Topband: Re Birdies

Jim Brown jim at
Thu Feb 21 13:05:45 EST 2008

On Thu, 21 Feb 2008 11:48:04 -0500, Alan Cook wrote:

>I am using a Linksys BEFW11S4  router. which is either wireless, wired
>or both.  I have run cables rather than open my self to interlopers 

There are very effective ways to use wireless and protect yourself from 
interlopers. A very simple one is to use authentication by MAC address. Go 
into the setup menu of the router, find the advanced settings for that 
function, and enter the MAC address of each of YOUR wireless cards, then turn 
that function on. 

>a mobile home park) and removed the router's antennas. 

The antennas are tuned to 2.4 GHz, and won't affect RFI in the HF and VHF ham 

>there is a severe
>birdie right on 50.125, which is the calling frequency on six meters.
>I can only eliminate this problem by disconnecting the power to the

Not surprising -- it is commonly radiated directly from the wiring within the 
router because it is not well shielded. OR it may also be radiated by the 
power supply wiring to the router. 

>the CRT noise only goes away when the ac power is disconnected from the 
>monitor, irregardless of it being on or off.  

That suggests it is the POWER SUPPLY for the monitor that is the cause of the 
problem. Again, not at all uncommon -- switching power supplies for all sorts 
equipment are common sources of RFI to us. 

To better understand what is going on, I suggest you study my RFI tutorial.


Jim K9YC

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