Ferrite Transformers, Core Material Type for 28 Mhz operation (43 or 61)?

[LeapFrog]

Inside the common "2879 class-c box" cb amplifiers, what is the 'preferred' material used for the transformers, type 43 or type 61? I'm considering a (x2) 2SC2879, 28-30Mhz non-linear amplifier that would be used for 10 Meters CW.
Example of transformers i'm talking about:
[photo="medium"]4417[/photo].
.

Thank you, & the best of regards!
-LeapFrog

 

[loosecannon]

use the type 61 material if you are building an amp that will only be used on the CB band or 10 meters.

if you are building an amp that needs to work on 160-10 meters, then type 43 will work better than the type 61 at the low freqs.
LC

 

[LeapFrog]

use the type 61 material if you are building an amp that will only be used on the CB band or 10 meters.

if you are building an amp that needs to work on 160-10 meters, then type 43 will work better than the type 61 at the low freqs.
LC

Thank you, Lossecannon this a straight forward answer that tells me everything I need to know.

Later I can look into the technical aspect if I need a deeper understanding, I tried at first to figure it out from some googling and I couldn't make heads or tales of what I was reading!

Thank you once again LC!
-LeapFrog

 

[BBB]

Not all are created equal. Sometimes bigger is better = More heat dissipation.

http://palomar-engineers.com/ferrit...Toroid-Cores/c/21444154/offset=0&sort=nameAsc

http://palomar-engineers.com/ferrit...errite-Beads/c/21444155/offset=0&sort=nameAsc

Big-Uns:



Little ones:

 

[LeapFrog]

Not all are created equal. Sometimes bigger is better = More heat dissipation.

http://palomar-engineers.com/ferrit...Toroid-Cores/c/21444154/offset=0&sort=nameAsc

http://palomar-engineers.com/ferrit...errite-Beads/c/21444155/offset=0&sort=nameAsc

Big-Uns:



Little ones:

Thank you BBB, great photos + links!

I found a chart on the palomar site thanks to your links!
I take it the "Tuned Circuits – Coil" column is not to be interpreted as an operating frequency range for the various types of ferrite.

"Wide Band Transformer" is the column for what frequency range you are using? I am uncertain though, can someome confirm if i'm reading the chart correctly?

I'm going to go with type 61 for this mono-band build.

Thank You Gentlemen.

Edit: Just saw that I mispelled Loosecannon, sorry brother. (no more edit time)

 

[Crusher]

Since you stated only those 2 materials, yes 61 is better. But on output, you may also want to play with 67. I have used that on some of the LDMOS stuff with great results.

 

[Crusher]

Since you don't want to take the time to understand the differences like permeability. Are you actually building amp or copying off of another's design? Just wondering because of tuning. Also if you are building for 28mhz/ 10M. Hopefully going more for quality. Not quantity. Are you going to use standard 120pf from collector to ground or different value? Will amplifier be biased ab2 or B?

 

[LeapFrog]

Since you don't want to take the time to understand the differences like permeability. Are you actually building amp or copying off of another's design? Just wondering because of tuning. Also if you are building for 28mhz/ 10M. Hopefully going more for quality. Not quantity. Are you going to use standard 120pf from collector to ground or different value? Will amplifier be biased ab2 or B?

Crusher, I'm taking baby steps, crawling before I learn to walk.
My plan is to copy a classic design that is a common "CB amp", then understand all of the parts of the circuit & how they go together after having built it. (backwards I know)

My plan is to add a proper thermal tracking bias circuit to the amplifier, after I have a working class C box (that may be used with F.M./C.W. for a brief period).
I need to understand the basic principles of how the amplifier works first, but the end goal will always be a linear operation of the amplifier. I would like the best possible reproduction of the original signal, I'm unsure what class of operation I will actually be able to reliably achieve.

I care to understand more about the different type of ferrite blends and how the permeability factors into the amount of transformer windings used for a desired ratio.

(Many different aspects of science are involved here (amplifier design), this is certain; I believe it will take quite some time to retain the information and have a general understanding of what is truly happening. Science is of much interest to me, & in order to do any accurate work with repeatability, I must first practice on my general discipline. After all, science is in the details! If I ever care to design something advanced of my own, I must first have a very thorough understanding of all the principles at play.)

At this point in the game I am only trying to copy a very simple design and then make it better.
The amplifier will have a proper "Low pass filter" for mono band use after the output stage, I don't quite understand yet what all is involved, but I believe it is an LC pi filter network I need to design for the intended frequency range.

I'm just in the infancy of understanding how an amplifier works, some of the concepts I'm discussing here I have no clue about so I must continue to read and ask some questions for people with experience when I get stuck.

I'm on a very limited budget for this project and will be using salvaged parts, like case/heatsink & some capacitors/resistors. The transistors, & transformers will be purchased new along with some mica capacitors and high watt resistors that I likely do not have here.

I am looking for quality not quantity, the ultimate goal is to create a proper amplifier for single side band use & A.M., the two 2SC2879's will not be pushed to (or beyond) the rated output stated in the datasheet, instead the amplifier should produce clean power and hopefully last a long time.

I do understand the current demands will be greater running the amplifier with any bias above Class C, this will be accounted for, as I'm not looking for huge output numbers.

Thank you to everyone who has contributed to the thread thus far, & I encourage anyone to jump in and add any criticism/comments/tips/suggestions.

73
-LeapFrog