the mw is penertrating through the 3m wall.

There is also a problem with back pentetration with mics, ie directly behind the detector. That is why dt's are so heavy when not using a horn in an effort to remove the reverse bubble. Horns still suffer from it a bit but not as much. Also as the freq is higher on kband the pentration is lower by default.

But the radio ham guys will know far more about this sort of transmission

I see, thanks for that.

I gave meself a crash course in radio transmission last week as i got some transmission kit to fit soon (hopefully anyway)

so how come gamma waves (0.03-0.003nm) can travel through walls, earths crust etc?

and why do they make your skin go green.

so how come gamma waves (0.03-0.003nm) can travel through walls, earths crust etc?

Approx transmission power?

Used to be a problem with mobile phones before they used all them mini transmitters in town centres.

Orange/T-mob use higher frequency range and often had reception probs in buildings.

Yepp.

In the nordic countries we had a system on 450MHZ. It worked everywhere, It actually worked so well that many boats replaced theri VHF radios with mobile phones.

then came the 900 Mhz system wich required a lot of new transmitters.

GSM was first at 900 and now uses 900 and 1800.

I dont remember the freq. of HDSPA but its higher and got lower coverage

mobs are different. as are gamma waves.

the mic bit in a dt is looking at the changes in reflected waves, ie those coming back. passing through aint the issue, those that passed through & are heading back are.