[Linrad] Re: Receiving sometimes stop

[Isao SEKI - JM1WBB <gongon.com; iseki@xxxxxxxxxxxxxxxx>]

Hello Leif,

Thank you for your advice. I repaired (changing) DC power supply and
an electric fan is installed in side of the systems. So, the problem
is not reproduced. And, I am going to modify the first step of Delta
44 (GND cutting at Dsub connector) soon. I'm not old age but my eyes
are presbyopic...

73,
Isao / JM1WBB

On 2009/05/15, at 4:33, Leif Asbrink wrote:
> Hello Isao,
>
>> At this moment I have another problems. One is receiving
>> sometimes stops (noise level downs -5dB and receiving
>> internal birdie only) for 5-20 minutes and returning. I
>> guess my power supply cause a trigger and already ordered
>> new one. But anyone has same problem and fixed, please
>> let me know your detail.
> In case your power supply becomes overheated so it switches
> off or reduces the +15 or -15 DC supply (or both) you should
> see it easily with a volt meter. I am not aware of anything
> else that could produce a similar effect. Maybe better
> positioning could improve coolign?
>
>> Two is a internal birdie on center frequency of each pass
>> band. In problem one situation, also it is.
> The center frequency corresponds to DC voltages and they
> are not amplified by the Delta 44.
>
> Near the center frequency there is 1/f noise. The normal behaviour
> of the Delta44 without anything connected to it is shown here:
> http://www.sm5bsz.com/linuxdsp/hware/delta44a.htm
>
> The center spur can be slightly reduced by modifications on the
> Delta 44.
>
> During normal operation on 144 MHz when your preamplifier should
> lift the noise floor by about 15 dB the center spur should not
> be visible or very weak.
>
> 73
>
> Leif / SM5BSZ
>
>
> 

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