Building a receiver

Building a receiver is not simple, you still must have enough building experience.
Murphy receiver B40 was easily available in the 60s and 70s of the last century.
In 2008 was rather different, I was looking for then a good receiver.
The B40 was still for sale (quite expensive) and he weighs 50kg or100 pounds, I took the decision to build it myself.
It took me eleven months, but it is excellent receiver.
He can be found on the internet with the diagrams of various types. 

http://www.portabletubes.co.uk/boats/murphy3.htm

I started out on building the receiver with air coils,as you can see below.

Mainly off tuning difficulties in aligning  I then later used the smaller former with a core inside to solve that problem, the receiver was working but was impossible to align him on both ends off the band.

That is also the main reason why it took so long to build the Murphy B40.

The Murphy B40

Gradual building up the receiver.

All IF can in place and working.

 

Construction off IF coils 455Khz.
The capacitor I changed then later to Styroflex for drift due to temperature in the receiver.
After the change there was no drift any more.

Here the right smaller former with core are here in use without the tuning problem.

Building a single conversion or a  double conversion is not exactly suitable for a beginner.
But do not be discouraged, everyone has to start some what easy-er.

It is best if you're just interested to start with a re-gen receiver.
You will work than with one  valve, and in doing so,you  learn how such receiver works best.
Don't underestimate it, the best thing to do is, to see how others have built one.
You learn from that as well.
It is an educational extension of your hobby as radio-amateur.
Once you have build one radio, I think the more you are going to build.
And what is more important you expanded your knowledge.

Determining the position off the parts.
A very important part before the begin of building the receiver.








Here you see a layout of the double conversion receiver B40DBLS.

On the right,the self-wound power transformer.

And also the layout of the bottom.
The arrangement of the components are very important.
Static as well as in inductive shielding is of great importance.
It determines whether you design is working or not.
You learn most from shielding of valves with respect to each other.
Because it is RF you work with, that affects the stages before or after.
And also a valve is to be screened off by itself, the input grid must be shielded from the anode of the valve.

The finished receivers.

Above the diagram and parts list for the Murphy B40DBLS.