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Author Topic: Newbie Question: Where's the magic in the high end transceivers?  (Read 32544 times)
K5TED
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« Reply #15 on: September 20, 2013, 06:45:26 PM »

During the last CQWW VHF contest, had an opportunity to compare a KX3 with a FT-857D, head to head, on the same table, on 6m, both running 10w. Wasn't any really discernible difference in experience with SSB operations. All signals were heard by both radios at relatively the same level and useability, contacts were made on both to the same stations, none of the far stations mentioned any obvious difference between stations. This was real-life, field use case. Not lab bench.

The KX3 is obviously a cutting edge, fine radio. The FT-857D is an inexpensive shack-in-a-box. Both similarly priced. Each is worlds apart from the other in design and functionality. Both performed about the same on 6m in the field.

That's all.

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M6GOM
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« Reply #16 on: September 21, 2013, 03:30:43 AM »

Software DSP filters have a sharper cutoff than typical crystal or mechanical filters but they aren't capable of completely eliminating all the signals but the one you want to hear. DSP is good, but it's not that good  Cheesy


Software DSP filters in a SDR are cliff wall responses. They completely block out all signals outside of the pass band. If the signal intrudes the passband and is strong enough to overwhelm the target one then they will and there is absolutely no way at all that anything will ever overcome that.
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M6GOM
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« Reply #17 on: September 21, 2013, 03:31:42 AM »

I might be wrong, but I don't think Elecraft has access to special components that the rest of us don't.  

Actually they do - custom FPGAs of their own design. Whilst you too can buy the bare FPGA you don't have the code they use.

Back to the original question: What you pay for to some extent is the R&D time. R&D is not cheap. Your Youkits kit will typically have very little R&D, using off the shelf circuit designs and pre-designed ICs. Something like a KX3 has a lot of R&D using very expensive gear, of which one device could cost more than the entire R&D budget of the Youkit, they don't use off the shelf designs and they also build custom ICs as well.
« Last Edit: September 21, 2013, 03:35:03 AM by M6GOM » Logged
KG6AF
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« Reply #18 on: September 21, 2013, 06:14:00 AM »

Software DSP filters have a sharper cutoff than typical crystal or mechanical filters but they aren't capable of completely eliminating all the signals but the one you want to hear. DSP is good, but it's not that good  Cheesy


Software DSP filters in a SDR are cliff wall responses. They completely block out all signals outside of the pass band. If the signal intrudes the passband and is strong enough to overwhelm the target one then they will and there is absolutely no way at all that anything will ever overcome that.

DSP filters can be designed to have sharp cut-offs, but they don't have infinite attenuation outside the passband.
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AF6WL
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« Reply #19 on: September 21, 2013, 07:40:49 AM »

I might be wrong, but I don't think Elecraft has access to special components that the rest of us don't.  

Actually they do - custom FPGAs of their own design. Whilst you too can buy the bare FPGA you don't have the code they use.


Not quite : neither the KX3 or K3 use FPGAs.
There are a few CPLDs used as IO glue logic as well as DSP and regular processors.
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W1VT
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« Reply #20 on: September 21, 2013, 09:03:35 AM »

From personal experience, if you actively do your part in open source by publishing new designs quickly,  you do get preferential treatment in getting new parts as they become available.  Thus, an active ham can actually get their hands on parts before the average company!  I think it has something to do with how parts are advertised and marketed--how better to sell a part than to see how someone actually uses it?

Zack W1VT
« Last Edit: September 21, 2013, 09:06:51 AM by W1VT » Logged
K5TED
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« Reply #21 on: September 21, 2013, 09:22:49 PM »

The ultimate DSP filter would be a "Smart" filter that could identify the individual zero beats on all signals in the presently selected passband, then extrapolate from there what actually belongs to each signal, show you each signal and let you select the one you want to listen to, then clean it up as best possible, eliminating all "improbable" material within that one particular slot. Of course, for signals on the exact same frequency, there is no recourse.
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WD8KNI
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« Reply #22 on: September 23, 2013, 02:13:11 AM »

Cory, first off good for you on asking.  Don't overlook the "wow" "look at me factor" when you look at price point of radios.  I remember a few years ago when a representative of a well know quality manufacturer stated that if they had known to call their filters "Roofing" they would have made a ton of money.  Today more so than in the past the definition of the ham "Shack" has changed.  You will find 50 thousand dollar setups in houses that are falling down, 5 thousand dollar rigs in 500 dollar cars. We have people who spend 50K just to be top dogs in the rudeness department (contesters).  We have people who proudly tell you about their 10K investment, and use it 100% for bragging rights, (never make contacts).  These are the people who drive up the cost. Do you need a hindi or a Rolls Royce to get to work and the store.  Will your Hundi be used everyday, or will your Rolls sit in the driveway of your "Shack" because you can't afford to put fuel in it.

Remember the old joke regarding a guy meeting friend for lunch, the friend was a car salesman.  While waiting he listened to the salesman selling Cadallics.  The buyer said "Why does this one have a Red engine, while the other engine is Blue.  The salesman replied, the one with the red engine is a much much better engine.  While at lunch the friend asked, is the red engine really better, to which the salesman replied. "It has to be a better engine as that car was more expensive".

How much worth is a receiver with that can hear .001 microvolt on a band that has 50mv of noise?..
.. welcome to the hobby, enjoy it for its true value.  Fred
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AE4RV
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« Reply #23 on: September 23, 2013, 07:43:06 AM »

On sideband it is usually hard to tell the difference. Weak signal CW in a crowded band is a whole different story. That's where you'll notice the extra $$.
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G3RZP
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« Reply #24 on: September 23, 2013, 12:39:37 PM »

I haven't seen a review of the KX3 regarding high order transmit IMD and phase noise. Those are figures that show how anti social (or otherwise!) they are.....
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K7RNO
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« Reply #25 on: September 23, 2013, 08:35:52 PM »

Cory,

First of all, congrats on getting your call. It will sound good in code, it's got rhythm!

Then, I need to express my awe when I hear that a kit builder will learn how to design transceivers. I have to admit that I am far below such a level. If I couldn't already do it, I would learn how to solder and assemble parts but I could never "decipher" the interaction of those parts that make the rig behave as it will when it is finished. At least not with a product as complex as those from Elecraft, be it made with traditional (large) or small surface-mounted elements. The design work in those kits has been done, "all" that is left is to assemble them, and not even in a sequence that would retrace the circuits' workflow, but in a sequence that makes assembly a feasible job. None of this wants to downgrade kit building, to the contrary, my hat is off to the builders. It is mostly how a person can learn transceiver design from such a job is what amazes me.

Arduino, I think, is a different subject. Have fun tinkering, and lots of "wow" moments!

« Last Edit: September 23, 2013, 08:41:54 PM by K7RNO » Logged

73,
aRNO
NAQCC #6870, SKCC #11131
K5TED
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« Reply #26 on: September 23, 2013, 10:12:57 PM »

I haven't seen a review of the KX3 regarding high order transmit IMD and phase noise. Those are figures that show how anti social (or otherwise!) they are.....

It'll be difficult to find that, as it will be difficult to find the leakage in those rigs publicized anywhere. It's fairly huge. Nuff said.
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G3RZP
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« Reply #27 on: September 24, 2013, 12:52:26 AM »

What is frightening is how much worse on high order IMD solid state rigs are compared to the last generation of tube PA stages. The average tube ones were more than 10dB better on 7th and higher order products than the average solid state PA - Yaesus in Class A excepted.

Funny that the math predicts that, too.
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M6GOM
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« Reply #28 on: September 24, 2013, 03:01:43 AM »

Downside of using 12V PAs. If you use 50V PAs the TX IMD improves immensely.
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K2GWK
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« Reply #29 on: September 30, 2013, 06:15:07 PM »

The rigs are only as good as their antennas. A good analogy is that a great stereo will only sound as good as the speakers attached will allow.
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