RF Attenuation

j.m.krell

Hi,

I'm working on a project and need a way to have an adjustable attenuator.· I'm going to operate at 2.4Ghz and want to use a potentiometer, but I'm having difficulties in finding the proper potentiometer.· Thank you very much, I greatly appreciate it.

stamptrol

At radio frequencies, its probably not going to be as simple as just sticking a pot in the circuit.

If I understand you correctly, you want to vary the strength of the radio signal, right?

The attenuator will likely go in the antenna lead and will come from the radio manufacturer.

Can you give us some details of why you want less signal? Most of us spend our working lives looking for stronger signals!

Cheers,

▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
Tom Sisk

http://www.siskconsult.com
·

j.m.krell

I want an adjustable rate of attenuation as my plan for the project is to have a system so when a remote system is too far away from a base an alarm will sound.· I want this to be adjustable so I can have differing distances.· My past two projects have both received awards at the International Science and Engineering Fair and I am hoping that this one is of the same caliber.· Thank you very much, I greatly appreciate it.

Jordan M. Krell

pjv

Hello Jordan;

At 2.4 GHz, things get a lot more complicated than at DC and low frequencies. An ordinary "pot" won't do. For things to work properly you need to keep the impedances closely matched, and there will also be a LOT of uncontrollable leakage arount the pot. If you are very careful, such as putting things in shielded enclosures, you can make a stepped attenuator with multiple outputs. And probably there is a stepped amplifier/attenuator chip you can purchase.

I do not know your level of RF expertise, but I'm guessing by your approach that you are not (yet) skilled in this field. And while I would not wish to discourage you from your endeavours (in fact very much the opposite), I would wish to caution you on a "too simplistic view". This stuff is not easy, especially at higher frequencies such as 2.4 GHz. It takes a lot of equipment...... I have invested well over $100,000 to do it professionally.

That said, you can get some amazing results if you study it hard and work at it dilligently.

Good luck!

Peter (pjv)

stamptrol

Jordan,

The other avenue is to go with a bit more sophisticated radio that reports the Received Signal Strength. This will allow you to check the RSSI just by checking the radio itself.

Some Parallax units and the ones I've used from Maxstream have this ability.

Cheers,

▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
Tom Sisk

http://www.siskconsult.com
·

j.m.krell

The radio that I have and have used in the past has an rssi pin and that was my preferred path initially. I discovered though that the recieved signal with my chip was all rf in the area.