what is a synthesized receiver?
what is a dual-conv receiver?

Synthesized means that it does not have a crystal (per-se) in the receiver and that it can "synthesize" or create any frequency in the band. Some call it "dial-a-crash" and those transmitter/receiver combinations are not that popular. The reason they are called that because you can select an operating frequency, one that is apparently vacant at your flying field, and then forget about it. Someone could come along with your frequency, and if you didn't take the time to pull your frequency off of the frequency board, well, when that person turns on the transmitter, well, you crash. Also, you could forget about your frequency, and leave. The next time you show up, you accidentally turn your transmitter on, forgetting that it is on that frequency, and someone else crashes. Lots of possible scenarios for this. Again, it's a nice idea, but not very popular. I had one for a short time, had trouble with it.. every other model memory channel caused servo chatter.. so I sold it.

With regard to RC receivers, “dual conversion” is a technique in which the receiver operates at two lesser frequencies besides the operating frequency. The basic dual-conversion receiver employs two crystals rather than one. Because of the “extra” level of conversion, these receivers can be made more selective and more immune to certain interference situations.

The basic dual-conversion receiver will, by nature, be slightly larger in size, weigh a little more, and be slightly more expensive than a single-conversion receiver. There is nothing wrong with single conversion, and several lines of RC receivers have used that type of circuitry successfully for many years. However, most receiver labels these days will identify the product as “dual conversion.”

This one is a bit less technical so I deleted the last one and put this one in instead. It still is a tad bit technical, but all this means that it is not as subject to inteference than single conversion receivers are.

CGr.

The "dial-a-crash" effect is mitigated by following proper proceedure... the same proceedure you would have to undertake with ANY 72mhz transmitter receiver except those that may have say a built in channel scanner.

Those with built in channel scanners circumvent the problem by checking for others on the same frequency before permitting you to proceed.

2.4mhz radios do not suffer from this problem....

However the RC community has dealt with the frequency allocation issues for many years and it is not as horrific as CGRetired's earnest message seems to make it.

Most novice pilots are trained to deal with pulling the pin, checking their frequencies and are warned that they can be responsible ( and liable ) for crashing someone else's plane if they are not careful.

Over the last three years at a very busy field I've only seen two times that frequencies have been stepped on by someone a bit negligent, and those tend to be caught on the ground...

It may look "earnest" to you, but I've seen it first hand. Thus "dial-a-crash". And that's why I sold it and went over to 2.4 GHz. I've seen jerks turn their transmitters on at sanctioned events, even. No matter how you look at it, it might be a great idea in theory, but in practice, well, it's far from perfect.

I do not disagree, however given that he asked because he was looking at 72mhz beginner's radios ....

One of the two occurances I saw did result in a crash, and the offender was singled out by everyone else rather quickly. It was "suggested" that he make amends to the person who's frequency he stepped on. They remain friends.

2.4mHz is great in it helps to reduce the problem, but it should not be used to overcome poor practices or inattention.

Umm.. his question was simply "What is a synthesized receiver". Nothing said about a beginners radio in the OP.

We try to enforce frequency control, but often times, people show up alone, then just fly. Later on, someone will show up and fly and one has a frequency pin, one does not. If they both opted not to take the pin, and they were both on the same frequency... well, you said it, didn't you... poor practices. It can be very hard to enforce so it has to become a habit.

i guess what i want to know is if i have a 72mhz channel 19 radio and buy one of thse rx how does it work. if some one has a 72mhz radio on but a different channel can it mess with me , how does it connect to just my radio channel 19

That is what CGRetired was talking about.

Yes indeed someone else using the same channel can cause your plane to crash, which is why most clubs use frequency boards to prevent this.


Bascially your receiver will "listen" to ANY transmitter on the same frequency.

It may not respond if the shift pattern is different, but the same channel is used by someone else, but YOU'll loose control.


A Synth receiver can be used on any channel.

If you have a fixed channel TX, then the synth RX should work with it, if the shift pattern is compatible.

If you also have a synth TX, and you get out to the field only to find that someone else is using your channel, you can select another channel on the TX and RX and fly on that channel instead.

I do this all the time.

I know I would like to have one..

how does my fixed channel radio link on to that rx, and not be effected by other channels ?

Let say your receiver is set to receive 72.555 mz in order to do this the 72.555 need to be changed to your I.F. (intermediate frequency) let say that your IF is set to 10.7mz this is called your band pass freq. because it will not allow any freq. above or below 10.7mz. To pass. So to receive 72.555 your mixing freq. needs to be 61.855mz (72.555 - 61.855 = 10.7mz) if you change your mixing freq. up by 1 mz to 62.855 you will now be receiving 73.555. The mixing freq. can be changed by changing a crystal or by using a programmable VFO (variable frequency oscillator) like tuning in a FM radio station. ( programmable VFO is a synthesized receiver) in a duel receiver this happened twice with two IF’s