DRM Converter for Degen 1103

[Siber]

The receiver is equipped with the repeater of IF 450 kHz signal .
+5V moves on the screen wire.

The converter is made on a separate board.
By selection of the condenser C7 it is possible to increase the frequency 462 kHz.
For IF 12 kHz Output connection to the computer it is necessary to use a screened cable.
Using of +5V from USB port is possible. In this case it is necessary to increase capacity of the condenser C10 to 1000 mF and to change the LED to easy diode.
The picture of revision I'll show later

[KD7YUF]

Interesting board but I have a question about the IF repeater. Is it because the IF needs to be amplified before it reaches the down mixer or for other reasons? The unfortunate thing is that the 465 KHz local oscillator might be a problem since that particular ceramic resonator or an equivalent crystal could be difficult or impossible to find in the US and I know I am having trouble finding one at this time.

[Siber]

Is it because the IF needs to be amplified before it reaches the down mixer or for other reasons?
The IF signal goes out of the receiver where are too much of noises. They can delve into the receiver. Besides it provides an influence minimum to recever's IF signal. It is a buffer cascade.
the 465 KHz local oscillator might be a problem
The 465 KHz oscillator is one of widely available in our shops.
The frequency of generator must be 462 kHz, use another one.

There is the picture of revision of the receiver board

[KD7YUF]

What would you recommend as a substitute for a 465 KHz ceramic resonator or crystal since I am unable to find one at this time? This down mixer actually looks a bit more easily done than the ON6MU one since the SA602 mixer is not used and I could very well get the parts at the local Radioshack electronics store except for a crystal or ceramic resonator for the given frequency. Except this is not for the Degen 1103 but rather the Icom IC-R75 communications receiver which has a much cleaner 455 KHz IF so the repeater board will most likely not be needed.

[Siber]

Instead of the ceramic resonator You may use induction coil of any IF 455 filter
Value of capacitances on the pic. are approximate. You should select them
See any circuit on SA 612. There is the same generator

[Siber]

I have found out the discrepancy in datasheet on TA7358.
In the converter I used amplifier of this microcircuit.
The most important thing is that among of MC there are examples which have 1 and 2 pins functions correspond to the scheme and another which functions are correspond to the bottom drawing. (The МС have different marks of the manufacturer)

[mvs sarma]

I have found out the discrepancy in datasheet on TA7358.
In the converter I used amplifier of this microcircuit.
The most important thing is that among of MC there are examples which have 1 and 2 pins functions correspond to the scheme and another which functions are correspond to the bottom drawing. (The МС have different marks of the manufacturer)

Sorry, i am late by 8 months
i never saw the comment so carefully. as I see now, i want to offer my comment. the first amplifier of the chip (FM front end) is a common base amplifier. thus base would be bypassed. and input signal is given on emiter.
there is no confusion on this , i personally feel.

[Siber]

there are examples which have 1 and 2 pins functions correspond to the scheme and another which functions are correspond to the bottom drawing.
I had in mind that in different chip batches the pin 1 and 2 can be mixed up
Regards,
Vladimir

[Siber]

Converter 450/12 kHz inside of Degen 1103

Continuing the theme Degen 1103
Pic 1. Distinction is the additional filter IF 450kHz
If You have a noise from the power supply or the computer, You can use the optical isolator board 2,pic2

[Siber]

Converter 450/12 kHz inside of Degen 1103

View of the converter board, pic 3,4 and pic 5

[Siber]

Converter 450/12 kHz inside of Degen 1103

Revised and Locations within the receiver

[mvs sarma]

Siber, all pcbs and especially the concept of Opto islator looks impressive.
but i fear most normal optos cant transfer 10KHZ band arouind 12KHz
May be 6N135 like devices might work

I admire the copncept of using opto isolator. A noval thought at voice band

[Siber]

Dear Sarma
I started experimenting with 6N135.
Then I studied the linearity and dynamic range of different optos.
You should know that the operating points of optron's LED(by R3) and phototransistor(by Mic In of Sound Card) are set by DC.
The main problem of using optos as analog isolator is the noise from the electricity-light-electricity conversion.