Title: Projekt: PA 20W for TRV Oscar-100 von SP3OSJ
Post by: SP3OSJ on 05. February 2020, 01:21:24
Title: Re:Projekt: PA 20W for TRV Oscar-100 von SP3OSJ
Post by: SP9BSL on 05. February 2020, 08:05:20
Hi Artur,
can you provide some more info like matching, bandwidth, harmonics, IMD?
One more question, the biasing circut consumes 1.2W, this turns into heat (the 78L10 dissipates 0.9W!), is it really needed to provide that high current? |
Title: Re:Projekt: PA 20W for TRV Oscar-100 von SP3OSJ
Post by: SP9BSL on 06. February 2020, 11:02:00
Thanks, I asked about matching because I assumed you used the FR-4 laminate. The input circuit looks similar to the reference board from Ampleon but they have used Rogers which has lower epsilon r. This is microvave circuit and heavily relies on transmission lines.
Fast calculation:
(0.046A+0.005)*18V+0.046A*5V=1.148W and that I meant saying 1.2W ;)
All this current you have from 27+82=109ohm connected to 5V. I asked why because all the mosfet idea is not to draw DC current at input. This particular transistor has gate leakage about 140nA@11V... I did not use this one and that's why I'm just curious... |
Title: Re:Projekt: PA 20W for TRV Oscar-100 von SP3OSJ
Post by: DF8OE on 06. February 2020, 18:02:30
For microwave designs using PCB material with different dielectric constant will result in serious uncorrectable malfunctions.
It is not possible to copy a PCB layout to a PCB material with different dielectric constant...
There are only these two possibilities:- copy layout and use 100% identical PCB material
- use PCB material with different electric parameters and redesign the layout to match this new parameters
vy 73
Andreas
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Title: Re:Projekt: PA 20W for TRV Oscar-100 von SP3OSJ
Post by: DF8OE on 06. February 2020, 18:42:12
Hi Artur,
I think ~1...1.5W is acceptable. You can test temperature using pyro measurement and look if it is ok. There is no oscillator next to thermal source so it is not critical.
vy 73
Andreas |
Title: Re:Projekt: PA 20W for TRV Oscar-100 von SP3OSJ
Post by: DF8OE on 06. February 2020, 19:27:27
If you go in theory, you can predefine that there is no "internal current to GND". Then you can replace stabilizers with resistors and P = U * I.
That is in theory.
In practice each semiconductor regulator draws internal current. How much, can be measured or approximated via datasheet. Normally you can forget internal current (because it is << 1mA) and replace regulators with resistors for calculating power loss.
You need voltage difference and current and multiply it - thats all.
For designing schematics I only use approximations and do not cross half of the value that I see as "critical".
EDIT:
loss at first regulator is 18V, current is 0,05A, we forget internal current ==> 0,9W power dissipation @ regulator 1.
vy 73
Andreas |
Title: Re:Projekt: PA 20W for TRV Oscar-100 von SP3OSJ
Post by: SP9BSL on 06. February 2020, 19:38:35
Artur,
No offense! I ask about measurements because I know you boght NWT4000 (or better) some time ago so I think you can measure it and that's all, if you don't want - OK.
The S11 At 2.4GHz can be measured this way with external cheap bridge.
I also used FR4 at few GHz (well... 6GHz) but designed the circuit from the scratch for the specyfic laminate (measure laminate, impedance match and then verify this by measurement as noted above).
Second thing the power- In my opinion this is too much to just power two resistors IMHO (!) therefore just ask knowing how MOSFET/LDMOS works.
The third thing new TRX (off topic) status: working hard on amplifier section, this is just not a simple copy&paste, it's completely new design...
PS. next time I will not ask public, will send a PM - my fault ;) |
Title: Re:Projekt: PA 20W for TRV Oscar-100 von SP3OSJ
Post by: SP9BSL on 06. February 2020, 20:43:22
Calm down man...
[Polish]
nie chcę kopiować chcę zrobić po swojemu i tyle.
Jak zwykle proste pytania na które nie potrafisz odpowiedzieć obracasz w awanturę...
Ehh szkoda słów.
[/Polish]
Best wishes and good luck. |
Title: Re:Projekt: PA 20W for TRV Oscar-100 von SP3OSJ
Post by: SP9BSL on 06. February 2020, 21:43:15
not at all... Really offtopic.
Two years ago I've built my version of NWT6000 as a tool for making tracking generator for my SA (HP8591E), it was quite useful. TG works just fine, the IF works in the range of 2.1...3.9GHz. All built home at first try thanks to Sonet software.
FR4 works at these frequencies but has loss due to substrate. In my NWT analyzer there is about -6dB at 6GHz but after calibration still has more thar 60dB dynamic range.
On the picture below the NWT6000 (left) and the NWT4400 (right). Same PCB, same firmware (switchable) different synth chips MAX2871/ADF4351.
Satisfied? |
Title: Re:Projekt: PA 20W for TRV Oscar-100 von SP3OSJ
Post by: SP9BSL on 07. February 2020, 07:44:05
Very nice!
Is NWT6000 finished?
I see that not everything is mounted.
I am asking because I have similar ones
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As said, both works, the design is mine (according to your earlier erased comment). Not mounted components are optional (DC/DC converter to power it up from USB and AD8307, I use internal ADC to be able to perform FIR filter bandwidth change and FFT in future, for example to measure IMD - I have STM32F4 on board).
How it works have shown here:
http://sp-hm.pl/thread-3568-post-40689.html#pid40689 (http://sp-hm.pl/thread-3568-post-40689.html#pid40689)
The left: NWT500, on the right: NWT6000
I have yet: NanoVNA.
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Great, so you have equipment...
And please read this before applying too much power to antenna:
https://forum.amsat-dl.org/index.php?thread/2963-do-not-exceed-nominal-power-on-the-transponder/ (https://forum.amsat-dl.org/index.php?thread/2963-do-not-exceed-nominal-power-on-the-transponder/) |
Title: Re:Projekt: PA 20W for TRV Oscar-100 von SP3OSJ
Post by: dc2pd on 11. August 2020, 19:47:05
Hello Artur,
I build your PA with your PCB, but I run into some problems. The provided output match has a maximum at 2.1GHz and falls down -13 dB to 2.4GHz. The design looks like the test circuit for 2.1Ghz from the datasheet. I was able to get a much better match for 2.4GHz by changing the existing ATC caps.
Your PTT needs DC from the input. I have changed it to external.
You have covered the backside of the board with a solder mask. It has has a thick one. I have scratched off most of the solder mask to get a better thermal contact to the heat sink.
With this modification, I get nice 16W at 2.4 GHz.
Peter DC2PD |
Title: Re:Projekt: PA 20W for TRV Oscar-100 von SP3OSJ
Post by: dc2pd on 23. August 2020, 20:36:23
You can also lower the bias current. I have changed the 82R to 50R. (100R || 100R)
The datasheet parameters are for 180mA and with 50R we have around 200mA.
I have tried to optimize the output match by cutting the drain area, but only with minor effects.
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