[TenTec] On Noisy Transmitters

Sun Jul 6 08:53:01 EDT 2014

What was the date of this letter from Wayne?

Carl Moreschi N4PY
58 Hogwood Rd
Louisburg, NC 27549
www.n4py.com

On 7/6/2014 8:46 AM, Rick - DJ0IP / NJ0IP wrote:
> THIS IS A LONG EMAIL.  DELETE NOW IF YOU ARE NOT INTERESTED IN THE TRUTH...
>
> Of course "noisy transmitters" is one of my hottest hot buttons.
> Every time I bring up the topic, it usually morphs into blaming it on the
> Lids.
>
> So this time I will put some meat behind my claim and invite all of you to
> read what one of the industry's top experts, Wayne Burdick, N6KR, co-found
> and chief technical architect for Elecraft, has to say about noise and other
> radios:
>
> -------------------------------------------------------------------
> Regarding K3 close-in phase noise vs. the Kenwood TS-590 and Flex radios
>
> By Wayne Burdick,  N6KR
>
> Phase noise was recently discussed on the K3 Yahoo group, and I
> thought I'd add my two cents. Or maybe three :)
>
> The K3's phase noise at 1 kHz is pretty much state-of-the-art for a
> DDS (direct digital synthesis) reference driving a wide-frequency-
> range, low-noise PLL (phase locked loop). We took things a step
> further by using a very narrow crystal filter after the DDS (about 2.5
> kHz), dramatically cleaning up the DDS even before application to the
> PLL. This forced us to use some pretty hairy math in calculating the
> PLL divider values, but it was worth the effort.
>
> The TS590 (and all currently shipping Flex radios) use a synth
> subsystem that is quite different from the K3's. They use an
> unfiltered DDS as their local oscillator, with no following PLL.
>
> There are some advantages to this design choice. First, and maybe the
> most relevant: it's cheaper than a DDS-driven-PLL overall, requiring
> very few analog parts, essentially no alignment, and far less PCB
> space. Second, such radios might have slightly lower phase noise at
> some very close offset--although at such spacings, other factors such
> as keying bandwidth or IMD typically dominate. Finally, use of a raw
> DDS allows the VFO to switch frequencies rapidly. Such agility might
> be useful for some digital modulation schemes.
>
> However, that raw DDS VFO comes with a price: its output has many
> discrete spurs that can, at specific VFO frequencies, cause "ghost"
> signals to appear. This is due to mixing between the DDS spurs and
> strong signals appearing anywhere inside the receiver's band-pass
> filter (many MHz in most receivers, but not the K3--more on that
> later). This is true even with the 14-bit DDS word size described in
> the TS590's sales brochure.
>
> The usual way to eliminate these wide-band spurs is to use a PLL to
> clean up the DDS's output. Ironically, that sales brochure I mentioned
> implies that eliminating the PLL was an advantage. Maybe they were
> thinking about reduced manufacturing cost, though this wasn't stated
> explicitly.
>
> (BTW, a typical lab receive mixing test done at just one test
> frequency will not necessarily show this characteristic. To reveal the
> DDS spurs, you'd need to do such a test at many frequencies, moving
> the VFO in very small increments. This is because the spurs are the
> product of multiple digital sampling phenomena; they vary rapidly in
> frequency and amplitude as the DDS's control word is changed. The lack
> of such testing and transparency in the industry could explain why
> mixing spurs are *not* a hot topic of conversation among those
> considering a radio using a raw DDS VFO. Yet, like real ghosts, the
> resulting signals could, nonetheless, sneak up on you :)
>
> It is certainly a lot more expensive to add a high-performance PLL
> into the system--just ask my engineering and manufacturing staff. But
> I guess it depends on what you're trying to optimize. We wanted the K3
> to perform extremely well in crowded band conditions, so we went to
> the trouble to use a DDS-driven-PLL synth. (Or TWO of these synths if
> you have the KRX3 sub receiver installed.) Flex may have elected to go
> with raw DDS because of the need for a very agile VFO for SDR
> applications. Kenwood may have been trying to keep costs low. Both are
> certainly worthy goals.
>
> Actually, we made it even harder on ourselves with the K3. We provide
> narrow band-pass filters on every ham band, painstakingly aligned at
> the factory, ensuring that as little out-of-band energy as possible is
> presented to the mixer in the first place. This makes the synth's job
> a little easier. Yet nearly all other transceivers these days use
> "half-octave" band-pass filters that are many times the width of the
> ham-band segment. They require no alignment, but they open the radio
> up to more interfering signals. (You can add general-coverage band-
> pass filters to the K3's main and/or sub receivers, of course, by
> adding KBPF3 module. This has no effect on the ham-band performance.)
>
> Note that like the K3, the KX3 uses a DDS-driven PLL synth. The K3 has
> an advantage in temperature stability since it uses a separate
> reference oscillator, but the KX3's phase noise is in the same very
> low range, as evidenced by Sherwood's numbers.
>
> Many other factors besides synth phase noise--including transmit
> signal purity and receiver AGC behavior--also contribute to
> performance in crowded conditions. This is why, some time ago, we
> undertook a major redesign of the K3's AGC subsystem. This resulted in
> excellent field reports from DXpeditions, etc., regarding the dynamics
> of within-filter signals.
>
> I won't go deeply into the SSB transmit purity issue, which has been
> adequately described by others. But I will mention that the K3's TX
> IMD at max power output is as good as or better than that of any other
> 12-volt-capable transmitter. And if you run at lower power when
> driving an amp (typically 20-70 W), the IMD numbers are outstanding by
> any measure.
>
> 73,
> Wayne
> N6KR
> --------------------------------------------------------------
>
> DON'T THINK THE PROBLEM IS LIMITED TO FLEX AND KENWOOD.
> Icom and Yaesu are generally just as bad, unless you purchase their high end
> radios!
>
> Next time you recommend someone buy a JA radio, first make sure the he lives
> far enough away from you that he won't pollute your airwaves.
>
> 73 - Rick, DJ0IP
> (Nr. Frankfurt am Main)
>
>
> -----Original Message-----
> From: TenTec [mailto:tentec-bounces at contesting.com] On Behalf Of Bob McGraw
> - K4TAX
> Sent: Sunday, July 06, 2014 2:30 PM
> To: Discussion of Ten-Tec Equipment
> Subject: [TenTec] On Noisy Transmitters
>
> Rick brings up a very good point on transmitter noise.  It is something most
> users won't likely realize is something that does truly exist.
>
> I find, with several I've measured, do produce wide band noise that is
> transmitted across the spectrum.  Basically it is polluting our bands with
> noise, somewhat like one throwing trash out along the highway or leaving it
> in the city park.
>
> I for one am glad to see RSGB does measure and report this.  I wish ARRL
> would do the same.  Of course it might affect their advertising revenue to
> report a certain brand and model radio is a broadband noise generator.
>
> I've just finished a weekend operation at Field Day.  Using the Eagle I
> found there was no noise generated when it went into transmit.  {I already
> knew this as I had measured it on the bench, which is one reason I elected
> to use the radio.}  To that end, I know, I had my spectrum analyzer sitting
> on the table.  As to other radios operating at the Field Day sight, well I
> could see the noise floor rise when they transmitted. Some worse than
> others.
>
> Many of the radio companies are "self certifying" thus indicated their
> product meets FCC specifications regarding purity of transmission.  The
> question is "do they really meet the specification or just say they do?".
> I strongly suspect if many of these brands and models were evaluated by an
> independent testing lab, they would not meet the requirements an thus would
> not be legal to be sold or used in the US or other countries for that
> matter.
>
> Be a good citizen, "Give a hoot and don't pollute".
>
> 73
> Bob, K4TAX
>
>
> ----- Original Message -----
> From: "Rick - DJ0IP / NJ0IP"<Rick at DJ0IP.de>
> To: "'Discussion of Ten-Tec Equipment'"<tentec at contesting.com>
> Sent: Sunday, July 06, 2014 6:37 AM
> Subject: Re: [TenTec] TT Mega Sale
>
>
>> Actually the FTdx3000 has a noisy transmitter.
>> You wouldn't know it by reading the ARRL review, but RSGB's Radcom
>> reported
>> that for it and the FTdx1200.
>>
>> 73 - Rick, DJ0IP
>> (Nr. Frankfurt am Main)
>>
>>
>> -----Original Message-----
>> From: TenTec [mailto:tentec-bounces at contesting.com] On Behalf Of Richard
>> Tschur
>> Sent: Sunday, July 06, 2014 12:39 PM
>> To: Discussion of Ten-Tec Equipment
>> Subject: Re: [TenTec] TT Mega Sale
>>
>>
>> Bry,
>> I just bought a second hand Eagle for pretty much the same price as they
>> sell a new one now, well it is a little annoying, but I got the best radio
>
>> I
>> have ever had and have! So I don't worry too much about that fact. I have
>> now 16 Ten Tec's and I love them all and they all stay here, means they
>> are
>> all keeper's! What I don't understand is, why do you wish you would have
>> bought an FTDX 3000??? For me, any Jap radio is Chicken Soup, a Ten Tec is
>> Eye Fillet! I would not want one for free.
>> I'm just listening to my Eagle in the background and it sounds sooo sweet
>> and quiet, RF gain down a fair bit, very much like FM with squelch. Just
>> beautiful. I will never buy another Jap radio whatsoever.
>> And in regards to the mega sale, I'm sure TT knows what they are doing and
>> I'm also very sure, that this is not the end for TT! Guy's, be happy, we
>> get
>> a nice discount on the best radio's on the market! I just wish they would
>> be
>> a lot more popular here in VK. They love their "Chicken Soup" ;-))!
>> 73's
>> Richard VK3KVK
>>
>>
>>
>> On 04/07/14 11:31, Brian Carling wrote:
>>> Annoying!! I just bought a used Omni VII for the same price they suddenly
>> changed to for the new ones. Now I wish I had bought an FTDX3000.
>>>
>>> Best regards - Bry Carling
>>>
>>>
>>>
>>>> On Jul 3, 2014, at 6:53 PM, Toby Pennington<w4cakk at centurylink.net>
>> wrote:
>>>>
>>>>
>>>> These rigs are way overpriced anyway and it is good to see some
>>>> realistic
>> pricing especially of the Omni 7 and the Eagle.
>>>>
>>>> I do feel for the guys who may be trying to sell these rigs on the used
>> market,  or those who bought something before the sale began. This kind of
>> sale is a FIRST for Ten Tec,   and obviously may signify more than just a
>> sale,  perhaps something new is about to appear,  or will come our way by
>> the end of this year.
>>>>
>>>> Toby K4NH
>>>>
>>>>
>>>>
>>>>> On 7/3/2014 5:44 PM, Jim Vohland wrote:
>>>>> Wow, that sure is a sale. Maybe some of the Ten Tec guru's can explain
>> but this sure doesnt make sense from a business perspective to me.
>> Knocking
>> a grand off the Omni VII. 800 off the eagle and 300 off a Agro. I wish I
>> was
>> in the market for a new rig. Kinda scary though and makes me wonder about
>> the future. Seems like a 'fire' sale. Just sayin.......Shoots the heck out
>> of the used market for those trying to sell eagles and omni's.
>>>>>
>>>>> _______________________________________________
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>>>>> TenTec at contesting.com
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>>
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