7159kc again !

Here is my latest 7159kc xtal based CW transmitter.
And 4diode  product detector or ta7358ap  DC RECEIVER IN MAKING.

I made chassis years ago and it was sitting around. Made the 2watt linear.The xtal 7.159mhz cw oscillator  small single transistor tx board was also made earlier. see relevant post back in time.

I was wondering if, i can put a xtal transmitter on air and come up on-air with cw. I had plenty of 40 meter 7159kc DC as well as 3579kc xtal based poliakov receivers. Interesting. I can put my another local ham into air with me to practice my slow cw skill.

logically i started building it. humm ..... with a big linear it produced around 15 watts. it can surely punch a hole through India. i can put dipole, random  longwire as well as EFHW vertical also.

Date 14-12-2018:---Then i started building the suitable box for linear as my previous experience with unboxed linear was that i broke two IRF640 mechanically. It did not breakdown due to heat or vswr !

i was making a box with a big fan, where i can put the linear board as we do in cabinet. But, that building experiment failed due to mechanical problems. Then i said lets do logical work. linear is working. we will put into box later on.

 Meanwhile i started searching the net and fake buck groups to find a c language code for Arduino to key my call in cw. CQ CQ CQ DE VU3INJ VU3INJ VU3INJ K  and in this quest, good hams helped me and lead me to various arduino based keyers. Wow. i said this is good keyers but my Task can be done even with the multivibrator driving relay which keys my tx on off.  So finally, i settled for a simple sketch which keys my tx. will upload that to my uno board and then explore digitally. but that will take time.

Date 18-12-2018:---Antenna is not ready, receiver is not ready. earlier i had bad results using the good receiver in vicinity of transmitter. So i will be using portable homebrew receiver and FSM to measure its LOCAL range. Second thing i want basically a point to point communication around 100km. two places are of my interest. one is my another home and my kids hostel.

Date 19-12-2018:--- I am trying out the QSK for receiver. i do not want any relay chatterings. Its clattering is not good for this small receiver. I will be using a diode based QSK which is well tested by my dear old friend VU2ATNs  in his 20 meter CW QRP transmitter. Fact is that, for the first time i etched the pcb and made a cw transmitter for a college project. OM Atanu is good ham and he published many ckt in Electronics For You Magazine. But in bitx bandwagon his projects did not get much publicity.

QSK

The receiver is a very modular approach. I made various modules over the time.I had a box full  boards from these i found two working modules. I am using jumpers etc so when i do want to replace any AF, PD board etc its just remove the wire and its done. Will try ring-diode based receiver as well as TA7358ap based receiver.  I am steadily working. My office-room looks like a scrap room. My client wondered that are you started dealing in radio repair ? Nope. Anyway.

I was in deep pain . It was physical one. There is some stomach problem and it itches. Then i heard that my beloved ELMER  vu2dev is SK.  In-fact i wanted to have QSO with him on my new TX RX. But alas that could nit happen.Anyway its better to finish it now.

On date 25 dec the xmus is coming here and i want to make QRM still rx is lagging by. Solved the diode series switch issue.  It reduces the antenna input going to ta7358 drastically but still it leaks. So i need a controlled gain rf amp and diode switch . filter tanks. Ohh Jesus, lots of work. :)

The dummy loads problem solved, RF indicator LED not lighting ? So i removed the 0.1 mfd cap and presto the LED lights up on RF. Good.

Fitted the receiver in place. Tested both the boards. I had made them on 2015 imagine 3 years they were sitting idle. Now show time. Solved dry connection. Put connectors. Okey and somehow my new soldering iron gone qrt. Tested rx without any front end. Ok. It can withstand rf. Time to put up qsk and then change xtal to 7024KC with RIT.

Now lets solve the  QSK . I will use the switch as suggested by m0dgq.

Its simple when diode is given firward dc bias it conducts and has low resistance. When reverse biased it has high resistance and blocks the passing of RF.  Higher the frequencies less the separation.  Bulkier the diode less usable in rf. We use back to back diode to get greater separation. Thats it folks. Now time to make rf switching filter tuned ckt FRONT END CARD. As antenna will be big there will be BCB. And QRM . So filter and amp needed.

Wait folks. I have requested a very seniour ham to give me some 7059 xtals. but i doubt it will ever arrive.



;-date 31 dec 2018.  Finally boxed up whole set up and trying to do some qrm-party.  I noticed few problems.
1- Loose connections due to homemade connectors.
2- RF is being leaked from keying amp  to succedding stages. So xtal osc needs to be keyed.
3- It seems antenna is not connected to RF fron end
4- I need to use relay to derive Tx-Rx voltage and Antenna Tx-Rx handover. Despite all these qsk diodes i need the relay.
5- For practical use the VXO is needed. Time to change vxo and rf amp.  Otherwize its good as standalone beep beep beep.

The 2Watt linear is OK when used with my 2 amp 12v DC supply the Vcc voltage line do not drop and i can get good power. at 12vdc 650ma current. and at key down 20 ma. Good enough for tx chain.  At present loading the antenna - a random wire of about 50 feets just 10 feet high. It does not show up in crude FSM made of diodes but its sounds OK in the DEV 40 meter analogue receiver without any antenna.

I will once again make the QSK ckts and see that whether the receiver gets the antenna. Thats it folks. So listen to my canary bird singing beeps on 7159kc. Thats it folks. End of this phase. The Tx-Rx are working. The wheel has been re-invented and re-used or abused. Its working. ENJOY.

IRF510 linear 2018

I wanted to make a small linear fact is a small TX system of course CW , beacone for my wish to reach 100km. Here i saw small linear. Hmmm its similar to my earlier experiments. Gave thought.

Then openeded my components BOXES. Yep i have original IRF510 from ine of my lemington road raids. Heatsink ok. Used All components  which i could find in boxes.  There are two pictures of course with beautiful womans.
First day placed the components during day time. My spectacles were broken so had hard time at seeing colourcodes but anyway i use digital multimeter. Finally put components.

Here is ckt diagrams.

Soldered, had a final visual inspection and behold on veroboard i forgot to put ground rail to sourse of IRF.  Soldered.  At night 2 am finished ànd load resistor connected. Applied  12v dc . LED ON. Anyway i had used 1N4007 protective diode.  Preset was at half position and it registered around 5-6 mili amp wuiesent without any rf applief and around 250 mili amp when RG apllied. Resistor becomes instantly warm. More than 1watt. When i put preset at max voltage current increased to around 290 mili amp.  Resistors instantly heats up. Line Voltage drops to 10volts. Hmmm .,,,

Put on metal plate. I am done. I dare not to put it on long wireantennas.  I will drive it to a big linear to produce around 15 to 25 watts RF.

Here is my linear running around 15 watt now question is to put it on AIR 7159kc (+\- 5 kc)


Well i had good time.

Will update

7159 kc dc receiver

               Here is the foto of my finished receiver assembled during Diwali holidays.  All modules and box was made earlier. I assembled it or to be exact reassembled individual modules made earlier for different project. Put. A xtal qrp tx on 1/4 wire antenna. (for this transmitter see this post :- https://vu3inj.blogspot.com/2014/12/7159kc-beacon-cw-tx.html ) .
receiver sounds good. Tested enough. Now need to increase tx power and see whether i can be received on 7159 kc xtal around 100km ?

i am putting the front end band-pass filter to load external antennas. its a very standard design i used with my other 40 meter xtal receivers.

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Here is fotos of test transmitter.

The cave Radios.

I had the nightmares last week, because i was also praying to save the Thia footfall team 11players+1 coach stuck into the cave. IT was a very daunthing task to save them. They have into there already 14 days/2weeks without any proper food, sunlight , information. It was the coaches budhist monk training that helped them keeping togather as a group. They silently sat there and waited for their search.
Thialand is not india. It has budhist rule and they value human being. India has secular view points. Even in rescue we think in terms of caste !

But any way. This incident has something to do with the HAM Radio. How they were able to communicate to the surface and other cave rescue team.

The British team had brougth along with them the cave radios. These cave radios operate on the very low frequency. there are atleast three types of radios in use now. hyphone, tesla, etc. there is difference in the range depending on the type of antennas on use. whethere you use loop 1 meter or a big tail antenna of 15-20 meter. hi hi we have good lenght of wire at the cave. other freq are not able to span the distance of cave rock. so CB or any VHF could not be used. So, we have to design something. our G3TDZ had done very interesting designs.

They use down converter for cb radio. usb only as the power is very  precisious at the cave.

 i think i should try one crystal based design 5ok and test in on my farm. will tell ya.

DDS VFO

        At last the the Dev Guru VU2DEV broke my hurdle and gifted me a working DDS VFO make by the great kerala om Saji VU3WIJ. I am thankful for that DDS VFO. it goes from 11 Mhz to 25 Mhz.   THANK YOU VU2DEV.