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Re: A datapoint comparing old vs new synthesizer

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giuliano-8

Re: A datapoint comparing old vs new synthesizer

A simple question :
the new synthesizer uses a DDS? If yes what is the type?
73
Giuliano I0CG
Italy
K1,K2,K3+P3

> Message: 18
> Date: Tue, 10 Mar 2015 15:54:24 -0000
> From: "Dave Olean"<[hidden email]>
> To: "Elecraft Reflector"<[hidden email]>
> Subject: [Elecraft] A datapoint comparing old vs new synthesizer
> boards.
> Message-ID: <3AE5C8AA7D6B4DF2A2932520B75DCF21@t30ce0d73e1b34>
> Content-Type: text/plain; charset="iso-8859-1"
>
> I recently got a new K3 and it was one of the first units supplied with the new and improved synthesizer board. In reading a few comments on the reflector, a number of people wanted to know if anyone could detect any difference between the old and the new. I also have some older K3s and decided to compare one of them head to head with the new one on ten meter CW using a 500 Hz bandwidth and check for MDS. I used the line out jack and an HP AC VTVM and 8640B signal generator. Here is what I found:
> K3 #8858 no preamp -137 dBm new synthesizer board
> preamp ON -139 dBm new synthesizer board
> K3 #1504 no preamp -134.5 dBm old synthesizer board
> preamp ON -137 dBm old synthesizer board
>
> I also ordered a pair of synth boards for one of my old K3s on March 1, but it will be awhile before it gets here I guess. I ordered a P3 kit with it and included comments that I was in no rush for the P3 so ship it all together. From the comments I have seen on how many have been ordered, I might be waiting a long time for the P3!! At my age, I'll probably forget about the order in another week or so. When it shows up, I'll wonder what it is and who ordered it!! The plan is to put new synth boards into #1504 and then I can check MDS again to see how it looks. From my checking, it looks like the newer K3 is almost 3 dB better than the older one at least as far as minimum discernable signals go. The new board definitely makes a difference, and my result tracks reasonably well with what what others have found.
>
> Dave K1WHS

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wayne burdick

Re: A datapoint comparing old vs new synthesizer

Administrator

The new synth uses a hybrid DDS-PLL architecture running at a very high frequency. Many newer transceivers use a DDS only. The PLL is critical to low-noise (low-jitter) performance.

The DDS-PLL subsystem is locked to the 49.380-MHz reference to within a small fraction of a Hz over the entire tuning range.

73,
Wayne
N6KR

On Mar 10, 2015, at 1:54 PM, Giuliano Carmignani <[hidden email]> wrote:

> A simple question :
> the new synthesizer uses a DDS? If yes what is the type?
> 73
> Giuliano I0CG
> Italy
> K1,K2,K3+P3
>
>
>> Message: 18
>> Date: Tue, 10 Mar 2015 15:54:24 -0000
>> From: "Dave Olean"<[hidden email]>
>> To: "Elecraft Reflector"<[hidden email]>
>> Subject: [Elecraft] A datapoint comparing old vs new synthesizer
>> boards.
>> Message-ID: <3AE5C8AA7D6B4DF2A2932520B75DCF21@t30ce0d73e1b34>
>> Content-Type: text/plain; charset="iso-8859-1"
>>
>> I recently got a new K3 and it was one of the first units supplied with the new and improved synthesizer board. In reading a few comments on the reflector, a number of people wanted to know if anyone could detect any difference between the old and the new. I also have some older K3s and decided to compare one of them head to head with the new one on ten meter CW using a 500 Hz bandwidth and check for MDS. I used the line out jack and an HP AC VTVM and 8640B signal generator. Here is what I found:
>> K3 #8858 no preamp -137 dBm new synthesizer board
>> preamp ON -139 dBm new synthesizer board
>> K3 #1504 no preamp -134.5 dBm old synthesizer board
>> preamp ON -137 dBm old synthesizer board
>>
>> I also ordered a pair of synth boards for one of my old K3s on March 1, but it will be awhile before it gets here I guess. I ordered a P3 kit with it and included comments that I was in no rush for the P3 so ship it all together. From the comments I have seen on how many have been ordered, I might be waiting a long time for the P3!! At my age, I'll probably forget about the order in another week or so. When it shows up, I'll wonder what it is and who ordered it!! The plan is to put new synth boards into #1504 and then I can check MDS again to see how it looks. From my checking, it looks like the newer K3 is almost 3 dB better than the older one at least as far as minimum discernable signals go. The new board definitely makes a difference, and my result tracks reasonably well with what what others have found.
>>
>> Dave K1WHS
>
> ______________________________________________________________
> Elecraft mailing list
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> Post: mailto:[hidden email]
>
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> Please help support this email list: http://www.qsl.net/donate.html
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ab2tc

Re: A datapoint comparing old vs new synthesizer

Hi,

One subject I haven't seen touched is the somewhat subjective "does it feel like an analog VFO" (with the 10Hz tuning step) like the old synthesizer? Technically that means fast settling, no overshoots, no skipped steps or resorting to a higher tuning step even when tuning fast. I have never had any problem with this in a real ham radio (IC-718, IC-7200, K3), but my portable Eton E1 is terrible in this regard. It's only use is to walk the street or take in the car for noise hunting. BTW it would be nice to see at least a block diagram identifying the major ICs used.

AB2TC - Knut

wayne burdick wrote

The new synth uses a hybrid DDS-PLL architecture running at a very high frequency. Many newer transceivers use a DDS only. The PLL is critical to low-noise (low-jitter) performance.

The DDS-PLL subsystem is locked to the 49.380-MHz reference to within a small fraction of a Hz over the entire tuning range.

73,
Wayne
N6KR

<snip>

Phil Wheeler-2

Re: A datapoint comparing old vs new synthesizer

Knut, if you're asking about the K3 with the new
synthesizer in '"does it feel like an analog VFO"
(with the 10Hz tuning step) like the old
synthesizer?', I don't notice any change in the
feel of tuning the radio.

Phil W7OX

On 3/12/15 7:36 AM, ab2tc wrote:

> Hi,
>
> One subject I haven't seen touched is the somewhat subjective "does it feel
> like an analog VFO" (with the 10Hz tuning step) like the old synthesizer?
> Technically that means fast settling, no overshoots, no skipped steps or
> resorting to a higher tuning step even when tuning fast. I have never had
> any problem with this in a real ham radio (IC-718, IC-7200, K3), but my
> portable Eton E1 is terrible in this regard. It's only use is to walk the
> street or take in the car for noise hunting. BTW it would be nice to see at
> least a block diagram identifying the major ICs used.
>
> AB2TC - Knut
>
>
> wayne burdick wrote
>> The new synth uses a hybrid DDS-PLL architecture running at a very high
>> frequency. Many newer transceivers use a DDS only. The PLL is critical to
>> low-noise (low-jitter) performance.
>>
>> The DDS-PLL subsystem is locked to the 49.380-MHz reference to within a
>> small fraction of a Hz over the entire tuning range.
>>
>> 73,
>> Wayne
>> N6KR
>> <snip>