[evlatests] 4band, interference and ea14

[Dan Mertely]

BTW:  The nearest TV02 station is K02KP out of Lordsburg, with
only 42 W.  -Mert

On 6/23/2014 3:47 PM, Frazer Owen wrote:
> On 06/23/2014 02:35 PM, Gregory Taylor wrote:
>> Hi Frazer,
>>
>>      The emission at 55.25 MHz is the video carrier for TV channel 2.
>> We see this quite strongly with LWA1. At 60 MHz we see a moderately
>> strong source to the North of LWA1 (see plot).  We might be seeing a VLA
>> antenna.  The extended source in the  NE is from power-lines.  They are better
>> following some mitigation earlier this month, but still obvious.
>> Ciao,
>>                              - Greg
>      I had noticed the coincidence with 55.25 and channel 2. The problem is that
> we don't see that signal, at least anywhere near as strong, on the other two
> 4band antennas, just ea14. Unless ea14's location at E8 allows it to see a
> channel 2 while the others are blocked, then I don't understand why we just see
> 55.25 on ea14. That signal is much stronger than anything else we see, including
> the other TV channels. For the other antennas channel 5 is by far the strongest
> of the clearly external signals.
>
>      Not sure where 60 MHz is coming from. We should find out.
>>
>>
>>
>> On Jun 23, 2014, at 9:40 AM, Frazer Owen <fowen at nrao.edu <mailto:fowen at nrao.edu>>
>>  wrote:
>>
>>>
>>>     We made a successful test of the the new 4band MJP dipoles using
>>> antennas 12, 14, and 19. 14 is important for interference tests because
>>> it has the new ACU.  The autocorrelations on 12 and 19 show the 5MHz
>>> clock comb that is thought to come from the old ACU. 60 MHz is
>>> particularly strong and variable for test to test. The autocorrelations
>>> for antenna 14 do not show the 5MHz comb. This seems to confirm that
>>> that the 5 MHz comb is from the old ACU
>>>
>>>      Antenna 14 also does not show interference at 64MHz, which I
>>> understood was a possible frequency from the new ACU. It does show a
>>> fairly strong spike at 55.25, much stronger than any else in the 54-86
>>> MHz band. The very narrow spike is clearly different from the 55MHz
>>> spike on 12 and 19, which is part of the 5MHz comb. 12 and 19 don't show
>>> a spike at 55.25.
>>>
>>>     Interestingly the 5MHz comb frequencies correlate on baselines to
>>> 14 (as they do on 12-19). Since the 5MHz clock is supposed to be
>>> incoherent from antenna to antenna, there must be a general source of
>>> the comb frequencies, especially 60MHz, which is being broadcast around
>>> the site. Could this be one very bad antenna ?
>>>
>>> ---Frazer
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>>
>
>
>
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