dB / dBm Terminology

The dB terminology is used for ratio between two power levels in communication equipment for example to compare power coming out of a component to that going into it. The dB number system can also be used to express absolute value of power as dBm. Power measured in dBm is just the power value that is being measured referenced to 1 mW (respect to mili). That's what the m stands for. To see how dB / dBm is used look at Figure above.

The transmitter power of 10 000 mW is 40 dBm; the loss of 0.4 in cable is -4 dB; the gain of the transmitting antenna is 300 which is 25 dB; the path loss is 4 x 10 power of -19 or -184 dB. The gain of the receiving antenna is 3000 which is 35 dB; the loss of the cable in receiving systems is -4 dB; the low noice receiver gain of 3 billion is 95 dB. The beauty of dB is we can easily add / subtract the losses of gain which gives a received power of 3 dBm which is 2 mW. We can try the calculation on the amateur radio transmission system. See yaa again. Bye2.

Reference : Allan W. Scott, 1993, Understanding Microwave, John Wiley & Sons.

Interpretation of Yeasu Serial Number

Actually, the Yeasu uses the same serial number scheme for all of their ham gear. The serial number has the form "YMLLNNN" where Y = the last digit of the year of manufacture, M = a letter representing the month of manufacture with "C" = January, "D" = February, and so on, the lot number is representated by the two digit LL (00 - 99), and NNNN (0001-9999) is the unit number within lot LL.

As an example on my Yeasu FT897, the picture of serial number above show 3C130790 means January 2003, lot 13, unit 790. The lot number is not linked to the year & month, i.e., LL do not reset to 00 each year. Have you ever check your Yeasu serial number ? :)

PCB UV Board Construction

Today, i decided to make PCB board using UV (Ultra Violet) method for sharing the knowledge on the procedures & process of UV PCB construction. Here are some of pictures with brief explanation.

Step 1: Print a circuit on laminate paper

Step 2: Buy a Kinsten Coated PCB - GS1015 for single layer and the manual instruction inside the product.

Step 3: Attach a circuit together with Kinsten Coated PCB and expose it with light (photoresis) using UV machine around 90 to 120 second.

Step 4 : A picture of PCB after photoresis process. Remove a circuit from PCB and you can use again the same laminate for other PCB.

Step 5 : Quickly bath a circuit with water and developer then shake it until the unwanted layer remove from the PCB.

Figure A : Picture sample of developer. You can used other product you like.

Step 6 : After wash a PCB, bath the PCB with ferrite chloride & hot water then shake the PCB again until the second unwanted layer removed from the PCB.

Figure B : Picture sample of ferrite chloride product. Caution! You are deal with dangerous chemical (developer & ferrite chloride). Wash you hand after using it. Please use a glove if possible and dispose the chemical properly.

Step 7 : Lastly, brush your circuit and see the different. Now, you can cut any PCB size and drill the PCB for soldering purpose. That's all :)

Add & Open UDP Port for EchoLink

Today at last, i am accomplish to figure out how to enable my UDP port for 5199 and 5198. Before this, i am try many method to enable my UDP port. This UDP port need to test pass for communicate on EchoLink. I has tried setting on my billion router, setting my windows XP firewall and setting my Anti Virus firewall; but those thing helpless.

The solution is on this page:

Figure : http://support.microsoft.com/kb/308127

On the IP, please open your window command prompt and type "ipconfig" to check your IP address status. Hope, its can help some user that facing the same problem. See ya then. Astalavista.. Bye2