Filter Cores question

[Wayne Rogers]

Hello, -  I found a schematic some time ago and decided to give it a go, this schematic is called a Nilma Radio; now this is my second attempt at it.

The first time I damaged the board tracks with excessive heat, by using an incorrect soldering iron, and I didn’t at the time feel like printing out and drilling another board so I dumped it.

However some years later for some reason I have decided to have another go at it.

This is a Hobby of mine and I need something to keep my interested in something.

Now this is what I wonder, this is what I presume to be a Butterworth Tee Filter, for the bottom and top side of the HF range.

The marked top line I presume has a cut off is at around 13 MHz and the bottom line at 28 MHz.



Now I believe that I read that a low pass filter allows through everything under its cut off mark and grounds everything over it.   

So I am wondering if I will get away with using T37-2 cores for winding  all of the inductors,  being that are meant to be rated between 2 and 30 MHz.

Or should I use them only for the top line and use T37-6 cores for the bottom line.

T37-6 cores are meant to be good from 10 MHz to 50 MHz.

I only ask because, in my junk box; amongst the other parts I was going to use in my last attempt, there were T37-6 yellow cores wound along with T37-2 red cores.

So there might have been a reason back then but I can’t remember what it was.

So is there anyone out there who can give me a hint to point me in the right direction of what I should use and explanation of why.

I look forward to some advice thank you

Wayne Rogers

 

[HarryA1]

What is a Nilma Radio?  Are these band pass filters used in the antenna input used when selection one of two radio bands?  If you have both types of inductor cores why not use them? As you are on the upper limit of the T37-2 cores and the T37-6 cores (lower limit) do not need to go below the upper limit of the T37-2 cores for the higher frequencies.

 

[Wayne Rogers]

What is a Nilma Radio?  Are these band pass filters used in the antenna input used when selection one of two radio bands?  If you have both types of inductor cores why not use them? As you are on the upper limit of the T37-2 cores and the T37-6 cores (lower limit) do not need to go below the upper limit of the T37-2 cores for the higher frequencies.

A Nilma radio is  some radio designed by some Indian bloke called Ashhar Farhan in the year 2014 I believe,

It was something I got interested in reading when I found the site years ago, 

The radio is meant to cover the whole HF range from 80 meters to 10 meters so I read, 

I have not got there  yet in its construction plus the fact if and when I do, a licence would be required to use it if it worked.

Something I would think about if I ever get there.

The radio it self is controlled by a Arduino Micro controller.

At the time of finding the site I was newly into learning a bit about those micro controllers.

In any case the radio is meant to cover AM and Side Band and also have Morse Code.

There are probably a couple of other tweeks it has too, but I am not fully up on Amateur Radio.

 For me it was just a challenge to build it and learn along the way basically on the circuitry side of how it works.

As for the T37-6 Cores I do have a couple of them yes but I would have to order more if I was going to fit them into the board.

There filters are used to filter what comes on and goes out of the circuit on the antenna line.

So I read they are meant to be from 1 to 15 MHz is one and from 15 to 30 MHz the other, however I did put those numbers into an online calculator and didn't come up with those figures. 

But for now  for me it is a suck it  and see thing, I have also added a piece into the board between the last trifilar transformer  as to where I can add a pair of pins, these can be jumped over or used to add a amplifier into that point.

Mainly because the filter come directly off the mixer through a relay.

There is a small amplifier I found designed by another bloke called Harry some wheres up around Canada I think which might work well if needed in there.

Anyways I will leave you with the schematic of this particular radio and if you would like more of what I have on it I would be happy to send it to you.