Calibrated

Knob

PERFORMANCE OF ZN414  AND EQUIVALENTS ON SW : 

Considering various coils mentioned above ZN414 performed fairly

well on SW. I could  regularly tune VOTurkey on the 41Meter Band

and at night  others were tuned both on 49 and 41Meter Bands.

However during daytime both with the 7 and 5 turn coil no other

broadcast could be tuned. Shortly in spite of AGC adjustment in

most cases performance was not very promising during daytime.

Reception of SW was only possible during the night time on both

the 49 and 41Meter bands.

Then a MK484 was tested instead. During daytime, I could tune

several broadcasts such as BBC, China, Moscow, Teheran, Balkan

Countries Radio Vatican and additionally some Arabic Broadcasts.

VOTurkey and several others of unidentified languages. The MK484

performed much better on higher frequencies compared to ZN414.

The third alternative was a TA7642 , which also performed well .

The performance on higher frequencies was better than ZN414

and almost similar to MK484.The AGC level related with TA7642

was much different and the Potentiometer had to be readjusted

for an efficient  result.

Finally a YS414 was tested and performed similar  to ZN414 .

To conclude ZN414 and YS414 performed till the 41 meter band,

whereas both MK484 and TA7642 went as far down as the 25Meter

Band performing much better during daytime, compared to former

two .You may however get identical results both with the former IC’s

Depending upon the distance and signal strength of the transmission

and individual parameters of the IC’s You own.There is no need to

remind about the time difference between Your Hometown and the

broadcast.I have to draw your attention to the fact that even at home

the quality of reception differs from one room to the other.

Components :

The reconstructed receiver is exactly the same as far as the

components are concerned except the 2K, VR1 was replaced with

a 2.2K one with an On/Off switch .

This was done rather forced as inspite of the efforts I spent, I was not successfull in finding a (B is the code )2K Pot with switch.

The panel of my Project Box is rather narrow for all the parts plus the telescopic aerial added to the body of the project box.

A Vernier or slow motion drive is definitely needed for efficient tuning

on SW. The former on/off switch I used now acts as the wavechange

switch as I am only using a 5 Turns single coil for SW.

My Future Plan is to use a tapped coil to cover the low frequency SW

Bands.

The Project Box used with this version is slightly larger than the former

one, sufficient for the receiver as some components like battery ,coil,

ferrite rod,VR1,telescopic aerial should not be too close to each other .

You have to be careful to avoid hand effects by touching or holding any

metal object in the circuit such as the antenna, the V/C etc.

Before I finalize I want to remind You about the performance

of the receiver, which is not as good as a superhet however with the

broadcasts received You will be satisfied that You have achieved a

“Mission Impossible”

Volume Control

The modified circuit is on the the next page.For the sake of simplicity it is

introduced again .The text reflects  full  information about the components

and coil details.

Knob with pointer

Project Box

Volume Control

Knob

470 Ohm Resistor