Can anyone help me to find some good chinese manufacturer of ceramic pcb ?
I want to order some ceramic pcb for the rf stage .
Example :
Can anyone help me to find some good chinese manufacturer of ceramic pcb ?
I want to order some ceramic pcb for the rf stage .
Example :
Uh.. why do you want a ceramic board for this?
Because i have already build my own unit ,but the problem in my case is the heat.
So i need an type of pcb which would be resistant to heat.
Because i have already build my own unit ,but the problem in my case is the heat.
So i need an type of pcb which would be resistant to heat.
Hello again to all.
In search of incredible, i return to identify a MX-RM3e or newer MX-H1-AV tip's plug.
May be anyone identify it?
I buy some SMB connector, and i was very close - but no, it is slightly different.
Outer diameter of SMB female socket is 3.7mm instead 4mm in Metcal's tips, and inner pin diameter is 0,5mm, instead 1mm in Metcal ;(
Hello again to all.
In search of incredible, i return to identify a MX-RM3e or newer MX-H1-AV tip's plug.
May be anyone identify it?
I buy some SMB connector, and i was very close - but no, it is slightly different.
Outer diameter of SMB female socket is 3.7mm instead 4mm in Metcal's tips, and inner pin diameter is 0,5mm, instead 1mm in Metcal ;(It is an "F" connector, most commonly used for 75 ohm TV antenna connections in North America.
Great, we are back.
What's new, My RF-Borad is finely working, the problem seem to be the XFMR, chris send me one of his and all problems went away. He only explanation that I can find is that RS send me the wrong ones. I will test them both next week with a network analyser to see what's the diference. I will also test a few Metcal tips.
Meanwhile I finished my controller board design placed an order at iTead, my board are already on there way to Portugal.
Paulo
Your undervoltage cutout seems to match my schematic, and I can confirm that a 2N7002 would be fine (or pretty much any other low power SMT MOSFET, it's not critical.
I don't remember the failure mechanism, but I remember several people reported blowing up the RF FETs, and Chris said cleanly shutting down the supply would always prevent it.
My next move is probably going to be to see if I can design both the Arduino board with the same fix as the PIC board and give hobbyists an option between the two. To me, it seems like either processor works well and should have no bearing on the final product - but for experimentation sake and builders' preference I am hoping to update both.
In my personal opinion this seems to be pretty useless ,because i think the rf-stage has more priority for now.
For example :
You can check what you can tweak or optimize on the rf-stage to make it less hot,you can optimize swr parameters etc, etc, etc ..... so basically leave for now the work on mcu's to later
Just my personal opinion .
Datasheets for convinience:
IRF510: https://www.vishay.com/docs/91015/sihf510.pdf
IRF530: https://www.vishay.com/docs/91019/91019.pdf
I haven't looked properly but I notice that the IRF530 has 3x more gate charge and all the switching parameters are slower. This is expected given you get the improved thermal performance by having a bigger die. It may well be a suitable MOSFET but I wouldn't just throw it in without re-examining the gate drive and testing on a prototype. If you unintentionally slow the switching then you will increase dissipation and it may very well run hotter despite the factor of two in RthJC. Essentially the real figure to consider for thermal performance is the change in sum RthJC+Rthinterface+Rthheatsink which is around a change of 6.5 C/W to 5 C/W with the 100x100mm heatsink and a greased mica insulator. Don't pay too much attention to the headline power figures in the datasheet, they're not really representative of real-world use (as in you can't usually get anywhere close).
I suspect the MOSFET-killing on switch-off relates unintended linear operation dissipating hundreds of Watts for milliseconds and taking it outside it's safe operating area. That should be fixed by the undervoltage lockout circuit.
I personally wouldn't change it, mine seems pretty robust and thermal performance seems sufficient with the 100x100mm heatsink everyone else has used. During testing I had it running continuously into a 50 Ohm load (equivalent of a cold tip that never warms up) for about half an hour and the MOSFET was only warm - maybe 40-50C.
If you do want to change it the datasheets offer hints but as they're not really specified for use as an RF power amplifier you will probably have to do it by experiment. I would stay away from the IRF540, as a minimum you would need to seriously beef up the gate drive (9x more charge needed, so 9x the current to do it in the same time), but the rise and fall times might still catch you out. Paralleled smaller MOSFETs might be simpler.
All I can really say is that I use mine fairly regulary and I haven't blown it up yet. I haven't looked at the mosfet failure in detail and it's not happened to so I'm really just speculating about the cause. I have even misused it as a 13 MHz source for immunity testing with no harm done.
The only bug it has is sometimes the power metering seems off, reporting that it's finished heating before it really has, etc. It may be a software bug but probably I should find time to tweak the thresholds which Chris has made configurable from the UI before I complain about it.
What I haven't done is tried a wide selection of tips.