Re: PCB Parts Layout

Rahul Srivastava

Some real efforts made there in labeling all components in original BITX layout. It appears the RIT is indeed the fine tune control.
Very true the Rx front end device indeed determines the overall sensitivity and performance. I suggest giving a try to devices like 2N3866, 2N5109, 2N5179, BFW16,BFR91-96 and other devices in its class,  for RF amp as well as for post mixer one too. In past I have used 2SC2570A ( very cheap CATV component) in these places with very good results. The resistive nature of the amp would lend themself to easy adaption as well as stability. I have also noticed that 2N3904/6 has a lesser loading capacitance than the BC547s
A true homebrew project in all aspect this is.
AGC design is now what we all look forward too.
Rahul VU3WJM

Arv Evans wrote:
Manuel - EB7HPM

Thank you for the quick reply. 
I had noticed the notation of "RIT" on the top-left of your PC Board image and took that to indicate
that you had a new way of doing that function.  Now I understand that this is actually the main
VFO tuning adjustment.

The web site you referred to is quite impressive.  It is nice to see home made (homebrew) ham
radio equipment that has a very professional look.

On my first BITX (a BITX20 version) I also experienced limited sensitivity, but when I replaced the
2N2222 RF amplifier with a 2N3904 that had been selected for high gain the performance
became very good.

You seem to be working on some very interesting modifications of the BITX design.  I am sure
that others would be very interested in more detail about your work.

Several persons have commented about interest in building a BITX-144 for 2 Meters.  It seems like a worthwhile effort, and your use of heterodyne oscillators to generate the required higher
frequencies would seem like the way to do it.  I am sure that others in this forum would be
interested in seeing your designs.


Arv - K7HKL
On Mon, 2004-09-20 at 01:21, eb7hpm wrote:
I'm sorry, but muy rig doesn't have RIT, although I hope soon to
have it. However you can try some configurations. I remember one
with suming AO. You can take it from here:

Sorry also for my bad english :-(

I have mounted a BITX15 in order to use it in 15m because I
am "licensed C" in Spain and it work very well. I use FI of 10MHz
and one external oscillator VXO to 31MHz. I have not mounted yet the
power amplifier.

However, the reception is a little weak and I added an cascode
amplifier with two transistors and a coil in the FI. How it change!!
Now I have the problem of excessive gain in some cases and I am
working in an AGC.

For the oscillator I am triying a VCO of 10 to 40MHz controlled by
PLL 145170 and when it work I will control everything with a
PIC16F84 with LCD and codec. Here some info:

I have put the diagram only for others have it like reference.
I want to prepare a PCB more ambitious, with multiband change, CW,
AGC, PLL and AM/ FM.

As I have each part working I will put the schematic.
I am not much spare time. :-(

The BITX can work to 144MHz?? I hope so.


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