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MOSFETs vs. Pills

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Re: MOSFETs vs. Pills

Post by 'Doc » Monday, 08 March 2010, 2:35 AM

And considering the heat generated by just one of those things (225 degrees C) the required cooling/refrigeration will probably set you back another $300. :)
Also recognize that the rated output is at VHF and is 'pulsed'.
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Re: MOSFETs vs. Pills

Post by Hypo » Monday, 08 March 2010, 3:14 AM

225 max junction temp max current was over 80 amps Found a company making FM broadcast modules with them in Florida.

http://www.broadcastconcepts.com/index. ... ucts_id=79" onclick="window.open(this.href);return false;

They rate their amp module at 800 watts in that application. SSB could do more due to its lower duty cycle.
It only requires 2.5 watts of drive for 800 out.

Insanely small dimensions to dissipate 800 watts at 4 by 2.25 inches but it is on a solid copper heat spreader.

Two of these would make a legal limit amp if you can keep the combiner losses down. Of course the board would need to be redesigned for HF and the MOSFET is rated for 10-500 mhz so the low bands would be out probably.

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Re: MOSFETs vs. Pills

Post by Fletch57 » Wednesday, 14 April 2010, 6:53 AM

I just finishing reading this post and I don't understand all of the tech talk. My questions is which transistor is the best: Mosfets or Pills? Unless I missed something, what is the final verdict?

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Re: MOSFETs vs. Pills

Post by madsage » Saturday, 15 May 2010, 9:21 AM

Fletch57 wrote:I just finishing reading this post and I don't understand all of the tech talk. My questions is which transistor is the best: Mosfets or Pills? Unless I missed something, what is the final verdict?
That is a very broad question. But I think its safe to say, until more development is done.
The old bi-polar junction transistors are the most reliable and are designed for RF application.

Not that there isnt RF mosfets, ofcourse there are. And they are as expensive if not more than BJT transistors.
Mostly we've been seeing experimentation and development of switching mosfets that are capable of switching at 27mhz,
However in most cases is beyond the manufectures specification. There are a slew of other issues involved too.

There are pro's and con's to both. At the moment I would have to say, an $18 dollar SD1446 that can output near 100watts is problably still the winner.
Also keep in mind, most mosfets require upward to 30-50vdc (depending on which were comparing with) to see the same gain. Not exactly an ideal requirement in comparison to the 12volt 1446 just for example.

I do believe the older bi-polars will someday be a thing of the past. Until then, for our "typical" applications here, (12volt supply @ 27mhz RF) bipolar is the best choice.

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Re: MOSFETs vs. Pills

Post by TheCBDoctor » Saturday, 15 May 2010, 18:36 PM

I have to agree with madsage. The Bi-polar transistor is best suited for CB transmissions. The problem is companies are no longer making Bi-polar transistors anymore. MOSFETS are cheaper to make and have come along way.

A Toshiba 2SC-1969 goes for $14 a piece. I remember when just 2 short years ago they were under $6 a piece. The same MOSFET replacement can go for under $4. It is now a question of economics. Some radios, such as, the DX 959 used to have a 2SC-2166 for a driver and a Toshiba 2SC-1969 for a final; the peak output was 16 to 18 watts max.

The new version uses 2 IFR-520 MOSFETS with a peak output of 24 watts. The manufacturer saves $10 a radio; multiply that by a million and Galaxy saved 10 million dollars. Not all radios convert that easily and the output is usually no more and mostly less then the original Bi-polar transistor's output.

Like 'Doc always says "I have no problem spending other people's money" :lol: In a year all CBs will be using MOSFETS, so save your scrap radios for parts.

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Re: MOSFETs vs. Pills

Post by Fletch57 » Sunday, 16 May 2010, 14:57 PM

Hey thanks for the information madsage and TheCBDoctor!

I had purchased one of the Skywalker amplifiers (the Mosfet-600-base-w). You can see it at http://www.skywalkerelectronics.com" onclick="window.open(this.href);return false;, I was told and it states in the advertisment that you will see around 550-600 watts. It has 8 mrf520's in it.

When I received it it and hooked-it-up, it would only dead key 20 watts and swing about 30 watts, And that was with the variable power knob turned all the way up.

I will definately stick with pills!

Thanks again for the information.

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Re: MOSFETs vs. Pills

Post by bama7474 » Wednesday, 19 May 2010, 18:27 PM

Fletch57 wrote:I just finishing reading this post and I don't understand all of the tech talk. My questions is which transistor is the best: Mosfets or Pills? Unless I missed something, what is the final verdict?
As of right now...I'd say Pills are the best due to price and ease of finding replacement parts.
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Re: MOSFETs vs. Pills

Post by Fletch57 » Thursday, 20 May 2010, 15:05 PM

Thank you bama7474,

I will go with the pills!

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Re: MOSFETs vs. Pills

Post by TheJerk » Wednesday, 26 May 2010, 7:33 AM

drdx wrote:Maybe I phrased it badly. It is just that we're seeing a few reports of extremely low amperage draw for the wattage seen on a wattmeter, as in 5 amps for 100 watts or more, much less than the typical 10 amps per 100 watts ballpark typically scene on a traditional amp with 2879's, 1446's, or whatever. Still, I'm hopeful.

-drdx


I'm thinking where the "less" power used for more output is getting lost translation, is in the fact that heat generated by the pill is wasted energy. But I am also under the impression that MosFets don't run nearly as hot as a transitor??

I could see these being used in small base boxes...less TVI possibly?

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Re: MOSFETs vs. Pills

Post by Sheriff Bart » Wednesday, 16 June 2010, 17:22 PM

Fletch57 wrote:Hey thanks for the information madsage and TheCBDoctor!

I had purchased one of the Skywalker amplifiers (the Mosfet-600-base-w). You can see it at http://www.skywalkerelectronics.com" onclick="window.open(this.href);return false;, I was told and it states in the advertisment that you will see around 550-600 watts. It has 8 mrf520's in it.

When I received it it and hooked-it-up, it would only dead key 20 watts and swing about 30 watts, And that was with the variable power knob turned all the way up.

I will definately stick with pills!

Thanks again for the information.
Did you contact Skywalker and tell him of the low output ? I've been considering going to a MOSFET base linear in the 3kW range. Did they exchange the amp ? Was there an explanation ? Bottom line...did you get satisfaction for the greenstamps you laid out ?

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Re: MOSFETs vs. Pills

Post by heavyD » Thursday, 17 June 2010, 11:16 AM

Fletch57 wrote:Hey thanks for the information madsage and TheCBDoctor!

I had purchased one of the Skywalker amplifiers (the Mosfet-600-base-w). You can see it at http://www.skywalkerelectronics.com" onclick="window.open(this.href);return false;, I was told and it states in the advertisment that you will see around 550-600 watts. It has 8 mrf520's in it.

When I received it it and hooked-it-up, it would only dead key 20 watts and swing about 30 watts, And that was with the variable power knob turned all the way up.

I will definately stick with pills!

Thanks again for the information.


yeah but that is no reason to make a decision. there is obviously something wrong there.. I've got a 2 mosfet amp that puts out about 90w's
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Re: MOSFETs vs. Pills

Post by Lost Ram » Thursday, 17 June 2010, 13:16 PM

My mobil 4 pill skywalker does about 175 watts.
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Re: MOSFETs vs. Pills

Post by Fletch57 » Friday, 18 June 2010, 5:12 AM

I contacted them and told them of the low watts, they could not understand why! There was no explantion, they just told me that it was tested before it was shipped. So, I got my money back! Since this was my first impression with mosfets, I will never buy another one!!!!!

GO WITH PILLS!!!

That's my advice.

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Re: MOSFETs vs. Pills

Post by 420Snowman » Friday, 18 June 2010, 6:33 AM

Pills all the way, I am a creature of habit and until they work all the bugs out of the mosfet amps, I will be a pill popper!!!

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Re: MOSFETs vs. Pills

Post by heavyD » Friday, 18 June 2010, 9:56 AM

Lost Ram wrote:My mobil 4 pill skywalker does about 175 watts.

4 pill or 4 mosfet?? Think they have both? If so how do you like it? I've been looking at skywalker for a while, I like to get 10-15 opinions and think it over for a few weeks before I buy. I'm wanting 250 Watt mobile but would consider that one at 175 if the price is right. Also aren't there mosfets high drive? What radio are you using with it, Do you recommend them? Thanks
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Re: MOSFETs vs. Pills

Post by 420Snowman » Friday, 18 June 2010, 10:33 AM

I am looking at a Palomar 200x tube amp right now, I need something clean with less TVI than my pill box. But I am not too sure about the Mosfet thing yet, I'm still on the fence about it.

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Re: MOSFETs vs. Pills

Post by Lost Ram » Friday, 18 June 2010, 12:25 PM

heavyD wrote:
Lost Ram wrote:My mobil 4 pill skywalker does about 175 watts.

4 pill or 4 mosfet?? Think they have both? If so how do you like it? I've been looking at skywalker for a while, I like to get 10-15 opinions and think it over for a few weeks before I buy. I'm wanting 250 Watt mobile but would consider that one at 175 if the price is right. Also aren't there mosfets high drive? What radio are you using with it, Do you recommend them? Thanks
My bad, It has 4 mosfets. I have both transistor boxes and mosfet boxes. The mosfet type are low drive but you can put a lot of volts to them. The skywalker keying transistor (switch) fails at just past 50 volts. I am not sure what the mosfets fail at but it sure does swing at 48 volts!!!! LOL. Its been awhile but seems it did about 500-600 watts or so. Filtering on these little skywalkers is minimal!!!!! So be sure your radio does not bleed or splatter!!! Keep the audio less then 100%. I also have a 4 mosfet (mrf455) box that is AB filtered. This is my favorite, its super clean. I drive it to about 225 watts with my 2510 and no one ever asks if I have power behind it, its that CLEAN!!! I also like my dirty class c transistor box as well. It claims class B on site I got it from, it seems to work OK on SSB. I can drive this dude to 1200 peak pretty easy, its a 6 transistor base box.
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Re: MOSFETs vs. Pills

Post by 420Snowman » Wednesday, 07 July 2010, 6:46 AM

OK guys, I am breaking down here, I am looking at the Skywalker 900 base MOSFET amp and would like to know if I am to expect the 8-900 watts they are claiming. It plugs into the wall so I dont see a way to "volt" it up at all, unless skywalker sets them high to begin with, any opinions?? Its about half the price of the equivalent pill base amp, (fatboy of course)!!!

Help, I am going to purchase it this week unless someone talks me off the ledge!!

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Re: MOSFETs vs. Pills

Post by Lost Ram » Wednesday, 07 July 2010, 7:30 AM

420Snowman wrote:OK guys, I am breaking down here, I am looking at the Skywalker 900 base MOSFET amp and would like to know if I am to expect the 8-900 watts they are claiming. It plugs into the wall so I dont see a way to "volt" it up at all, unless skywalker sets them high to begin with, any opinions?? Its about half the price of the equivalent pill base amp, (fatboy of course)!!!

Help, I am going to purchase it this week unless someone talks me off the ledge!!

Snowman
I have the mobile (300). It claims 250 to 300 watts PEP. Mine at 13.8 does a very honest 175 watts PEP. Nice little unit for the money, The case is kinda like a good home-made unit. The filtering is fair at best but good enough for AM usage. I have not had any problems with mine at all. If the 900 base is anything like the output of mine you could expect about 700 watts I would guess, if the power supply does 13.8 volts. I feel I got a fair deal for the money I paid.
Also note: I built a power supply to do 38-52 volts and got about 600 watts from it pretty easily, 50 volts it the limit of the keying transistor before it fails. And yes the mosfets seemed to take about 10 minutes of 50 volts with no issues so far.
Its used now in my mobile on a daily basis.
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Re: MOSFETs vs. Pills

Post by Lost Ram » Wednesday, 07 July 2010, 7:33 AM

420Snowman wrote:OK guys, I am breaking down here, I am looking at the Skywalker 900 base MOSFET amp and would like to know if I am to expect the 8-900 watts they are claiming. It plugs into the wall so I dont see a way to "volt" it up at all, unless skywalker sets them high to begin with, any opinions?? Its about half the price of the equivalent pill base amp, (fatboy of course)!!!

Help, I am going to purchase it this week unless someone talks me off the ledge!!

Snowman
(This part is old info)
I have the mobile (300). It claims 250 to 300 watts PEP. Mine at 13.8 does a very honest 175 watts PEP. Nice little unit for the money, The case is kinda like a good home-made unit. The filtering is fair at best but good enough for AM usage. I have not had any problems with mine at all. If the 900 base is anything like the output of mine you could expect about 700 watts I would guess, if the power supply does 13.8 volts. I feel I got a fair deal for the money I paid.
Also note: I built a power supply to do 38-52 volts and got about 600 watts from it pretty easily, 50 volts it the limit of the keying transistor before it fails. And yes the mosfets seemed to take about 10 minutes of 50 volts with no issues so far.
Its used now in my mobile on a daily basis. (This part is old info)

09/27/10 new update.
I am going to add some new updated info here. I have made a couple tests with some better equipment. I posted it as well in the other forum (mosfets first look).

OK, I was able to get some real numbers on this amp with some higher voltage put to it. This is the smallest one by skywalker, the 300 mobile (four pill mosfet). I tested the amp with my power supply floating at 31.5 Volts, under Load it dropped to the mid 27 volt range. Peak power was at just a touch over 400 watts. Second test was with the supply floating at 44.5 Volts. At this voltage the power reading was the same, just a touch over 400. So I guess for a amp that cost $100 to $130 it really makes some respectable power if you have a power supply that can hit about 30 Volts! I also want to add that I did blow the key relay (transistor) twice at the 44.5 Volts test.
Last edited by Lost Ram on Monday, 27 September 2010, 18:47 PM, edited 1 time in total.
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Re: MOSFETs vs. Pills

Post by 420Snowman » Wednesday, 07 July 2010, 7:41 AM

Thanks Lost Ram, I think thats enough info for me to give it a whirl actually, it cant be a bad amp, right??? I am going to drive it with two Galaxy's, a peaked 959 and a stock, (just tuned) 55v that swings about 10-15. Should I use a driver with this mosfet box or no?? I have a one pill Fatboy I could drive it with if needed, but from reading this thread I dont think you should drive them that hard....

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Re: MOSFETs vs. Pills

Post by Lost Ram » Wednesday, 07 July 2010, 7:52 AM

420Snowman wrote:Thanks Lost Ram, I think thats enough info for me to give it a whirl actually, it cant be a bad amp, right??? I am going to drive it with two Galaxy's, a peaked 959 and a stock, (just tuned) 55v that swings about 10-15. Should I use a driver with this mosfet box or no?? I have a one pill Fatboy I could drive it with if needed, but from reading this thread I dont think you should drive them that hard....

Snowman
If you are doing that much you should be OK with no driver. I do not have to push mine at all but, then again mine is only 4 transistors and I think the 900 has 16 so you might play with it and see.
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Re: MOSFETs vs. Pills

Post by 420Snowman » Wednesday, 07 July 2010, 7:56 AM

Well sir, I think I am going to order it right now, lets give it a whirl!!! I hope they have added filters on the base unit so I am not splattering everywhere!!

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Re: MOSFETs vs. Pills

Post by Lost Ram » Wednesday, 07 July 2010, 12:22 PM

420Snowman wrote:Well sir, I think I am going to order it right now, lets give it a whirl!!! I hope they have added filters on the base unit so I am not splattering everywhere!!

Snowman
They are really no worse then the class "c" boxes. I also see that the larger ones have a SSB switch, this would leave me to believe it would have a better filter arrangement then the little 300 w/o a SSB switch (maybe??!!). Let us know how this base unit works for ya. I have thought about getting one.
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NOT DOING WHAT THEY CLAIM MOST OF THE TIME

Post by eGroupSales » Friday, 16 July 2010, 13:35 PM

Most of these amps aren't doing what they claim nor are they doing what the meter claims. Meters pick up distortion, harmonics blah blah blah. Four 20 watt finals don't create 175 watts. They'll distort enough so the meter thinks they are. I know, ratings are based on 12 volts maybe and we run them at 13.8 volts and the ratings may be at 30 mHz at times, like the ERF7530. You can get maybe 110 watts out of the 80 watter but not too much more than that.

PALOMAR FET250HD - 10 WATT DEAD KEY AND 50 WATT SWING POWER RATING - 225 WATTS OUTPUT (NOT BAD FOR $150 BUCKS OR SO) DON'T EXPECT TO GET THAT DRIVING IT WITH A COBRA 29. YOU'LL WANT A DUAL MOSFET RADIO LIKE A CONNEX 3300, GALAXY DX33 OR 55.
PALOMAR FET450HD - 20 WATT DEAD KEY AND 100 WATT SWING POWER RATING - 450 WATTS OUTPUT (NOT BAD FOR 250 BUCKS OR SOMETHING LIKE THAT) YOU JUST NEED A BIGGER RADIO LIKE A CONNEX 4300, GALAXY DX94, RANGER C1, OR A MODULATOR TO DRIVE IT.

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Re: MOSFETs vs. Pills

Post by Hypo » Saturday, 25 September 2010, 13:16 PM

New MOSFET technologies are coming out fast.

http://www.mwrf.com/Articles/ArticleID/22966/22966.html" onclick="window.open(this.href);return false; Freescale has a new MRF , MRF6VP41KH RF power FET

Microsemi has a Silicon Carbide transistor for radar apps pushing 2200W in 300 microsecond pulses 350 decree C operating temperature limit on that one.

http://www.freescale.com/webapp/sps/sit ... MRF6VP41KH" onclick="window.open(this.href);return false; 10-500 MHZ 1000W

primarily for pulsed digital applications but can do CW with adequate cooling

$607 each at Future electronics..........OUCH Guess they will stay in the commercial world for a long time at that price.

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Re: MOSFETs vs. Pills

Post by warlock35po » Sunday, 26 December 2010, 12:26 PM

You tellem 127, next thing you know they will be trying to convince me that electron flow is from positive to negative.I hope there are no takers on that. All the best and Happy New Year warlock35p0

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Re: MOSFETs vs. Pills

Post by ramboo111 » Thursday, 30 December 2010, 21:43 PM

Im old school im sticking with my home brew valve stuff cheaper and handle lots punishment

Happy New Year everyone from ozzz
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Re: MOSFETs vs. Pills

Post by WV 545 » Wednesday, 26 January 2011, 13:02 PM

ramboo111 wrote:Im old school im sticking with my home brew valve stuff cheaper and handle lots punishment

Happy New Year everyone from ozzz
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Rambo... many of our members living outside of the UK and Australia don't know what radio valves are.
I'll let you tell them what a "valve" is.

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Re: MOSFETs vs. Pills

Post by WV 545 » Wednesday, 26 January 2011, 19:31 PM

Well, I guess Rambo111 is not on... in the UK and Australia they call a tube a valve.

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Re: MOSFETs vs. Pills

Post by 420Snowman » Thursday, 10 March 2011, 20:27 PM

I can tell you now after using both, Mosfets are the way to go!! BUT ONLY if they are the actual RF Mosfets, the Mitsu RD100HHF1 and NOT the IRF520's, the IRF's are not actual RF mosfets and do not perform like one either. The box I just had build by the ONLY guy in the country right now using the Mitsu is AWESOME! Its performing way better than I ever expected. There are a few things you should know, number one, you are not going to get more power for less voltage. These run on the same voltage and draw just about exactly the same amps as a traditional pill box. The claims that they draw next to nothing are false, as you probably guessed. The advantages of Mosfets are great though, they have CRYSTAL clear audio even when drivin hard and they run WAY more efficiently, which translates to way less heat. These can be keyed eternally and not burn up, and you can talk for hours and they will get luke warm and thats it. My builder did a test with a 6 "fet" box and I was a witness to this, he keyed the amp and it was running about 500W output at this time. He rubber banded the key down ALL NIGHT LONG and played a radio station, (dont worry, it was on a high channel) and when he woke upis the box was still keyed, still putting out 500W and was room temperature!! Now try that with a pill box and you wont last 2 hours, thats not a fact, just my opinon. All in all I am very glad I made the switch and will not switch back to pills from now on, they are just "old" technology compared to the Mitsu Mosfets!

This is just for reference, not to start a debate, please dont take it as putting pills down, I still own pill amps and always have, I just stepped up my mobile!!!

I will post a few pics of my box right after this post.
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Re: MOSFETs vs. Pills

Post by 420Snowman » Thursday, 10 March 2011, 20:40 PM

Here are a few pics, as promised, sorry for the slight blur, it was my phone camera.
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Re: MOSFETs vs. Pills

Post by drdx » Friday, 11 March 2011, 12:44 PM

So how big does that guy make, as far as pill count? An 8 around here is just enough to not be embarassed. I'm doing a 2nd mobile soon and may play with one for a change.

Then next question would be just as with the pill deal. Are they a feasable way to go as far as bigger amps go? I'm under the thought that if you need anything larger than a 16 pill it is tube/AC time. I wonder if the mosfet approach changes any of that. My next mobile will have lots of room to accomodate either but like many I only want to do it once. I see that the per pill cost of that mosfet is about $32, in line with a 2879, but with availability issues the mosfet may turn the 2879 into the next vacuum tube in the eyes of many. They look to be rated at 100w with 12.5 drive unless I read it wrong and I'm curious if that is RMS and how conservative that rating is.

And, as mentioned elsewhere, what does it look like as far as purity, with the harmonics and all? Misused pills can be pretty nasty, maybe these are cleaner, but anything can be ran clean with the right design and operator.

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Re: MOSFETs vs. Pills

Post by sparky17 » Friday, 11 March 2011, 13:27 PM

You're pretty much limited to about 8 mosfets per box.. Anything more than this and they start interfering with themselves from the field effect.. (Or it's incredibly difficult to 'tune' this out').

They have some massive mosfets out there tho.. Some 1kw ones.. If you look around, a ton of the big mosfets were phased out..

Unlike bipolar transistors, the mosfets LOWER in resistance with heat, so thermal runaway doesn't occur. They're also more efficient at peak output.

Class D/E/F boxes w/ Mosfet is the way to go. > 95% efficiency (The mosfet efficiency themselves isn't usually 95% tho, so factor that in).

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Re: MOSFETs vs. Pills

Post by 420Snowman » Friday, 11 March 2011, 15:31 PM

Sparky beat me to the punch, he builds them in 8 per box, BUT he builds combiner/tuners so you run multiple boxes in series. One of my buddies locally here is now up to 32 mosfets and is doubling that in the next few months. Grim builds custom brackets so you can mount them together how ever you want to, you can make some really cool looking setups with angled brackets, etc. The price per mosfet is about the same as teh 2879, but the pills are getting harder to find and I assume the price will go up. The Mitsu mosfets are really the way to go DrDx, if you check my videogates on youtube you can hear mine on 4040's most recent gate. I have it tagged on my page so you can check it out if you like. No, its not blowing over everyone, but the difference in the audio is clearly noticable when you hear the others coming in there with me.

PM me for more info DrDx.......

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Re: MOSFETs vs. Pills

Post by drdx » Friday, 11 March 2011, 16:17 PM

Good deal. My 16 is 3 years old now and it is still a great box in great shape but it is time for something new once funds open up. I'll have my 2nd radio vehicle hopefully by May, a big honkin van, and it will become my war wagon and I may or may not have my jeep set up. My ultimate goal is a minimum 5kw rms range setup with an eq for audio, a delay phased 90 degree spaced, 135 delayed directional array or something in that ballpark in a daily usable format. I'll never run it that hard but I like headroom. The vehicle will have multiple alternators and a bank of batteries. If the mosfets sound that good, and I've heard they do, then it will be the way to go but it may boil down to logistics, as in if I can sort out a steel tube setup or stay DC. I always try to be able to run 100 watts for every year I've been on the air and I'm about to pass that up time wise. I'm bored with the current deal. It is bullet proof, works great, but wattage is like a drug and my tolerance is on the rise.

I noticed years ago that tokyo hypower had big mosfet hf amps and figured it is only a matter of time. I like the modular build up of the combiner deal as you can build it slowly and all of your cash isn't wrapped up in one box. Does the combiner bring in much loss?

I talked to 4040 a few minutes ago on 28. I guess he's using that new yaesu. It doesn't sound near as good as the old one. He said he'll be in Manchester this June.


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Re: MOSFETs vs. Pills

Post by sparky17 » Friday, 11 March 2011, 17:19 PM

Lets do the math..

$0.40 IRF520 = 25 watts (conservative)
$19.00 1446 = 100 watts

That's 2 cents a watt for Mosfet
That's 20 cents a watt for bipolar transistor

So for 10x the price, you can buy something that's no longer made...

On the flipside, I've never blown a 1446, but I have blown Mosfets in every mosfet box I've owned. They don't tolerate going out of spec...

I had no idea about the combiners..

How's the board thickness on the skywalkers?

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Re: MOSFETs vs. Pills

Post by drdx » Saturday, 12 March 2011, 6:55 AM

sparky17 wrote:Lets do the math..

$0.40 IRF520 = 25 watts (conservative)
$19.00 1446 = 100 watts

That's 2 cents a watt for Mosfet
That's 20 cents a watt for bipolar transistor

So for 10x the price, you can buy something that's no longer made...

On the flipside, I've never blown a 1446, but I have blown Mosfets in every mosfet box I've owned. They don't tolerate going out of spec...

I had no idea about the combiners..

How's the board thickness on the skywalkers?

The mosfet's 420Snowman is referring to are supposedly more specific to the use and are 100w units. They are about $32. How many, from a construction angle, of the RD100HHF1 fets have to be put into an amp for the same performance? What is their wattage rating?

The 1446 I think is rated at 80 watts.

The 2879 from what I understand is or has been discontinued but everyone knows that where there is a demand, there will be a supply. On another forum this was discussed and some company has 2879 replacements but they're only available in large lots, but not too large for a big builder to buy and still build with. I'm interested in the mosfets more out of curiosity and I hear they sound good. My only hangup so far is that the makers are limited and those skywalkere boxes, the cases, don't look that great. Users of mosfet boxes in general have had mixed luck. One user on here had one fail early, another user loves his but the power isn't near what is promised, and 420Snowman loves his, and is the first I've heard using that other more expensive Mosfet. I've got an open mind myself and may wait a little longer, start with a small 4 or 8 pill one, see what's up, and then move up.

Either way, I'm intrigued on the combiner possibility for reasons mentioned- you can build as you go, if one part fails, you're still in business, and easier to sell. These days, if you buy a bigger box new, the resale suffers because as a general rule people in the market for them can't rake up the money. Just as in the ham world, a large amp can easily be the largest single investment in your system. I'm also a fan of reliability and my boxes have been rock solid. I've personally never blown a 2879 as I usually keep fresh gear and loaf it. This 3 year run on the same box is a record for me and that's because of the lack of resale value. They're $1350 or more new but try to get 2/3 that back and you'll probably be waiting a while.

-drdx
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Re: MOSFETs vs. Pills

Post by Rooster173 » Saturday, 02 April 2011, 23:05 PM

Rumor has it mosfets are going to be replacing a lot of old finals. They already started putting them in radios

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Re: MOSFETs vs. Pills

Post by Rooster173 » Saturday, 02 April 2011, 23:24 PM

drdx wrote:Good deal. My 16 is 3 years old now and it is still a great box in great shape but it is time for something new once funds open up. I'll have my 2nd radio vehicle hopefully by May, a big honkin van, and it will become my war wagon and I may or may not have my jeep set up. My ultimate goal is a minimum 5kw rms range setup with an eq for audio, a delay phased 90 degree spaced, 135 delayed directional array or something in that ballpark in a daily usable format. I'll never run it that hard but I like headroom. The vehicle will have multiple alternators and a bank of batteries. If the mosfets sound that good, and I've heard they do, then it will be the way to go but it may boil down to logistics, as in if I can sort out a steel tube setup or stay DC. I always try to be able to run 100 watts for every year I've been on the air and I'm about to pass that up time wise. I'm bored with the current deal. It is bullet proof, works great, but wattage is like a drug and my tolerance is on the rise.

I noticed years ago that tokyo hypower had big mosfet hf amps and figured it is only a matter of time. I like the modular build up of the combiner deal as you can build it slowly and all of your cash isn't wrapped up in one box. Does the combiner bring in much loss?

I talked to 4040 a few minutes ago on 28. I guess he's using that new yaesu. It doesn't sound near as good as the old one. He said he'll be in Manchester this June.


-drdx
He said he'll be in Manchester this June. IF you go to manchester tell my good friend 427 Mr. Shoe. That Rooster says hello I'll be out of town for it so unfortunately wont make it. 73s

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Re: MOSFETs vs. Pills

Post by TheCBDoctor » Sunday, 03 April 2011, 11:33 AM

Hi,

Mosfets are like tubes; both are voltage controlled devices. Bi-polar transistors are current controlled devices. MOSFETS were never designed to handle too much current. They are being used because they are cheaper to make, not because they are better for RF transmissions.

I like Bi-polar transistors better. I was never a fan of of MOSFETs being used in a CB. The world is changing; I guess we have no choice but to go along for the ride.

Respectfully,
Best Regards,

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Re: MOSFETs vs. Pills

Post by crazy_cooter » Tuesday, 21 June 2011, 8:23 AM

GO TUBES!!! LOL
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Re: MOSFETs vs. Pills

Post by Runt » Sunday, 03 July 2011, 12:59 PM

2 pages of good reading. Way over my head on the technical side , but thumbs up regardless.
I do know this.....Tubes would not last long in a big truck.LOL!

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Re: MOSFETs vs. Pills

Post by crazy_cooter » Sunday, 03 July 2011, 13:29 PM

ramboo111 wrote:Im old school im sticking with my home brew valve stuff cheaper and handle lots punishment

Happy New Year everyone from ozzz
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WOW! I really like that amp! Someone built that thing right!
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Re: MOSFETs vs. Pills

Post by 420Snowman » Wednesday, 06 July 2011, 21:07 PM

As far as I know 311( grim reaper) is the only one making these with the Mitsubishi mosfets, everyone else is using the 50 cent jobbies. I am still very happy with my box and am saving for another 8 and the combiner, I have a very unique mount thought out that will be totally original for sure. The days of hooking it up and throwing it in the trunk are coming to an end, its gonna be like car audio, the looks and performance are going to make you stand out!
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Re: MOSFETs vs. Pills

Post by 352 Smiley » Friday, 19 August 2011, 16:43 PM

mosfets are run cooler and are better
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Re: MOSFETs vs. Pills

Post by 420Snowman » Saturday, 20 August 2011, 4:15 AM

Well, nice call sign snowman, I'm surprised we can both have one that's so close. You are right about the fets running cooler, they are much more efficient, thus run cooler.

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Re: MOSFETs vs. Pills

Post by Sniper X » Friday, 04 January 2013, 16:38 PM

I have both PLL and Mosfet amps. Both are great in their own ways. I have a DX400 BiLateral, and a DX667V. Both rock. I also have a little KL203P and a KL503 and both do realy well for not much in the way of power hungry needs. I have the little one in my 2004 Focus SVT Focus, on a trick 29, and the other in my 1991 Dodge Power Wagon 4x4 behind a DX77HML, and the KL503 and the little one allow me to talk skip and locally great.

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Re:

Post by silvereagle1 » Tuesday, 12 November 2013, 11:27 AM

Cain64 wrote:ya, if there were plans to build a MOSFET amp i would jump on that. Probly would be some what simpliar then a regular pill amp.
Original post was 2009
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