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Author Topic: RM Italy Amplifiers  (Read 7011 times)
VK6HP
Member

Posts: 151




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« Reply #15 on: October 16, 2017, 02:54:24 AM »

Peter

Any test equipment requires a measure of understanding, I agree.  But I've seen some real light-bulb moments when people use even simple spectrum analysers, or even SDR suites, in basic modes.  One of the pluses of the internet era is a wealth of fairly decent on-line tutorials. And it's not that hard: if you can get through the relevant sections of the ARRL or RSGB handbooks, you're well on the way to being able to conduct and interpret the tests, possibly with some hand-holding the first time around.

I understand your comments but I think they are too negative.

73,
Peter.
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ZS5WC
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Posts: 631


WWW

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« Reply #16 on: October 16, 2017, 05:54:44 AM »

 :)To be safe I would rather invest in an ACOM 600s or used Expert amp.
Lots of guys upgrading to 1.5K-fa from the 1K-fa.

I run the 1K-fa Expert amp. myself and it is Super!.. Auto everything -simply switch on you rig and go!.. (Amp can be wired to turn on by itself when rig is on.)
I use Band Data for band switching..
My FTDX-3000 is now 1Kw rig.

73 de William
ZS4L / ZS5WC
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K6AER
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Posts: 4669




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« Reply #17 on: October 16, 2017, 08:38:54 AM »

I went out and looked at the MRFE6VP5600 devices used in the amplifier. They look to go into 1 dB compression at about 600 watts so marketing the amplifier as a 500 watt amplifier is good. Gain on the devices is 25 dB so the amplifier gain will have input attenuators to hold the gain below 15 dB for the FCC. The manual is well written but I would have liked to see a amplifier schematic. It appears the main supply is a analog transformer/bridge/filter cap arrangement. All in all the amplifier looks to have the necessary controls for good operation. If the amplifier is for sale then the FCC acceptance should be available on line. We'll see what can be found. I would like to see a fan noise measurement 18 inches in front of the amplifier.

The amplifier looks to be a winner but time will tell where is settles in the price wars.
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WY7CHY
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Posts: 638




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« Reply #18 on: October 16, 2017, 10:50:52 AM »

I can't speak for the amp in question, but a couple years ago I tested and then bought an RM Italy HLA-300V. Not the newer HLA-305 but the previous HLA-300V. Puts out 300 watts FM/CW and 350-400 watts in SSB mode. Personally, I think it's a great amp. I use it for most of my Stateside contacts when I need a 6db bump. For DX out of the country, I use my bigger amp if needed. But for the $400 I paid for the 300-400 watt HLA-300V amp, I am very pleased with it.
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Born Wild - Raised Proud: 73
Cheyenne, Wyoming
W3RSW
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Posts: 536




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« Reply #19 on: October 16, 2017, 12:27:58 PM »

Yes, interesting
http://cache.freescale.com/files/rf_if/doc/data_sheet/MRFE6VP5600H.pdf

This device has been around since 2010.
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Rick, W3RSW
KB4MNG
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Posts: 265




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« Reply #20 on: October 16, 2017, 04:43:13 PM »

$2500 for 500 watts. Are they nuts? Who buys something like that? Evidently folks that have money to burn. They have a ship date of 11/20
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K6AER
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Posts: 4669




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« Reply #21 on: October 16, 2017, 06:33:30 PM »

looks to be is the same class as the KPA-500 with power supply included in the case. The ALS-600 is a separate power supply and has the built in the garage look. Array Solutions will drop the price if the marketing needs better targeting. I have to think there is some margin at $2500.
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K1ZJH
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Posts: 3303




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« Reply #22 on: October 16, 2017, 06:42:29 PM »

Regarding IMD, a dirty, poorly designed amp always will be dirty.  A properly designed amp has the chance of being used properly and delivering a clean signal. Even a simple monitor scope to show flat topping would go a long way to clean up some of the signals I hear during contests and DX pileups.

Pete
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K6AER
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Posts: 4669




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« Reply #23 on: October 16, 2017, 07:01:48 PM »

Regarding IMD, a dirty, poorly designed amp always will be dirty.  A properly designed amp has the chance of being used properly and delivering a clean signal. Even a simple monitor scope to show flat topping would go a long way to clean up some of the signals I hear during contests and DX pileups.

Pete

Even a amplifier that looks to not be flat topping can produce IMD products that are only 20 dB down on the third and fifth IMD signals. Remember 20 dB is 1 %. A RF trapezoid will look perfect with only 1% distortion. With a S9+30 dB signal your products are S9+10dB. Still even an amplifier with IMD number of only 35 dB is better than most transceivers.

The mic. gain control is the biggest contributor to spectrum width.
« Last Edit: October 16, 2017, 07:06:15 PM by K6AER » Logged
VK6HP
Member

Posts: 151




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« Reply #24 on: October 16, 2017, 09:37:28 PM »

It is true that -20 dB is about the visible limit on a monitor scope but it's also often true that over-driving and flat-topping are big contributors to distortion (as you and the previous poster suggest).  The monitor helps greatly in preventing that and, if you do use a spectrum analyser (or SDR, or good bandscope) on an occasional basis, your eye gets practiced at interpreting two-tone and other test setups to best advantage.  

Interestingly, my old FTDX-560 manages a just a bit better than -20 dB relative to the two-tone RF outputs.  Its advertising blurb (c. 1969) proudly trumpets a figure of -25 dB, but that's relative to PEP of course, making the proper specified number -19 dB. Out of consideration for my ham neighbours I rarely use the radio, and then only at reduced drive.  Conversely, my Collins S-line and 30L-1 exceeds the performance of many contemporary combinations.

You don't have to pay a fortune to support a present-day transceiver manufacturer/model that will hit -35 dB (or better) when correctly aligned but, unfortunately, there are plenty of significantly poorer examples around. Follow those with a poor "linear" and it becomes downright un-neighbourly.
« Last Edit: October 16, 2017, 09:41:59 PM by VK6HP » Logged
AC2RY
Member

Posts: 280




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« Reply #25 on: October 17, 2017, 05:32:01 AM »

It is true that -20 dB is about the visible limit on a monitor scope but it's also often true that over-driving and flat-topping are big contributors to distortion (as you and the previous poster suggest).  The monitor helps greatly in preventing that and, if you do use a spectrum analyser (or SDR, or good bandscope) on an occasional basis, your eye gets practiced at interpreting two-tone and other test setups to best advantage.  

Interestingly, my old FTDX-560 manages a just a bit better than -20 dB relative to the two-tone RF outputs.  Its advertising blurb (c. 1969) proudly trumpets a figure of -25 dB, but that's relative to PEP of course, making the proper specified number -19 dB. Out of consideration for my ham neighbours I rarely use the radio, and then only at reduced drive.  Conversely, my Collins S-line and 30L-1 exceeds the performance of many contemporary combinations.

You don't have to pay a fortune to support a present-day transceiver manufacturer/model that will hit -35 dB (or better) when correctly aligned but, unfortunately, there are plenty of significantly poorer examples around. Follow those with a poor "linear" and it becomes downright un-neighbourly.

Good IMD is only important with SSB and some digital modes. Others should NOT hear your SSB transmission when they tune 3kHz up or down from your frequency. If this is the case, IMD is good enough for voice mode work. Bad IMD with phase modulated digital modes simply REDUCE chances of being heard on the other side.

With CW or frequency modulated digital modes IMD is not important at all. Out of band emissions are the main problem there.

 
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G3RZP
Member

Posts: 8123




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« Reply #26 on: October 17, 2017, 05:36:47 AM »

A few years back, I investigated QST equipment reviews back to the 1970s - over 115 of them. The last generation of tube PA transceivers  - 1973 to 1983 - averaged around -36dB IM3, around -44dB IM5, around -58dB IM7, and more than -66dB on IM9.

The average values for transceivers between 2000 and 2013 - obviously solid state PAs - were -30dB for IM3, -41dB for IM5, -47dB for IM7 and -52dB for IM9.

Draw your own conclusions!
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VK6HP
Member

Posts: 151




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« Reply #27 on: October 17, 2017, 05:59:09 AM »

It is true that -20 dB is about the visible limit on a monitor scope but it's also often true that over-driving and flat-topping are big contributors to distortion (as you and the previous poster suggest).  The monitor helps greatly in preventing that and, if you do use a spectrum analyser (or SDR, or good bandscope) on an occasional basis, your eye gets practiced at interpreting two-tone and other test setups to best advantage.  

Interestingly, my old FTDX-560 manages a just a bit better than -20 dB relative to the two-tone RF outputs.  Its advertising blurb (c. 1969) proudly trumpets a figure of -25 dB, but that's relative to PEP of course, making the proper specified number -19 dB. Out of consideration for my ham neighbours I rarely use the radio, and then only at reduced drive.  Conversely, my Collins S-line and 30L-1 exceeds the performance of many contemporary combinations.

You don't have to pay a fortune to support a present-day transceiver manufacturer/model that will hit -35 dB (or better) when correctly aligned but, unfortunately, there are plenty of significantly poorer examples around. Follow those with a poor "linear" and it becomes downright un-neighbourly.

Good IMD is only important with SSB and some digital modes. Others should NOT hear your SSB transmission when they tune 3kHz up or down from your frequency. If this is the case, IMD is good enough for voice mode work. Bad IMD with phase modulated digital modes simply REDUCE chances of being heard on the other side.

With CW or frequency modulated digital modes IMD is not important at all. Out of band emissions are the main problem there.

 


Whether or not others hear your SSB transmission out of channel will also depend on how strong your signal is and often, by extension, how close the listener, or unintended receiver, is.  

(And yes, even the FTDX-560 can do nice CW!).
« Last Edit: October 17, 2017, 06:11:39 AM by VK6HP » Logged
AC2RY
Member

Posts: 280




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« Reply #28 on: October 17, 2017, 09:34:18 AM »

A few years back, I investigated QST equipment reviews back to the 1970s - over 115 of them. The last generation of tube PA transceivers  - 1973 to 1983 - averaged around -36dB IM3, around -44dB IM5, around -58dB IM7, and more than -66dB on IM9.

The average values for transceivers between 2000 and 2013 - obviously solid state PAs - were -30dB for IM3, -41dB for IM5, -47dB for IM7 and -52dB for IM9.

Draw your own conclusions!

Solid state circuit requires more headroom than tubes. If you de-rate amplifier even by 1dB f output power, IMD numbers will look much better. That is why we should see graphs: IMD vs. output power to make a conclusion if amplifier is good or not so.
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G3RZP
Member

Posts: 8123




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« Reply #29 on: October 17, 2017, 01:19:57 PM »

The levels of the high order IMD products comes down to the transfer characteristics of the device: the logarithmic characteristic of the bipolar transistor will, under like for like circumstances, be worse than the tube. The MOS devices aren't that much better. What will turn the whole matter upside down is SDR with pre-distortion, provided the system is good at 'self training'.

Of course, nothing will help with those few contest stations who believe in having a wide signal to keep people away from 'their' frequency!
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