Saturday, June 27, 2015

BITX, Single Frequency Receiver-1

Time signal receiver,  10 MHz, using the  BITX IF module...


I was searching for some receiver and lots of things going on. Till this date I was using the reactive elements in the amplifier. Used chokes, LC , transformers etc... but now a days we don't get the alladin type tunable L using the ferrites.  Generally metal IF cans are found, but how to re-wind and what will be the  behaviour is  problematic. I liked the resistive RF amplifier. They behave predictably. Just take care of the "beta". transistor gain on that freq.

As everybody was saying build the bitx, build the bitx. I have two pcb  to be populated plus one kit waiting for repair.

I say, just to understand the design,  why not give it a try ? and presto, here is the baby of the bitx.. The inspirations was Farhan's first dual band transceiver, then came beach40 and its variations by various hams KNOBLESS wonder. JR8DAG

Here is the project:-


I used two IF amplifiers. two/three matched xtal as filter. Only frequency selective element here is the xtals. At first I was not believing how the xtals can pass signal. My belief was not helping me. I said don't think just do as directed.

There is RA3AAE, sub-harmonics detector for CW, Single stage oscillator using 5mhz xtal. Why this type of detector ? I don't wanted to use the ferrite core / toroid. See that there is no ferrites used ! By the way the time signal is AM so a envelope detector / single diode / should be used. 

In the BPF I will make some air core L and filter such that it does not require any tuning and become wideband.

Then the standard bc549c pre amplifier, volume control, LM386 audio amplifier. Give 12 volt power connect a small 1 meter antenna and beep, beep, beep the 10 Mhz time signal is clearly heard. As in the day-time propagations fad, its less audible. In night-time its loudest. There is no am break-through. The carrier note is annoying , I will change Product Detector to the AM detector...

There is no need of any further RF Pre-amplifier. Just connect a choke and only small antenna and it works.

Basically I have intermarried  all working modules... but the end result is impressive.

For completeness sack i made the pcb patterns , see the pictures ( will upload pictures later on ) give it a try for making the receiver. Then again will make second pcb pattern for DSB transmitter using the  7159kc xtals. I have plenty of it.

PCB pattern of audio and if stage.

The project for contest-4 ends here. (As promised to 2dev.)

Something Similar.

A dsb/ssb transceiver ? I am thinking of making test bench type pcb so there you can test the freq by just changing the LO-xtal and Xtal filter... It will be interesting instruments to check my cw-tx.

Further in  project;-

I have made one transistor mixer, will brew up a local oscillator and try to receive the 20 meter band signal... Superhet receiver. As  the eaty-beaty receivers mixer did not work properly, time to redesign it also. will see to it later. There is no receiver on shack, dc rx gone, bitx-20 gone, marine gone bust, its high time I make something on 20 meter.

My second prototype is successful. I made the pcb. Its mixed tech. For oscillator RA3AAE demodulator used the copper island for IF amp and AF amp used no hole pcb. Fact is I don't have suitable drill and my big drill has broken all the bits... Its sound good.  Its a good project...
( here is the link )

Will try to make the DSB tx using ta7358ap and RX using this topology. I already have one analogue superhet receiver.... will see what I make,,, after all its time-pass.... ( not done yet- aug 2015)

Pious Me

Will also finish up the 14.315kc receiver based on this bitx IF. If it works then one of my friend will get to complement  cw-tx on 14315kc. But, that will require on air test with another friend. If I hear the tone then can pass it to other. Possibly he will come on air with it... and might break his jinx... I am committed to help him break the jinx.

( as of 17 august 2015 I converted this into a 20 meter receiver. Ohh that is the reason I could not find it on my archieve  here is the link  )

And its possible I will finish up my own bitx also he he he, who knows, the possibility is immense. but, what will be the time frame for making my bitx... not sure... personally I am QRT.

Well this is just time pass, a very good time-pass and I like it...ENJOY

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