Thursday, February 20, 2014

toroid transformers

RM96 second part is written here. (3march2014).

 Toroid transformer winding

I was making the linear of rm96. wanted to see the toroids. Put query on facebook then searched the web, i was surprized that in google search my web page was showing the rm96 of vu3kod, it was clear in one aspect.
that how to wind the primary.
Rule of thumbs are:-
One turn is one pass from core.
idealy 30  %  of core should be free i.e to spread the wire equally on rest of the portion.

Secondary should be wound over the primary. not spread like primary.
where to put the secondary - in middle. Now, which one is hot /inphase of secondary? (still to know i feel that the same directions starting points are in phase. Inphase means the sinusoidal signal cycle is sympathetic to input . Out of phase means -it is opposite of input cycle). Secondary winding starts from the arrow shown and the same way and direction as the primary.

T1 (L11 of rm96 )an T2 (L12 of rm96 ) turns details are.

L11- 30 turns primary, 4 turns-secondary, 28 swg, on t-05 hfa.
L12- 6 turns primary, 4 turns-secondary,28 swg, Looped through an 1/2" balun core.

To put in the paper and actually see the thing is both a different type of experience, intelligence. I still want to see others rm96 boards which used different type of toroids. Over the years we have made lots of rm96 , ats-1,hmy2k8 etc etc but no one has put the internal picture of the ckt.  Its okey. Once you know one, then you know all.

Indicators i rely

These are not proper instruments with accuracy. But, they gives the tale tale sign and as a rough estimate useful for quick test. here are they.

(1) a simple diode with 10k resistor to test whether the dc supply is present or not.

(2) it is a simple diodes (as a rectifier)  which drives a small led to indicate the rough presence of rf. I put it with dummy load to see the presence of rf. it does not measure anything.

(3) same as first but two LEDs back to back. connect one end to ground and other to test the vcc.

(4) Another not shown here is a rf sniffer. It just indicates the presence of rf with led light. ckt is same as 2 but a two direct coupled transistors are put as amplifiers to drive the LED. this can even work as a very crude fsm.

(Please note these probes should not be used with ac line voltages , it will give you plenty of electric shock ! )

RF Power calculations:- 

dummy load & rf power calculations
In the age of microprocessor and digital age who wants to measure the power in old fashioned analogue way. No need to have those latest fency equipments, if you dont want accuracy and exact quantity.

A time proven method can work for you.

All the theories and practice see in the picuture. Resistive load is designed for qrp. i could  only find 100 ohm ,2 watt  in carbon but high powers resistors were all wire wound. So, be careful what resistors are you using as a load. For RF load t should be carbon variety. If high wattage resitors are are not available ,then you can use smaller values carbon resitors, whose parallel value is roundabout 50 ohm.

For measuring , use the dc range of voltmeter. for a 1 watt ,5 watt a 20 volt range will be okey. calculate the power as given in the formuas. You can make a little cheat shit. showing the power read on the meter and rf watts. Thats it.

Further notes on Linear rf amp, RM96 ( to be conitnue... voltage charts as given by vu3prx and a little writeup by vu2hmy ) and then will finish this topic here.

Thank you all from whom i liberally took ckts, notes and other details to put as a study to make a working transmitter. Hope, my quest will help the new hams. If anything is amiss please do tell me, it will be corrected.

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