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Author Topic: Flex 1500 Amplifier Recommendations ?  (Read 39024 times)
KF5EXC
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« on: April 16, 2012, 01:52:34 PM »

Our club is looking into buying a Flex 1500 for the ham shack and plan to add an amplifier.  Anyone have suggestions as to models compatibility and cost? Huh
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NI0Z
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« Reply #1 on: April 19, 2012, 09:12:04 AM »

Maybe the Elecraft 100 watt when it comes out, see their site for details.  I think the challenge is with many amps is having enough power to meet the minimum exciter requirements.  I have never googled QRP Rig Amps, that might help you as well.

NI0Z
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WN2C
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« Reply #2 on: April 19, 2012, 10:07:29 AM »

Why buy a QRP rig when for a few more sheckels you can buy the 3000.  You can turn it down to QRP level and then turn it up to drive a higher power amp when needed.
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NI0Z
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« Reply #3 on: April 19, 2012, 10:51:14 AM »

I definitely second the idea on getting the 3000, more power and a better class rig as well.  Besides, the money you might spend on the amp my be more than just getting the more capable radio.
« Last Edit: April 19, 2012, 01:48:26 PM by EVERSTAR » Logged

KE5JPP
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« Reply #4 on: April 20, 2012, 03:54:36 AM »

I definitely second the idea on getting the 3000, more power and a better class rig as well.  Besides, the money you might spend on the amp my be more than just getting the more capable radio.

Why buy either?  Just go for the Flex-5000a if you are hell bent on getting a Flex.  The Flex-3000 is "limited" to 92 kHz sampling by the manufacturer to differentiate it from the 5000a, and the Flex-1500 is "limited" to 48 kHz sampling to differentiate it from the 3000 and because it uses the slower full speed USB versus high speed USB.  You will get only about 80 kHz and 40 kHz of spectrum view respectively in the panadapter.  The 5000a will sample at 48, 96, or 192 kHz.  192 kHz will give you about 180 kHz in the spectrum panadapter to see.   If you say you don't care about the panadapter bandwidths then you need to ask yourself why you are buying a SDR in the first place.   For the same price range you could go with a FT-450D or something in its class and already have 100 watts.

The 1500 RF PA IMD is really bad as demonstrated in various reviews and tests, and following its dirty 5 W signal will a big amp just "amplifies" those problems.   

Gene
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K0OD
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« Reply #5 on: April 20, 2012, 11:27:40 AM »

48 kHz of band is adequate for many operating purposes. Even on 6 and 10, it will tell you whether the band is open. Most activity on six centers tightly around calling frequencies.

On HF I zoom in with my Flex-5000a and watch just a few kHz of spectrum when S&Ping  in contests. Looking at a 180 KHz swath of 40 meters during a contest tells you nothing. Broader panadaptor range obviously means less resolution. I only use the full 180 kHz panadaptor range occasionally on ten and six.  

Still, I don't understand those who buy QRP radios and add outboard amps, preamps, audio gizmos, DSP boxes and whatnot. I like my station clean and uncluttered.

While it's certainly not cost effective, you can do QRP with a Flex-5000; minimum power is about 3/4 watt as I recall.

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Why don't you ask the various Flex groups for info about an amp for a 1500?
« Last Edit: April 20, 2012, 11:35:12 AM by K0OD » Logged
KE5JPP
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« Reply #6 on: April 20, 2012, 11:49:03 AM »

48 kHz of band is adequate for many operating purposes. Even on 6 and 10, it will tell you whether the band is open. Most activity on six centers tightly around calling frequencies.

On HF I zoom in with my Flex-5000a and watch just a few kHz of spectrum when S&Ping  in contests. Looking at a 180 KHz swath of 40 meters during a contest tells you nothing. Broader panadaptor range obviously means less resolution. I only use the full 180 kHz panadaptor range occasionally on ten and six.  

Still, I don't understand those who buy QRP radios and add outboard amps, preamps, audio gizmos, DSP boxes and whatnot. I like my station clean and uncluttered.

While it's certainly not cost effective, you can do QRP with a Flex-5000; minimum power is about 3/4 watt as I recall.

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Why don't you ask the various Flex groups for info about an amp for a 1500?

The point is that you have that option of zooming in and out with the Flex-5000, where you are limited by the Flex-1500 48 kHz only sample rate.  There are also many instances when you want to see AT LEAST the 180 kHz spectrum that the Flex-5000 offers.

Gene
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K0OD
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« Reply #7 on: April 20, 2012, 12:35:27 PM »

Quote
where you are limited by the Flex-1500 48 kHz only sample rate.

Can't a Flex-1500 zoom in with PSDR? I've never used one.

BTW, used my Flex-5000 in the ARRL FMT last night. Good example of when you'd want to examine a tiny slice of spectrum.  Results won't be out for a week, but my 5000a, with its built-in scope and incredible stability, will surely beat plenty of entrants with racks of costly outboard frequency standards and lab test equipment. I use the panascope mode in a FMT.
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KE5JPP
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« Reply #8 on: April 20, 2012, 01:00:34 PM »

Quote
where you are limited by the Flex-1500 48 kHz only sample rate.

Can't a Flex-1500 zoom in with PSDR? I've never used one.


Yeah, sure you can zoom in.  But that is only 40 kHz (at the widest) or less spectrum on the panadapter.  When you are on 15, 10, or 6 meters looking for band openings, it really helps to be able to go out much wider, like at least the 5000's 180 kHz.  Of course the direct sampling receivers like the QS1R or Perseus can go out to 2 MHz or 1.6 Mhz respectively for the ultimate look at the band conditions.

Gene
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K0OD
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« Reply #9 on: April 20, 2012, 01:44:54 PM »

10-20 times wider means each little blip, whether juicy DX or neighborhood birdies, is going to be far less prominent. No doubt, wider sells radios. Probably really nice for test purposes once in a blue moon. For spotting 6 meter openings, watching 50.110-50.140 KHz might make more sense, I think (I work almost no six).

Not trying to bash the QS1R. I joined their Yahoo group yesterday. I've been wondering how they work on 500 KHz and below, the "new" ham frontier. The 3000 and 5000 are worthless down there, although some have claimed the 1500 is better in that regard.

I've heard that lots of 1500's are being sold to SWLs. I'm sure many readers of this board are trying to understand the advantages of the $900 QS1R. 
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ZENKI
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« Reply #10 on: April 20, 2012, 01:59:26 PM »

The Flex1500 is radio with marginal TX IMD performance. You then take this radio with poor IMD performance and then feed it into another cheap 12 volt amplifier with equally poor IMD performance. The end result is that you end up with radio that is far from satisfactory in terms of the transmitter spectral purity.

We have a huge issue now on the ham bands and especially 10 meter where CB type hams are messing up 10 meters with crud because they are using  CB  amps on the ham bands. Everyone who buys the Flex1500 ends up needing more power, ie they dont buy it to use as originally intended as a low power QRP radio. Why dont they just buy the Flex3000 which has built in PA and might produce a better outcome than a cheap solid PA?

Most 12 volt ham PA's either are CB kits or nothing more than CB designs with  extra low pass filters. Their bias circuits are very poorly designed. You would be far better off buying a good PA   with 50  volt fets  like the Ameritron ALS600 and  use that  as your PA rather than some cheap 12 volt junk PA.  Even a  homebrew 6146 amplifier or a grid driven low drive tetrode amplifier would make a better choice than a cheap 12 volt solid state PA. Designers of QRP radios overlook this  advantage of QRP radios, that is their ability to drive low drive tetrode amplifers. A  Flex1500 would have made a wonderful driver for a QRO station if they designed the Flex1500 with a low IMD PA. I could easily drive a 4cx1500B with 5 watts for a kilowatt out, however I would not do this because the Flex 1500 is such a dirty radio on transmit. The same mistake is made with the HPSDR Penny transmitters, they design the radio to have the cleanest possible PA and then they  develop accesory PA's that are as filthy  as CB amplifiers. This is a exercise in gross design stupidity.

The ARRL had a competition for low cost PA designs. Unfortunately all the designs were horrible IMD producers. It would be great if the ARRL  had a competition for amplifier designs that were both clean and cheap, rather than cheap and nasty IMD producers.








Our club is looking into buying a Flex 1500 for the ham shack and plan to add an amplifier.  Anyone have suggestions as to models compatibility and cost? Huh
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KE5JPP
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« Reply #11 on: April 20, 2012, 03:41:50 PM »

The Flex1500 is radio with marginal TX IMD performance. You then take this radio with poor IMD performance and then feed it into another cheap 12 volt amplifier with equally poor IMD performance. The end result is that you end up with radio that is far from satisfactory in terms of the transmitter spectral purity.

We have a huge issue now on the ham bands and especially 10 meter where CB type hams are messing up 10 meters with crud because they are using  CB  amps on the ham bands. Everyone who buys the Flex1500 ends up needing more power, ie they dont buy it to use as originally intended as a low power QRP radio. Why dont they just buy the Flex3000 which has built in PA and might produce a better outcome than a cheap solid PA?

Most 12 volt ham PA's either are CB kits or nothing more than CB designs with  extra low pass filters. Their bias circuits are very poorly designed. You would be far better off buying a good PA   with 50  volt fets  like the Ameritron ALS600 and  use that  as your PA rather than some cheap 12 volt junk PA.  Even a  homebrew 6146 amplifier or a grid driven low drive tetrode amplifier would make a better choice than a cheap 12 volt solid state PA. Designers of QRP radios overlook this  advantage of QRP radios, that is their ability to drive low drive tetrode amplifers. A  Flex1500 would have made a wonderful driver for a QRO station if they designed the Flex1500 with a low IMD PA. I could easily drive a 4cx1500B with 5 watts for a kilowatt out, however I would not do this because the Flex 1500 is such a dirty radio on transmit. The same mistake is made with the HPSDR Penny transmitters, they design the radio to have the cleanest possible PA and then they  develop accesory PA's that are as filthy  as CB amplifiers. This is a exercise in gross design stupidity.

The ARRL had a competition for low cost PA designs. Unfortunately all the designs were horrible IMD producers. It would be great if the ARRL  had a competition for amplifier designs that were both clean and cheap, rather than cheap and nasty IMD producers.

Here's a suggestion, "Zenki" aka "Plebian99". Since you are one of the biggest whiners/complainers about IMD, why don't you come up with a solid state PA design that can be easily duplicated and publish the schematics and design info?  Then with this info these experimenters can duplicate your design so that they have sparkling clean amps to run with their DUC or QRP designs.   Put your money and supposed experience where your mouth is.  Let's see if you have the technical chops to do it. I bet you don't.  People who do, DO, people who don't just sit around and whine/complain like you.

Gene
« Last Edit: April 21, 2012, 05:16:15 AM by KE5JPP » Logged
N8FNR
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Posts: 150




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« Reply #12 on: May 08, 2012, 07:48:32 AM »

Well at least if you get a Flex-1500 you have the 11th best receiver money can buy. And I would count that as a big deal for the price.

http://www.sherweng.com/table.html

N8FNR
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WD5GWY
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Posts: 406




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« Reply #13 on: May 10, 2012, 05:08:53 PM »

Well at least if you get a Flex-1500 you have the 11th best receiver money can buy. And I would count that as a big deal for the price.

http://www.sherweng.com/table.html

N8FNR
I've been using a Flex 1500 off and on for over 5 months now and find it is a
decent QRP radio. I even get on 40 SSB and ragchew with some guys I know.
When I first started using it, several of the guys could not believe I was only
running 5 watts. Most thought I had an amp in line. ( I don't) I have yet to hear
anyone complain about the audio or anything concerning transmitted signal.
  It might not be the top of the line as far as IMD performance, but, it is far from
being as bad as some say it is.
james
WD5GWY
 
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G6HVY
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« Reply #14 on: May 18, 2012, 03:35:01 AM »

So, uh...

...can anyone recommend a decent 100w amplifier for the Flex 1500?

R


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