USB Adapters and RF
Locked
 
|
I run legal limit on some contests. I seem to burn up USB to Serial devices. I am grounded properly. I am suspect of these things in high RF fields. But...what is a guy gonna do when RS232 Serial ports are totally discontinued. Turn down or turn off the amp. Hmmmmmm! Lee - K0WA In our day and age it seems that Common Sense is in short supply. If you don't have any Common Sense - get some Common Sense and use it. If you can't find any Common Sense, ask for help from somebody who has some Common Sense. Is Common Sense divine? Common Sense is the image of the Creator expressing revealed truth in my mind. - John W. (Kansas) Never interfere with anything that isn't bothering you. ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
|
|
Lee Buller wrote:
> >I run legal limit on some contests. I seem to burn up USB to Serial >devices. I am grounded properly. I am suspect of these things in high >RF fields. But...what is a guy gonna do when RS232 Serial ports are >totally discontinued. Turn down or turn off the amp. Hmmmmmm! > Look very carefully at that statement "I am grounded properly"; because the evidence suggests otherwise. More specifically, it suggests that the ground terminals for various parts of your shack are not correctly bonded together. Another very common source of RF in the shack is a bad shield connection inside a PL259. A few minutes applying a clamp-on RF current meter to various connecting cables could tell you a great deal. -- 73 from Ian GM3SEK http://www.ifwtech.co.uk/g3sek ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
|
|
Very interesting.... Maybe I should have said..."I think I am grounded properly!" I will have to check this out. Lee K0WA ________________________________ From: Ian White GM3SEK <[hidden email]> To: [hidden email] Sent: Wed, November 2, 2011 2:18:56 PM Subject: Re: [Elecraft] USB Adapters and RF Lee Buller wrote: > >I run legal limit on some contests. I seem to burn up USB to Serial >devices. I am grounded properly. I am suspect of these things in high >RF fields. But...what is a guy gonna do when RS232 Serial ports are >totally discontinued. Turn down or turn off the amp. Hmmmmmm! > Look very carefully at that statement "I am grounded properly"; because the evidence suggests otherwise. More specifically, it suggests that the ground terminals for various parts of your shack are not correctly bonded together. Another very common source of RF in the shack is a bad shield connection inside a PL259. A few minutes applying a clamp-on RF current meter to various connecting cables could tell you a great deal. -- 73 from Ian GM3SEK http://www.ifwtech.co.uk/g3sek ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
|
|
In reply to this post by k0wa@swbell.net
> I run legal limit on some contests. I seem to burn up USB to Serial > devices. I am grounded properly. I am suspect of these things in high > RF fields. It is odd that I just answered this same question in a different form on the N1MM Logger list ... > *Any time* one feeds an unbalanced antenna with coax and does not have > a current "balun" with a high choking impedance, the coax will act > like a random length "radial" or half of the driven element. When that > "radial" is an odd multiple of 1/4 wave long, the "end" of the radial > will be at a high RF voltage. Old timers will recognize this at the > "hot mic" (RF bites the lips!) scenario. When the RF voltage is high > enough, it can upset electronics ... a 5V P-P voltage at the USB port > of a computer/peripheral can "cancel" the 5V (or 3.3V in some systems) > USB power and shut down the port. RF voltages higher than 5V P-P can > result in *reverse bias* permanently damage some components. Bottom line, be *absolutely sure* to use choking impedance common mode chokes, properly installed, at the appropriate places in your antenna system. Proper points are at the antenna feed point and at the "entry window" to the building (outboard of the point at which the cable shields are grounded so the choke is working against a low impedance). If you can't do that, only purchase interface products that include a proper over voltage suppressor on the USB power line (to clamp any voltage to 0/+5.5V). Before anyone asks - I do not know which low cost USB to serial converters include voltage suppressors. 73, ... Joe, W4TV On 11/2/2011 2:34 PM, Lee Buller wrote: > > I run legal limit on some contests. I seem to burn up USB to Serial devices. I > am grounded properly. I am suspect of these things in high RF fields. > But...what is a guy gonna do when RS232 Serial ports are totally discontinued. > Turn down or turn off the amp. Hmmmmmm! > > Lee - K0WA > > > In our day and age it seems that Common Sense is in short supply. If you don't > have any Common Sense - get some Common Sense and use it. If you can't find any > Common Sense, ask for help from somebody who has some Common Sense. Is Common > Sense divine? > > Common Sense is the image of the Creator expressing revealed truth in my mind. > - John W. (Kansas) > > Never interfere with anything that isn't bothering you. > ______________________________________________________________ > Elecraft mailing list > Home: http://mailman.qth.net/mailman/listinfo/elecraft > Help: http://mailman.qth.net/mmfaq.htm > Post: mailto:[hidden email] > > This list hosted by: http://www.qsl.net > Please help support this email list: http://www.qsl.net/donate.html > Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
|
|
I see my cut/paste from the other reply left out some important information. The following is edited to add the missing references. *Any time* one feeds an unbalanced antenna with coax and does not have a current "balun" with a high choking impedance, the coax will act like a random length "radial" or half of the driven element. When that "radial" is an odd multiple of 1/4 wave long, the "end" of the radial will be at a high RF voltage. Old timers will recognize this at the "hot mic" (RF bites the lips!) scenario. When the RF voltage is high enough, it can upset electronics ... a 5V P-P voltage at the USB port of a computer/peripheral can "cancel" the 5V (or 3.3V in some systems) USB power and shut down the port. RF voltages higher than 5V P-P can result in *reverse bias* and permanently damage some components. There are two good tutorials on common mode chokes on-line - one by K9YC: http://www.audiosystemsgroup.com/RFI-Ham.pdf and one by W1HIS: http://www.yccc.org/Articles/W1HIS/CommonModeChokesW1HIS2006Apr06.pdf I strongly recommend studying both. Bottom line, be *absolutely sure* to use high choking impedance common mode chokes, properly installed, at the appropriate places in your antenna system. Proper points are at the antenna feed point and at the "entry window" to the building (outboard of the point at which the cable shields are grounded so the choke is working against a low impedance). If you can't do that, only purchase interface products that include a proper over voltage suppressor on the USB power line (to clamp any voltage to 0/+5.5V). Before anyone asks - I do not know which low cost USB to serial converters include voltage suppressors. 73, ... Joe, W4TV On 11/2/2011 3:59 PM, Joe Subich, W4TV wrote: > > >> I run legal limit on some contests. I seem to burn up USB to Serial >> devices. I am grounded properly. I am suspect of these things in high >> RF fields. > > It is odd that I just answered this same question in a different form > on the N1MM Logger list ... > >> *Any time* one feeds an unbalanced antenna with coax and does not have >> a current "balun" with a high choking impedance, the coax will act >> like a random length "radial" or half of the driven element. When that >> "radial" is an odd multiple of 1/4 wave long, the "end" of the radial >> will be at a high RF voltage. Old timers will recognize this at the >> "hot mic" (RF bites the lips!) scenario. When the RF voltage is high >> enough, it can upset electronics ... a 5V P-P voltage at the USB port >> of a computer/peripheral can "cancel" the 5V (or 3.3V in some systems) >> USB power and shut down the port. RF voltages higher than 5V P-P can >> result in *reverse bias* permanently damage some components. > > Bottom line, be *absolutely sure* to use choking impedance common mode > chokes, properly installed, at the appropriate places in your antenna > system. Proper points are at the antenna feed point and at the "entry > window" to the building (outboard of the point at which the cable > shields are grounded so the choke is working against a low impedance). > > If you can't do that, only purchase interface products that include a > proper over voltage suppressor on the USB power line (to clamp any > voltage to 0/+5.5V). Before anyone asks - I do not know which low > cost USB to serial converters include voltage suppressors. > > 73, > > ... Joe, W4TV > > > On 11/2/2011 2:34 PM, Lee Buller wrote: >> >> I run legal limit on some contests. I seem to burn up USB to Serial devices. I >> am grounded properly. I am suspect of these things in high RF fields. >> But...what is a guy gonna do when RS232 Serial ports are totally discontinued. >> Turn down or turn off the amp. Hmmmmmm! >> >> Lee - K0WA >> >> >> In our day and age it seems that Common Sense is in short supply. If you don't >> have any Common Sense - get some Common Sense and use it. If you can't find any >> Common Sense, ask for help from somebody who has some Common Sense. Is Common >> Sense divine? >> >> Common Sense is the image of the Creator expressing revealed truth in my mind. >> - John W. (Kansas) >> >> Never interfere with anything that isn't bothering you. >> ______________________________________________________________ >> Elecraft mailing list >> Home: http://mailman.qth.net/mailman/listinfo/elecraft >> Help: http://mailman.qth.net/mmfaq.htm >> Post: mailto:[hidden email] >> >> This list hosted by: http://www.qsl.net >> Please help support this email list: http://www.qsl.net/donate.html >> > ______________________________________________________________ > Elecraft mailing list > Home: http://mailman.qth.net/mailman/listinfo/elecraft > Help: http://mailman.qth.net/mmfaq.htm > Post: mailto:[hidden email] > > This list hosted by: http://www.qsl.net > Please help support this email list: http://www.qsl.net/donate.html > Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
«
Return to [K3]
|
1 view|%1 views
| Free forum by Nabble | Edit this page |