[evlatests] P band, 4 band and power levels

[Charles Kutz]

Just now took some snapshots of P-Band bandpass.

See attached.

Chuck

Rob Long wrote:
> 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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