[evlatests] 3-bit Friday

[Keith Morris]

Vivek --

You are correct regarding ea12.  These two T304s were moved to ea23, which
is scheduled to receive 3-bit samplers.  You should expect noisy, if any,
data from ea12.



> Here is a quick summary, we can discuss the gory entrails (alas)
> on Monday.
>
> 1. 3-bit data from C-band tests. The best 3-bit modules, like
>     the previous versions, are ~10% worse than 8-bit.
>
> Only bits 1-2-3 were used in this test. There are still some
> system issues before we test other variations, see below.
>
> RFI on the 3-bit  (not seen in 8-bit because of restricted
> bandwidth) was a problem as well.
>
> ea12 3-bit did not have the right flavor of T304 to drive it
> properly (right Keith, Michael?) and it performs the worst.
> Excluding it and antenna 7 which had other woes, the best
> 3-bit paths are about 8-10% worse than the 8-bit.
>
> Bandpasses for 6C1 and 12C1 changed by ~5% over 3 days.
> The rest were stable to better than 1%. Other than RFI,
> things look pretty stable over the 1-hour test.
>
>
> 2. Dropouts and system oddities:
>
> The dropouts that have appeared recently are more pronounced
> (~50%) in short-dump data. They are on specific antenna/IF
> paths, and seem to be related to delay models because of
> the 10sec periodicity, but more is not known.
>
> In the 3-bit data, ea07C1 is very strange with lots of time
> variable drops. ea07C2, ea12C1,C2, ea14C1 have 10sec drops.
> The rest of the 3-bit paths and all BD 8-bit paths show no
> drops. This pattern has repeated now on about 5 datasets over
> several days. I do not think it affects all 3-bit data, but
> it would be nice to remove this thorn before proceeding.
>
> There were also other periodicities in the fast-dump data,
> I hope they are triggered by fast dumps and not a new problem
> in regular 1-sec data.
>
> We will get (or already have) new antennas for 3-bit next week.
> X-band should be tried I guess.
>
> Michael Rupen wrote:
>> Hi Vivek --
>>
>>   please have a look at two 3-bit data sets from today:
>>
>> * _50msec: 50msec dumps -- what do our drop-outs look like?
>>
>> * _offset: this is 3C286 + offset blank field, run for an hour.
>>   How does the noise look? and how stable is everything?
>>
>> Would also be interesting to compare bandpasses with Thursday's
>> data.
>>
>> Thanks --
>>
>>      Michael
>>
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