IRF520A

[4600turbo]

LOL, if I want a big box I will build a big box for myself. But I have more fun just building and experimenting with the stuff. Trying new stuff out.

That's cool. Your building a box with MosFets. God knows why, but expermenting is fun.

I just thought you wanted a bigger radio.





Still the owner of the biggest Galaxy radio in the world.
550-600 watts PEP. Hope to stay that way for awhile.

 

[Crusher]

If i wanted big numbers, I would keep to a stock radio, and then get 2-3 amplifier stages to get some big numbers. LOL. Buying one of those big radios with all the extras is a waste. Unless you like all those little toys on the export radios. I like a standard SSB chassis or one of the true amatuer radios. Not an export radio. From my dealings with them in the past, they are overpriced garbage. Just my 2 cents though.

Crusher

 

[Crusher]

I did a little more testing using the irf520A and the IRF520N. I get a noticeable difference of almost an additional 8-10 watts average on a bird. One other difference was that the input was alot harder to get a low SWR. i got it down to a 1.5 on the input with the N type were as i had a 1.05 on the input with the A type. This was using my LP-100. Just thought someone would like to know this. I believe that the N type has a higher capacitance that is harder to cancel out.

 

[AudioShockwav]

Thanks Crusher.
Kudos for sharing what you are learning.

73
Jeff

 

[GRTS]

I did a little more testing using the irf520A and the IRF520N. I get a noticeable difference of almost an additional 8-10 watts average on a bird. One other difference was that the input was alot harder to get a low SWR. i got it down to a 1.5 on the input with the N type were as i had a 1.05 on the input with the A type. This was using my LP-100. Just thought someone would like to know this. I believe that the N type has a higher capacitance that is harder to cancel out.

You didn't say which mosfet "A" or "N" you saw higher power on.

Also the datasheet shows the IRF520N has lower input capacitance than the IRF520A however datasheets are not all created equal.

 

[Crusher]

The IRF520N is the mosfet that i am seeing a higher ouput level. I did get the input SWR down significantly. Down to about a 1.1:1 SWR I could have gotten it lower, but as the radio swings forward, the SWR would approach closer to a 1.3:1 SWR which, still is pretty good. I may have to put some kind of padding /swamping circuit on the input to decrease the input drive. It works great, it dead keys approximately 25 watts and swings 45 almost 50 watts. using a 50 watt slug. While I was testing it though, I have a thermal remote reader for measuring temperatuers at a distance. I was reading somewere in the vicinity of 180-190 degrees F. Just thought I would metion that as trying to get the few extra watts may cause a much shorter life span of the transister.

 

[freecell]

the max junction operating temperature for the irf520 is 175 C or 347 F.

 

[Damo666]

My rig uses 2 x irf520 for its final stage. My radio does 10w am/fm and peaks at just over 20 watts on a whistle on ssb. Will they last? Also, anyone know the swr ruggedness on these cheap mosfets?

 

[dudmuck]

My rig uses 2 x irf520 for its final stage. My radio does 10w am/fm and peaks at just over 20 watts on a whistle on ssb. Will they last? Also, anyone know the swr ruggedness on these cheap mosfets?

That should really be a bullet-proof setup.
Because the irf520 is rated at 60 watts dissipation.
And can also handle 100 volts on output (drain), and 10A of current (but not at same time).

Compare that with the common barefoot CB transistor 2SC2078 is an 80volt part that can take 3 amps of current and dissipate 10 watts.

Or the common "export" device 2SC1969, which is rated at 60 volts and 6A of current, with dissipation rating of 20 watts.

With any device, death occurs when you exceed one of those three: voltage, current, or power dissipation limits, which can certainly happen if you push them hard into a bad VSWR.

 

[Damo666]

Thanks for that dudruck. That's put my mind at ease.