Modem Killing HF? Try This LOL

[ridgescan]

I knew I was saving this Zenith Transoceanic shell for something
Transoceanic Faraday Cage - YouTube

The complete noisekill happened when the ground jacket on the modem contacted the metal of the shell-which leads me to think that the enclosure should be grounded. Any experts please jump in!

 

[KC4RAF]

Ridgescan, that's quite interesting info you posted.

You can bet there will be some on this site that will try your trick and feel blessed that you shared with 'em!!! It really made a difference to your overall reception ability. Thanks for sharing with us sir.

 

[ridgescan]

I hope this helps someone else I was pretty happy when I tried it. Thanks Rafdav.

 

[corbintechboy]

Nice find.

I just wonder how many people have the shell of that radio laying around? I may end up surprised.

 

[GTR8000]

Nice going! Another thing that really helps is using shielded LAN cables. UTP absolutely kills low frequencies, the cable becomes a radiating antenna spewing out all that horrible Ethernet hash/RFI. If you do decide to try shielded cables, just make sure your modem/router/LAN card have the metal shielding around the jack, otherwise they won't work as intended because the shield won't be grounded. Some of the cheaper devices lack the shielding and are all plastic.

 

[ridgescan]

Nice find.

I just wonder how many people have the shell of that radio laying around? I may end up surprised.

ha me too CTB! But I imagine you could use any metal enclosure. A bonus is that shell is in pretty good shape so I stood it in the corner and it's like a faux Zenith on display (this was a parts donor-luckily I have a working one too).

Nice going! Another thing that really helps is using shielded LAN cables. UTP absolutely kills low frequencies, the cable becomes a radiating antenna spewing out all that horrible Ethernet hash/RFI. If you do decide to try shielded cables, just make sure your modem/router/LAN card have the metal shielding around the jack, otherwise they won't work as intended because the shield won't be grounded. Some of the cheaper devices lack the shielding and are all plastic.

Good tip Chauffeur6. This was so strong I was getting it on the table radio on MW out in the living room! Not any more

 

[zl2taw]

ok with the modem, if you removed the cables & used wireless only would that work or is the modem itself radiating the noise ?

I see its not a wireless modem, but I have one & curious if its worthwhile getting usb wireless sticks ?

 

[mitaux8030]

ok with the modem, if you removed the cables & used wireless only would that work or is the modem itself radiating the noise ?

I see its not a wireless modem, but I have one & curious if its worthwhile getting usb wireless sticks ?

Its the Ethernet cables that are acting as an 'antenna' radiating that noise. So removing those 'antennae' and using wireless instead would definitely cut down on the noise. The case of the modem shouldn't radiate much if any. If you must use Ethernet cables, some hints to keep the noise down are:
Use shielded Ethernet cables, and ensure at least one end is earthed.
Keep the Ethernet cable as short as possible, and use as few of them as possible.
Set the speed to 10BaseT. The higher the speed, the higher in frequency into the HF spectrum they'll cause interference.

But eliminating the Ethernet cables all together by using wireless would be the biggest benefit. It certainly helped a lot here.

If its a DSL modem, then the DSL telephone line is also going to be a source of noise as well. DSL is effectively pumping hundreds of RF data carriers down the telephone line at LF, MF & lower half of HF. There's not a lot you can do about that.
If its a cable modem with coax feed, there shouldn't be too many problems with those - just make sure all the connections are tight and unsure good double/triple/quad shield coax is used.

 

[ridgescan]

In my case with this particular modem, the cables are not emitting-the modem is. It's pretty clear in the video that all the cables are outside the box. Matter of fact, my body was an emitter as I held the modem and at about 1:03 you can hear the remaining RFI drop off as I let go my left hand from it. That shows you how strong this RFI is.
zl2taw-do what I'm doing-experiment and see what works

 

[Violation]

Good job, Ridge. Kinda like the "Tip of the day"........PW

 

[ridgescan]

Thanks V throw that damn modem in a box!!

 

[7designs]

I see its not a wireless modem, but I have one & curious if its worthwhile getting usb wireless sticks ?

Actually that modem is a wireless modem. My parents have the same one and I just set up the wireless on it last night. Makes the first wireless I have seen that is antenna-less too.

 

[7designs]

I have ran a ground wire to all of my computer equipment, switches and routers. Seams to help.

My main noise source was my main PC's power supply. I haven't replaced it yet, I just shut it off and use laptop when I am listening.

 

[k9rzz]

Lessons learned:

- never throw anything away

- knowledge is priceless (building a homebrew faraday cage to kill HF noise from a highspeed internet router? Oh yeah ... )

 

[ridgescan]

and don't forget the "ABE" rule-Always Be Experimenting ya never know what you may find!

 

[SCPD]

Its the Ethernet cables that are acting as an 'antenna' radiating that noise. So removing those 'antennae' and using wireless instead would definitely cut down on the noise. The case of the modem shouldn't radiate much if any. If you must use Ethernet cables, some hints to keep the noise down are:
Use shielded Ethernet cables, and ensure at least one end is earthed.
Keep the Ethernet cable as short as possible, and use as few of them as possible.
Set the speed to 10BaseT. The higher the speed, the higher in frequency into the HF spectrum they'll cause interference.

But eliminating the Ethernet cables all together by using wireless would be the biggest benefit. It certainly helped a lot here.

If its a DSL modem, then the DSL telephone line is also going to be a source of noise as well. DSL is effectively pumping hundreds of RF data carriers down the telephone line at LF, MF & lower half of HF. There's not a lot you can do about that.
If its a cable modem with coax feed, there shouldn't be too many problems with those - just make sure all the connections are tight and unsure good double/triple/quad shield coax is used.

This is why you buy RF-Shielded Ethernet cables. They do work.