[time-nuts] HP-3586B SSB L.O. Mods...

paul swed paulswedb at gmail.com
Wed Mar 23 01:07:24 UTC 2011


Oooops 3 more decimal places to the right.

On Tue, Mar 22, 2011 at 9:05 PM, paul swed <paulswedb at gmail.com> wrote:

> Welll I sort of went past this and have a reasonable answer.
> All system locked to a rb ref.
> A HP8660 as source gen and set to 3 MC.
> The 3586 if is 15.625KC.
> Set a HP 3335 to the IF frequency and on a scope the signals lined right up
> and are stable. Bob I think you or someone else mentioned this fact and I
> verified it.
>
> Then I went to the audio out on the 3586. That signal should be 1.850KC.
> Set the 3335 to 1.85 KC and watched the drift rate for USB and LSB.
> The answer is for 1 cycle drift rate is;
> 2.68 seconds for lsb or 2.0X10-4 (This will bring responses)
> 9.97 seconds for usb or 5.4X10-5
>
> Have to say that drift is way below what my ears can hear these days.
> So though I could change the DDS for FMT use and drive the decimal point at
> least 3 more digits to the left. I really have to say good enough and a
> success from just two weeks ago.
>
> Regards
> Paul
> WB8TSL
>
>
> On Tue, Mar 22, 2011 at 8:45 PM, Bob Camp <lists at rtty.us> wrote:
>
>> Hi
>>
>> My assumption is that to do any of this, some sort of calibrated clock on
>> the sound card would be needed. Either a mod to the card, or some luck with
>> the built in clock source. It's going to be needed weather you use an FFT or
>> some other DSP process. For a "fully locked" system, mod the sound card for
>> an external clock and whip up a phase locked loop to drive it.
>>
>> The mix down source would likely be purely digital. Inserted after you had
>> the sample stream. My first choice would be to use a 2 KHz "stupid clock" (0
>> 1 0 -1)  with an 8 KHz sample rate. Pretty simple math.
>>
>> Bob
>>
>>
>> On Mar 22, 2011, at 6:23 PM, Alberto di Bene wrote:
>>
>> > On 3/22/2011 5:24 PM, Bob Camp wrote:
>> >> The other approach would be to simply take the samples, do a mix down,
>> and
>> >> get the phase from an ATAN calculation on the I/Q results. That would
>> give
>> >> you pure phase and thus frequency.
>> > How do you intend to generate the numeric LO stream to use for the mix
>> down ? It must have a sampling rate
>> > with a precision comparable to what you intend to measure...
>> >
>> > 73  Alberto  I2PHD
>> >
>> >
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