[time-nuts] New NTBW50AA

Bob Camp lists at rtty.us
Fri Sep 20 23:29:41 UTC 2013


Hi

GPS uses a model of the earth. It calculates position relative to this model. The model does *not* correspond to sea level. It's very common to be driving along the beach and see negative altitude numbers with an honest GPS. If you are located within 100' of sea level, you may see negative altitude from a GPS. In other areas you may of course see significant positive altitudes when sitting on the beach.

Bob

On Sep 20, 2013, at 7:23 PM, Jim Sanford <wb4gcs at wb4gcs.org> wrote:

> Mine insists on determining a negative altitude.  sometimes it's called a good position, sometimes not.  Eventually, it becomes 'good" even with -altitude!
> 
> Now I understand why it goes in and out of holdover, but what about the bad altitude??
> Jim
> wb4gcs at amsat.org
> 
> On 9/20/2013 6:22 PM, Bob Camp wrote:
>> Hi
>> 
>> If the unit is dropping into holdover, something is wrong with the number of sat's it's seeing. If you have saved a location properly, it will only go into holdover when it's got zero sats. If it does not believe it's got a proper location it will drop into holdover when it goes below 4 sats. The number of sats visible isn't what counts here, it's the number that are locked up, above the elevation mask, and above the AMU threshold. Set either the elevation or the AMU to high and you will go in and out of holdover.
>> 
>> Bob
>> 
>> On Sep 20, 2013, at 2:13 PM, quartz55 <quartz55 at hughes.net> wrote:
>> 
>>> I was thinking of keeping a couple of batterys floated across the supply, since it will run on 24V.  I'll have to figure out what I'll need for maybe 2 hours.  Not sure what it's drawing now at 30V, but wouldn't be hard to measure.
>>> 
>>> Couple more things.
>>> 
>>> What is the foliage filter and will it work on the Nortel?
>>> 
>>> I keep seeing my holdover going up but haven't seen any sat drop out or yellow light on the front.  Is there any way to re-set the holdover without turning the unit off?  It's up to 468 now, not sure where it started the other day but probably in the 200's.  I may be dreaming too.
>>> 
>>> I've dropped the idea about choke ring or ground planes after reading what I could about it.  I may try building my own turnstile antenna (ala K7KKQ) and amp just for fun.  Amps are cheap from Mouser and have less than 2 dB NF unlike mine which is 4 dB.  Has someone made a DIY helix?  I liked the pinwheel antenna but it may be hard to make.
>>> 
>>> Dave
>>>  ----- Original Message -----
>>>  From: Charles Steinmetz
>>>  To: Discussion of precise time and frequency measurement
>>>  Sent: Friday, September 20, 2013 1:01 PM
>>>  Subject: Re: [time-nuts] New NTBW50AA
>>> 
>>> 
>>>  Dave wrote:
>>> 
>>>> We have plenty outages here, so I may look into a UPS of some sort
>>>> but I have a rather large generator that I always turn on after
>>>> about 1/2 hour or so.
>>>  The UPS is to keep master oscillators (and for some of us, ovenized
>>>  voltage standards) running uninterrupted from the time of the failure
>>>  until the generator is running.  Best practice is to use a "double
>>>  conversion" UPS to avoid even a short outage as it kicks in.
>>> 
>>>  Best regards,
>>> 
>>>  Charles
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