[evlatests] P band, 4 band and power levels

[Rob Long]

We got onto ant 21 yesterday and measured total power in both P and 4 
bands (RCP and LCP).  On this antenna, we added 7 dB attenuation to the 
4-band input of the T301 (to balance total power between 4 and P) and 
looked at the spectral display.

Rob

Paul Harden wrote:
> 
> Barry Clark wrote:
> 
>>But 15 dB sounds too much - it will decrease the headroom 
>>available to the P band.
> 
> 
> In the 4/P Converter, the 4- and P-band signals are combined just prior 
> to the mixer.  Attenuating the 4-band signal would not affect the P-band 
> power to the mixer.  The mixer is the limiting device that determines 
> overall gain headroom.  At present, the higher power at 4-band causes 
> the mixers to go into gain compression about 10 dB before P-band.
> 
> It would seem that by attenuating the input power at 4-band *only*, this 
> would improve the 4-band headroom and leaves the P-band headroom as it 
> is (about 36dB).  The 4-band attenuation would equalize the two bands to 
> about the same power level, and the same headroom.
> 
> I agree that 15dB sounds too much and could start interfering with the 
> noise figure.
> 
> Paul H.
> 
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