Mosfet Amp

[BOOTY MONSTER]

if we agree then it must be true !!!

BTW , herd anything else about world wide amps ? im not a class C fan , but they were one of the better looking ones .

 

[psycho]

if we agree then it must be true !!!

BTW , herd anything else about world wide amps ? im not a class C fan , but they were one of the better looking ones .

WTF is with that braid over the transistors.....the whole board is one big copper board and the braid makes no sense. That looks like the Freddy Kruger of amps.
At the present time they are building a few every now any then, just to get rid of the cases, boards and parts that were leftover. The owner of the outfit is still disabled and unable to work plus his builder has been going through all kinds of medical problems too....he'll build a few when he can.
No sense in hiring someone else when people are holding onto their money!
He'll be glad to hear that someone was asking......I like mine. Later from the 96 deg 95% relative humidity State of Florida!

 

[dudmuck]

WTF is with that braid over the transistors.....the whole board is one big copper board and the braid makes no sense. That looks like the Freddy Kruger of amps.

The braid is there precisely because the board is one big copper board.
Meaning the board has no plated-thru holes to the bottom layer, also known as "vias".
So because of that, there is insufficient ground connection between the pills and to the (-) power lead, which is compensated for by having a thick braid soldered to all ground connections on the pills.

 

[psycho]

The braid is there precisely because the board is one big copper board.
Meaning the board has no plated-thru holes to the bottom layer, also known as "vias".
So because of that, there is insufficient ground connection between the pills and to the (-) power lead, which is compensated for by having a thick braid soldered to all ground connections on the pills.

That being said it is unnecessary. The transistors are grounded to the board which is one big ground plus the ground leadand SO239 connectors are soldered directly to that. I have seen the transistors tied together in Messenger amps where the board has sprayed on traces and very little actual ground surface.
In that picture the braid actually looks like desoldering braid. Never saw ground braid soldered to transistors on competition amps before.
AM Power no longer builds amps, go figure. I think the bird in Booty's signature must have assembled that amp.

 

[fnkycoldmedina]

this amp was discussed in great detail on another forum .the owner (fireball)even joined the forum to debate the amp .
this amp was a prototype and was built by the same guy who built the rfx75 add on mosfet amp .
this is what was said ,i have no first hand knowledge.
anyway so the amp was built by the builder of the rfx75 and was his prototype ,that said ,it looks it right?
well here is another more refined edition of a amp he built .i took this pic from the other forum for you guys .
have fun looking,this is the future of amplifiers here
this is a 4 driving 16

 

[fnkycoldmedina]

this is that first amp from ebay being tested on a bird meter .
watch this on youtube and look at the user name under the video .
you will surely know this person from dx land .








16 Mosfet amp test - YouTube

 

[eagle1911]

IDK.. looks overly complicated and not all that cleanly built to me.. soldering still seems a tad sloppy, but it is far better than that other pic..

The future of amps is in LDMOS technology.. As it is already being experimented with in Amateur amplifiers (working on an MRF6VP11KH design myself currently) I have little doubt that it will eventually filter down to CB type amps. The BLF578 from NXP produces 1.2kW PEP or CW 1.8-500MHz from a single push-pull device, the MRF6VP11KH from Freescale produces 1kW PEP or CW 1.8-150MHz, again from a single push-pull device. These devices run about $150-200 each, but only one is needed and no drive stage is required. Given the straightforwardness of an amp with a single-push-pull stage it would be much simpler and very likely cheaper in the long run to use these new devices instead of building complex, parallel push-pull designs.

 

[Se7en]

beauty is usually in the eye of the beholder ...... sometimes its in the eye of the uninformed . remember that crappy azz lookin base amp zman made with the butchered copper board and the case butchered and bent with hammers ? some folks on another forum were very impressed with it . but ,thats what happens when a forum protects its sponsors .

i was told to put a copper braid like so across the transistors on my ts500v, looks like snake oil..... is there really any real benefit to this?

 

[eagle1911]

^It just helps ensure a good ground.. it's optional unless you find through real-world operation that your grounding needs improvement.

 

[AudioShockwav]

and was his prototype ,that said ,it looks it right?

I am the one that started the thread because the ad on flea bay said 'New"
( and for the record)
The whole point of the post was how can something that looks like it has been re-built ten times be sold as new?
If it had been listed as used, with something describing it as a prototype i would probably not thought much about it..but I scrolled down to the pictures and went WTF? New?
This amp pictured, i will say looks better than the last one, but i still would not try to sell it as new, somebody would call me on it, because you can see that it has also been reworked.
Like selling factory re-furbished radio as new.

As far as the future of Amps.... some Cb style amps maybe, but I would have to agree with eagle on his post.....why go through all that mess, when a amp can be built with two output devices that can do as well with out having multiple failure areas?
And Bi-polar transistors are still out there, just because Toshiba is not making 2879`s any more is not the end of the world, MayCom is still building them.
The thing I think these guys looking at is these small mosfets are cheap, so you can string a bunch of them together and get some watts out of them, but the gain is not very high, you need a lot of drive to get big numbers out.
And all the combiners and everything needs to be balanced.
Maybe you can get the builder to come over here and let us know what kind of drive is needed to get the output shown and current/voltage used in the Video posted.
I am not being an ass, I just do not buy that this is the end all to amps just yet.

73
Jeff

 

[dudmuck]

That being said it is unnecessary. The transistors are grounded to the board which is one big ground plus the ground leadand SO239 connectors are soldered directly to that. I have seen the transistors tied together in Messenger amps where the board has sprayed on traces and very little actual ground surface.
In that picture the braid actually looks like desoldering braid. Never saw ground braid soldered to transistors on competition amps before.
AM Power no longer builds amps, go figure. I think the bird in Booty's signature must have assembled that amp.

A copper board such as that is not "one big ground", unless it has plated-thru vias at regular intervals.
For some perspective: a 4inch piece of 20AWG wire has 6ohms of inductive reactance at 27MHz. (at Inductance of a Straight Wire: A Calculator)
Braided wire has lower inductance because of skin-effect behavior.

Anyways, nobody is packaging mosfets in TO-218 package anymore. I would be fearful of source of such parts.

 

[fnkycoldmedina]

definitely not the end all of amps ,but the future of cb style amps will surely go this way .
with the cost of 2879`s going up and their availability being in question in upcoming years builders will be forced to go this route .

and the amp did not look new to my eye either .but being it was supposedly a prototype i can see a prototype looking like that .

i am all for new technology ,if someone can get us the same watts for less money its a win ,win, for everyone.

ps- the builder did not show ,only the owner of the amp .but he knows who the builder is obviously.

 

[eagle1911]

with the cost of 2879`s going up and their availability being in question in upcoming years builders will be forced to go this route .

You must have missed my last post as well as Audioshockwav's. Why will they be "forced" to go that route when, as just described, there are already FAR superior ways to get that power for less money and effort? Even if a builder wants to go the BJT route instead of MOSFETs, there are several other devices that can be used in an HF amplifier other than just 2879s, and the latest LDMOS FET stuff is just plain amazing compared to BJTs in terms of performance and ruggedness.

 

[psycho]

AMPOWER was forced to sign a statement in his contract when went to work for Galaxy as head technician stating he would discontinue building his line of amplifiers as they harmed Galaxy's hp line of radio sales and sucked the life out of the less power line Galaxy sells........

Just like Radioactive completely redesigns the transmit and receive of superwackpacked radios.

 

[eagle1911]

If AMPOWER was the dude I saw in a video not too long ago standing under some trees touting himself as some sort of amplifier guru, then I will never own a Galaxy product again as long as he's employed there. They guy in that video was beyond clueless, so I can only imagine what his input into a company would produce.