+++++++++++++++++++++++++++++++++++++++++++++ Date: Thu, 05 Apr 2001 18:42:58 -0600 From: Larry East Subject: Re: [Elecraft] Antenna static build up and the K2 At 08:36 PM 4/5/01 +0100, DeniGm3skn wrote: >Looking for a recommended method of continuous bleeding of static charge >from my antennas, (NOT a spark gap please) and NOT looking for lightning >protection. I am going to operate portable with a kite lifted antenna wire >worked >against a counterpoise. I have done this before and was plagued with static >shocks and very concerned about zapping my Rx front end or worse! I know it >is possible to use a bleed resistor of say 50k ? That's a very workable solution -- I install 1 or 2W resistors in the range 10K - 100K in all my antenna tuners (that don't already have a DC path to ground via an inductor) and that has eliminated static build-up problems. A choke would also work, but one might encounter problems with self resonance. Not a problem with a carbon resistor -- DON'T use a wire-wound resistor! On a windy, dusty day here in Idaho, I can get a 1-in. arc from my long-wire if the resistor path to ground is removed! :-) 73, Larry W1HUE/7 +++++++++++++++++++++++++++++++++++++++++++++ Date: Fri, 6 Apr 2001 19:12:54 -0400 From: "Michael Harris" Subject: Re: [Elecraft] Antenna static build up and the K2 Hi, > On a windy, dusty day here in Idaho, I can get a 1-in. arc from my > long-wire if the resistor path to ground is removed! :-) Recently, during a distant thunder storm I noticed that there was much rattling of the relays in the K2 whenever there was a lightning discharge. Both ANT 1 and 2 had antennas connected, one a long wire with counterpoise, the other a delta loop. Needless to say both antennas were removed immediately. The relay rattling stopped. The K2 was battery powered with no real connection to ground. Regards, Mike VP8NO GQRP-10148 (GD18BH) IOTA SA-002 K2 #1400 +++++++++++++++++++++++++++++++++++++++++++++++++++ Date: Sat, 07 Apr 2001 10:15:20 -0600 From: Larry East Subject: [Elecraft] Static Discharges, etc. Someone pointed out that there is a DC path to ground via a couple of resistors from the K2's antenna jack. However, this is the "basic" antenna jack which is not used if the autotuner is installed. There are NO DC paths to ground from the two autotuner antenna jacks when the relays are not energized. And someone also made the comment that he heard relays popping when his K2 was off, antennas were connected and there was a thunderstorm in the area. So ... seems like a good idea to put resistors to ground across the antenna jacks in the K2 tuner. The jacks are mounted to the board that is accessible when the top cover is removed, so adding resistors to ground is a simple thing to do. I used 47K 1/2W resistors. Someone mentioned that 1W-2W resistors should be used as static bleeders because of "the high voltage involved" -- however, the whole idea of adding a static bleeder is to keep any high voltage from developing. I therefore believe that a 1/2W resistor is fine -- probably a 1/4W would be OK as well. And anything physically larger than 1/2W across the ANT 1 jack would interfere with the 160M module if it is installed. And on the subject of the 160 module, I also added a 47K resistor across the aux. receive antenna jack. Better safe than sorry. Of course, the best cure is prevention -- which means remove antennas from the rig when it is not in use! But I sometimes operate on windy days (like today...) and some pretty large static buildups can occur on my GAP vertical and my inverted vee. (My longwire has a 9:1 matching transformer with a DC path to ground outside the house ... so no problems from it so far.) I hope this does not start a whole new thread about "lightning protection" (which a bleeder resistor IS NOT), the proper size of resistor to use (anything from 10K to 100K seems fine to me), what wattage resistor to use (I already stated my views on that), etc. :-) 72/73, Larry W1HUE/7 ++++++++++++++++++++++++++++++++++++++++++++ Date: Sat, 7 Apr 2001 13:00:13 EDT From: LHLOUSEK at aol.com Subject: Re: [Elecraft] Static Discharges, etc. Hi Larry, <<>> That was me. I was wondering when you were going to come back to me on that. You can put an ohmmeter on the active ATU jack or the direct jack and see that you will always get less than an ohm to ground. Whether or not the power is switched on. The circuit from the active ant jack on the ATU and the unused direct jack are always connected to chassis ground. Only the non active ATU jack is open circuit. All the inductors in the ATU are in series so as far as DC goes, it doesn't matter which position the inductor relays are in. You will always have DC continuity from the active ATU jack through the ATU. (Being energized or not isn't relevant since the relays are latching and could be in any state.) Once past the ATU there are the resistors to ground in the RF Output Detector (abt 1.75K) and once through the low pass filter the secondary of the power amp output transformer is always in the circuit and connected to ground. It is possible for all the relays in the low pass filter to be open, in which case the only path to ground would be through the RF output detector. I don't believe that to be a normal state of the unit, however. I always keep a small dummy on the unused ATU jack but if an antenna was hooked up I would think a bypass resistor might be a good idea and certainly wouldn't hurt. Luigi W7DZN +++++++++++++++++++++++++++++++++++++++++++++ Date: Sat, 07 Apr 2001 12:05:43 -0600 From: Larry East Subject: Re: [Elecraft] Static Discharges, etc. At 01:00 PM 4/7/01 -0400, you wrote: >Hi Larry, > ><<resistors from the K2's antenna jack.>>> > >That was me. I was wondering when you were going to come back to me on that. > >You can put an ohmmeter on the active ATU jack or the direct jack and see >that you will always get less than an ohm to ground. Whether or not the power >is switched on. ...etc... Well, yeah, you are right! However, I STILL like resistors to ground directly across the antenna jacks so pulses generated by distant lightning discharges don't have to go through inductors, capacitors, etc. before finding a path to ground. Probably doesn't matter for plane 'ol static buildup, so I stand corrected on that point. And I suppose for pulse stuff, the physical size of the resistor might matter ... but I'll stick with 1/2W carbon composition resistors across the K2 antenna jacks. I also have 10K 2W resistors and gas discharge tubes across the antenna feeds inside a remote antenna switching box mounted out in my "antenna farm", so the bleeder resistors in the K2 are rather redundant when operating from my home location. But not when operating from the field (which I occasionally do). I know I should have kept my fingers off the keyboard... :-) 72/73, Larry ++++++++++++++++++++++++++ Reply-To: From: "Ron D' Eau Claire" To: "elecraft" Subject: RE: [Elecraft] Grounding Date: Sun, 17 Feb 2002 12:40:24 -0800 Dave G3YMC wrote: > ...Having strung an antenna up and leaving its feeder across > the floor... we suddenly saw large sparks > between the feeder and > the metal surrounds of the floor tiles! There was no sign of > thunder anywhere in > sight. I have seen that happen on ships while stringing a new wire MF antenna. Normally, they are carefully grounded at all times, either through the ATU or direct to ground by the antenna switch on the radio console when they are not in use. Wind and even rain can build up tremendous static charges on a well insulated antenna. I got into the practice of making sure that the wire itself was always grounded at one end while we were stringing a new antenna after seeing a buddy get knocked off of his feet when he reached up to grab the end of an antenna wire that was sitting on a non-metallic surface one windy day. It was more surprise than shock, but enough to make me more cautious. And it's never comfortable or safe to be "knocked off of your feet" on a steel ship with steel decks and steel bulkheads . And, of course, it does not take a direct hit from lightning to put fantastic voltages and currents in the wire. A hit in the neighborhood even some distance away can induce a surge in an antenna wire that instantly make toast any rig... or the operator. Ron AC7AC K2 # 1289 +++++++++++++++++++++++ From: "Rick Shindley" To: Date: Sun, 17 Feb 2002 15:31:25 -0600 Subject: [Elecraft] Antenna grounding idea When I had to select an antenna I first got an R7 vertical (no flames, please!) because it looked cool and I have a small lot. I placed a lightning arrestor at the base of the vertical. Occassionally I would hear repetitive "pops" from the receiver as the spark gap discharged. I didn't figure this out right away. The receiver became useless at times due to the incessant discharges. >From an old Air Force safety film, I remembered that the electric potential in clouds is followed by an equal, but opposite, charge along the ground beneath the cloud (ground is not a perfect conductor so local potential differences can exist). Clouds would pass over my R7 vertical and an opposite charge on the ground increased the potential difference between the driven element and ground (the ground potential changed but the insulated driven element remained at its original potential (probably zero volts)). When the voltage got to be too much, a spark would occur! I tried loading the arrestor with a 1k resistor to bleed off electric potential. Apparently the resistance could not conduct the charge away fast enough. Later, I switched to a ladder line-fed dipole and experienced the same phenomenon. Finally, I bought a 4:1 balun and placed it outside the house and grounded the center tap on the antenna side (ladder line to ant). I ran coax into the house (abt 10 ft) and to the K2 (now with a KAT2). No more static discharges! Both dipole elements are at DC ground, so no charge buildup can occur. I hope this idea helps someone! Rick KC0OV K2 1360 +++++++++++++++++++ From: "Don Wilhelm" To: "Rick Shindley" , Subject: Re: [Elecraft] Antenna grounding idea Date: Sun, 17 Feb 2002 19:12:14 -0500 Rick and all, It used to be common practice back in the 'old' days when we made our own vertical antennas - to put an RF choke across the feed end of the vertical to bleed off static charges. A 44 uH inductor at 160 meters has about 500 ohms reactance and anything bigger will work FB. Wind 12 to 15 turns of wire (I suggest #20 wire) on a FT114-43 toroid core - connect one side to the antenna and the other side to ground. This is not lightning protection!!! - it is only to bleed off static charges that can lead to pops and clicks in your receiver. A 4:1 balun will also do the same function - but a 1:1 current balun will not. You could use a similar inductor at the feedpoint of a dipole or use it at the shack end of the feedline. If you are using a multiband antenna, figure the impedance of the antenna system at the point you want to place the RF choke - and size the RF choke so it has about 10 times the impedance of the antenna system at that point - otherwise the RF choke may be too small and swallow up part of your precious watts. 73, Don Wilhelm - Wake Forest, NC W3FPR home page: http://www.qsl.net/w3fpr/ QRP-L # 485 K2 SN 0020 mailto: w3fpr at arrl.net ++++++++++++++++++++ From: "Don Brown" To: "Wallace, Andy" , Subject: Re: [Elecraft] potential of static damage Date: Fri, 14 Mar 2003 12:40:59 -0600 Hi The KPA100 has a big choke connected from ground to the antenna connector placing the antenna a DC ground. The basic K2 the DC path is from the antenna through the LP filter toroids and T4 to ground so the antenna is also at DC ground. In the K1 the RF detect circuit is across the antenna placing 1.7K to ground discharging any static build up Don Brown KD5NDB > > -----Original Message----- > > From: Wallace, Andy > > > > An interesting side-conversation: what sort of protection do the > > K1/K2 have against ESD coming from the antenna? (Wind can induce > > static charge there, too, as you say.) > > > > Andy > > Whoops - to clarify, I don't mean ESD at the antenna damaging > devices in general, inside the rig; I mean damaging RF circuits > DIRECTLY in the signal path -- front end FETs, etc. > > In the old days, they had neon lamps between the antenna jack > and ground, etc. > > Andy ++++++++++++++++++ Reply-To: From: "Ron D'Eau Claire" To: "'Wallace, Andy'" , Subject: RE: [Elecraft] potential of static damage Date: Fri, 14 Mar 2003 14:10:56 -0800 I don't have a K1. On the K2 there is a 1.5k path to ground from the antenna terminal r-f detector circuit, so I'd not expect a damaging amount of static to able to accumulate on an antenna. What would be of concern to the front end, as in ANY rig, is the induced surge from a nearby lightning strike. In that case everything in the house from the phones to the TV is also at risk, especially if you have above-ground utilities. Ron AC7AC -----Original Message----- An interesting side-conversation: what sort of protection do the K1/K2 have against ESD coming from the antenna? (Wind can induce static charge there, too, as you say.) Andy ++++++++++++++++++++ From: "Leo Starrenburg PA5LS" To: "Elecraft Reflector" Subject: Re: [Elecraft] potential of static damage Date: Fri, 14 Mar 2003 23:28:41 +0100 > What would be of > concern to the front end, as in ANY rig, is the induced surge from a > nearby lightning strike. Hi Ron and Elecrafters, a couple of months ago we had a strike of lightning nearby, and I had left the antenna connected to my K2. There was no damage other than a "confused" K2: I had to do a full reset and re-program my personal settings. After this experience I rearranged the layout of the antenna feeders to allow for easy disconnecting the antennas from the rigs after operation. 73' Leo. ++++++++++++++++++++ From: "Bob - AG5Q" To: "Elecraft Reflector" Subject: Re: [Elecraft] potential of static damage Date: Fri, 14 Mar 2003 16:56:12 -0600 When a transmission line is completely disconnected, there may be a charge build-up. I've seen this happen even in a light rain with no lightening activity present. When connecting an antenna, short the center conductor before sticking it in the antenna connector. The xcvr's internal resistance to ground can probably prevent a gradual voltage build-up after the antenna is connected, but the capacitance of the already charged up transmission line may give it a big jolt. 73/ Bob - AG5Q ++++++++++++++++++++ From: "Karl" To: "Bob - AG5Q" , Subject: Re: [Elecraft] Charge build-up on antennas Date: Wed, 21 May 2003 17:48:57 -0500 Your idea of a shunting resistor across the antenna terminals (I'd do it at the antenna insulator) of about 50K to 100K will do just fine. Some folks use r.f. chokes, but they are not as "broadbanded" as a 1-watt carbon resistor of 50-100K. Yes, a one-watt resistor, at 50-100K will handle over a kilowatt of transmitted power IF the VSWR at the feedpoint is reasonable. A little known fact: the water pouring from the shower head in your home can produce as much as 15 kV of static electricity! Now let's see.... where do I connect that 100K resistor in my armpit to the shower stall? Karl K - W8TIF McKinney, Texas ----- Original Message ----- From: "Bob - AG5Q" To: Sent: Wednesday, May 21, 2003 5:03 PM Subject: [Elecraft] Charge build-up on antennas > During a rainstorm, how fast does charge build up on an antenna? > I suppose the area of the wires and tubing would affect this, as > well as the amount of rain and wind. I'm wondering if a large resistor across the antenna connector (say, 10K to 100K) would be able > to discharge an antenna that is not connected to a rig or is a much smaller resistance required (like a short circuit) to limit the > voltage to no more than a few volts. > > I'm assuming just an ordinary rain storm and neglecting the effect of lightning in the area. > Several years ago I noticed enough charge building up on a 20 meter dipole to jump across a small air gap of a ground switch that > wasn't closed completely. This occured during a light rain storm. However, I didn't take any quantitative data at the time. > > This is a potential hazard to a rig if you connected an antenna without shorting the connector terminals first, but would it be > enough to just put a resistor across the connector? > > 73/ Bob - AG5Q > ++++++++++++++++++ From: "Stuart Rohre" To: "Bob - AG5Q" , Subject: Re: [Elecraft] Charge build-up on antennas Date: Wed, 21 May 2003 22:03:39 -0500 You get static build up from any friction, wind, sandstorm, etc. The resistor will discharge the build up. The one watt suggested is fine and more durable than 1/2 watt resistors, unless you use flexible braid for leads. A wind storm took out the 1/2 watt resistor we had on the club G5RV across the center insulator. But, it is nice to have a discharge resistor when the wind gets going. 73, Stuart K5KVH +++++++++++++++++