[time-nuts] WWVB Dephaser Question

[Tim Shoppa]

The NIST WWVB transmitter antenna is very massive and very well documented: https://apps.dtic.mil/sti/pdfs/ADA299080.pdf

For receive on VLF there is no reason to go so big. A short whip produces plenty of atmospheric noise so there’s no purpose at going bigger. A loop (including ferrite core loop) has a useful null to remove local noise sources. A tuned loop with reasonable Q helps reject a lot of noise before it reaches the first active stage.

Tim N3QE

> On Oct 9, 2020, at 5:14 PM, John C. Westmoreland, P.E. <john at westmorelandengineering.com> wrote:
> 
> Bob,
> 
> Thanks for the answer; but does anyone actually have a documented
> specification posted for one of these 'massive' WWVB 60kHz antennas
> someplace?
> 
> Thanks.
> 
> 73's,
> John
> AJ6BC
> 
> 
>> On Fri, Oct 9, 2020, 08:35 Bob kb8tq <kb8tq at n1k.org> wrote:
>> 
>> Hi
>> 
>> At least to me, anything dimensioned in the 100’s of feet is “massive”
>> compared to
>> the rod antennas normally seen in WWVB use ….
>> 
>> The other point being that if the antenna is some sort of large loop, it’s
>> going to be
>> a good long ways away from the receiver. You get both a larger signal
>> voltage and better
>> isolation …..
>> 
>> Bob
>> 
>>> On Oct 8, 2020, at 11:30 PM, John C. Westmoreland, P.E. <
>> john at westmorelandengineering.com> wrote:
>>> 
>>> Hello All,
>>> 
>>> Are there any design details someplace regarding these massive antennas?
>>> 
>>> Thanks,
>>> John
>>> AJ6BC
>>> 
>>> 
>>>> On Thu, Oct 8, 2020, 19:27 paul swed <paulswedb at gmail.com> wrote:
>>> 
>>>> Hello to the group.
>>>> Ray as Bob mentions you are taking a 10s of uv signal to a logic level
>> of
>>>> maybe 4V.
>>>> If the loop is any place close to the divided down signal, it will
>>>> oscillate. It would take incredible shielding to protect the receiver.
>>>> Thats why you often see a solution that doubles to 120 KHz and modifies
>> the
>>>> detectors to work at that frequency. That means hacking the radio
>>>> internally. Not fun. The other really annoy effect is that the doubling
>>>> slips phace due to noise and propagation. So if charting suddenly you
>> get a
>>>> 180 degree flip. Thats messy.
>>>> The doubling solution can work. Search for carter and there are several
>>>> others.
>>>> But having tested and used all of the alternates and lots more on the
>> east
>>>> coast decided they were too much trouble. You should see the box of
>> boards
>>>> I have chuckle.
>>>> For me I am very happy with the d-psk-r. Though in being above board I
>>>> designed version 1 and Rodger and I did version 2. Its solid and no
>> mods to
>>>> any receiver. Everything has always been released to the time-nuts
>> group.
>>>> As they say have fun.
>>>> Regards
>>>> Paul.
>>>> WB8TSL
>>>> 
>>>> On Thu, Oct 8, 2020 at 5:39 PM <rcbuck at atcelectronics.com> wrote:
>>>> 
>>>>> Bob,
>>>>> 
>>>>> I am using a ferrite rod antenna for the receiver. No outside antenna.
>>>>> 
>>>>> Ray
>>>>> 
>>>>> -------- Original Message --------
>>>>> Subject: Re: [time-nuts] WWVB Dephaser Question
>>>>> From: Bob kb8tq <kb8tq at n1k.org>
>>>>> Date: Thu, October 08, 2020 12:40 pm
>>>>> To: Discussion of precise time and frequency measurement
>>>>> <time-nuts at lists.febo.com>
>>>>> 
>>>>> Hi
>>>>> 
>>>>> A lot depends on your antenna setup. You can also swamp out the
>> incoming
>>>>> WWVB signal…….
>>>>> 
>>>>> Bob
>>>>> 
>>>>>> On Oct 8, 2020, at 2:07 PM, <rcbuck at atcelectronics.com> <
>>>>> rcbuck at atcelectronics.com> wrote:
>>>>>> 
>>>>>> I have read several different articles where the WWVB phase shift is
>>>>>> eliminated by doubling the signal to 120 kHz. Several members of the
>>>>>> list have built these units.
>>>>>> 
>>>>>> Assume I build a circuit to double the incoming signal and use a
>>>> schmitt
>>>>>> trigger to get a 120 kHz square wave. If I then divide that signal
>> back
>>>>>> down to 60 kHz will that signal be strong enough to swamp out the WWVB
>>>>>> signal? I'm guessing it will be since it is at the 5 volt level and
>>>>>> somewhere in the +25 dBm or greater range.
>>>>>> 
>>>>>> Ray,
>>>>>> AB7HE
>>>>>> 
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>>>>> 
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