ADC-40 FI ? (KD1JV QRP)

[QRP'er]

HI,
I'm building the ADC-40 made by KD1JV.
I would like to know what kind of 10.7 FI is used as filter because there
are several type of FI with different characteristics spotted by different
color.

Could someone tell me the color I need ?

Thanks a lot.

Here the link of ADC-40 : http://kd1jv.qrpradio.com/ADC/ADC-40.htm

72

[Tim Shoppa]

He says he used a Mouser 42IF123 "green" IF transformer but he notes
that 42IF122 "brown" works too. It's there primarily to be a easy 7
MHz resonant circuit although the impedance transformation is a useful
side effect here.

Tim.

[QRP'er]

> I'm building the ADC-40 made by KD1JV.
> I would like to know what kind of 10.7 FI is used as filter because there
> are several type of FI with different characteristics spotted by different
> color.

He says he used a Mouser 42IF123 "green" IF transformer but he notes

that 42IF122 "brown" works too. It's there primarily to be a easy 7
MHz resonant circuit although the impedance transformation is a useful
side effect here.

Thanks a lot Tim.
But it is amazing because the two FI have very different impedances :
42IF122 = 15K/0.3K
42IF123 = 25K/4K
Which are rather distant from one another...

OK I will try

[Dave M]

I think the objective of the 10.7 MHz IF transformers here is their ability
to be retuned to resonate in the 40M band (7000-7300 KHz). The actual
impedances aren't critical as long as 40M resonance can be achieved.

--
David
masondg44 at comcast dot net

[Tim Shoppa]

On Oct 26, 3:36 pm, "QRP'er" <nexiste...@free.fr> wrote:
> But it is amazing because the two FI have very different impedances :
> 42IF122 = 15K/0.3K
> 42IF123 = 25K/4K
> Which are rather distant from one another...

KD1JV is using them as readily available components that can be made
to resonate on 40M.

That section is both a narrowband filter and a matching network; the
topology around two coupled resonant LC's guarantees the
narrowbandedness more than any individual component values. And
mismatches can largely be accomodated by tweaking the cores. I'm sure
there's some difference in core position depending on what part you
use but as long as it peaks up in the 40M band you're good to go.

If you don't have those Mouser cores, don't worry, you can tear apart
any FM radio from the past chunk of a century and find 10.7MHz
transformers in it.

Tim.

[Kenneth Scharf]

For that matter you can also get a T-37-6 or T-50-6 toroid and make your
own transformer. You'll have to use a trimmer cap to tune it since
toroids don't have tuning slugs but the end result won't be much bigger.
www.kitsandparts.com has toroids cheaper than anybody else and they have
all the winding data on their site.