[evlatests] X-band birdies

[Dan Mertely3]

Hi David.  It should be noted that the passband of the VLA
and current (transition) EVLA X-band receivers is only:

8000 - 8800 MHz.

The default (VLA) frequencies for X-band are:

AC center = 8435.1 +/- 25 MHz
BD center = 8485.1 +/- 25 MHz

If you are seeing something at 9140.1 MHz, it must be either
extremely strong (if radiated), or injected by the EVLA
signal processing hardware, since the X-band receiver has
very little sensitivity that far above it's 8800 MHz upper
band edge.

-Mert


David Sevilla wrote:
> I am writing this message to report some new findings.
> The setup was as follows:
> 
> Antenna 14
> standard X-band:         8268.10 MHz to 9292.10 MHz
> IFs  A and B
> channel bandwidth = 65 kHz
> 
> I found a single channel always at the frequency 9140.1 (152.0 MHz from
> the edge) to be above a threshold level of about 1.5 dB's above the noise
> level for about 42%(+/- 10%) of the time. The mean value for that channel
> was 6 dB's (+/- .5%) above the normal level.  The rest of the channels did
> not show any similar behavior. The rest of the channels were only above
> that threshold for about 3% (+/- 1%) of the time which is normal.
> 
> This is the first I've seen of this behavior.  Walter and I do not know
> the origin of this signal
> 
> David Sevilla
> 
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