receiver question
 

What is the difference between a dual conversion and single conversion receiver?

RE: receiver question
 

WRX,

The long answer:

The 72 MHz signal from our transmitters has to be converted down to a low frequency for the information to be extracted from it. The conversion is done by mixing the 72 MHz signal with another steady signal to generate a lower frequency result. In a single conversion RX the Incoming 72 MHZ signal is mixed with another 72 MHz steady signal to yield the output PPM or PCM information directly.

In dual conversion the signal is first mixed with a steady signal that will result in some intermediate frequency (often 455 kHz) and then this signal is mixed again to yield the actual information.

In general the single conversion RX has fewer parts and can be lighter and use less power. However it can be more prone to interference because the filter has to be fairly broad.

The dual conversion RX wil have a larger parts count but can include a very precise filter for that intermediate frequency so they usually have better range.

RE: receiver question
 

The short answer.

Single conversion receivers are good for park flyers and when you won't be flying with many other people. Dual conversion are for larger planes and flying with others.

Single conversion are much more prone to getting "hit" by stray signals.

That being said, soem single conversion receivers are fine, like Berg. But for the most part, unless you're flying something like a GWS Stick, I'd use dual.
Dennis-

RE: receiver question
 

Great explanation found here:

http://www.torreypinesgulls.org/Radios.htm

RE: receiver question
 

Glen had it really close. Actually the 72 MHZ received signal is converted to 10.7 MHZ, amplified, and then converted again to 455 KHZ, where it is then "detected", the process that extracts the information from the RF signal.

Most FM broadcast receivers work the very same way.

RE: receiver question
 

Ahh yes, detection ...

Thanks Dick. It's been a while since I built my last Heathkit.

RE: receiver question
 

Try a google search some rainy day on the term "superheterodyne"

Read until your eyes hurt. There is THAT MUCH info around.

Have fun! :)

RE: receiver question
 

I disagree, in fact Dual Conversion receivers are over-rated. If the above were true you would not see anyone flying single conversion - the fact is 99% of all receivers in r/c are single conversion. The new generation hybrid single conversion receivers have excellent range, exceptional power usage and one less crystal to break or malfunction.

Quite frankly the front ends of JR, Fut and MPX receivers are exceptional and have outstanding noise immunity. Hits occur on any receiver when large sources of RF inference are present (i.e. bad plug wires, metal on metal vibration, etc). A DC receiver will have a small advantage over SC due to better isolation of the encoded signal from the carrier (72Mhz) but IMO, its negligible.

There are some instances where a DC RX might make sense to use - flying around EMI sources like power lines, transformers, transmission towers, and airports - but then again - all places you don't want to fly.

Some people use DC receivers when they have a "history" of getting hit on a particular frequency - personally - I'de just change frequencies before taking that chance. ..

DP