[time-nuts] Difference between Oncore models

Bob Camp kb8tq at n1k.org
Thu Mar 17 07:39:07 EDT 2016


Hi

A lot of “dead” Z3801’s have a blown fuse link input on the power supply. I’d check 
that first.

Bob

> On Mar 16, 2016, at 9:56 PM, Joseph Gray <jgray at zianet.com> wrote:
> 
> Thanks to all for the comments. I recently traded for another Z3801A
> that I was told didn't work. I don't know what is wrong with it, as I
> haven't had time to put it on the bench yet. I understand that the
> OCXO is putting out a decent 10 MHz, so perhaps it also has a bad
> Oncore.
> 
> Joe Gray
> W5JG
> 
> 
> On Wed, Mar 16, 2016 at 3:56 PM, Artek Manuals <Manuals at artekmanuals.com> wrote:
>> Joe
>> 
>> The newer Motorola VP-Oncore  receivers are known to be an improved design
>> over the original Oncores that came with the Z3801A's .
>> 
>> I have recently done some  side by side comparison's with two z3801A's on
>> the same antenna the newer Vp-Oncore's ran SS numbers 15-30 points higher on
>> the same bird than the older receiver. In all fairness the older receiver is
>> on its last legs (see last paragraph below)
>> 
>> I also found out that there are two versions of the newer VP-Oncore. These
>> can be distinguished by the antenna connector, One version has a right-angle
>> chassis mounted connector like the original 6CH Oncore, the 2nd version has
>> a straight on antenna connector. This 2nd version while they will work in a
>> Z3801A, have an interference fit problem with a an IC  on the board below
>> when the antenna cable is plugged in and you can't tighten down all the
>> receiver board mounting screws. I am told that the straight on version fits
>> the Z3816A with no problem. I have not verified this since I don't have a
>> Z3816. I have no info  on the other Z38xx models and the fit of the later
>> VP-Oncore
>> 
>> The older 6ch Oncore receivers receivers are beginning to die apparently.  I
>> have had one fail here a few months ago and recently acquired a 2nd Z3801A
>> that is displaying similar symptoms to the first failure in that the
>> receiver just stops working after a few hours...over time the symptom  are
>> the receiver drops out for no apparent reason then revives if the unit is
>> powered off for a while. Over time the time to receiver drop out gets
>> shorter and shorter after each successive power cycle, I have one receiver
>> that will now fail within 20 minutes predictably.
>> 
>> Dave
>> NR1DX
>> 
>> 
>> 
>> 
>> On 3/16/2016 7:03 AM, Joseph Gray wrote:
>>> 
>>> I understand that the Oncore GPS in the Lucent units is a newer module
>>> that tracks eight satellites, vs the older Oncore in the Z3801A that
>>> only tracks six satellites.
>>> 
>>> I decided to do a re-survey with my Z3801A that has been in holdover
>>> for some time, just as a test. Watching the status screens from both
>>> GPSDOs, both are seeing the same number of satellites, however, the
>>> Z3801A is consistently locking to 3-4 fewer than the Lucent.
>>> 
>>> This begs the question, is the older Oncore module that deaf, or is
>>> mine defective. BTW, same antenna on a 4-port splitter, same elevation
>>> mask.
>>> 
>>> Joe Gray
>>> W5JG
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>> 
>> 
>> --
>> Dave
>> Manuals at ArtekManuals.com
>> www.ArtekManuals.com
>> 
>> ---
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