Gary,
You bring up a couple of very good points which I would like to address, but it
is not exactly in line with the subject line. I will start two new threads:
1. 16-bit dynamic range
2. IP3 and receiver performance
That way people can choose to follow or delete without reading.
73 - Rick, DJ0IP
(Nr. Frankfurt, Germany)
-----Original Message-----
From: TenTec [mailto:tentec-bounces@contesting.com] On Behalf Of Gary J
FollettDukes HiFi
Sent: Sunday, September 11, 2016 6:15 AM
To: Discussion of Ten-Tec Equipment
Subject: Re: [TenTec] Scads of used Icom IC-7300
Well, for years I have followed the listings at Sherwood, and, not seeing the
explanation you presented on the site, drew what may be an erroneous
conclusion. I do recall, however, his rather strident statement that IP3 is the
most important trait in receiver performance which is why the radios are listed
in the order in which they are listed, based only on close in IP3.
The very reason I began to question the validity of this list was that SDR
radios, which have NO mixers, began to get such high rankings for a rating that
has no relevance whatsoever for an SDR. It matters not whether folks have been
saying for years that IP3 is irrelevant for SDR’s when the IP3 ratings for
SDR’s keep right on coming.
The credibility gap arises when this pointless ranking continues in full
knowledge of its worthless value in sorting SDR’s or in comparing them against
good heterodyning radios.
Regarding the Flex 6500 and 6700 and front end filters, I had never had either
in my hands but the high performance ratings these radios consistently get “on
air” told me that they HAD to have such filters. With a 16 bit A to D, such
excellent performance would not be possible without band limiting filters.
Regarding the S9+80 dB clip point, is that in band or out-of-band? That’s a lot
of signal dynamic range for a 16 bit A to D. The audiophiles want to talk to
you about that… Even the most optimistic protagonists of massive oversampling
(in audio applications) only claim 106 dB signal dynamic range as fruit of
their labor. How is it that a 16 bit A to D can now handle a dynamic range of
132 dB (in band)?
Massive oversampling and narrow output filtering does, as other have said,
improve the NOISE dynamic range. I see no explanation describing how anything
can deliver 132 dB SIGNAL dynamic range with 16 bits…
I’m not trying to be difficult, I am only trying to understand how this can
work.
The reason this is relevant for this reflector is that the next Ten Tec radio
(if there ever is one) will, as others have said, almost certainly be a DSP
radio with direct sampling. Thus, the more we understand about this DSP
process, the better prepared we shall all be to make value judgements prior to
plunking down $3000 or more for the new set.
Since I still don’t know how one could offer or claim to offer 132 dB SIGNAL
dynamic range with a 16 bit A to D, I obviously do not understand this topic
well enough and seek to learn from those who do.
Again, stay away from NOISE dynamic range, I get that. We did in fact enjoy
very radical signal to noise improvement in chemical analysis spectrometers via
signal averaging, but this form of “DSP" required repetitive and repeatable
signals. With this method, and enough scans, you could take a signal to noise
ratio less than unity and produce spectra with signal to noise better than 20
dB or so, if you waited long enough. Radio signals are not that way.
I am not being critical, I am just trying to learn when something does not
agree with what I learned about these things 40 years ago.
Gary
W0DVN
> On Sep 10, 2016, at 3:23 PM, rick@dj0ip.de <Rick@DJ0IP.de> wrote:
>
> Well Gary, being as I've had my Eagle nearly 6 years now, you were slightly
> off on your year count for the Eagle.
> So that only re-enforces your argument.
>
> When you speak of the "receiver testing laboratory", if you mean Sherwood,
> then you need to do a bit of homework.
>
> Rob has NEVER EVER said that his list is a ranking of the overall performance
> of the radios. In fact in EVERY presentation he makes, he points that out.
>
> That list ranks radios according to their measured "close-in DR3". That's
> ALL.
>
> In addition Rob and several others have been saying for years now that DR3 is
> no longer a good indication of the performance of SDR radios, and that there
> are other important factors contributing significantly to SDR performance.
>
> For nearly every radio added to the list in the past dozen years or more,
> there is an accompanying full review showing ALL measured data and then a
> subjective opinion from Rob on how the radio actually performs on the air.
> Most of the ones that are considered to be contest radios were also used in
> one or more contests by Rob.
>
> You will find all of Robs tests on my web site:
> http://www.dj0ip.de/sherwood-forest/sherwood-xcvr-tests/
>
> It is important to read all of the information and not just look at the
> snapshot that list presents.
> Fundamentally we need to separate the SDR radios out from the heterodyning
> radios.
>
> A couple of days ago I posted some data on the stuff Rob found wrong with the
> 7300.
> Although it may be that I posted it in the Eagle group and not in this group.
> There are similar threads in both groups.
> If so, let me know and I will post it here too.
>
> From that information, it is obvious that Rob does not rate the radio above
> the Eagle and Orion, etc.
>
>
> 73 - Rick, DJ0IP
> (Nr. Frankfurt, Germany)
>
>
> -----Original Message-----
> From: TenTec [mailto:tentec-bounces@contesting.com] On Behalf Of Gary J
> FollettDukes HiFi
> Sent: Saturday, September 10, 2016 6:20 PM
> To: Discussion of Ten-Tec Equipment
> Subject: Re: [TenTec] Scads of used Icom IC-7300
>
> Well, for one thing, the Eagle has been in the marketplace for maybe 4 years.
> In addition, during the fire sale, Ten Tec gave them away fully loaded for
> ~$1200, thereby loading up the market with LOTS of them. One might expect to
> see numerous listings for Eagle’s under these conditions, and they are still
> selling for almost 90% of the fire sale prices, because the “new” price for
> them is well over $1500 depending upon options.
>
> The high number of listings for “used” samples of a radio that has only been
> in the marketplace for a few months is, however, unexpected and suggests some
> significant degree of buyer’s remorse.
>
> Icon’s own response to complaints regarding receiver performance ("use a
> preselector") suggests the they agree with those who find it inadequate in
> SOME listening situations.
>
> I agree with the statement that the Eagle is not for everyone. It is very
> Spartan. Its appearance is on a par with the entry level Icom radios, not
> very pretty. Early ones did not even have an IF out for use with a bandscope.
>
> I have had two of them myself, loved the receiver performance in every way,
> but found that the Spartan nature of the radio was annoying and I really did
> not like the display - not a criticism, just personal preference.
>
> Maybe the term “garbage” was harsh, but even the noted receiver testing
> laboratory rated this thing as being better than an Orion and an Eagle, and
> only slightly worse than the $20,000 Hiberling, a rating nothing that is
> nothing less than ridiculous. This rating exaggeration is on a par with the
> “garbage” exaggeration.
>
> Making a good DSP transmitter is trivial compared with making a good DSP
> receiver. The signal levels are always the same, and of very low (and always
> predictable) signal dynamic range. 8 to 12 bit audio would suffice for
> communications purposes. Thus it makes the achievement of good transmitter
> performance somewhat lame when the receiver’s actual on-air performance is so
> marginal that its manufacturer must recommend a fix that, while commonplace
> in the 1960’s, has been unneeded for a long time, until now, a preselector.
>
> I stand by my previous statement that you COULD produce an exceptional DSP
> receiver, one that would blow the socks off any heterodyne receiver, if you
> used 24 bit data and a tracking preselector to limit the impact of strong
> out-of-band signals.
>
> Remember this, the signal at the input of the D to A is the linear
> superposition of ALL of the RF signals that come in at the antenna terminal.
> The relative phases of all of these contributing components is always
> changing but, so long as your total input signal voltage is below the highest
> allowable level for the A to D, all is well. The A to D only samples once the
> analog signal has been held long enough for a stable reading by the
> track-sand-hold so this constant variation poses no problem. However, once
> you have an input signal strength greater than the largest allowable signal
> level for the A to D, things get very bad very quickly and at that point, no
> additional signal energy makes any difference on the A to D reading. Thus you
> hear nothing at all above saturation. This is the digital equivalent of
> blocking, only far more severe than that which takes place in an analog
> heterodyne receiver.
>
> These principles were known decades ago, in areas of digital data acquisition
> of analytical signals in chemical instrumentation. We found that, for Xray
> Photoelectron Spectroscopy, as an example, 32 bits of data were required to
> be able to extract the counts of a small signal sitting on top of a huge nose
> floor. That’s 1 part in 4 billion (192 dB signal dynamic range). While that
> was a pulse counting scenario, the outcome is the same. If we were trying to
> extricate a 10,000 cps Carbon 1S signal sitting on top of a 1E9 cps noise
> baseline (a typical real world situation) with a 16 bit data converter, we’d
> have seen nothing but a flat line at pulse saturation in the data plot.
>
> A 1 megawatt shortwave broadcast station 2 kilometers away adds up to some
> pretty significant amplitude at the A to D converter in your radio. Your
> desired tiny 3 microvolt QRP DX station is sitting on top of that huge signal
> which is already above the “largest allowed voltage” for the A to D, in the
> absence of significant input band pass filtering. What do you think your
> chances are of hearing that 3 microvolt signal, even on a very quiet band
> (from a random noise perspective)?
>
> A tracking preselector could easily be produced to reduce that out-of-band
> signal to a level that would be acceptable for the A to D, especially if that
> A to D were 24 bit, more than enough bits for the expected signal dynamic
> range for Ham radio receivers.
>
> Gary
>
>
>> On Sep 10, 2016, at 9:25 AM, Tim <tim@ke4ke.com> wrote:
>>
>> Rick,
>>
>> Forgot to mention the number two radio has a typo in the first link's list.
>> It is an Eagle.
>>
>> TS-599at should read TT-599at
>>
>>
>> Tim
>> KE4KE
>>
>>
>>
>> On 09/10/2016 03:01 AM, rick@dj0ip.de wrote:
>>> We had similar with the Eagle, especially right after the fire sale.
>>> The Eagle is not for everybody.
>>> There are lots of things to not like about an Eagle but receiver
>>> performance is not one of them.
>>>
>>> IMO this boils down to people being too darn lazy to do their own due
>>> diligence.
>>> Rather than dig through the specs and try to understand what they are
>>> buying, they just follow the marketing hype.
>>>
>>> There was a time in my life when I also did that, because I had more money
>>> than I had time. I would buy things while on business trips, take them
>>> home, eventually test them and if I didn't like them, dump them for a spot
>>> price. I'm sure there are lots of hams who can relate to that. When
>>> you're traveling 4 days per week, mostly out of country, you don't have a
>>> lot of time for the hobby.
>>>
>>> Unfortunately but also fortunately those times are long gone for me. Life
>>> is simpler now, less hectic. I still have little time but more time than
>>> money, so I take the time to study the stuff.
>>>
>>> IMO IT IS UNFAIR to call the 7300 garbage.
>>> It is what it is and does what it is advertised to do and all that for a
>>> fair price, considering the bells and whistles and relatively good
>>> performance.
>>>
>>> You can make just as many arguments that the Eagle is garbage... even
>>> though it remains my favorite radio for my style of operating.
>>>
>>> GARBAGE: radio's like the FT-450D that have an IMD of as much as 29dB
>>> worse than a 60 year old Collins 32S3 on some of its higher order IMD
>>> products. Radios that broadcast broadband noise (i.e. FT-1200, FT-3000,
>>> FT-5000, TS-590 (but not the SG), IC-7600 and many others) may be fine for
>>> hams living out in the boondocks but for hams in the city, they are
>>> probably unknowingly disturbing all hams within 2 or 3 miles AND THAT IS
>>> GARBAGE THAT MUST STOP! The IC-7300 does not do this so IMO I see no
>>> reason to call it garbage. It is a great radio for the price - if you are
>>> looking for a all-mode, do everything radio.
>>>
>>> 73 - Rick, DJ0IP
>>> (Nr. Frankfurt, Germany)
>>>
>>>
>>> -----Original Message-----
>>> From: TenTec [mailto:tentec-bounces@contesting.com] On Behalf Of Gary J
>>> FollettDukes HiFi
>>> Sent: Saturday, September 10, 2016 7:04 AM
>>> To: Discussion of Ten-Tec Equipment
>>> Subject: Re: [TenTec] Scads of used Icom IC-7300
>>>
>>> Companies don’t take back equipment that does not perform to buyers’
>>> expectations. They are only required to honor warranties for defects in
>>> parts or workmanship, NOT defects in design. They meet their published
>>> specifications and get great bench top lab test results that do not
>>> describe actual performance.
>>>
>>> Thus the only recourse for buyer’s remorse is fire sale pricing to recoup
>>> SOME of their investments.
>>>
>>> No one in their right mind would pay more than 75% of new price for a used
>>> item, regardless of what it might be. Thus you see the bargain prices for
>>> what is indeed an entry level radio with lots of great features and
>>> marginal RF performance.
>>>
>>>
>>> 16 bit Analog to Digital direct conversion with no (or poor) band limiting
>>> input filters is a sure-fire formula for performance disaster. Icom admits
>>> this fact in their “solution” to the overload problem - use a preselector.
>>>
>>> As I said previously, IP3 means nothing in a radio that has no mixers.
>>> Synthesizer phase noise rating means nothing in a radio that has no
>>> synthesizer. The fact that the 7300 “shines” in these characteristics in
>>> lab tests says nothing about real performance and new standards need to be
>>> developed to assess performance of direct digital conversion designs.
>>>
>>> The “first adopters” of this particular model found this out for themselves
>>> on the air and found the results very disappointing. That’s why they sell
>>> them after a few weeks of use.
>>>
>>> Gary
>>>
>>> W0DVN
>>>
>>>
>>>> On Sep 9, 2016, at 10:55 PM, Bwana Bob <wb2vuf@verizon.net> wrote:
>>>>
>>>> That's amazing that people would buy and then dump them so quickly. There
>>>> must be several things that are disliked, like maybe they can't get used
>>>> to using a touch screen. I, myself, would prefer traditional knobs and
>>>> buttons to a touch screen. They always get smudgy and scratched.
>>>>
>>>> Bob WB2VUF
>>>>
>>>>
>>>> On 9/9/2016 11:19 PM, Gary J FollettDukes HiFi wrote:
>>>>> Someone questioned my statement that there were “scads of IC-7300 radios”
>>>>> on the used market already.
>>>>>
>>>>> Today, there are three on QTH alone, and one can be had for ~$1050!
>>>>>
>>>>> Garbage depreciates in value pretty quickly, faster than an open can of
>>>>> Coors Lite!
>>>>>
>>>>> Gary
>>>>> _______________________________________________
>>>>> TenTec mailing list
>>>>> TenTec@contesting.com
>>>>> http://lists.contesting.com/mailman/listinfo/tentec
>>>>
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