Re: GIF image for Ivan (96MHz 4W BS170)

by dare4444 Tue Sep 21, 2021 12:38 pm

Ivan wrote:You are a lucky man !!

VBR from Ivan

Yeah spice results were close to real life for anything over 20mW. It did show 2dB additional gain for <20mW amplifiers. For my parallel pn2222a fm amp spice predicted voltage swing of 10.4V peak and I got 10.3V peak on diode power meter using DMM.

by **Ivan** Mon Sep 20, 2021 7:18 pm

You are a lucky man !! Cool

VBR from Ivan

by dare4444 Mon Sep 20, 2021 4:59 pm

Ivan wrote:I am not familiar with the latest version of LtSpice. Does it take the PCB and wiring topology into account? If not, it is not accurate, it is a sort of approximation only. Comparing the RF gain of one amplifier stage is not enough. Do you need examples? Here you are:
- Unwanted coupling of nearby PCB tracks may cause instability mainly in RF circuits.
- Coupling via non-filtered supply lines may cause lots of problems.
- Ground loops may ruin even a simple AF project.
But it is undoubtedly a good tool for the first stage of circuit design.

VBR from Ivan

I've tested spice from 1 to 108 MHZ, no pcb tracks, only short component leads and ugly bug construction on a copper clad board. Spice is quite accurate here.

by **Ivan** Mon Sep 20, 2021 8:18 am

I am not familiar with the latest version of LtSpice. Does it take the PCB and wiring topology into account? If not, it is not accurate, it is a sort of approximation only. Comparing the RF gain of one amplifier stage is not enough. Do you need examples? Here you are:
- Unwanted coupling of nearby PCB tracks may cause instability mainly in RF circuits.
- Coupling via non-filtered supply lines may cause lots of problems.
- Ground loops may ruin even a simple AF project.
But it is undoubtedly a good tool for the first stage of circuit design.

VBR from Ivan

by dare4444 Sat Sep 18, 2021 12:13 pm

You're right Ivan. I have put LtSpice to extensive tests, each time simulations were accurate on computer vs in real life prototype. Now I've chronic back pain so avoiding home brewing as I took a lot of painkillers for a year. Last year each and every prototype performed identically. BS170 had 13dB of gain on Spice at 100MHz and exactly same in real love too, boosting 15mW to 350mW on a prototype board. The bs170 was original though, 100% original part. Generic parts might not have worked. They may work at DC and lower HF only genuine parts give the results equal to spice simulation. It's no ordinary software. Thousands of hams trust it.

by **Ivan** Sat Sep 18, 2021 9:52 am

Hi,
any computer simulation is as accurate as the models of the parts and connections (their capacitances and inductances, proper grounding, shielding etc.) are. Neglecting any parameter may make the simulation useless. Taking the variations among different lots of the same part into account is very useful as well - e.g. by implementing the tolerance analysis and the Monte Carlo method. Analysis of temperature sensitivity may be required as well. Simulation programs have made a HUGE progress during my professional life, but I still insist on making and thorough testing of a REAL sample before the production starts resp. before the docs are published. Maybe I am really old Crying or Very sad

Why do you not make and measure a prototype by yourself?

VBR from Ivan

by dare4444 Fri Sep 17, 2021 10:44 pm

Ivan, if simulation works, then real prototype would work too? Spice is accurate. If Harry could build this project and test it and publish it, it would be a cool new addition. Don't you agree?

by dare4444 Sat Sep 11, 2021 8:47 pm

GIF image for Ivan (96MHz 4W BS170) Fmamp11

Hi Ivan,
It should be clear now. Input is 360mW at 96MHz. Dissipation figures given in the other post. Three BS170 can burn 1.5W as heat. Tube heatsink required or glued to one aluminium heatsink? 19.2V is laptop DC adapter power supply.

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