[R-390] computer swtiched source

[GENE BALINSKI]

ALCON,
 
RE: Laptop PS.   I had to purchase a replacement PS for my HP laptop as the original died.  I bought a unit from ePay.  

It charges the battery just fine.  It is also a MILITARY GRADE JAMMER!   It is so bad, that I cannot listen to the local 50 kW AM news station (I am 35 miles away) on my clock radio upstairs when the charger is plugged in downstairs!  It also clobbers 160 - 15 and even up to 10m.  

Yes it was made in China.  However least you think that it is only the cheap Chinese gear that is the culprits, the switching PS INSIDE my HP printer exhibits similar characteristics, and must be completely unplugged (not just turned-off) for the RFI to stop.  It may be from China as well. That cannot be easily determined.     

I have used a Radio Shack in-line AC noise filter.  It actually **did** make some difference, but not enough to reduce the 40 noise level much below ~ S-7. Perhaps the filter just reduced the power line conducted emissions while leaving the radiated emissions.   

73, 
Gene K1NR 


> On 01/30/2022 10:03 PM Larry H <larry41gm at gmail.com> wrote:
> 
>  
> Hi Jose,  Unfortunately, some laptop power supplies generate very bad emi.
> And, it's not  just laptop supplies, it's a lot of 'wall warts' that are
> major offenders.  And the bad thing is that with most 390s and other rx's
> with good power line filters built in, the emi from the wall warts enters
> the rx through the antenna, and not the power line.  You can test this
> fairly easily by tuning in the emi and then disconnecting your antenna.
> When you do this, make sure you have tube shields on for the sensitive
> tubes,  all covers on the 390, and it is correctly grounded.
> 
> So, the answer to your question is: no, an additional emi filter in the
> power line of a 390 will not help.
> 
> If you are not using coax or twisted pair to feed the 390, then that makes
> it much easier for noise to get into the rx.
> 
> Regards, Larry
> 
> PS: Please delete any unnecessary verbiage at the end of your post
> before you send it to the server.  Thanks.
> 
> On Sun, Jan 30, 2022 at 11:59 AM jm <josemic at gmail.com> wrote:
> 
> > Hi guys,
> >
> > I've realised that the noise level increases when the power source of the
> > laptop is on. In that case, the noise  makes extremely difficult to hear
> > weak signals.
> >
> > Found on ebay some kind of device called "EMI individual phase noise
> > filter" to be placed between the line and the radio. It's very cheap but I
> > don't know whether or not would be useful.
> >
> > Does somebody have any experience with such type of device?
> >
> > Thanks, and regards
> >
> > Jose
> > EA8DCP
> >
> >
> >
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