dual conversion vs. single conversion ????

[C2]

this is my favorite subject

what's an image?

 

[W5LZ]

The biggest difference between a single and dual conversion radio is selectivity. The single conversion has a bit more sensitivity, but isn't quite as selective as it could be. The dual conversion is slightly less sensitive but has more selectivity, which means getting rid of stuff you don't want to hear. If done correctly, that dual conversion has more sensitivity than is really required. So, pick the one you think supplies the most of what you think you need. I'll that that dual, or triple, or quad conversion over a single conversion receiver any day. Suit your self.
- 'Doc

 

[C2]

but i think what i'm hearing here is that, in context of singular side band and cb radios, there is only singular conversion.

 

[dudmuck]

this is my favorite subject

what's an image?

The HR-2510 uses a first (and only) I.F. of 10.695MHz.
This radio's PLL injects a carrier (into first mixer) at 37.88MHz to receive CH19.
37.88 - 10.695 = 27.185MHz.
But the problem there is that 37.88MHz + 10.695MHz = 48.575MHz
So if there is a really strong signal there, then you should receive 48.575MHz on CB Ch19.
However, there is a 26 - 30MHz bandpass filter before the first mixer. And CB antennas dont work too well at 48MHz, so its shouldnt be much trouble.

By contrast, the cobra 29 PLL injects at 10.695MHz below the CB frequency. And also uses a 2nd I.F. of 455KHz. This the clever approach of the cobra-29 design is that the reference crystal of 10.24MHz is 455KHz away from the 10.695MHz first I.F. So this makes the cobra 29 a nice inexpensive way to have a dual-conversion receiver.

The selectivity of a receiver comes from the I.F. bandpass filters. Dual or single conversion or whatever.

 

[MarkIV]

Chiming in on a ancient post. I have never heard a single conversion CB on AM we're talking here. (There all single on SSB). That sounded near as good as a dual conversion. They always sounded muddy. Dual in my book is the way to go!

 

[LeapFrog]

Chiming in on a ancient post. I have never heard a single conversion CB on AM we're talking here. (There all single on SSB). That sounded near as good as a dual conversion. They always sounded muddy. Dual in my book is the way to go!

It's in reference to the receiver,
The transmit characteristics of my Cobra 142GTL are close to that of a 2000GTL, but the the 2000GTL has a "tighter receiver" if that makes sense, it's a "dual conversion" setup.
The "single conversion" 142GTL receives okay, while still being sensitive.. it is not as "selective" as the 2000GTL (more adjacent channel noise and "mud").

 

[ButtFuzz]

I like donuts

 

[LeapFrog]

I like donuts

I like turtles

 

[Tallman]

Dual conversion is more selective in that adjacent channel signals are rejected and enhances the desired signal quality. Not the cheapest way to build a radio or easiest way to go. From a manufacturing point of view, "Less is More."
If a manufacturer can shave a nickel off of the cost of one unit you can bet your bottom line they will. Over 100,000 units that will give the company $5,000.00 in extra profit.

I LIKE JELLY FILLED DOUGHNUTS!

 

[Onelasttime]

If you have substitution boxes for resistors and capacitors you can make a single perform almost as well as a double. THe problem is you have to go through the entire receiver circuit one part at a time sub'ing values to see what will improve the receiver. It is not universal from one chassis to another so it is not CB Trick type mod that you can write down the values and expect it to work on every like chassis. It is time-consuming at $75 an hour bench time. So it is easier to start with a double than it is to go through all the work to make a single come close. You will notice it is harder at times to copy a signal you can hear but the voice is just too muddy to understand even though it has plenty of audio in the signal. It does not matter if we are talking AM only or AM/SSB it holds true in my experince. That said I own a President Lincoln and 2 TRC 465's and I think they work just fine in spite of being single conversion. All my other radio's though are dual and it does make a difference.

 

[hotrod]

If you have substitution boxes for resistors and capacitors you can make a single perform almost as well as a double. THe problem is you have to go through the entire receiver circuit one part at a time sub'ing values to see what will improve the receiver. It is not universal from one chassis to another so it is not CB Trick type mod that you can write down the values and expect it to work on every like chassis. It is time-consuming at $75 an hour bench time. So it is easier to start with a double than it is to go through all the work to make a single come close. You will notice it is harder at times to copy a signal you can hear but the voice is just too muddy to understand even though it has plenty of audio in the signal. It does not matter if we are talking AM only or AM/SSB it holds true in my experince. That said I own a President Lincoln and 2 TRC 465's and I think they work just fine in spite of being single conversion. All my other radio's though are dual and it does make a difference.

i too own a president lincoln .i also have a uniden washington and far away stations are better heard on my washington. channel bleedover seem about the same

 

[Onelasttime]

If you have a decade machine or substitution box changing out the resistors and caps in the receive and then realigning can make a huge difference on a single het radio! It will almost sound like double conversion. It is time-consuming to do so most tech do not do it. You can do the same thing to the rx audio/

 

[kopcicle]

this is my favorite subject

what's an image?

http://www.arcticpeak.com/radiopages/imagefrequencies.htm

 

[Norman H]

Yep

Remember, the Uniden 8719 SSB Chassis (148GTL, 2000GTL, Some Grants, etc) is dual-conversion on AM only. SSB Mode is Single Conversion.

Yup. My RCA Co-Pilot 14T302 is a dual as well. Hooray for our side!! Norman.H.