Will New Power Transistors End the Need for Tube Amplifiers in the Future?

[KG6WOU]

I'm pretty sure that tubes will eventually be replaced in amateur use by some sort of solid state amplifiers.  It seems inevitable eventually.  As many have pointed out, the modular amplifiers in use in AM and FM service will likely be eventually pressed into amateur service, since they are designed for continuous service, they should work pretty well for us.

But all the additional hardware required to keep a solid state amp happy is just going to cost us all.  Tubes certainly have the advantage of being pretty robust when lightly abused - meaning that they survive the hamhanded learning cycle for tuning long enough for the owner to gain the needed experience to do it correctly.

I suppose the real question is "When" not if.  I wonder how many 3-500's are sold every year now.

[K4XU]

If you replace the G with a 6, you get close to a real part number:

MRFEGVP1250 -> MRFE6VP1K25H ?

Bob

I wondered if he was talking about Freescale, but he said Motorola and it appears to be a Motorola part number, of sorts.

A little history:

The MRF150 has been on the market since 1970. Originally made by Motorola, in 2002 they sold off their VDMOS operation to MACom and spun off their LDMOS operation to form Freescale. MACom was bought by Cobham in 2010 who then sold off the VDMOS part of the business to a venture capital group who formed MACom Technology Solutions. As a fully depreciated "cash cow", they will keep making these old MRF150s until it's no longer profitable.

In 2002 Advanced Power Technology, an unsuccessful bidder for Motorola's VDMOS line, started developing modern enhanced versions of the old Motorola 50V MRF parts. In 2004 they introduced VRF150, VRF151, and a bit later VRF2933 (parallel 151s in a single package), VRF154 and 157 (4x 151). In 2006 APT was acquired by Microsemi. The VRF parts have better linearity and much higher breakdown voltage than the older MRF parts. The VRF series parts are used in the THP HL-1.5KFX, the Yaesu FTDX5k and the Elecraft KPA500.

rf

[WX7G]

The power transistors of the last century have made HF tube amps obsolete.

[K7PEH]

An earlier posting suggested the use of liquid cooled solid-state devices.  Seymour Cray invented the first liquid cooled solid-state component for the Control Data Corporation 6600 computer in the mid-1960s.  At that time, some medium scale integration was taking place and used in the IBM 360 series computers but the CDC 6600 was all discrete components that were very tightly packed into these component cards.  Packing was so tight that normal air flow cooling was insufficient and that was the reason for the liquid cooling.  The CDC 6600 was as much a plumbing problem as it was a computer and electronics problem during maintenance.  My early formative days as a programmer were spent with CDC 6000 line computers at CDC Sunnyvale Ops.

[W6RMK]

Right now, liquid cooling is pretty complex and very individual design sensitive: that is, every design needs a different cooling design, either from a thermal standpoint or a packaging standpoint. That translates to expensive.  What's needed is something that is mass produced to meet a consumer need, which we as amateurs can then repurpose to our own needs.

There is some hope because the increasing power density the CPU and GPU world means that just about every laptop made these days has a heatpipe in it, and there are quasi-off-the-shelf liquid cooling schemes for PCs.  The cost of chillers has has also come down: either using Peltier devices (very inefficient) or just because of the inexpensive off-shore-manufacturing of simple mechanical devices (kegerators, bar fridges, etc.). You see chillers for aquariums at remarkably low prices compared to what we used to pay for a standard lab chiller.

Sooner or later some inventive ham is going to start looking at how do you bolt a set of FETs onto the "coldplate" of a CPU chiller, and still get the RF part of the design to work ok.  And gradually, the articles will change from "how to build a chimney and blower for your power grid tube"  and "how to make your own socket for that broadcast pull" to "how to turn an icemaker into a chiller" and "how to safely bend the heat pipe on a laptop CPU chiller".

[K6AER]

Even though you can cool the transistors with a water cooled heat plate you still have to cool the magnetics (combiners) and filters with air. A two KW amplifier can have over 200 watts in harmonics that have to be dissipated.

Currently tubes  give you much lower distortion vs. cost for a 1500 watt amplifier. Also with most hams no longer being technical, tubes are much more forgiving.

[W6RMK]

power density isn't as troublesome in the magnetics though. You can always get bigger cores, etc.   The problem with the transistors is that the dice are just so small, so that's where the big thermal issue is.

(After all, there are millions of liquid cooled transformers around already)

[KH6DC]

I replaced my Ameritron AL811 with a Tokyo Hy-Power Hl1.2KFx ss linear several years ago.  The THP is a great amp and the build inside is breathtaking.  The THP is instant on, no-tune but I sure do miss the glow and warmth of a tube amp.  Thinking of picking up an ACOM sometime soon in addition to keeping the THP.

[KG4NEL]

Economical solid-state audio amplifiers capable of driving inefficient speakers and ugly impedance curves ended the need for tube designs decades ago, yet new-production SET amps have come back in vogue.

The little devils are resilient...