Single and Dual Conversion Receivers - RCCanada - Canada Radio Controlled Hobby Forum
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Old 08-02-2007, 08:17 PM   #1
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Single and Dual Conversion Receivers

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When talking about recievers, what is meant by single or dual conversion ???

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Old 08-02-2007, 09:09 PM   #2
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In simplest terms...when an FM receiver converts a 72 MHz signal into usable information, it first needs to clean up the signal it has received. In a single conversion receiver, it does this by mixing in another frequency and obtaining a new Intermediate frequency (IF) of 455KHz, then the resulting IF signal is decoded. This eliminates unwanted noise. A dual conversion receiver does this twice. First it converts 72 MHz to approx 10MHz, then again to 455KHz. This produces an even cleaner signal prior to decoding. The receiver crystal provides the correct mixing frequency(s) to obtain the desired IF(s). The only drawback to dual conversion is that two IF circuits are required making the receivers larger.
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Old 08-03-2007, 07:42 AM   #3
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I'd like to add, 10.7MHz (instead of about 10) and that it is against the law to transmit on 10.7MHz and 455kHz so as not to interfere with regenerative receivers. (these are worldwide standards).

JR uses a special patent regenerative process called ABC&W that is a single conversion that seems to work as well as dual conversion.

So basically,

Single conversion xtals are your transmitter frequency -455kHz giving you a 455kHz signal to decode

Dual conversion xtals are transmitter frequency -10.7MHz then mixed with 10.245Mhz (a xtal permanently inside the receiver) giving you a 455kHz to decode, better filtering.

Experts say that with DSP microprocessors dual conversion is no longer necessary. You have to trust the programming though.
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