[PCR-1000] Noise Floor

[Patrik Norqvist]

Traugott Goll wrote:
> 
> I used TalkPCR to make a spectrum analysis of the 2-25 MHz range an found
> that at exactly 15 MHz the noise floor drops from -80 dB to -110 dB.
> Abruptly and just like that.

There is a partially different set of filters in the RF stage used for 1.8--15
MHz than for 15--30 MHz. These filters, however, don't seem to bee tuned by
EEPROM settings.

> Suspected that maybe something was wrong with
> the EEPROM, so compared the original contents with its present value and
> yes, there was a discrepancy. Restored the original contents. Made another
> spectrum analysis 5 min later. Now the noise floor has risen across the
> board by at least 5 dB. Same when restoring so-called median values.

I interpret "across the board" as all frequencies are more or less affected.

Was this change in noise level measured with external equipment or with the
S-meter readings from the radio? There are "calibration points" for the S-meter
that are stored in the EEPROM. As a result of this, a change of EEPROM values
could change the S-meter readings even if there is no change in noise level.

>Someone has an explanation for this 

Well, this is a humble try.

Regards
    /Patrik