[time-nuts] RFDO - Experience and questions

Alan Melia alan.melia at btinternet.com
Tue Mar 7 15:09:59 EST 2017

Paul the off-air standards I have and another UK make I dont posses divide 
the 10MHz standard and the off-air carrier down to 2kHz for locking. It may 
not be the best but it is generally adequate for off air LF standard 
distribution. My unit will cover 162kHz or 198kHz.


----- Original Message ----- 
From: "paul swed" <paulswedb at gmail.com>
To: "Discussion of precise time and frequency measurement" 
<time-nuts at febo.com>
Sent: Tuesday, March 07, 2017 5:52 PM
Subject: Re: [time-nuts] RFDO - Experience and questions

> Gilles
> I went back over the starting thread and believe your home brew oscillator
> may prevent you from getting all of the accuracy out of TDF.
> As I was thinking about a TRF radio and locking the question I arrived at
> is how do you turn 162KHz into something useful like 100 KHz 5 MHz or 10
> MHz??.
> By getting to standard references there are many very good oven 
> oscillators
> available.
> Regards
> Paul.
> On Mon, Mar 6, 2017 at 10:35 PM, paul swed <paulswedb at gmail.com> wrote:
>> Actually as I think about it from the earlier part of the thread. Locking
>> to the carrier with a 2-4 second time constant removes the phase 
>> modulation
>> since its only in the first 200 ms. The 0 Phase is 800 ms in length or 
>> more
>> for all bits.
>> Now to find some nice coils for 162 KHz.
>> Regards
>> Paul
>> On Mon, Mar 6, 2017 at 8:30 PM, paul swed <paulswedb at gmail.com> wrote:
>>> A bit more reading if you block the phase comparison from -50ms to 150ms
>>> of the tick you get a 0 carrier phase no modulation. That also explains 
>>> why
>>> I thought I could here some sort of phase modulation because there is.
>>> So as an example if you use a GPS tick its really simple to block the
>>> phase changes and only measure the 0 phase carrier. Essentially a 200 ms
>>> carrier gap per second.
>>> Thats quite a clean format you have to work with.
>>> Regards
>>> Paul
>>> WB8TSL
>>> On Mon, Mar 6, 2017 at 8:19 PM, paul swed <paulswedb at gmail.com> wrote:
>>>> I checked out 162KHz at 2000 local and now have what I believe to be 
>>>> TDF
>>>> using the 67 ft vertical antenna. I am reading -82 dbm near Boston in 
>>>> the
>>>> US or 3400 miles. A comfortable signal at least in the winter. As a
>>>> comparison wwvb at 60 KHz is -77dbm some 2000 miles but also not at a 2 
>>>> MW
>>>> power level like TDF.
>>>> Since I had not heard TDF before I listened to Pieters online SDR radio
>>>> to see what to listen for. The easiest point to notice is the 59 second
>>>> phase. Its funny that also seconds 0-10 should be the same phase but it 
>>>> did
>>>> not seem to be true. Unless what I am hearing is the local oscillator 
>>>> of
>>>> Pieters SDR radio.
>>>> So thanks for sharing some new knowledge with Time-nuts.
>>>> Regards
>>>> Paul
>>>> WB8TSL
>>>> On Mon, Mar 6, 2017 at 1:46 PM, Pieter-Tjerk de Boer <
>>>> ptdeboer at cs.utwente.nl> wrote:
>>>>> On Sun, Mar 05, 2017 at 10:42:52PM +0000, Iain Young wrote:
>>>>> > That's TDF from France. Their equivalent of WWV/MSF/DCF.
>>>>> > Average phase and frequency deviation is
>>>>> > zero over 200msec (see link above for details)
>>>>> This is not quite correct, since the transmitter does not just carry 
>>>>> the
>>>>> time data (one bit per second, in the first 200 ms of the second), but
>>>>> also some more data during the next 700 ms of each second.
>>>>> The latter data is coded in a way which does not guarantee that the
>>>>> phase
>>>>> or frequency average is zero other than when averaging over the entire
>>>>> 700 ms block.
>>>>> Then again, I've been told that although there is a nicely defined
>>>>> framing
>>>>> format, in reality it has only ever transmitted idle frames, so in
>>>>> practice
>>>>> it's a fixed pattern which repeats every minute and thus could be
>>>>> cancelled
>>>>> for use as a frequency reference.
>>>>> I have a live online decoder for TDF's signal at
>>>>>    http://websdr.ewi.utwente.nl:8901/tdf/
>>>>> Regards,
>>>>>   Pieter-Tjerk, PA3FWM
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