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  1. S

    Frequency divider on FM transmitter

    I have an FM transmitter with integrated PLL and VCO synth. I want to use the transmitter on a lower frequency. Is there any easy way to divide the signal by 2? I have another chip that has a built in divider that outputs a square wave. If i use the divider function of this chip and modulate...
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    What info is needed to designate location for PCB assembly process?

    So there are some other questions similar to this, but none of them talk about how to designate the placement of components for the manufacturer. I use a pretty uncommon piece of software for designing my PCBs (sprint layout), so I can't just send the project file because they won't be able to...
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    Help with loop filter for FM transmitter

    So right now I am building an FM audio transmitter based on the ADF4360-8. I have the evaluation board for this device and what I am working on right now is changing the loop filter that they included on the board with my own that will work best for audio modulation. What they have included on...
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    Design broadband matching network for amp - beginner

    Hi, I am a beginner to RF design, but I want to know where to start when designing a broadband impedance matching network. I want to make 1W FM amplifier 88-108MHz using RD01MUS1 mosfet. I have the s-parameters, so what are the calculations I need to make a matching network. What type of...
  5. S

    Calculate dBm from dBuV without Ohms

    Hi, I've come across many datasheets for RF transmitter ICs where the power output is given in dbuv, but no ohms are given. Is it correct to automatically assume 50ohms when trying to calculate the power in dBm. In other words, I need to find power in dbm when I am only given dbuv? Thanks!
  6. S

    What is a good NEW PLL chip for FM transmitter?

    I want to use a PLL IC with the minicircuits POS-150 VCO for an FM broadcast transmitter. All the schematics I find use very old chips that are only on ebay from china and maybe fake (TSA5511, MC145170, etc.) I want a new chip that I might be able to get from a reliable source like digikey or...
  7. S

    ADF4360-8 FM broadcast transmitter

    I want to design a simple FM transmitter circuit, but also not compromise the spectral purity by using one of those all in one transmitter ICs. After hours of research, I've come to the conclusion that the ADF4360 is probably the best option for low component count and high spectral purity...
  8. S

    Reduce FM PLL noise

    I am using one of those all in one FM stereo transmitter chips. It works very well, but there is a lot of phase noise from the PLL. The chip's default crystal clock speed is 32khz, but the datasheet says the device can be programed for several crystals all the way up to 38.4mhz. Would increasing...
  9. S

    FM transmitter chip RDA5820 PLL unlocking?

    I have built an FM transmitter circuit using the RDA5820. (It is one of those all in one FM stereo transmitter chips). Anyway, it has a problem with what I think is the PLL unlocking after a few minutes of transmitting. It makes a loud popping noise and the carrier is shifting on the analyzer...
  10. S

    Modern DSP DDS FM transmitter schematic/tutorial

    I am looking to design/build a high quality FM broadcast transmitter. I already designed a simple transmitter with PIC controller and FM IC, but these are very low quality. The only schematics I can find are very outdated and use old chips from the 80s like BH1415F, TSA5511. I want a tutorial on...
  11. S

    Calculate total power from spectrum

    This would seem to be a pretty common question so I'm surprised I can't find any information on it. This makes me think I might not be thinking clearly. Anyway, how do I calculate the total RF energy in a spectral range? Peak and average power is easy, but how do I calculate total power (you...
  12. S

    Sprint layout SMD soldermask

    I am pretty new to PCB layout. I am using sprint layout and I don't understand the difference between soldermask and SMD soldermask when I generate gerber files. The soldermask and SMD soldermask files seem to be the same. There is no through hole in my project.
  13. S

    MMIC (op-amp) vs transistor amplifier noise

    What type of amplifier typically has more noise, a MMIC or a transistor amplifier? Most of the MMICs seem to have a noise figure around 3dB. What is the noise figure range for a transistor amplifier? In other words, if I'm looking to design an amplifier with the lowest noise possible, should I...
  14. S

    I2C sometimes works PIC18F

    I am using a PIC18F to communicate over I2C to the RDA5820 FM chip. I have a suspicion the problem has nothing to do with the RDA however, because I've tried other chips in place and experienced the same problems. About 50% of the time the PIC will halt (just stops executing as if i2c...
  15. S

    PIC beginner - digital input randomly turns 1

    I wired up a project using a PIC18F26K22, a 16x2 LCD, and three buttons. I first tested the project in proteus and everything worked fine. However, in real life the buttons seem to randomly activate from me putting my finger near them or just attaching an open wire to the pin on the chip. Any...
  16. S

    JDM programmer won't program PIC18F26K22

    I am trying to use a JDM programmer to program a PIC18F26K22 (that's a 5V enabled one). The problem is I'm getting "Verify failed at address 0000h" using PICpgm. I see this problem posted many times, but it's from people building their own programmers. I bought this programmer AND IT WORKED ON A...
  17. S

    [PIC] SD card with 5V PIC18 in Proteus

    I'm pretty new to PIC programming and I'm trying to interface an SD card with a PIC18F4685. I began by doing a simulation with proteus because I don't have the actual hardware yet. This PIC chip is a 5V and the SD card is 3.3V so I have this extra circuit: The problem is this doesn't work in...
  18. S

    New to SPI - SRAM interfacing with PIC18 in Proteus

    I'm trying to interface an SPI SRAM chip with a PIC18F4685 in Proteus. The data appears to be sent if I look at the SPI debugger, but right after that there is a receive with ?? and Proteus returns "Unrecognized command code [00]". Right now I'm only trying to write. I will later implement the...

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