[time-nuts] WWVB Dephaser Question

Bob kb8tq kb8tq at n1k.org
Sat Oct 10 14:24:38 UTC 2020 

Hi

The standard 3’ loop was not anything really exotic. There are a lot of ham / SWL
articles out there showing very similar designs. 

One of many hits from Google:

https://www.rfcafe.com/references/electronics-world/vlf-loop-antenna-january-1963-electronics-world.htm <https://www.rfcafe.com/references/electronics-world/vlf-loop-antenna-january-1963-electronics-world.htm>


Bob

> On Oct 9, 2020, at 8:04 PM, John C. Westmoreland, P.E. <john at westmorelandengineering.com> wrote:
> 
> Paul,
> 
> Thanks for that detailed explanation.  I've done something similar for MARS
> but of course higher frequency and that was transmit also.
> 
> I've seen the site of something similar but I think that was a 3' diameter
> design; and I've looked at some of the Symmetricom schematics I've
> been able to find but have yet to find a schematic of one of
> the Symmetricom receive antennas.  I was hoping to find the one they had
> for outdoor pole mount.  It's mentioned in a lot of their documents and
> even some pics but no schematic details or BOM for that I've been able to
> find.
> 
> Thanks to Tim also for the response and have a good weekend!
> 
> 73's,
> John
> AJ6BC
> 
> On Fri, Oct 9, 2020, 15:24 paul swed <paulswedb at gmail.com> wrote:
> 
>> John I don't think so as not sure how many have built a large antenna.
>> Certainly any of the old wwvb receivers have details and thats pretty much
>> what most people copy.
>> Essentially a 3 foot copper loop with numbers of turns of wire connected
>> together. Like 25 pair telco cable connected end to end. A large capacitor
>> is then put across the loop to resonate it at 60 KHz. Then the preamp. Some
>> use a FET transistor followed by a line driver transistor. Power is sent
>> over the coax so a blocking cap and inductor.
>> Really big is 10' by 10' using shielded 36 wire ribbon cable. ( did not use
>> all 36 conductors it was to much L but 800 ft worth. The shield acts like
>> the copper pipe and it must be broken so that it does not look like a
>> shorted loop. Add the cap and preamp.
>> In this case I built a 2 transistor NPN 2n3904 preamp.
>> On the large antenna I use a 2 X 6 post 4ft in the ground with cement. A
>> mast above that to support the antenna and to allow it to be turned a bit
>> to null MSF.
>> Thats it no real magic. Its been operational for 7 years with an occasional
>> transistor replacement. Also coax, darn woodpeckers!
>> Regards
>> Paul
>> WB8TSL
>> 
>> 
>> On Fri, 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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