RX 20 - Initial Circuit

Hello :)

I had been QRL with college and did not find time to update this blog.

I quickly opened the BITX circuit diagram and made some quick changes (removing the TX RF/IF/AF amplifers) ....

Take a Look at the circuit here . It looks much simpler now doesnt it :)

There are several optional additions to the circuit such as a Automatic Gain Control, Digital Frequency Display and also a Active/Passive AF SSB respsone filter which will be added later on


More in the next installment :))

73's

RX 20 An Adaptation Of The BITX 20 :)

Hey people!

There has been a lot of buzz about the BITX transceiver over the internet. A friend of mine expressed his need to get a RX in his room as a bedside Receiver for monitoring DX and other traffic on the 14Mhz Band. Although propogation is bad on 20M we still decided to go hunting for the best Rx design with the usual criteria :

1. Should be a low cost design without compromising on performance.
2. Should be a easy to construct and troubleshoot design.
   
3. No hard to find / Exotic components.
4. Should be well documented as the Rx may be used for Research at a Undergraduate Level

We were still not satisfied after looking at almost all designs on the internet. After a Quick convincing session me and my friend decided to make a Rx based on a exsisting TRX design and we did not go anywhere else except The BITX site.

We decided to make a few modification though. The extra amplifiers needed for Tx are to be omitted and a Xtal Controlled LO with varactor tuning is to replace the LC VFO (We know that the tuning range will be limited but it is a sacrifice we are willing to make to avoid the Coil.)

Other Inclusions are a 3 Khz Active / Passive Audio Filter for SSB reception along with a AGC with a Override Switch. An S-Meter is also a fancy option which we might just add.

The only thing troubling us (lest we forget the College QRL) is the VXO. I was planning to get a standard 4.00Mhz Crystal available in the market for usage with the clock timer chips. The trouble is to pull the Frequency of the LO upto +/- 60 Khz using a super VXO design. I was thinking if these xtals would be able to do that.

The first step in this project would be is to complete the LO along with a Buffer and feed the signal to a frequency counter to see how far these xtals could be pulled.

Rest in the next Installment :)

73's

Other Homebrew Projects ...Plans for the Future ?

Hello,

These are the plans I had in mind for the Semester holidays :

1. Homebrew
2. Travel
3. Homebrew
4. Homebrew
5. Homebrew

As you can see from my planner I have decided to spend some serious(??) time for homebrewing.

Here are a couple of projects I saw and was quite Fascinated\Interested\Curious About....

1. A Double Conversion RX for 7 Mhz with a S-meter Option

2. A Portable 7 Mhz Superheterodyne Receiver

3. A L and C Adapter for a Mulitmeter

More to come ....

73's

Test Equipment :)

Hello :))

Its been a long time ... My College QRL and Other things have been pushing me to the limits.

Today I had a Eyeball with 3UBR and we were Discussing the prospects of the FCL-X meter we are currently working On....

I also came across this Interesting Homebrew Project .... A Single IC based RF signal Generator.
The Link for the project is here .

An exteremely useful and a versatile tool :) ... Looks Compact too :)

Oh well I guess its time to go back to the homebrew bench ....

73's

Homebrew PCB's :-}

This is my favourite and most used method of making PCB's...The Toner Transfer Method.

I dont have a digital camera now. I will post the pictures as soon as possible. Here is How I do it:

• Make the PCB CAD file using EAGLECAD. (I use the student version).I usually add text such as my call to make sure that the design in inverted.
  
• After making sure the board is inverted I print the whole thing on a PHOTO GLOSSY PAPER. Other types dont work!!! It costs around Rs. 10/Sheet here in Chennai.
• After geting the print onto the glossy paper, Cut a Blank Copper clad PCB material Board. One Sq.Mt of this costs Rs. 100/- and give you a lot of PCB's(depending on the size of your design.)
• To cut the board use a metal ruler and a good quality Pen knife(US:X-acto Knife). Score a couple of times with the pen knife on both sides of the board and you can very easily break the whole thing with a snap.
• Use a dish scrubber(I use a Scotch-Brite vessel scrubber) and scrub the whole PCB material you just cut.
• Wear Proctection over your Face as the copper dust is potentially unsafe.Once you Have cleaned the whole thing just make sure you dont touch the board directly(to avoid the nasty finger oils). Use Gloves Or something :))
• Place the PCB material on a waste newspaper and place the PCB on it.Place the design on top of the PCB and secure it if needed.
• Switch on your Clothes Iron and set it at Max. Temperature.
• Iron for 5 to 6 minutes until the paper turns brown.
• Soak the pcb without removing the paper in a dish of water.slowly peel of the paper.
• If the toner is not transfered well use 2 to 3 coats from a permanent maker(AKA OHP maker/US: Sharpie).
• Use Your Favourite Etchant to etch the board. Although I use Ferric Chloride now, I am planning to switch to acidic cupric chloride . This seems to be easily available and environment friendly :)

As a standard disclaimer Act Responsible Now. I will not take balme if you go wrong somewhere.
Knifes,Etchants,copper dust etc. are dangerous. Take Adequate Protection.

Have Fun,

73's

Homebrew Planner....

Hello!

Here is a list of projects I hope to get up and running in my Homebrew bench up and soon ...

• Variable 1 Amp 1.2 - 12 v power supply ( LM 317 Based )
• PIC programmer ( RCD programmer )
• 30 Mhz Offsetable Frequency counter( Py2RLM's Design )
• 40 Meter DC-40 Standalone Receiver ( VU2FAX's Design )
• BITX 20 And the RM-96 Transceivers (Scroll down below)
• Multiband Dipole 20 and 40 meter Ones ( Hamuniverse )
• LC meter (PY2CSU's Design)

Tempting to See on other's pages....My hands are already twitching to get started :))

73's

Software Defined Radio :)

I had tried to post messages before on the blog but strangely my browser just did not allow me to upload my posts and would keep showing errors and now that I have upgraded to Firefox I can go ahead and Blog without any other problems.

I recently saw a couple of Software Defined Radio Rx which are quite simple to construct on YU1LM 's Homebrewing Site. I was quite Impressed with what can be done with very little components.

The circuit of Interest to me is the DR2C . I am planning to homebrew this Nifty Little receiver to 14 Mhz (20 meters).

Rest later :)

73's