Dual Conversion, Single conversion, etc! What does it mean?
07-31-2002, 06:46 PM
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Dual Conversion, Single conversion, etc! What does it mean?
Ok, I think its about time to post this question. I know Dual converion is preferable, but I would like to know exactly why. How does it work? WHY is it preferable? I have heard that PCM is more reliable, and wont get hit as often, because it has a narrower band or something? Is PCM preferable if you are running a gasser?
Come on electronics wizards, tell me what you know! Thanks
Come on electronics wizards, tell me what you know! Thanks
10-05-2002, 12:01 AM
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Dual Conversion, Single conversion, etc! What does it mean?
Ok first off I am not a radio engineer. Dual conversion filters the signal twice. Single filters once. Dual conversion is always better. PCM Pulse Code Modulation is a way of encoding the signal in an FM transmission. You don't get less hits with the PCM you don't see them because the failsafe stays on the last input so long as the loss of signal is not to long you will not notice. I have 3 PCM capable radios I use non of them in PCM mode. I hope I answered some of your questions. If you search on PCM here in RCU you will find more technical answers than I have given.
10-05-2002, 01:05 AM
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Dual Conversion, Single conversion, etc! What does it mean?
Hey thanks, I had forgotten about this thread! 
I have since figured out all about PCM-vs-FM. I've found that both of them have there perks. I think I will go with PCM for my expensive stuff. I can tell when FM gets hit, the plane can go any and everywhere during the interference. I dont care for that. PCM will at least hold the last transmission, and I can at least tell when i get hit if the hit is long enough. In my opinion, With PCM I dont have to worry about a hit shoving my plane into the ground. Thats good enough for me.
I have since figured out all about PCM-vs-FM. I've found that both of them have there perks. I think I will go with PCM for my expensive stuff. I can tell when FM gets hit, the plane can go any and everywhere during the interference. I dont care for that. PCM will at least hold the last transmission, and I can at least tell when i get hit if the hit is long enough. In my opinion, With PCM I dont have to worry about a hit shoving my plane into the ground. Thats good enough for me.
10-05-2002, 06:32 PM
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Dual Conversion, Single conversion, etc! What does it mean?
Copied this from a web site:
Scanning For RF Interference In Your Turbine Installation
By Gordon Dickens
.................................
A Rudimentary Explanation of How RC Receivers Work
..................................
There are two popular types of receivers in use, single conversion and dual conversion. All receivers actually transmit a radio signal, called an “image signal” for the purpose of processing the incoming signal from the transmitter. Single conversion receivers transmit an image signal that is offset 455 kHz above the transmitter’s signal while dual conversion receivers transmit an image signal that is offset 10.700 MHz below the transmitter’s signal. In other words, the crystals for your receivers are not actually oscillating at the transmitter’s frequency printed on them but are oscillating at the receiver’s image frequency. The receiver essentially combines this image frequency with the transmitter’s signal to produce a resulting signal that is 455 kHz for single conversion receivers and 10.7 MHz for dual conversion signals. In dual conversion receivers, the 10.7 MHz signal is then converted electronically to 455 kHz, hence the “dual conversion” nomenclature. In other words, regardless of what transmitter frequency that you are operating on, all receivers eventually convert the signal to 455 kHz. The primary reason that the receivers are designed this way is so that the receivers can be tuned to various transmitter frequencies and yet all have a standard internal operating frequency.
As an example, RC transmitter channel 20 transmits on 72.190 MHz. The single conversion receiver image signal is 72.645 MHz and when mixed with the 72.190 transmitter signal yields an internal frequency of 455 kHz. The dual conversion image signal is 61.490 MHz and when mixed with the 71.190 transmitter signal yields an internal frequency of 10.7 MHz which is then converted electronically to an internal frequency of 455 kHz. As an experiment, scan your airplane installations for the image signal being transmitted by your receivers. You can readily detect these signals with the ICOM device 455 kHz above the transmitter’s frequency on single conversion receivers and 10.7 MHz below the transmitter’s frequency for dual conversion receivers.
Scanning For RF Interference In Your Turbine Installation
By Gordon Dickens
.................................
A Rudimentary Explanation of How RC Receivers Work
..................................
There are two popular types of receivers in use, single conversion and dual conversion. All receivers actually transmit a radio signal, called an “image signal” for the purpose of processing the incoming signal from the transmitter. Single conversion receivers transmit an image signal that is offset 455 kHz above the transmitter’s signal while dual conversion receivers transmit an image signal that is offset 10.700 MHz below the transmitter’s signal. In other words, the crystals for your receivers are not actually oscillating at the transmitter’s frequency printed on them but are oscillating at the receiver’s image frequency. The receiver essentially combines this image frequency with the transmitter’s signal to produce a resulting signal that is 455 kHz for single conversion receivers and 10.7 MHz for dual conversion signals. In dual conversion receivers, the 10.7 MHz signal is then converted electronically to 455 kHz, hence the “dual conversion” nomenclature. In other words, regardless of what transmitter frequency that you are operating on, all receivers eventually convert the signal to 455 kHz. The primary reason that the receivers are designed this way is so that the receivers can be tuned to various transmitter frequencies and yet all have a standard internal operating frequency.
As an example, RC transmitter channel 20 transmits on 72.190 MHz. The single conversion receiver image signal is 72.645 MHz and when mixed with the 72.190 transmitter signal yields an internal frequency of 455 kHz. The dual conversion image signal is 61.490 MHz and when mixed with the 71.190 transmitter signal yields an internal frequency of 10.7 MHz which is then converted electronically to an internal frequency of 455 kHz. As an experiment, scan your airplane installations for the image signal being transmitted by your receivers. You can readily detect these signals with the ICOM device 455 kHz above the transmitter’s frequency on single conversion receivers and 10.7 MHz below the transmitter’s frequency for dual conversion receivers.
