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Author Topic: High dynamic range radios...  (Read 5751 times)
KT0DD
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Posts: 283




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« on: December 25, 2012, 04:18:21 AM »

Most everyone knows about Rob Sherwoods receiver ranking site. I do pay attention to dynamic range numbers when considering a radio purchase.

I heard a very knowledgeable ham say that most hams don't need a super receiver with a 90+ dynamic range at 2 khz spacing because very few hams live so close together ( + /- 1/2 mile ) that they need a radio to handle " field day / near field overload conditions " 365 days a year.

My question is this...Sometimes conditions will propagate a 40+db/S9 signal from stations 1000 miles away, and if they're sitting 2-3 khz away from me while I'm working a weaker DX signal...wouldn't the better dynamic range receivers help in that situation too?

Thanks. Todd - KT0DD
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W9FIB
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Posts: 880




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« Reply #1 on: December 25, 2012, 04:55:25 AM »

It is simple, the better the reciever, the easier it is to hear what you want to hear.
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WX7G
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Posts: 6192




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« Reply #2 on: December 25, 2012, 10:07:08 AM »

I presently have an Elecraft K3, a Yaesu FT-857 and a Kenwood TS-480HX. They are very different in dynamic range but the only time I find the K3 dynamic range to be useful is during 160 meter CW contesting. I am considering selling the K3 and using the TS-480 instead. That's how much I need the K3 dynamic range and I'm a CW DXer and contester.
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WB2WIK
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Posts: 20629




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« Reply #3 on: December 25, 2012, 01:36:04 PM »

Sherwood does a great job of lab testing stuff, but I go by what I like.

I have a few ham neighbors within 2 miles running 1500W to beams, and they are very line of sight, so strong signals abound.  And with all that, most modern rigs have more than enough dynamic range to handle the signals.  In fact, my 34 year-old TR-7 is better in this respect than my more modern rigs designed 30 years later. Wink
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KE5JPP
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Posts: 0




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« Reply #4 on: December 26, 2012, 08:55:44 AM »

Most everyone knows about Rob Sherwoods receiver ranking site. I do pay attention to dynamic range numbers when considering a radio purchase.

I heard a very knowledgeable ham say that most hams don't need a super receiver with a 90+ dynamic range at 2 khz spacing because very few hams live so close together ( + /- 1/2 mile ) that they need a radio to handle " field day / near field overload conditions " 365 days a year.

My question is this...Sometimes conditions will propagate a 40+db/S9 signal from stations 1000 miles away, and if they're sitting 2-3 khz away from me while I'm working a weaker DX signal...wouldn't the better dynamic range receivers help in that situation too?

Thanks. Todd - KT0DD

Sherwood's website is enjoyed by many who are into "specmanship" - the "my rig is better than yours" or "I feel justified in spending the money for my rig" because it is near the top of Sherwood's list.  The list only takes into account a very narrow window of receiver specs and says nothing about how the rig is to live with day in and day out.  It may be at the top of the list, but it could  be a real POS to operate.  Most of the numbers in Sherwood's list could not be discerned by someone without expensive test equipment and then they are only applicable in the test lab, not the real world.

Gene
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K8AC
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Posts: 1477




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« Reply #5 on: December 26, 2012, 09:05:33 AM »

Hi Todd.  I think it's important to understand exactly what the Sherwood chart is.  Contrary to what some think, it's NOT a ranking showing which receivers are the absolute best.  What it is, is a list of receivers and measured performance numbers sorted by narrow spaced dynamic range.  If that's the most important factor to you, then maybe the list does rank the best receivers for your situation.  But, there are many other factors that are more important to most folks, such as the ergonomics of the rig's controls, the transmitter performance (does it have key clicks or shortened dits in QSK), etc.  If you haven't read it, see this page at the W8JI site: http://www.w8ji.com/receiver_tests.htm .  It addresses the dynamic range question and makes the comment that 99% of the time, a close-spaced dynamic range of 80 dB is perfectly adequate.  For years I used an Icom 756 Pro III for CW contesting (close spaced dynamic range only 75 dB), yet I was able to score better than all of the K3 and Orion users locally.  On rare occasions on 20 and 160M, the band was jammed with very strong signals and I did experience some IMD problems, but, simply inserting 6 or 12 dB of attenuation in the receive antenna line eliminated that problem with negligible effect on reception. 

It appears I'm with WX7G in that I believe that the vast majority of folks who've bought a K3 because of the great dynamic range ranking don't experience any benefits over less costly rigs just because of the dynamic range number.  Apparently, Rob Sherwood feels the same way since his favorite rig is the old Icom 781, and its dynamic range number is far down the list.  Lastly, I don't think that a single 40 over S9 signal 2-3 KHz away from the frequency you're listening on would even be noticed on most modern rigs - or the TR7 for that matter.

73, Floyd - K8AC
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WX7G
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Posts: 6192




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« Reply #6 on: December 27, 2012, 06:32:36 AM »

As others have said, there is more to a good receiver than just dynamic range. I can only speak to CW receiving as CW is all I work. 

The "new" DSP signal enhancement features can be superb. For example, the Elecraft K3 APF feature can pull a CW signal out of the noise. In some instances I can copy a signal in APF mode that I cannot detect without it. And there is DPS noise reduction that greatly reduces the fatigue of listening to a noisy band or the APX feature that creates audio "space" and again reduces listening fatigue. These things don't show up in the Sherwood data.



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ZENKI
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Posts: 972




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« Reply #7 on: December 29, 2012, 02:26:41 AM »

Most hams need cleaner and better designed transmitters so that other hams can enjoy their chart topping high dynamic range numbers. Without improvements in transmitter IMD and keying bandwidth we just wasting engineering resources pursuing such high  dynamic range numbers. Its unfortunate that all the top performing transmitters on SHerwoods list have transmitters  that are such poor performers. The exception is the Hilberling radio that most hams cant afford. You should not have to spend 20 thousand dollars to get a radio with decent TX IMD, it can be done for 1000 dollars if designers paid attention to the design details.

Another area of concern is the audio amplifier chain. Most radios have such poor audio amplifier chains with horrible distortion and IMD. No regard is paid to the inband RX IMD performance. The K3 is such a radio, with horrible
inband RX IMD  that annoys my ears.

The other area of concern is AGC performance. Most SDR radios have very poor AGC's that cause a lot of distortion and created the impression that the band is noisy. I am constantly amazed when i switch between any analog radio
and any SDR radio. The bands especially the low bands all of sudden become bearable. There is just something about how SDR receiver handle impulse  and pulse noise burst and how they mathematically  handle these noise sources that make SDR radios sound noisy.

Another way of better characterizing receivers is doing a NPR test. Reciprocal mixing is another important test that shows flaws not detected by  2 tone dynamic and IMD testing. The ARRL has only recently  begun doing this.

The next  thing that the ARRL should do is abandon measuring receiver performance and  then using a spectrum analyzer to dig the IMD products out of the noise. What human being can dig receiver IMD products out of the phase noise. The method that the ARRL uses is flawed if we talking about real world performance and only serves to make poor performing look better than they really are.


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WB6BYU
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Posts: 13446




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« Reply #8 on: December 30, 2012, 08:30:10 AM »

That's not to say that receiver dynamic range isn't important - it just needs to be good
enough for your use in your own situation.

I bought a brand new rig when it first came out some years back and really enjoyed using
it - until a ham on the other side of town got on 20m.  I could hear him all the way across the
band.  So I just didn't operate 20m whenever he was on.  After a couple of years I decided
to fix it, and improved the mixer and the VFO drive levels.  About that time we moved again and
I ended up 1 block from the same ham, but he didn't bother me nearly as much as he had
originally before I made the changes.

Generally speaking, the better your antennas are, the stronger the signals you will pick up,
and the more important the ability of the receiver to deal with strong signals.  And if you
have one or more kW ham (or other) stations in the vicinity, you may want to choose
something further up the list.

While many of the modern rigs have adequate dynamic range for many purposes, it can still
be a problem on Field Day (even running QRP.)  But there other problems as well - especially
phase noise ("does not play well with others"), which has been a major problem with a number
of popular inexpensive radios.

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WX7G
Member

Posts: 6192




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« Reply #9 on: December 30, 2012, 10:32:00 AM »

Last night I operated the Stew Perry 160 meter contest and was shown once again the utility of having a high dynamic range receiver/transceiver. The Elecraft K3 allowed me to copy weak signals 500 Hz away from front-end-melting signals. The APF feature allowed a JA contact that would not have happened without it. The DSP noise reduction made listening much less fatiguing as did the AFX feature. So, the robust hardware made for high dynamic range and the DSP made it all that much better.

I have decided to keep the K3 as the home rig and the TS-480HX for mobile.
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WD4ELG
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Posts: 877




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« Reply #10 on: December 30, 2012, 08:40:04 PM »

Not trying to be a Flex Radio shill, but I was able to put brick wall shaped filters and do the same with stations very close by on my Flex 3000.  EU 579, US S9+20
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WX7G
Member

Posts: 6192




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« Reply #11 on: December 31, 2012, 06:54:34 AM »

WD4ELG, the Flex Radios look great. I'm used to turning a tuning knob and wonder how this is done with a SDR. I am tempted to buy a Flex 1500 as a start.
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K5TED
Member

Posts: 773




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« Reply #12 on: December 31, 2012, 06:34:16 PM »

IF you are getting satisfactory or better performance from a Flex radio, you must be doing something wrong. That's what I've learned on this forum. Even after reading all of the warnings here, I made the huge mistake of buying a 1500, then a 3000. I'm pretty sure most of the QSO's I've logged with them left the other station rolling on the floor, laughing at my stupidity for having wasted my hard earned cash on such a pile of junk, and any other stations within several MHz must have been cursing my very existence...  Wink
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ZENKI
Member

Posts: 972




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« Reply #13 on: January 10, 2013, 10:36:33 PM »

I would rather brag about the best antennas than radios. The most fortunate hams are those with the best antennas on high towers. Nothing more ridiculous than having a killer numbers high performance radio on a indoor attic dipole.

I hear so many hams with 20,000 dollars of the latest transceivers, another 10,0000 dollars in audio rack gear  and then they feed this expensive junk into terrible antenna.  This is despite the fact that they can  put up better antennas.
While some hams do have to live with limited real estate or covenants etc, the point is that any radio regardless of the brand is useless without a good antenna. I can gain 30 db of performance using better antennas and make the worst radio the best in the world just by using better antennas. When most hams live in city areas and  have S6 or S7 noise levels, your best super radio is not going to help you much fighting the noise or hearing better. What brand of radio can hear through the noise, who tests for that?

Its all a matter of perspective and  antenna performance should be emphasized over trivial  measurement  difference whose difference is  less than 10db. Since most hams cant hear their receiver collapse under stress why bother
endlessly  pick on radios that cant help most hams hear better.  Since very few hams have high stacks and live far away from the big cities, receiver performance numbers gymnastics is truly an exercise of doing it into the wind!

When I can buy a receiver that  actually makes life better on the air, or actually delivers a feature that can be as clear as night and day in the performance that it delivers over current models I will but it and sing its praises. At the moment all the current radios have no  real advantage in the real world  that really makes it superior to oldest piece of crap from 40 years ago. Its then no surprise that so many hams stick with old boatanchors because nobody cant actually say " look I will prove that its better" Can you?
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