RF and Wireless calculations?

You could start by reading

and follow the links.

Thank you, I'll check it out.

The Friis Equation is the classic formula for describing for the power transfer between two antennas. I would check that out as well. Take care not to mix linear with logarithmic units.

If you are modeling signal propagation over long distances, you may also want to look a propagation models. There are many methods to choose from. ...with the Bullington model being one of the easier to understand, but Longley-Rice being generally more useful (IMHO).

Of course, depending on what you are trying to do, there could certainly be many other more suitable propagation models to choose from. Let us know if you get stuck.

But I agree, a quick refresher on link path budgets is a great place to start. Good luck.

-mpm

Thank you again, I am making a lot of progress understanding the frii's transmission equation, and the link budget, but there were a few points of confusion.

My understanding is that the friis transmission equation deals with the power received at the Rx antenna depending on the power at the Tx antenna, and the antenna properties/distances, and the link budget deals with entire systems.

my system uses 2 identical antenna pairs (Rx and Tx), so using the link budget equation terminology from

get do I have another set of Gtx, Ltx, Lfs, Grx, and Lrx values?

If the link budget takes in to account the antenna transmissions, when would you use the friis transmission equation?

The way I understand it, the link budget equation assumes that all components are matched, so how does that change the picture when I have a high resistance oscilloscope attached to the device?

And finally, what can I assume the losses are for SMA adapters like this

seeing as there are no data sheets or anything from radio shack*how helpful*

Thanks for all of the help, I am supposed to learn all of this stuff next semester for the first time, but I was given a research project for the summer so I have a lot to learn.

One should remember when dealing with Friis equations or their derived logarithmic (desiBel) counterparts, these equations seems to indicate that the path loss is frequency dependent.

This is not the case.

While it makes perfectly sense to talk about "gain" with the transmitter antenna, i.e. the way the power is concentrated in one direction and removed from other directions (directivity).

"Gain" for a receiving antenna is a strange (artificial) beast.

It would be more appropriate to talk about capture area and for an omnidirectional receiving antenna, this is proportional to the square of wavelength (and hence inversely proportional to the square of frequency).

This explains, why in some derivations of the Friis equation, the path loss would appear to be frequency dependent (which it is not).

With both omnidirectional transmitting and receiving antennas, the received power drops inversely proportional to the square of frequency. For this reason unpacked HDMI transfer at 60 GHz does not work with omnidirectional antennas on both ends even inside a room and other tricks are needed.

Assuming an omnidirectional transmitting antenna and a parabolic receiving antenna pointed towards the transmitter, the received power remains constant regardless of frequency.

Assuming a parabolic transmitter antenna pointed towards a parabolic receiver antenna looking in the correct direction, much more of the transmitted power will hit the receiver antenna and thus the received power increases with the square of frequency. Of course, there are other limiting factors that prevents increasing the frequency constantly.