Re: FDM DUO Attenuator behaviour


Neil Smith G4DBN
 

Indeed it does, about 11.8dB 
Odd...
Neil

-------- Original message --------
From: Tony_AD0VC <canthony15@...>
Date: 06/02/2020 19:17 (GMT+00:00)
To: EladSDR@groups.io
Subject: Re: [EladSDR] FDM DUO Attenuator behaviour

Assuming a 50 ohm load, that looks like a 12-13 db attenuator to me (?).

Tony


From: EladSDR@groups.io <EladSDR@groups.io> on behalf of Neil Smith G4DBN <neil@...>
Sent: Thursday, February 6, 2020 10:07 AM
To: EladSDR@groups.io <EladSDR@groups.io>
Subject: Re: [EladSDR] FDM DUO Attenuator behaviour
 

Attenuation is fixed at 20dB Bob, R67/68/69 switched in by RL2.

I guess you are hearing the faint click of RL2 when you enable attenuation? If you can measure the input impedance, you could check if the input impedance goes weird, with R69 gone open circuit or a relay contact fault or a short to ground.

Full input diagram is attached to message https://groups.io/g/EladSDR/message/14141

Neil G4DBN

On 06/02/2020 16:17, Bob G3PJT wrote:
When I set the attenuator all the signals disappear. Its as if the antenna is disconnected
Is there a setting somewhere to set the level of attenation. My DUO has only just started to do this
I have done a reset and no change
Any ideas?
73 Bob G3PJT

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