Re: Topband: New Linear amp
This MRFE6VP61K25H solid state device is catching on fast in amateur radio circles. HF Amps next. http://www.m2inc.com/pdf_manuals/2M-1K2.pdf Here is the tough time with this, because I'm sure most people take device manufacturer's data at surface value. All of this stuff, to this point of time, is mostly vaporware. Here are the worries: 1.) While manufacturer's make wild claims about device VSWR tolerance, those specs are really just creative marketing fantasy. A 2:1 SWR would instantly blow the device up if peak voltage breakdown is exceeded, or over a short period of time if heat limits in the junction are exceeded. If you do not see SWR fault protection, and there are no current limits, you can bet devices will fail with some conditions of mismatch. Their popular U-tube video is at pulsed service with a power limited supply. I can do the same thing with MRF150's, and actually designed a medical device that ran 1000 watts of peak output power on two MRF150's, without SWR protection, on 27.120 MHz. The reason it lived is the power supply would barely supply 100 watts average power, and it was pulsed duty cycle with very low Q filters and matching. 2.) No SSB IMD spec's. 3.) All public data appears to be matched narrow-band class-C pulsed service. 4.) Getting heat out of a small surface transfer area at high power and high duty cycles is a major problem. There was a good marketing presentation by the device manufacturer, but nothing indicates it is anything special for HF or linear service, or going to catch on fast. 73 Tom ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
Re: Topband: New Linear amp
Hi Tom, The new Harris Flexiva 10 KW FM band (not pulse) stereo transmitter is not having a heat problem with air cooling, in a reasonably small package . It has individual modules that can be hot switched. Will have more info when we install it next few weeks. It's going up on a mountain with no automobile/ truck road, so transporting takes time. I only meant that it was catching on fast in general. A French design is also making a 2 meter amp. A pair of the devices, with an built in ALC, to keep the output below the non linear portion could could be one approach to a 1.5 KW Amp.. The Harris Salesman, Engineer, Ham, said there was already a W2 using a pair, but had a small water cooled system. 73 Bruce This MRFE6VP61K25H solid state device is catching on fast in amateur radio circles. HF Amps next. http://www.m2inc.com/pdf_manuals/2M-1K2.pdf Here is the tough time with this, because I'm sure most people take device manufacturer's data at surface value. All of this stuff, to this point of time, is mostly vaporware. Here are the worries: 1.) While manufacturer's make wild claims about device VSWR tolerance, those specs are really just creative marketing fantasy. A 2:1 SWR would instantly blow the device up if peak voltage breakdown is exceeded, or over a short period of time if heat limits in the junction are exceeded. If you do not see SWR fault protection, and there are no current limits, you can bet devices will fail with some conditions of mismatch. Their popular U-tube video is at pulsed service with a power limited supply. I can do the same thing with MRF150's, and actually designed a medical device that ran 1000 watts of peak output power on two MRF150's, without SWR protection, on 27.120 MHz. The reason it lived is the power supply would barely supply 100 watts average power, and it was pulsed duty cycle with very low Q filters and matching. 2.) No SSB IMD spec's. 3.) All public data appears to be matched narrow-band class-C pulsed service. 4.) Getting heat out of a small surface transfer area at high power and high duty cycles is a major problem. There was a good marketing presentation by the device manufacturer, but nothing indicates it is anything special for HF or linear service, or going to catch on fast. 73 Tom ___ UR RST IS ... ... ..9 QSB QSB - hw? BK ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
Re: Topband: New Linear amp
On 7/7/2012 1:18 PM, Bruce wrote: Hi Tom, The new Harris Flexiva 10 KW FM band (not pulse) stereo transmitter is not having a heat problem with air cooling, in a reasonably small package . It The problem with starting with a saturated amplifier and then backing off the power for linearity is that the dissipation actually goes UP when you reduce the output power. The maximum dissipation occurs at something like 1/3 of maximum power. Therefore, this FM transmitter is not really proof that a linear amplifier is practical. I have done a lot of work with Dick Brounley's laser drivers. He gets up to 750 watts (continuous duty) out of a pair of MRF150's at 81.36 MHz, just below the FM band. Dick's design is great for its intended application, but doesn't translate to a ham amplifier. Furthermore, it is water cooled. The biggest problem Dick has thermally is cooling the ferrites in the output transformers. He actually has to heat sink them with copper sleeves. RF lasers are lucky to have 10% efficiency in terms of converting RF to light. Therfore, they are all water cooled and this makes water cooling for Dick's amplifiers basically free. Rick N6RK ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
Re: Topband: New Linear amp
Hi Bruce, The new Harris Flexiva 10 KW FM band (not pulse) stereo transmitter is not having a heat problem with air cooling, in a reasonably small package . It has individual modules that can be hot switched. I'm sure Harris did a great job. The modules can be swapped while the TX is on, even power supply modules, which is a nice feature. But hot or live swapping does not mean the modules are hot switched, as in allowed to have no load while amplifying. Generally a module is designed to remove power first when pulled, and apply power last when plugged in, which is nothing at all like some ham transmitting with an arcing tuner, or without a feedline. You will also note Harris protects the modules, which is what everyone should do. VSWR ratings in data sheet are really useless marketing hype, because near full power in longer duty cycle modes, as little as a 2:1 VSWR can blow a device out. My point is about Ham gear use where people are thinking they do not need to watch SWR or other parameters. There is little worry in a commercial transmitter that runs the device at 600 watts or less per device with adequate protection for SWR and thermal issues, and most likely current limiting. We should not translate what Harris did into something with no thermal protection, no SWR protection, and twice the power on the device!! The Harris Salesman, Engineer, Ham, said there was already a W2 using a pair, but had a small water cooled system. I played with a thick copper heatsink and air cooling, but concluded it was too expensive, and it would be a manufacturing PITA to get the surface machining flat enough in production. With 1000 watts of heat in such a small footprint, the surface almost has to be polished flat. The copper spreader would have cost about $30-40, plus the aluminum heatsink would need to be reasonably flat all across the surface. I'm not even sure that would work without liquid cooling. It makes sense hearing the W2 used liquid cooling. At current costs for cooling and the devices, it is better to use more lower power devices and spread the heat around. Especially when the devices are just as reliable, have a history of good SSB IM performance, and cost less per watt. My guess is the marketing blitz and creative specs are why we find a few amateur soon to be released products without any final specifications. They probably believed a single 1200 watt device would be linear at 1200 watts, and would actually handle high SWR without protection. Anyone who has actually worked with high power RF semiconductors knows the VSWR specs are meaningless marketing drivel. Like I said, I ran a pair of MRF150's in pulsed service, in deep class C, and they were safe and reliable at a kilowatt without any SWR protection, other than power supply limiting. Because they worked in pulse service deep class C in a low-Q system at 1000 watts without worry doesn't mean 2x MRF150's would work on CW at that power, or be reliable at 200 watts CW without SWR and thermal protection. Apples and oranges. When the device price comes down a bit, or if they make a smaller device that allows spreading the heat around, you'll probably see the Freescale device in Ham gear. 73 Tom ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
Re: Topband: New Linear amp
BEKO in Germany uses them in their 2m amps for about two years. Last year I was operator at a contest station with 3x HLV-2000 into three antenna groups. They worked perfectly at 2KW out for the 24 hours. The HLV-1000 uses one of those transistors and is upgradeable with a second, the HLV-2000 uses two and the HLV-4000 uses four MRFE6VP61K25H. http://www.beko-elektronik.de/index.php?do=03,01,01,02,05lang=en Wideband and HF seems to be more difficult. 73 Peter, DJ7WW -Original Message- From: topband-boun...@contesting.com [mailto:topband-boun...@contesting.com] On Behalf Of Bruce Sent: Samstag, 7. Juli 2012 20:47 To: topband@contesting.com Subject: Topband: New Linear amp This MRFE6VP61K25H solid state device is catching on fast in amateur radio circles. HF Amps next. http://www.m2inc.com/pdf_manuals/2M-1K2.pdf 73 Bruce-K1FZ ___ UR RST IS ... ... ..9 QSB QSB - hw? BK ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
Re: Topband: New Linear amp
On 7/7/2012 11:28 PM, Chortek, Robert L wrote: Uh, I thought the legal limit was 1.5 KW Only in the US. Limits vary by country with some as high as 5KW others as low as 400W. 73, ... Joe, W4TV On 7/7/2012 11:28 PM, Chortek, Robert L wrote: Uh, I thought the legal limit was 1.5 KW Sent from my iPhone On Jul 7, 2012, at 7:49 PM, Peter Voelpel df...@t-online.de wrote: BEKO in Germany uses them in their 2m amps for about two years. Last year I was operator at a contest station with 3x HLV-2000 into three antenna groups. They worked perfectly at 2KW out 73 Peter, DJ7WW ___ UR RST IS ... ... ..9 QSB QSB - hw? BK ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
Re: Topband: New Linear amp
On Sat, 2012-07-07 at 23:45 -0400, Joe Subich, W4TV wrote: On 7/7/2012 11:28 PM, Chortek, Robert L wrote: Uh, I thought the legal limit was 1.5 KW Only in the US. Limits vary by country with some as high as 5KW others as low as 400W. 73, ... Joe, W4TV And by band. This is a top band list but other bands have already been introduced into the discussion. 73, Bill KU8H ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
