Antenna Question - Electronic Circuits Projects Diagrams Free

meriad · 17th February 2007, 12:20 PM

Hello:

I am hoping you guys may be able to help me. I am creating a ultra small short range tx/rx. And although, I am moderatly comfortable, with electronics, I am a novice when it comes to antennas. For the reciever I am using digikey part #LTC5505-1ES5#TRMPBFCT-ND with this antenna (digikey part #ANT-315-HETH-ND). My question is this... the antenna is created so that both "ends" are connected to the circuit, but my output IC only has one output antenna connection, so how do I connect these together? The transmitter is tuned to transmit on the 315 mhz band, the recieving antenna is tuned to the same frequency. and it only needs to work for 20-30 feet. Even better would be if someone could point me to a website that would allow me to create a PCB antenna for this circuit.

Thanks in advance

aircond_gypsy_63 · 19th February 2007, 11:32 AM

I dont know if this will help as my understanding of RF is limited to the 11meter band, but here goes... the broadcast antenna needs a driven element (likely the output lead from your IC) and a ground to reflect from.
the signal travel on a 1/4 wave antenna travels to the antenna tip along the Outside of the antenna then reflects off of its ground base ( Ie what it's mounted to) into the aptmosphere. This can be very directional as the RF signal "pulls or reflects if you will " toward the greatest amount of reflector.
hopes this helps in some way...

JimB · 19th February 2007, 03:22 PM

Regarding the antenna, after looking at the datasheets in digikey, I think it is supposed to be a "normal mode helix".
To use this antenna, one end is connected to the antenna pin of your Tx or Rx module, and the other end is just soldered to a small pad on the circuit board, (for mechanical support, not connected electrically to anything).

I must question your use of the LTC5505 as a receiver.
This chip is intended to be used as an RF power monitor for a transmitter, it has very poor sensitivity for use as a reciever.
Your "short range" may be quite a bit shorter than you expect.

JimB

meriad · 19th February 2007, 03:30 PM

Thanks for your replies, The range only has to be under 50 ft, so I'm hoping it will work, I just wasn't sure wether to connect the other end to the ground or not

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17th February 2007, 12:20 PM	(permalink)
meriad	Antenna Question Hello: I am hoping you guys may be able to help me. I am creating a ultra small short range tx/rx. And although, I am moderatly comfortable, with electronics, I am a novice when it comes to antennas. For the reciever I am using digikey part #LTC5505-1ES5#TRMPBFCT-ND with this antenna (digikey part #ANT-315-HETH-ND). My question is this... the antenna is created so that both "ends" are connected to the circuit, but my output IC only has one output antenna connection, so how do I connect these together? The transmitter is tuned to transmit on the 315 mhz band, the recieving antenna is tuned to the same frequency. and it only needs to work for 20-30 feet. Even better would be if someone could point me to a website that would allow me to create a PCB antenna for this circuit. Thanks in advance

19th February 2007, 11:32 AM	(permalink)
aircond_gypsy_63	I dont know if this will help as my understanding of RF is limited to the 11meter band, but here goes... the broadcast antenna needs a driven element (likely the output lead from your IC) and a ground to reflect from. the signal travel on a 1/4 wave antenna travels to the antenna tip along the Outside of the antenna then reflects off of its ground base ( Ie what it's mounted to) into the aptmosphere. This can be very directional as the RF signal "pulls or reflects if you will " toward the greatest amount of reflector. hopes this helps in some way...

19th February 2007, 03:22 PM	(permalink)
JimB	Regarding the antenna, after looking at the datasheets in digikey, I think it is supposed to be a "normal mode helix". To use this antenna, one end is connected to the antenna pin of your Tx or Rx module, and the other end is just soldered to a small pad on the circuit board, (for mechanical support, not connected electrically to anything). I must question your use of the LTC5505 as a receiver. This chip is intended to be used as an RF power monitor for a transmitter, it has very poor sensitivity for use as a reciever. Your "short range" may be quite a bit shorter than you expect. JimB __________________ Experience is directly proportional to the value of the equipment ruined.

19th February 2007, 03:30 PM	(permalink)
meriad	Thanks for your replies, The range only has to be under 50 ft, so I'm hoping it will work, I just wasn't sure wether to connect the other end to the ground or not