[time-nuts] Z3816A alarm

Bill Jones, K8CU k8cu at realhamradio.com
Sat Jan 22 06:19:17 EST 2005


Rex,

Searching the Z3801A forum with the phrase "Z3816A alarm" results in a
resistor work-around much like you have already described.

I am not aware of a way to actually disable the low current alarm.

Bill Jones, K8CU
www.realhamradio.com


----- Original Message ----- 
From: "Rex" <rexa at sonic.net>
To: "Discussion of precise time and frequency measurement"
<time-nuts at febo.com>
Sent: Saturday, January 22, 2005 4:21 AM
Subject: Re: [time-nuts] Z3816A alarm


On Sat, 22 Jan 2005 01:09:34 -0000, "Bill Jones, K8CU"
<k8cu at realhamradio.com> wrote:

>Rex,
>
>Unlike the Z3801A, the Z3816A has an alarm specific for the antenna.  I
>suggest that you view a thread on my site that describes this condition as
>well as a work-around for it:
>http://realhamradio.com/cgi-bin/yabb/YaBB.cgi?board=1;action=display;num=10
36696003;start=4
>
>Bill Jones, K8CU

Thanks, Bill and Brooke,

You were correct. The problem is that the 2nd antenna does not draw
enough current. This one has slightly better signal than the HP antenna,
so it is too bad that it draws too little current to satisfy the Z3816A.

I verified by causing the "problem" antenna to draw more current. I
found an N bias-T with no DC blocking and put it in series with the
antenna. The signal was still there and alarm still on. Then I added a
620 ohm resistor across the bias-T DC input port to make the cable draw
about 8 mA more. Alarm went out and antenna still works.

Frustrating that the error status register does not indicate this
condition. Seems like there ought to be some way to view status that
indicates this error condition is what is causing the alarm.

Bill, you mentioned a workaround, but I didn't see any in the thread you
referenced. Is there some way to disable the low current alarm?

Anyway, thanks for pointing me at the problem.

-Rex


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