nrgkits.nz wrote: ↑Sun Apr 12, 2020 4:06 am Another modification I have done to this Chinese PA is replace the 4x 100p ATC DC blocking capacitors (in the center of board between the pieces of coax) with 4x 1n ATC capacitors - this allows for better efficiency and slightly more power out.

I suspect the reason why the Chinese vendors used 100p caps is because they probably had loads of them in stock or managed to purchase a bulk lot cheaper than 1n caps, and when you're a Chinese vendor is all about having the cheapest price and a product made from the cheapest parts - even if corners have been cut and that product only performs at around 80% of what it should.

For RF by passing and/or DC blocking at VHF, as has been done here - usually you'd use 1n caps, not 100p.

Hi nrg.nz, I was recently told to change the 4x 100p caps to 2x 1000pF caps as I was guaranteed that it would make it do more power straight away but it just instantly blew the transistor!
Thankfully though I have replaced it and put the old 100p caps back down and it is working again.
I was assured that it would be fine and to just replace those 4x 100p with 2x 1000p but I have since seen this post and that it says to change it to 4x 1000p not 2x like I was told to do.
But I have been told it makes no difference having 2x high power 1000p instead of 4x but the transistor instantly blew so I don't think this is correct, what do you think?

From my experience I get lot of power with 1nF per chanel... also I truy 2x1nf per chanel.. but no big difference... you need to use ATC 100B CC.
for all rf line from power feeding line to LPF... I have problems with normal CC 100V...

follow this CC order.---
And you can have another , to many possible problems... why is burned.. if LPF is not tuned, SWR less than 1.15 and not 50R +-1R...
power stuced between mosfet and LPF.... or coax match...
what is your power before? drive power? BIAS current? ..
MRF9180 is also very sensitive on electrostatic discharge or reflection also...
up to 200W RF power feeding power supply need also good CC (SMD ceramic capacitor 1812 102J 1KV 1NF 1000V NPO COG 5% high frequency high pressure MLCC) above 200W ATC !
what is lenght of your coax match 25R and 50R?

I put a Genuine Motorola MRF9180 in my 150W linear amplifier 30/11/2019

That's a little over 2 years ago it runs at 26V 8A 16hrs a day = to 11,680 hours

BriansBrain wrote: ↑Sat Dec 04, 2021 1:49 pm

I put a Genuine Motorola MRF9180 in my 150W linear amplifier 30/11/2019

That's a little over 2 years ago it runs at 26V 8A 16hrs a day = to 11,680 hours

Brian's 150W Linear 26V @ 8A-S.jpg

sure if efficiency good less heat.. i build 180W run fine and cool

rigmo wrote: ↑Tue Dec 07, 2021 11:02 pm sure if efficiency good less heat.. i build 180W run fine and cool

We have extreme summers, some days the ambient temperature can get up to 43C°
And I don't have enough power available to put in an air conditioning system
So it's better for me to run it at 150W

Anyone no where you can get the freescale 9180 ?
Or a decent mrf9180
I set bias to 2.6v with 22v 1w input drive and only ever get around 80w max at the bottom of the band
I did once change the Zener diode to run the mrf186 but can't remember I'f I changed it back over again would that make a difference

The MRF9180 is meant to be a UHF device. It's a "controlled Q" device, optimised for frequencies around 900 MHz. It's not meant to be used on Band II. You'll have much less hassle if you use an appropriate bevice!

Vinylizer wrote: ↑Thu Aug 10, 2023 9:57 am Anyone no where you can get the freescale 9180 ?
Or a decent mrf9180
I set bias to 2.6v with 22v 1w input drive and only ever get around 80w max at the bottom of the band
I did once change the Zener diode to run the mrf186 but can't remember I'f I changed it back over again would that make a difference

If you tune (match) well, you will not have any problems. max 100uA idle current. protection is desirable for Hi SWR and inductance coil for electric discharge.

sounds like a lot of stuff that would blow up on a bench ^^