Originally Posted by Tesla23

Most radio manufacturers would know how to drive multiple receivers from a single antenna (it's basically what Mike says). Are you sure it isn't a diversity receiver.

A diversity system requires two antenna's. Dk is talking about just one antenna and two receivers.

Originally Posted by Tesla23

Most radio manufacturers would know how to drive multiple receivers from a single antenna (it's basically what Mike says). Are you sure it isn't a diversity receiver.

Please see my previous post which should answer this. It is a diversity system, but each "module" often has two parallel antennas right beside each other on the receiver. Between the two antennas on each module, they are providing neither diversity from orientation or blocking. The diversity is provided by using multiple modules (though one module actually has two antennas that are mounted 90 degrees to each other and this was the one that made me start to wonder whether it was receiving two signals at two different polarities each, or two signals at only one polarity each which is dependent on whether the antenna is able to simultaneously receive multiple signals).

Originally Posted by dknguyen

Please see my previous post which should answer this. It is a diversity system, but each "module" often has two parallel antennas right beside each other on the receiver. They are providing neither diversity from orientation or blocking between themselves. Multiple modules are used to provide diversity.

Gadzooks, make up yer mind.

Okay, so I know that a single antenna can be designed to transmit/receive multiple frequencies.

So is it a single antenna or multiple?

I think they didn't bother to add extra circuitry to use the same antenna to simultaenously receive two signals (now that I know it is possible and from looking at some of the receiver PCBs). They needed to have 2 radio modules anyways for dual frequency redundancy, and they either had the choice of extra circuitry (so they could use just one antenna), or extra wire (an extra antenna). I guess they went with the piece of wire.

Oh yeah, I've been talking about wire antennas the whole time. None of those special dual polarity ones.

What initially sparked this question (in case it's gotten lost), was the receiver had two antennas- each oriented 90 degrees to each other. I knew it transmitted on two frequencies, but I was not sure whether it was receiving one frequency per antenna (Channel A at Polarity X and CHannel B at Polarity Y) or if it was receiving two frequencies per antenna (Channel A at Polarity X&Y and Channel B at Polarity X&Y).

Maybe you can post the advertisement, and allow us to evaluate it.

It's kind of every page for all their air receivers:
Spektrum RC

Originally Posted by Tesla23

?? Are you sure it mightn't be a dual polarity antenna ??

Pretty sure. THe antennas are just straight pieces of wire- no fancy coiling or anything. Is that what you mean?

The spatial and polarity diversity is supposed to come from placing the base units and satellite units at different locations in different orientations (except for the odd unit where the antennas are mounted in different directions which provide polarity diversity in the same unit).

THe two smallest units have just one antenna- I know these ones do not transmit on dual frequencies.

Those guys are using CDMA/GSM type technology... So it is like like FDMA.