Mobile Expedition

Here is write-up for my short expedtion on HF 14.315kc.
The following "image" inspired me to make my own experiments, which I was post-poning for sometimes.

vu2mau_7388_Small_Emergency Mobile

After hearing from the GJ1-CD-7388 mobile of VU2MAU. I was inspired. Why I also don't put the receiver on my bike.

As I did not want to be big eye-catcher and explain to the public and police what and why I have put antenna on my bike ??? he he. But, first time I took my original license with me to make them understood in case I find some idiots.....

So I took a 1 meter telescoping antenna, put it onto the small direct conversion receiver. See my blog for xtal controlled ra3aae poliakov 20 meter receiver. I used three 4.4 volt battery to arrive at 12 volt. So receiver was ready,concealed into a cloths carry bag I checked signal upto 6 km. It clearly gives me the beep beep on 14.315kc. Wow ! tx was pumping 20 watts, antenna was dipole, I did not care for SWR. It should be around 2.7 to 3.0 a very high but okey for me. It was a very nice experience. Almost at all places the signal report I gave was 55 to increasing into 59 at one heigh place and near my qth... So, good experience. I will make proper quarter wave antenna and another direct conversion receiver with good gain.... will see how far my ground wave goes. This auto-beep for testing is the penalty for being lonely and only hams....

If I make the 40 meter transmitter 7059kc and test them, its possible that I might reach my friend at 100km with 20 watts.. Waiting to hear from other friends what is their experience with vertical antennas for mobile use.....

10 December 2015
I find this article very useful... have a look for portable antenna.... http://www.zerobeat.net/g3ycc/yccwhip.htm 

BITX, Single Frequency Receiver-2

Peter VK3YE  made a wonderful signel freq transceiver based on the BITX. My previous experiment is here. http://vu3inj.blogspot.in/2015/06/bitx-singlefrequency-receiver.html write up looks similar.

Frequency is 14315kc , ( 20 meter band )

 I had one 14315kc transmitter and made two three single frequency receiver. Those receivers work for Testing my local signal only. I wanted something air worthy. Which can receive other hams signal. So, made this...

Lets start from back-wards.

1.AF Amplifier stage:-
LM386 In standard form with BC549C af preamplifier.

2.Product detector:-
Using subharmonics detector... he he... I don't have third 14.318kc xtals. So used the available 7.159xtal. Also did not had the balun core. If you have balun cores use them please. Another option is to use  differential 3 transistor Single balanced demodulator.

3.IF Amplifiers:-
 As given in bitx. As frequency is higher the gain will be low. Ohh this is the reason for Rx being so much deaf. Need to add one amplifier in Front end. { Read last para, finally found out the true reason, the xtal  had moved a little and loose connection happened. It works fine. No need of extra gain }

4. Front end band pass filters.
Even after making this working receiver I did not put the filter. Could not find the RFC nor a IFT. Was lazy to wind it up. One day legendary VU2DEV suggested to me K&R Filters. Here the tap is taken from the capacitor instead of the L.  My problem with filter was that I could not find suitable component for L and taped L does not work as receiver BPF. You can see VU2DEV use this type of filter for his JOTA, S7 trx, GR40, ISDR etc. Somehow I managed to make a suitable filter.

Have a look at his blog

5.Cabinet and Speakers.
All standard things.... I really homebrew cabinet.  In our kitchen we buy 15Kg oil in metal pack. So, when it is used up, I cut the metal box which is 2foot x1 footx1foot. So, it give a good one box for my projects. I buy paint from local store. Generally black paint . It is a thin metal, so I can do most of the mechanical work without any problem and it last more than 10 years.  After that give a pint job and it look new. He he. this tech is 15 years old.

The schematics and pictures will be updated. With full details.

PCB Sketching:-
I sometimes make the pcb very very old style. Using the oil paint, paint brush and Feric Cloride as etchant. It is no hole , surface mount type pcb. Of course for normal components. This is the process to make a quick prototype. Draw it, etch it, make it and test it. The prototype is ready within a day.


 Here AF amplifier stage pcb patter before it is etched. In the blank right hand side I have put the detector using manhattan style.

Af Pre amp + LM386 audio amp. 

RF amplifier, Second stage is cascade.

RF Amplifier with Xtal filter.

If I make further project then will integrate all the ckt in single board with replaceable filter assembly.

Schematics 
You will often see the similar ckt. reason is simple. The modules have given me time proven performance. So, they are innovated and used.





AF pre amp, LO,detector, IF2,xtal filter, IF1 Amp.

The last write-ups and this write-up looks similar. It should be as it is one and the same thing.
I intend to put up a BPF and do some on air test for my beacon. From one QTH to another QTH and measure its performance.

Testing:-

I  finally boxed up with last screw.  I want to make it as a black box. Literally its painted black. The VXO does not deviate much... I need to make some components change in VXO... add one rfc.

It is quite sensitive. There was one glitch. signal was intermittent. Did the screw driver test. I put screw drive at the second IF amp. It did sound loud. Then put at antenna side. No signal. so somewhere is dry solder. Pressed one xtal. Presto the signal boomed in. Did heat up all joints. Then suddenly once again signal went down. So, I looked minutely. Oh the real culprit was second leg of xtal. It was loose. So soldered it. And all is well.

Now.....Installing the bandpass filter. Installed and working fine. Will do some field test ..........



 

One  ham  VU3YFD, informed, he had also made the transceiver for single freq. But, I have not seen his ckt  nor the picture of that project.

 

VK3YE , Peter had made it and worked successfully. He has put it website. Both hams done transceiver in 40 meter, mine is just single receiver.

 

 I have tested and found working. Will try to design the pcb and offer kit also so that  others do not have struggle.

 

The wheel is re-invented  Worth try it.

On air, part-3

This is my third part for being on air. 

I had tx, I had rx. I was having problem in the QSK.  I was literally furious as I had spent lots of good money over the junks. From few good hams I bought secondhand  equipment's, and to reduce their own burden, those good man passed the buck and it stopped with me.....

I saw my own homebrew-junk-box. I was seeing that I had all types of modules. Be it modulators, demodulators, IF amp.TX amp, Linears, Power supply, Diodes mixer etc but no DDS VFO. I was finding it very hard to make it work. I am not digital-man, I am just a disecret tinkerer. Then I has realizations and I started boxing the things.

So excused myself from the  Indian Homebrewers facebook group. I was angry. I had the valid reasons. Only because you fill up some etchy-bitchy pcb with success does not mean the end of worlds. There are many things in RF world.

I dedicated my two -three days in perfecting and boxing the existing system.

I made two 20 meter antennas. Put the qsk in DC receivers and Superhet receiver. Will further improve it with tr-switching. This time the slow tuning and qsk ckt worked the miracles.

Then started the test. Many peoples helped me, coaxed me to make the dds vfo, I said the dds vfo will wait. Let me finish first what I make perefectly. And the test come ok.

Even with 2.5 to 3swr and 15 to 25watt I was able to put the signal through the south india. Then was also able to receive the control signal in my receiver. The receivers need fine tuning. Otherwise its all operational. Now final little glitches needs to be removed and it will successfully give the scheduled contacts. Sked. 14314kc.

Will upgrade to high power and dsb...

I have to thank one person for helping me out in air test, listening to me, checking with me regarding the progress...... thank you........... de vu3ink....