About Alarm antenna wire

[thedag]

Sorry?
Miss Understood what you said.

 

[thedag]

I Draw what I Understood from what you all said.


is that correct ?

Thanks in advance

 

[WimRFP]

Hello,

Yes, this (your picture) has high probability of succes. keeping wire lengths below 2 cm is OK. It is also OK to twist the braid into a wire so that you can connect it.

 

[thedag]

OK, Thanks, I Will try it.....

 

[thedag]

BTW, Thin 50 Ohm Coax, is ok ??

 

[WimRFP]

Thin 50 Ohms cable is OK (for example RG174). Because of the polyethylene dielectric in RG174, do not run it close to hot parts (PE softens at relative low temperature). If you can't avoid it, you may use teflon dielectric cable (expensive and less easy to get). If you can't get 50 Ohms cable, you may try 75 Ohms as well.

 

[thedag]

I Think the cable i have, called "RG316" , is he ok ?

 

[thedag]

Damn, I've build this antenna, and im still not satisfied with the results....
i made it like this picture, with calculation to 325MHz :

BTW, The legs of the dipole are something like 1.5mm i think...
maybe its too big?

Please Help....

 

[WimRFP]

Hello,

If you measured the length from the point where the cable splits into shield and center conductor, this is OK.

Where did you locate the antenna (make picture or drawing)?

If the antenna isn't the problem, the problem can be in the link budget (combination of transmitter power, distance, receiver sensitivity, noise, interference, etc). What is the actual range and what is the desired range? Is this a system where a keyfob is used to operate the alarm, or does the alarm transmit to a home-based receiver?

 

[thedag]

i measured the the length from the point where the insulate starts, the center insulate, its incorrect ?

Where to measure the point from, i draw 4 points,please tell me from where, to where.

Thanks.

 

[WimRFP]

Hello,

Best is from yellow dot to where the copper stops, If the copper stops at the pink dot, you should use distance between yellow and pink dot.

Please note that some percent change in length will not change a non-functioning solution into a well-functioning solution. So if with your dipole the range is half what you want, it will not become what you want when you change the length 1 centimeter. Antenna placement has large influence. What range do you want and what do you have now?

Some additional information may be helpful to give other tips.

 

[thedag]

Something like, 30 meters in front the car,
7 meters behind the car..

Im feel like this antenna and the previous antenna is the same range,
Now the antenna i made is in the A-Pillar,
I Tried also on the mirror(for check) and actually out the car(for check also)
Still the same,
im also tried to change the frequency in the Remote.
little helped but not that much....
its should be very good range with this antenna.....

BTW, Between the braid and the ground pin have something like 3-4 cm.
I Cant get it shorter....
its ok?

 

[thedag]

BTW, The Shield connected this way:

Look at the "Blue Circle" I Draw there...
I mean I cut the gnd cable, and added the shield, and i twist all the copper's together...(start gnd wire, shield, the rest gnd wire).

Thanks, thedag

 

[thedag]

OK, I Cutted the dipoles from the split of the coax to the end of copper, still not that good...
I think the problem is the GND Wire, I mean its connected to the shield by 3-4cm wire.
You think this is the problem ?
And tell me if the connection of the wires is ok (From the picture I've posted before)...

Thanks...