Call Search
     

New to Ham Radio?
My Profile

Community
Articles
Forums
News
Reviews
Friends Remembered
Strays
Survey Question

Operating
Contesting
DX Cluster Spots
Propagation

Resources
Calendar
Classifieds
Ham Exams
Ham Links
List Archives
News Articles
Product Reviews
QSL Managers

Site Info
eHam Help (FAQ)
Support the site
The eHam Team
Advertising Info
Vision Statement
About eHam.net

donate to eham
   Home   Help Search  
Pages: Prev 1 2 3 4 [5] 6 7 Next   Go Down
  Print  
Author Topic: Flex 1500 Amplifier Recommendations ?  (Read 65620 times)
N0YXB
Member

Posts: 1136




Ignore
« Reply #60 on: February 27, 2013, 08:58:37 AM »

... and no responsible amateur who knows and understands the facts would place any amplifier downstream of the 1500's output.

 All they care about is cheap, they don't care how it affects other users of the bands.



Very true, saving a few dollars seems to trump spectral purity, objectivity, and even common sense.    Embarrassed
Logged
W4HIJ
Member

Posts: 402




Ignore
« Reply #61 on: February 27, 2013, 01:14:43 PM »

Quoting directly from the QST review "Transmit IMD on 40 meters was still not great, but typical performance on the other bands is good."
 Even so I doubt very much that my little 50 watt signal on 40 meters is hurting anything compared to the multitude of 1KW and beyond stations I hear splattering up and down the bands. Oh and BTW, I'm not using the full five watt output to drive my amp on any band. But whatever, any way possible to bash Flex as usual. Roll Eyes Roll Eyes Roll Eyes
Michael, W4HIJ
« Last Edit: February 27, 2013, 01:33:39 PM by W4HIJ » Logged
K9IUQ
Member

Posts: 2798




Ignore
« Reply #62 on: February 27, 2013, 04:53:04 PM »

Very true, saving a few dollars seems to trump spectral purity, objectivity, and even common sense.    Embarrassed

Flexradio proved they did NOT care about signal purity when they IGNORED the 160/80 mtr xmit Spur problem on the Flex 5K. Even tho the then President of the ARRL and many other prominent well respected hams complained to Flexradio about the problem Flex continued to ignore the problem. Why? Because it was going to cost Flexradio a lot of $$ to fix the problem. So they did nothing.

Flexradio did nothing to eliminate spurs for THREE YEARS until K9IUQ went public with the spur problem here on eham.net.  Wink Wink

Objectivity and common sense are 2 words that can never be used around Flex owners.  Cheesy Cheesy

Stan K9IUQ
Logged
PJ2BVU
Member

Posts: 153




Ignore
« Reply #63 on: February 27, 2013, 08:19:32 PM »

-22dB measured by ARRL!
That is -16dB as ARRL numbers are inflated by 6dB.

Jean-Claude PJ2BVU
Logged
K9IUQ
Member

Posts: 2798




Ignore
« Reply #64 on: February 28, 2013, 05:34:40 AM »

-22dB measured by ARRL!
That is -16dB as ARRL numbers are inflated by 6dB.

Jean-Claude PJ2BVU

Jean-Claude, please remember you need to make it easy for the Flexers to understand the ARRL Flex 1500 review. Most do not know what -22db xmit 3rd order means. I will help.I enjoy helping others especially my Flex Friends.  Wink

Listen up Flexers, the ARRL provides nice colored graphs so theory challenged Flexers can understand the tests. Yellow and red are BAD. Green is good.  The more Green, the better. If Yellow or Red, look elsewhere for a different radio, unless you only want to RX  Wink Cheesy Cheesy

See those large bumps on the xmit Spectral display just to the right and left of the main signal? Those are called SPURS...  Cheesy

Amplifiers of any kind only going to make the 1500 signal WORSE.

And for those Flexers that say it is ok because of all the splatter already on the band I say BALONEY. Do not worry about the other signals. Worry about your signal.. Just because other hams have poor signals does not make it OK for you to do it too.

Stan K9IUQ
Logged
K3GM
Member

Posts: 2224




Ignore
« Reply #65 on: February 28, 2013, 07:04:54 AM »

As I mentioned earlier, I'd have cash in fist at the Dayton Flex booth this May if the 1500 wasn't so dirty on xmit.

Graphs aside for a moment, here's an example that even a novice should follow:
Suppose you're sitting on 14200kHz USB and you put a two tone test signal of 700Hz and 1900Hz into the transmitter.  You will get RF carriers at 14200700Hz and at 14201900Hz which is what you want.  Unfortunately due to any non-linearity in the 1500's transmitter you will get rich IM products.  The first set, called second order products, will occur at the sum and difference of the two carrier frequencies, 28402600Hz and 1200Hz.  Both of these are sufficiently removed in frequency from the desired signal that they can be attenuated by a simple bandpass filter tuned for the 20m band.  The second set of IM products, called third order products, will occur at 2f1-f2 and 2f2-f1 or 2*14200700 – 14201900 which equals 14,199,500Hz and 2*14201900 – 14200700 = 14,203,100Hz.  As you can see both of these signals fall within the 20m band so they cannot be filtered out.  It turns out that all even order IM products fall out of band if the band is less than one octave wide and all odd order products up to a limit fall in band.

This example uses simple tones but the transmitter must pass complex signals such as voice or PSK31 where we don’t know the precise frequencies in use at any one time so we can’t get clever and use narrow band notch filters to get rid of the inband products.

Users who state, "I've got (X number) of watts of clean power" must either A) Be bending the rules of physics, or B) Have no idea what they're dealing with.  Using the 1500 behind a 500W amplifer like the respected Elecraft amp will generate several watts of IM products in the band you're operating within; it's irrefutable.  I can can work the antipodes with several watts of power, so your spurs are capable of being heard world-wide.  In short it does not appear that the Flex 1500 will ever be a good exciter for a high power amplifier.  I wish it were...

« Last Edit: February 28, 2013, 07:18:58 AM by K3GM » Logged
K9IUQ
Member

Posts: 2798




Ignore
« Reply #66 on: February 28, 2013, 07:23:15 AM »

I'd have cash in fist at the Dayton Flex booth this May if the 1500 wasn't so dirty on xmit.

This is the action ALL intelligent hams should take. One way to get manufacturers to improve products to acceptable xmit levels is to punish them by withholding sales. In other words only reward companies that provide clean xmitters by buying their products.

Also do not put ANY amplifier behind dirty xmitters such as the 1500. It will only aggravate the situation.

Stan K9IUQ
Logged
PJ2BVU
Member

Posts: 153




Ignore
« Reply #67 on: February 28, 2013, 08:19:34 AM »

Tom and Stan, you are correct and it is also true that these numbers can be meaningless when one is not use to dBs. Even for myself dB is not my natural language and I always have to rely on conversion tables, not forgetting that dBs relative to voltage are not the same as dBs relative to power.
The best is to take a concrete example.
ARRL says that IMD3 on 40m is -22dB for the Flex-1500. As this number is inflated by 6dB the real value will be -16dB.
What does that mean?
If the PEP power of the 2 tones is y Watts the PEP power of the 2 IMD3 products will be 16dB below y Watts.
When considering power -16dB means that the power in the IMD3 products will be y * 0.0251 Watts.
If you use a 100W linear following the rig IMD3 won't get better, only worse. Let say that this linear is perfect:
100 * 0.0251 = 2.51 Watts. Not bad!  Grin
Now another example:
Some years ago I built an early Softrock RX/TX (using a 2N3866 for the PA). I built it for 40m and it was delivering 750mW.
I used it with a magnetic loop 2m above ground.
My best QSO: a Russian station 10,000km away. Sure it took the ham a lot of time to copy my call sign but we made it.
Now imagine 2.51 Watts into a beam.

Jean-Claude PJ2BVU
Logged
PJ2BVU
Member

Posts: 153




Ignore
« Reply #68 on: February 28, 2013, 10:13:58 AM »

I want to add to the latest part of my previous post in order to avoid any confusion.
The contact was made in CW which is similar to transmitting one tone and there is no IMD in this case as there is no other tone to intermodulate with. It was just to show that you do not need much power to pollute the band.
IMD is a problem only in SSB (voice or digital).
Now do not think that because SSB transmits only the upper/lower side band the ARRL measurement makes sense by considering only one IMD product.
It is true that right after the XTal filter you have only USB/LSB and that the low power stages following the filter are usually class A, not contributing much to IMD. The problem is in the final(s), it is were IMD is produced, and the final(s) is fiollowed by a low pass filter which, as mentioned previously by Tom, will not filter these spurs.

Jean-Claude PJ2BVU
Logged
W4HIJ
Member

Posts: 402




Ignore
« Reply #69 on: February 28, 2013, 02:30:22 PM »

-22dB measured by ARRL!
That is -16dB as ARRL numbers are inflated by 6dB.

Jean-Claude PJ2BVU
If I'm not mistaken, that's being measured at full power output. It NEVER takes full power output of my 1500 to drive my amplifier, it's typically less than half depending on the band. But hey, let's not let more  real world application of how the XCVR is actually used get in the way of a good bashing session. What fun would that be? Roll Eyes Roll Eyes Roll Eyes
Michael, W4HIJ
Logged
K9IUQ
Member

Posts: 2798




Ignore
« Reply #70 on: February 28, 2013, 02:46:01 PM »

Quote from: W4HIJ
NEVER takes full power output of my 1500 to drive my amplifier, it's typically less than half depending on the band. But hey, let's not let more  real world application of how the XCVR is actually used get in the way of a good bashing session.

Flexers always have a need to defend their product no matter how silly the reasoning.

Reminds of when I was complaining about CW performance on the Flex 5K. Flexers would always say it is not a problem I only use SSB. Or when I complained about 160/80 CW mtr spurs I was always told no one uses CW on those bands.

Here is what never has made sense to me and I wish someone would explain the reasoning to me. Why would any ham buy a QRP rig and then put a 50/100 watt amp behind it? Does it not make more sense to buy a 100 watt radio and turn it down to 5 watts for those QRP moments? And less IMD to boot.....

Stan K9IUQ
Logged
PJ2BVU
Member

Posts: 153




Ignore
« Reply #71 on: February 28, 2013, 06:36:22 PM »

-22dB measured by ARRL!
That is -16dB as ARRL numbers are inflated by 6dB.

Jean-Claude PJ2BVU
If I'm not mistaken, that's being measured at full power output. It NEVER takes full power output of my 1500 to drive my amplifier, it's typically less than half depending on the band. But hey, let's not let more  real world application of how the XCVR is actually used get in the way of a good bashing session. What fun would that be? Roll Eyes Roll Eyes Roll Eyes
Michael, W4HIJ

I wonder why Flexers think they are always under attack.
We are taking about the Flex-1500 and someone stated that ARRL measured IMD at -22dB on 40m. I cannot attest of the veracity of this statement but as no one said anything to the contrary I assume it is true.
I also assume that whatever they measured -22dB is accurate.
I also assume that when they found -22dB they double, triple checked the result as -22dB is not that good.
It could be that the unit they tested was below the norm or that Flex improved the rig after the review.
It is not the point, I just used -22dB as it was what was posted.
Or may be you think that when I say "inflated by 6dB" it is a form of bashing.
You are free to Google "Transmit IMD". May be you will find a link to National Instruments for example:
Quote
If F1 and F2 are the frequencies of the two tones, then the third-order distortion products occur on both sides of these tones at 2F2 – F1 and 2F1 – F2. Assuming that the power levels of the two tones are equal, IMD3 is the difference between the power of the fundamental signals and the third-order products, as defined in the following equation:

IMD3 = Po -Po3

where o refers to the output of the UUT, Po3 is the power level of one of the output third-order products, and Po is the power level of one of the fundamental tones.
I placed the emphasis on one, it is not in the original text.
Wherever you look, only ARRL uses this 2 tone PEP stuff.
Yes, IMD is measured at full power, that's the way ARRL does and not specifically for Flex radios but for any radio. Do you think ARRL is bashing all the rig manufacturers? That is a way to compare different rigs, you compare bananas with bananas (2 tone PEP at full power is still a valid comparison).
You said that you never (need to) drive your amp with 5W, I never said you did and I never recommended to do so. You drive it at around 2W and it is a good thing, it will improve things but until someone measure the IMD at 2W you cannot tell by how much.
Now imagine the guy who want to drive an amp to get 100W and does not have an idea of what this IMD stuff is and buys a 100W amp. If it is FCC approved it cannot have more than 15dB gain if I am not mistaken. If it is 15dB gain he can drive it with a little more than 3W, if it has less than 15dB gain he will drive it at 5W.
What I was trying to do was to show the guy who think it is Chinese, it is not. It is not rocket science: if it is a linear scale - like I double my power or I halve my power - you use multiplication and division. If it is a log scale like when using dB you use addition and subtraction. You don't know what is 100dB? I don't, I just use a conversion table or a dB calculator. Just remember to use the correct table depending if it is relative to voltage or power. For the transmit IMD just do a little reading, nothing complicated. And when you read the review of the Flex-1500 and it says 3rd order products IMD -22dB on 40m you have an idea of what it means and what will happen when you drive your 1kW amp with the Flex at full power (the 6dB difference is just a factor of 2 difference and it won't make much of a difference for the station on the adjacent frequency).
You can even use the ARRL handbook as a reference, there is some valuable information in there.
Oh my Gosh!
ARRL Handbook 2002 page 17.5
Quote
IMD Ratio
If a pair of equal-amplitude signals create IMD products, the IMD ratios (IMR) are the difference, in dB, between each of of the two tones and each of the IMD products (see Fig 17.6).
Fig 17.6 - Top: IMD ratio (as displayed on a spectrum analyzer).
It looks like they had to call it IMR in order to use their 2 tone PEP magic formula.

Now if you think that my previous post was a personal attack on you or Flex you have serious problems.
May be the Flexer syndrome  Grin

Jean-Claude PJ2BVU
Logged
PJ2BVU
Member

Posts: 153




Ignore
« Reply #72 on: February 28, 2013, 06:39:00 PM »

Disclaimer:
I have nothing against bananas.

73 de PJ2BVU
Logged
PJ2BVU
Member

Posts: 153




Ignore
« Reply #73 on: February 28, 2013, 06:44:35 PM »

Correction:
The Flexer Persecution Syndrome.  Cheesy Cheesy Cheesy Cheesy Cheesy
Logged
K9IUQ
Member

Posts: 2798




Ignore
« Reply #74 on: March 01, 2013, 04:59:15 AM »

The Flexer Persecution Syndrome.  Cheesy Cheesy Cheesy Cheesy Cheesy

Symptoms of this terrible Disease include denial of provable truths and the addiction of defending Flexradio at the public posting of anything detrimental to the Reputation of Flexradio. Other symptoms include an aversion to anything CW and a religion like love (faith) for all things Flex.
 Wink

Stan K9IUQ
Logged
Pages: Prev 1 2 3 4 [5] 6 7 Next   Go Up
  Print  
 
Jump to:  

Powered by MySQL Powered by PHP Powered by SMF 1.1.11 | SMF © 2006-2009, Simple Machines LLC Valid XHTML 1.0! Valid CSS!