What's wrong

I have a problem with the amplifier board. One channel have a good signal the other a bad signal.

This is the normal situation

Channel A is the good one. Channel B the bad one.

When I change the UTP cable and switch pin 4 and pin 5 then is this the situation.

The problem is replaced. The problem isn't the controllerboard.

When I change antenna a to b and b to a, the problem is always channel B. The rods aren't the problem.

I have replace the opamps from a to b and b to a. The problem is always channel B.

I have controlled the soldering from the PCB with a 3X loupe. They are OK. I was one forgotten. After that the problem is the same.

I set the amplifying for both channels 53X. Jumpers 2 and 4 set.

What's wrong.

The amplifier from my brother I have made too. There wasn't a problem.

This is an board than runs 24 days and has the whole time the same problem. It's due the assembly of the second station that I have see the difference.

Whit soldering is nothing wrong. It's not my first project. In the past I have solder many projects with 0603 smd and Atmega88P-20AU TQFP 32 package. I have soldered with Kester Sn63/Pb37 eutectic solder 0.5mm.

The resistors are 100% correct placed. Side A is a mirror of side B. I don't think there is anyone happy with 30Mb high quality photo's.

Maybe I draw a new PCB with 0603 SMD too compare with the TH PCB.

I have tested with 10V18 after D1.

Pin 2: 4V91
Pin 3: 5V09
Pin 6 with gain 53 8V8. I have measure the gain resistance between pin 2 and junction C17/R16..R19. These was 1Ω91. Calculated it must be 1Ω92.
Pin 6 without gain 5V16. With 1 gain jumper set it is every time 8V8.

edit 1: I don't have a 22n in my assortment. 47n, 100n, 1n7, 22p, 15p aren't problems.

edit 2: I have removed C17. C17 is 21n1. Nothing wrong I think.

edit 3: resistor R15 is 99k2. switching opamps have always the same result.

I think the problem is solved

I have removed C17 and soldered back.

Robo many thanks.

Where a forum is good for.

edit: There is too much difference between channel A and channel B. I have ordered new22n capacitances by Farnell. Normally tomorrow at home and then replace C17 by a new one.

edit: I think the problem is definitely solved. I have made a new PCB with most SMD components. Resistors and capacitors in 0603 case. Op-amp in SOT23-5 case. The PCB is 83mm X 69,4mm.

Click able. Left top side, right bottom side. Bottom side have one little fault with the ground plane.

Built up top side.

Click able.

result

price PCB 27€ incl shipping for 10 pieces. Delivery time 17 days incl shipping.

Hi buckfast_beekeeper,

how did you solder the SMD parts?

Egon

With hand. A Weller WECP-20 (20-years old) solder station with a tip ET-H 0,8mm. Kester eutectick solder 0.4mm.

Soldering is possible within 1,5 hour. A little solder on one pad, place the component with a little heating. Solder the other pad(s). And resolder the first pad.

My solder station stay on 300°C.

TQFP package is possible to solder with hand if you have enough experience. SMD 0603 is maybe to dificult to start with smd. Maybe 0804 is better.

PCB from Itead

Maybe I make the processorboard in smd too. With possibility to place the FTDI USB-TTL controller on the board or taking the breakoutboard from SparkFun.

Very nice keep good work
i also find SMD solder easily then TH.
When you have time i would relay appreciate if you could make PCB also for controller

The PCB has the same dimension. Only a few components at the bottom side. A 10cm * 10cm costs by itead the same as an 9cm * 6cm. Why making it smaller? It has a few extra possibility's.

Bottom side (click-able):

Only a few C, R, one D and crystal. C and R 0603.

Top side (click-able):

What is different?
A IDC connector with latches (PL1). (Farnell 1106757) The connection is safer then a connector without latches. On the same place it is possible to place a connector like Farnell 2112438.
Switches to set baudrate GPS and baudrate communication.
Using a TSR1-2450 switching regulator (Farnell 1696320) in place of a 7805. The efficiency of the TSR-1 is much better than the 7805. The pinning is equal. The 7805 is possible.
Using 0603 LED for display. It is possible to switch of the PCB led. Al the led are 2mA types.
Placing an optional Molex connector (Farnell 9732560) to bring the reset, test and led to the outside. The Molex connector needs a not so cheap hand tool. It is also possible to use a normal 0.1" header. On this way it is easy to place the PCB in a box and to remove the cover. It isn't need to solder wire on the normal places.
Using a normal 10-way ISP connector (Farnell 1106832) or the ISP that I always use. That is a configured TAG connect. It takes not a lot of place on a smd PCB.
Possibility to work with a USB-TTL cable like I do (Farnell 2143329), SparkFun break out board or solder a FTDI232RL chip. If you will use the FTDI chip, there is the possibility to choose USB power for the chip or powered by the board. In that case the chip must be programmed.

The PCB isn't in production. Maybe in a few weeks.

edit: I have reworked the PCB. At the moment it is possible to place the adafruit V3 GPS. It is possible that I send tomorrow the files to Itead for making 10 pieces of the PCB.

top side click-able:

bottom side click-able:

PCB

Top side click-able

Bottom side click-able

Greatings

Theo