RC Radios, Transmitters, Receivers, Servos, gyros Discussion all about rc radios, transmitters, receivers, servos, etc.

Single VS Dual Conversion RX's & Interference

Reply

Old 06-18-2007, 11:53 AM
  #1  
dasintex
Thread Starter
My Feedback: (10)
 
dasintex's Avatar
 
Join Date: Sep 2004
Location: Displaced Canadian in Central Texas TX
Posts: 2,598
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default Single VS Dual Conversion RX's & Interference

Are you more likely to get glitches/interference with Single Conversion Receivers then Dual Conversion? And would you be more likely to get Inteference when in the Air with several other Planes like in Combat, even though everyone is on different channels?
dasintex is offline  
Reply With Quote
Old 06-18-2007, 12:30 PM
  #2  
BarracudaHockey
My Feedback: (11)
 
BarracudaHockey's Avatar
 
Join Date: Jul 2003
Location: Jacksonville, FL
Posts: 23,389
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default RE: Single VS Dual Conversion RX's & Interference

There are fine single conversion recievers that use different schemes for noise rejection.

DC does nothing to help "glitches" its to prevent interference with other transmitters in the same band, you can read all about it here http://www.torreypinesgulls.org/radios.htm
BarracudaHockey is online now  
Reply With Quote
Old 06-18-2007, 12:58 PM
  #3  
dirtybird
My Feedback: (5)
 
Join Date: Jan 2002
Location: San Tan Valley, AZ
Posts: 5,768
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default RE: Single VS Dual Conversion RX's & Interference

Dual conversion receivers are the best. Thats why nearly all professional applications use it. As for glitches no receiver is better than another.
For your application in combat I would think it would be required. The purpose of the dual conversion is to eliminate the image frequency. Image frequencies will only exist where many transmitters are in use.
I have a Multiplex IPD SC receiver, and it works just fine, but I would never use it in a high density environment like a combat tournament.
dirtybird is offline  
Reply With Quote
Old 06-18-2007, 12:59 PM
  #4  
BarracudaHockey
My Feedback: (11)
 
BarracudaHockey's Avatar
 
Join Date: Jul 2003
Location: Jacksonville, FL
Posts: 23,389
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default RE: Single VS Dual Conversion RX's & Interference

So why are nearly all JR recievers single coversion?
BarracudaHockey is online now  
Reply With Quote
Old 06-18-2007, 01:34 PM
  #5  
hebertjj
Senior Member
 
Join Date: Jan 2002
Location: Knoxville, TN
Posts: 324
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default RE: Single VS Dual Conversion RX's & Interference

This question points out some interesting things that are happening in the R/C electronics world. There are SC Rxs and then there are SC Rxs with additional technology. Used to be, JR was the only one with additional tech ( ABC tech ) and all the others (as far as I know) were short range (500 to 1000 ft) Rxs meant for indoor and park flyers. Now Hitec, Castle Creations Berg, and probably others offer SC Rxs that claim full range and even Tx recognition that offers protection even if some else turns on a Tx on your chan. Not to mention the lowering prices (probably due to SS competion). FMA offers 6 chan DC Rxs for $45; Tower has Hitec Electron 6 DC Rxs for $44, and 6S SC Rxs for $28. Castle Creations 4 chan SC Rxs are $27 and 7chan SC Rxs are $46. All of these Rxs are full range and tiny enough for about any park flyer.
hebertjj is offline  
Reply With Quote
Old 06-18-2007, 01:59 PM
  #6  
fizzwater2
My Feedback: (60)
 
Join Date: Aug 2004
Location: Paola, KS
Posts: 2,765
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default RE: Single VS Dual Conversion RX's & Interference

There's another thing to consider in the single / dual conversion receiver discussion. The crystal in the receiver is arguably one of the most vibration sensitive components, and subject to fail if you get enough vibration.

A single conversion RX uses one crystal. A dual conversion uses at least two, if not 3 (10.4 crystal filter) in it's design. Yes, a dual conversion RX is better at image rejection. JR gets around this by not offering any receivers below about channel 15, if I remember correctly. This puts all of the image frequencies outside of the normal RC band, and significantly reduces the problem with image.

You pays your money, and you takes your chances.. same as with anything else. I use the DC electron 6, the JR SC R700 and R770, and a miscellaneous handful of Futaba DC receivers, and knock on wood, haven't had much in the way of trouble with any of them.

fizzwater2 is offline  
Reply With Quote
Old 06-18-2007, 04:28 PM
  #7  
dirtybird
My Feedback: (5)
 
Join Date: Jan 2002
Location: San Tan Valley, AZ
Posts: 5,768
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default RE: Single VS Dual Conversion RX's & Interference

The problem with SC receivers is the image frequency. As pointed out in an above post, JR gets around this by not offering a receiver where the image frequency is likely a problem. A single conversion receiver is cheaper to make and lighter. Berg,FMA and others contain circuitry that will reject transmissions that are not of the correct signature. However if the image frequency is there it will activate the automatic gain control and reduce the receiver sensitivity.
In the final anaylsis the dual conversion receiver is the best overall way to do it. Yes there are more crystals in one than the SC receiver. In the five years I served as the factory rep for Kraft and Logictrol I never saw a bad crystal that wasn't caused by a crash.
I dumbthumbed a Pitts full bore special straight into the concrete. I broke the crakshaft, ignition module, the receiver and totaled the aircraft. All three crystals and the ceramic IF filters were intact but the receiver didn't work.
dirtybird is offline  
Reply With Quote
Old 07-11-2007, 08:32 AM
  #8  
golfingguy27
Senior Member
 
Join Date: Oct 2002
Location: Frederick, MD
Posts: 277
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default RE: Single VS Dual Conversion RX's & Interference

I have a Multiplex 3030 Tx that I haven't used in a few years and am getting back into flying again. The Rx I have is Multiplex's Micro 7 channel Single Conversion IPD. The plane I am putting together is a somewhat big, slightly expensive gas (possible rf noise??) plane. Should I be worried about this Rx being single conversion? Would something like there 9 channel dual conversion IPD be better? Are there any other relativley inexpensive (under $100) Rx's I should think about? I don't want to lose this plane due to sub par equipment, but also can't afford to spend a fortune either. Thanks for any advice!

Todd
golfingguy27 is offline  
Reply With Quote
Old 07-11-2007, 12:07 PM
  #9  
dirtybird
My Feedback: (5)
 
Join Date: Jan 2002
Location: San Tan Valley, AZ
Posts: 5,768
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default RE: Single VS Dual Conversion RX's & Interference

I flew a 72"Weeks Special powered by a G-45 for many years with the Multiplex IPD single conversion receiver.
dirtybird is offline  
Reply With Quote
Old 07-11-2007, 02:26 PM
  #10  
bruce88123
 
Join Date: Nov 2004
Location: Memphis, TN
Posts: 11,703
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default RE: Single VS Dual Conversion RX's & Interference

This one time, at band camp................
bruce88123 is offline  
Reply With Quote
Old 07-11-2007, 03:43 PM
  #11  
Flying Geezer
My Feedback: (14)
 
Flying Geezer's Avatar
 
Join Date: Apr 2003
Location: Bowling Green, KY
Posts: 1,326
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default RE: Single VS Dual Conversion RX's & Interference

Dual conversion receivers have better rejection to all unwanted signals (those not on your specific channel) than single conversion.

You must be concerned about signals other than other RC transmitters.

In my work I talk to RCer's all over. I have developed a habit of asking what radios they fly, just out of curiosity.
I talked to a modeler in Oklahoma city that said most at his club fly JR. He went on to say that they used only Hitec Receivers because the field was close to the interstate. Their theory was that they were getting hit by the truckers on CB radio. He said the switch to Hitec, (dual conversion) solved the problem.

Which is safe to use depends on a lot of variables. Range check and take glitches seriously. If glitches are common at your field, or with your radio, find the cause.
Flying Geezer is offline  
Reply With Quote

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off


Thread Tools
Search this Thread

Contact Us Archive Advertising Cookie Policy Privacy Statement Terms of Service