At 09:01 AM 12/9/2007, you wrote:

>Hello to all SoftRock builders,

>

>Can anybody explain me - is it possible to use T30-2/T37-2 (red) cores

>instead of T30-6/T37-6 (yellow) ones in the SoftRock RXTXv6.2 40m_30m?

>Is it critical change?

>

>--

>Best regards,

>Sergei UA6LGO

>

Red and yellow cores can be used at slightly different but

overlapping ranges, here is some information;

Red #2

Frequency range 250KHz to 10MHz (good to 30M)

stability 90 ppm

AL is higher that #6 cores so it takes fewer turns to arrive at the

same inductance.

Yellow #6 cores

Frequency range is 3MHz to 40MHz

stability 35 ppm

AL is lower than Red so it takes more wire turns to achieve the same

inductance as a red #2 core.

As you can see they both cover the 3MHz to 10 MHz range but because a

different AL value they need different number of turns.

The formula is Inductance in uH = (AL * (Turns^2))/1000

Here is a link to a site that has some useful information and more

important a piece of software that will let you calculate the number

of turns required in and inductor;

<

http://kitsandparts.com/toroids.php >

Since those transformers in the Softrock constitute tuned circuits if

you substitute the cores with their range of compatibility you must

change the number of turns of all the windings. In substituting a red

core for a yellow core all the windings need to have fewer turns.

I have substituted the other way around in some cases because I like

to use the bigger cores so a few times when building a SoftRock I

have substituted a larger yellow core for a smaller red core and

changed the number of turns to compensate for the differences in the AL factor.

I hope this helps, the schematics of the SoftRocks have both the

number of turns and the desired inductance so plug the into the

calculator and the core type and it will tell you the number of turns

needed. On the input transformer the primary and secondary have the

same number of turns so you would adjust both number of turns together.

Cecil

K5NWA

www.softrockradio.org www.qrpradio.com

"Blessed are the cracked, for they shall let in the light."