[hpsdr] FW: Sensitivity of dual mercury system differs significantly

[georg Prinz]

Hi Jim,

I am not shure. I put the slave mercury as master and the reading was 
correct.
Now I will put the old master as a slave. We will see what will happen.

73, Georg, dl2kp




Am 06.06.2014 20:10, schrieb Jim Gailer:
> Hi Georg
>
> I posted this earlier today, but it doesn't seem to be appearing.
>
> You have a 20dB attenuator and a 20dB gain block on your board, both of
> which seem possible culprits.
>
> Cheers and 73
>
> Jim, G3RTD
>
> -----Original Message-----
> From: Jim Gailer [mailto:lists at kingstag.net]
> Sent: 06 June 2014 11:54
> To: 'hpsdr at lists.openhpsdr.org'
> Subject: RE: Sensitivity of dual mercury system differs significantly
>
> Hi Georg
>
> I had these symptoms on a home built Hermes (the only fault) and it turned
> out that I had broken the pre-ADC amplifier LTC6400-20 (or, less likely had
> fitted a broken one). This amplifier has a gain of 20dB and in its failed
> state showed a unity gain. It is quite easy to check the signal path using
> an oscilloscope (inject a low frequency signal) provided you have physical
> access to the board. I found this to be a difficult chip to fix, as it has a
> bottom ground pad. If this amplifier is showing near zero gain, check the
> solder joints and measure the voltages on the chip, including the chip
> enable pad. Measure using a sharp pin on the chip's copper rather than on
> the solder. With luck, the fault will be caused by something else! Check
> that the attenuator relay K1 switches too.
>
> To remove the broken chip, I used Chip Quick alloy, but the ground pad would
> not release. I eventually ground the plastic through to the copper at the
> bottom of the chip (not the PCB foil!) using a miniature burr drill (I used
> a microscope). This time I used more bottom heat and an infra-red top heater
> to solder the chip (not for the faint hearted). Mask off the board with
> aluminium foil to protect other components (especially the plastic ones).
>
> Good luck and 73, Jim, G3RTD
> ------------------------------
>
> Date: Thu, 05 Jun 2014 16:03:01 +0200
> From: georg Prinz <getpri at t-online.de>
> To: hpsdr at lists.openhpsdr.org
> Subject: [hpsdr] Sensitivity of dual mercury system differs
> 	significantly
> Message-ID: <53907895.4060901 at t-online.de>
> Content-Type: text/plain; charset=ISO-8859-1; format=flowed
>
> Hello,
>
> during my initial tests with my dual transverter system on 2m, I realized
> that my dual mercury system with Metis has unequal sensitivity.  The
> difference between mercury one and two is about 20dB (measured without Alex
> after running through the calibration routine). The attenuation for RX1 and
> RX2 is set to 0dB in PowerSDR  mRX PS v3.2.9(2/23/14). The two mercuries are
> set up as Joe(K5SO) proposed for a clock feed of two mercuries.
>
> Did anybody encounter something similar? What could be the reason?
>
> Furthermore, I have another testsystem with OZY and one Mercury on my
> workbench. This system shows a noisefloor at about less than -130dBm,
> visually. My above mentioned dual system has a noisefloor at about -110dBm
> on both receivers. I have no explanation why a dual system should be worse.
> Any idea?
>
> 73, Georg, DL2KP
>
>
>
>
>


-- 


Internet: in progress
**********************************************************************

IMPORTANTE/IMPORTANT                      CONFIDENCIAL/CONFIDENTIALITY

Este mensaje ha sido elaborado únicamente para uso de la persona
o entidad a la que es remitido, ya que puede contener información
personal, confidencial y de acuerdo a ley no puede ser difundido.
Si el lector de este mensaje no es el destinatario señalado, o la
persona responsable para entregar el mensaje a quien está dirigido,
advertimos que cualquier divulgación, retransmisión o copia de
esta comunicación esta estrictamente prohibida. Si usted ha recibido
esta comunicación por error, por favor sírvase informarlo de
inmediato al remitente por correo electrónico o teléfono y borrar
inmediatamente el mensaje original.
    

This e-mail may contain confidential and/or privileged
information. If you are not the intended recipient (or have
received this e-mail in error) please notify the sender
immediately and destroy this e-mail. Any unauthorized copying,
disclosure or distribution of the material in this e-mail is
strictly forbidden.

Diese E-Mail kann vertrauliche und/oder rechtlich geschuetzte
Informationen enthalten. Wenn Sie nicht der richtige Adressat
sind oder diese E-Mail irrtuemlich erhalten haben, informieren
Sie bitte sofort den Absender und vernichten Sie diese Mail.
Das unerlaubte Kopieren sowie die unbefugte Weitergabe dieser
Mail ist nicht gestattet.
**********************************************************************


---
Diese E-Mail ist frei von Viren und Malware, denn der avast! Antivirus Schutz ist aktiv.
http://www.avast.com