Help Me Find Special Single Conversion Rx - RC Groups
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Dec 27, 2003, 05:27 PM
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Help Me Find Special Single Conversion Rx

A couple of months or so ago I ran across an article, where I do not know, by a vendor explaining a new receiver (Rx). This is a very unique Rx. It is a single conversion Rx that could not only block out signals from adjacent channels with the same excellence as a dual conversion Rx but also a transmitter (Tx) on the same channel!

The vendor described this as being discovered inadvertently during bench testing when they were testing the Rx with a TX and turned on a second Tx on the same channel and found that the 2nd Tx did not interfere at all with the reception of the Rx from the first transmitter it was working with. they further explained that they were confident this behavior was a result of the design of the care they had put into the discrimination of the single conversion circuitry or software, Iím not sure which.

It any of you are aware of this product please help me find it by posting to this thread.

Thanks in advance.
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Dec 27, 2003, 07:35 PM
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CiprianGugu's Avatar
This is hard to believe. How would the receiver know if the signal comes from a different radio if it is on the same channel? Maybe someone can explain more.

Dec 27, 2003, 09:44 PM
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KeithK's Avatar
I remember some talk about another tx being turned on and I think it was the Berg-4. Excellent rx even if it can't filter out another TX on the same channel!
Dec 28, 2003, 11:35 PM
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Mr.RC-CAM's Avatar
Some microcontroller equipped Rx's can measure/identify the Tx channel count and frame rate period. This allows them to ignore signals on the same frequency that do not match the pattern it has memorized.

However, this does not mean that you can have two transmitters on the same frequency and expect proper operation. The strongest signal will nearly always win. In other words, you will not be able to ensure control of the model from your Tx, even with the additional special protection.

The one fallout of the smart Rx's is that if you buddy box, both Tx's must have the EXACT same encoded signal. For example, if one Tx is a basic 6-channel and the other is a 4-channel, the Rx will not recognize both Tx's. Keep this in mind if you are planning on using the Tx's trainer feature. {Note: Some high-end Tx's, working as the master, can mix the trainer Tx into its native encoded signal. These can be setup to avoid this problem}.

Dec 29, 2003, 01:57 PM
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I think you're talking about certain FMA receivers. A club member brought one to a meeting a few months ago. It was an M5 if I recall correctly. The FMA M5 is actually dual-conversion.
Dec 29, 2003, 05:03 PM
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LawrenceHare's Avatar
The FMA FS5, and now FS9, both build a "signature" of the transmitter which allows them to uniquely identify the source of a signal and so ignore a second signal. Of course, two signals on the same channel result in jibberish as they tread on each other so I am not sure how a receiver would pull pertinent information from the combination of two signals. I presume if one is weak and the other strong then perhaps the weaker signal can be isolated and ignored. The FS5 can go into a fail-safe mode like PCM receivers only it is very much easier to set up. They are dual-conversion as well.

I presume if the Rx transmitted back what it received AND The Tx would listen, ie. it had a receiver, then the Tx would see that the Rx is receiving rubbish as it could compare what it sent with what was received. It could then take action and leap into disaster mode - change channel maybe, which the receiver could match. Wow!

All this would send the price skyrocketing. I think clothes-pegs with numbers on 'em and a modicum of sense at the field would be at the best solution!

This problem btw is comparable to the same issue that exists in local area network communication when two devices try to transmit on the same medium at the same time. There are some fascinating protocols to help avoid this, token-ring and CSMA/CD being two of the most common. These could be applied to R/C - It is the cost issue however that always raises its ugly head...