My antennas are always dc grounded and i lost a pin diode.
Sent from my iPad Chuck, KE9UW (Jack for BMW motorcycles) On Feb 22, 2013, at 12:12 PM, "Ron D'Eau Claire" <[email protected]> wrote: > Are you keeping your antennas grounded when they are not in use? It does not > take low humidity or wind or rain or snow to put an electric charge on your > antenna if it's well insulated. The action of the earth's atmosphere > maintains a huge charge between the ionosphere and the ground - almost > 400,000 volts - in spite of a constant leakage current through the > atmosphere from the ionosphere to ground of over 1,500 amperes. Near the > ground the voltage gradient is close to 100 volts per yard of altitude. > Given some time, depending upon the number of free ions in the air, an > insulated antenna will lose electrons until is develops the voltage > associated with its height above ground. And then, "pow" when you connect > the antenna to a piece of equipment and electrons from the earth rush in. > The amount of current is proportional to the mass of the insulated antenna. > > Nowadays any metal high above the ground in buildings is connected to an > earth ground, but in the past that was not always so, and workers were > occasionally shocked when they touched metal even on a dead calm day. > > At least one Ham, troubled by almost constant high-level popping QRN, > finally traced the source to a large copper cupola roof on his home that was > not grounded. At night, he could see occasional flashes of sparks from the > roof to nearby grounded metal even though the air was still. Bonding them > together fixed it. > > Usually these currents are so small that you are not aware of them, but the > voltages can be enough to puncture sensitive semiconductor gates and > junctions. The most sensitive areas in most rigs are in the diodes used in > the SWR bridge at the antenna jack or in diodes used in T/R switches. Other > semiconductors in a typical rig may be more sensitive to damage, but they > are well protected by the intervening circuits between them and the antenna > connector that provide a d-c path to ground. > > If an antenna has been left floating, connect it to an earth ground for a > moment before you connect it to the rig. > > Good quality antenna switches provide a d-c path to bleed off the charge as > it accumulates. The KAT500, for example, provides such a d-c ground path > whenever it is turned off and for any antennas connected that are not in > use. > > 73, Ron AC7AC > > > > -----Original Message----- > From: [email protected] > [mailto:[email protected]] On Behalf Of John K3TN > Sent: Friday, February 22, 2013 5:45 AM > To: [email protected] > Subject: [Elecraft] K3, KPA500 - PIN Diode Failure in KPA When K3 Subrx > Turned on During Xmit? > > Here's the set up: K3 to KPA500 to KAT500, all Aux bus connections. Began to > have high attenuation on receive when the KPA500 was turned from STBY to > OPER. Determined by Elecraft to be a blown PIN diode, which makes sense. But > why did the PIN diode blow? > > Could be that it just failed, could be I mistakenly QSYed and transmitted > with KPA at high power before KAT was tuned for new band. But I also > remember this scenario happening a few times before I noticed the RX > attentuation: > > Running N1MM software in a CW contest. I was transmitting some N1MM message > and while transmitting went to hit the ESC key to do something and instead > hit the ` key, which in N1MM turns on the sub-RX in the K3. In the heat of > a contest exchange, hard to remember exactly what happened but I think that > did cause a hard fault with the KPA. Not long after that the PIN diode was > blown. > > Craig, the guy who repaired my KPA, said he didn't see how an inbound SUBRX > ON command to the K3 while transmitting cause lead to a condition where the > K3 is transmitting into the KPA while the KPA is in RX mode, but I'd figured > I'd cast a wider net to see if it triggers any possible thoughts. I'm also > cross-posting to the N1MM reflector. > > John K3TN > > > > ______________________________________________________________ > Elecraft mailing list > Home: http://mailman.qth.net/mailman/listinfo/elecraft > Help: http://mailman.qth.net/mmfaq.htm > Post: mailto:[email protected] > > 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:[email protected] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
