+++++++++++++++++++++ Date: Sat, 16 Feb 2002 07:23:50 -0800 From: Tree N6TR To: cdh at hctc.net, elecraft at mailman.qth.net Subject: Re: [Elecraft] Grounding & Receivers > Two questions: I find a lot of info on the K2's receiver being very > good. Is the K1's receiver just as good? No. But that really depends on what attributes you are looking for. For many applications, they can be considered the same. For maybe one or two, the K1 is a better receiver. However, the K2 has so many more features, it is hard to compare them. > What types of grounding do most use on the K2? I want to be able to > operate from second story and grounding is a problem with higher > powered rigs...does the K2 have this problem? I made the first answer short to make up for this one. This depends on what you perceive your grounding problem to be. The short answer is that grounds are really independent of what type of radio you have. One radio isn't going to "need" a ground more than another. However, if you are feeling that you need a ground because you don't like getting RF burns - then the answer could be yes since the K2 (being a QRP radio) will probably not generate enough RF to create a burn... although in the right circumstances, it still could. Your antenna has a lot more to do with your ground situation. I once operated from an apartment - and probably experienced similar problems to the ones you are having. It is not essential to have a ground for your radio. Most "proper" antennas provide their own ground reference if you will, and there should be no current wanting to flow from your radio to ground. But, you probably don't have a proper antenna in an apartment. To solve this problem, you will need to describe your antenna configuration and what bands you are trying to operate on. Hopefully, with this information, some suggestions could be made about changes that would help eliminate your ground "problem". >From a simple perspective, you might think about quarter wave wires to act as ground stubs for the frequencies you are trying to use. If you are using a simple wire out the window, then these become the other half of your antenna - and the radio is sitting at the feedpoint. Quarter wave wires are about 256/frequency (in MHz) feet long. They will work for odd multiples (one for 40 meters will work for 15 as well). 73 Tree N6TR tree at kkn.net +++++++++++++++++ Reply-To: "Don Wilhelm" From: "Don Wilhelm" To: , "Dudley & Mona Henderson" Subject: Re: [Elecraft] Grounding & Receivers Date: Sat, 16 Feb 2002 12:14:17 -0500 ----- Original Message ----- > > What types of grounding do most use on the K2? I want to be able to > operate from second story and grounding is a problem with higher > powered rigs...does the K2 have this problem? > Dudley and all, I will jump in here with one of my hot buttons - Grounding!!! RF ground is not the same as AC ground is not the same as Lightning ground is not the same as Earth ground!!! (But they CAN be the same - they DO function differently and for different purposes). The ground pin on your AC receptacles should take care of any AC grounding concerns assuming that your house, apartment, etc. is wired in compliance with NEC standards of the past 30 or more years. There is no need for an RF ground on any receiver. The need for an RF ground comes into play with the antenna system. If you are using a truly balanced antenna system, one side of the antenna system works as an RF ground for the opposite side. If the antenna system is unbalanced, an RF ground must be provided somewhere in the radiating path - and that point is usually not at the transmitter/receiver - it is things like the ground system for a vertical antenna or the counterpoise on a ground plane antenna (just because it has ground in its name does not mean that it needs to be connected to earth ground - it acts as the 'ground' reference for the vertical {or other} part of the antenna). In some installations (like an end fed antenna), the antenna feedpoint is brought right into the shack and connected to the transmitter/reciever and this is the situation when an RF ground must be provided right at the transmitter/reciever. That kind of an RF ground could be provided with quarter wavelength wires - one for each band of operation. (The quarter wavelength wires also are often used to cure difficult cases of "RF in the shack" in addition to any normal RF ground reference) Lightning ground is a whole different consideration - lightning contains Mega-Amps of current over a very wide range of frequencies (DC to Daylight) and requires really fat multi-wire conductors to provide a path for a direct hit and this much power will make its own path - most anywhere it wants and finds easiest. The normal ham cannot afford really good protection against a direct hit - leave that stuff for the commercial radio installations. The best advice is - do not operate when a lightning storm is nearby AND get those antenna feedlines outside. Even lightning many miles away can produce a very large voltage across an antenna feedline - the antenna is capable of picking up RF - and lightning contains a lot of RF itself which can be induced into the antenna system. Yes, do ground those feedlines when not in use - the best thing is to ground them outside and ground them to a GOOD earth ground. Install lightning arresters on any feedline just to be safer, but do not depend on them - there will not save you or your equipment in the event of a direct (or very close) lightning strike. If you are in a second floor apartment, this part could cause you a problem to implement properly, and when faced with a similar situation in times past, I simply put the feedlines outside and crossed my fingers. Get a good earth ground connection outside the building the shack is located in for this purpose if you possibly can. OK, soapbox off now- just be safe and understand the limitations of your grounding system. 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: WA9GQT at aol.com Date: Sat, 16 Feb 2002 13:03:43 EST To: elecraft at mailman.qth.net Subject: [Elecraft] Grounding Yes! Always disconnect and ground antennas to earth when not in use. Never operate when a storm is nearby. I had a second story shack once and used a ground wire running down along the siding to earth ground. I always grounded my antennas to that ground wire when I was off the air. One day the antenna got disconnected from the ground by about 3/4 to 1 inch. There was a nearby storm & I happened to check my shack & noticed a spark jump from the ground wire to the antenna. WOW. Just think if a radio had been connected to that antenna!!! This system worked for me even when we had a direct hit in our backyard. I think there is truth about the ground umbrella affect! Never fried a radio yet! 73, Rod WA9GQT K2 # 1900 +++++++++++++++++++++ From: "James Giercyk" To: "Dan Barker" , "Elecraft" Subject: Re: [Elecraft] Grounding & Receivers Date: Sat, 16 Feb 2002 17:47:16 -0500 There is no such thing as lightning protection, just lightning precaution - BE VERY CAREFUL....please ++++++++++++++++++++++ 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: "Stuart Rohre" To: "Dudley & Mona Henderson" Cc: "elecraft" Subject: Re: [Elecraft] Grounding & Receivers Date: Mon, 18 Feb 2002 14:09:52 -0600 Dudley, If you review the Elecraft achieves, I think some who have the K2 and then bought the K1 noted the receiver is not quite as good as the K2. The K1 sells at a lower price point and does not have all the features of the K2. Grounding the K2 is only needed as a safety measure to operation around storms. But, far better is to not ever leave it connected to an antenna if storms are even 50 miles away and approaching. Antennas in wind can build up high voltage static charges, and discharge thru a front end even on a grounded receiver, even if no storm is near. You can mitigate this on dipoles by having a discharge resistor across the end of the feedline of say 150 k ohms. You can, on a second story, address any RF in the shack issues if they arise, by use of quarter wave counterpoises attached to the rig chassis. You do not want, from a second story, to run a single ground conductor all the way to earth, as its RF length will be resonant on the higher bands. This could add to RF in the shack. RF in the shack is mainly a problem of improperly matched to the antenna, high powered, rigs. RF in the shack is not much of a problem with balanced antennas, beams, and loops. It is a problem with shortened verticals that are end fed, end fed wires, Zepps end fed, or any unbalanced antenna arrangement, such as random wires. I have never had RF in the shack from a resonant horizontal dipole, or half wave center fed vertical dipole. 72, Stuart K5KVH ++++++++++++++++++ From: "Guy Olinger, K2AV" To: "Elecraft Reflector" Subject: Re: [Elecraft] potential of static damage Date: Fri, 14 Mar 2003 21:43:37 -0500 For those of you worrying about grounding, part of the problem in understanding what goes on is that the amount of charge delivered by a lightning strike completely overwhelms the ability of the material in the "ground" to "absorb" the strike. For most of our everyday uses, the ground is a huge electron sponge that behaves as a huge neutral. Not so in a lightning strike. The capacitor effect formed by a charged cloud overhead can accumulate the opposite charge over hundreds of acres below. When a strike occurs, the short circuit to the capacitor occurs JUST AT THE POINT OF THE STRIKE. This means that all the charge meant to neutralize acres of opposite charge is present in a tiny area around the point of the strike while the opposite charge is still spread over the acres. The next thing that happens is that the huge charge at the strike, and the opposite charge all over the acres flow toward each other to neutralize each other. This can occur with an ionized path in the ground itself (killer of buried telephone cables) or in a "wave" that spreads out over all or a large part of the compass. THAT is when all of the damage occurs that is not precisely at the point of the strike. This is sometimes called induced, though that is a bit of a misnomer. There will be a very large current that will spread out from the strike point, that does not come to equilibrium until the opposite charges are satisfied. This ground charge equalization current is subject to the same ohms law and impedance issues as any current. What goes wrong if ALL THE GROUNDS IN AND AROUND THE HOUSE are not tied together? Remember that the charge is moving AWAY FROM the strike point to equalize. The house may have a crawl space or a basement. Either is a BLOCK to current. The crawl space will be drier than around the house (or you wish it was) and less conductive. The basement is just an impassible block. Grounds on the strike side of the house will charge up to whatever the ground is as the charge "wave" goes by. If that ground is directly and heavily connected to a ground on the other side, the charge will use the ground tie to move through/under/whatever your house to the other side. If not? For the period of time that it takes for the charge to move AROUND the house (not long, really, but long enough), the strike-side GROUND WILL BE HIGH POTENTIAL to anything connected to a ground on the other side of the house. If there is a connection, but it is circuitous, or has an impedance to it, and cannot carry a large surge current, the effect is reduced but still present. If there is not a single point entry and ground for EVERYTHING conductive, and I mean EVERYTHING, then grounds have to be connected across. EVERYTHING includes ANY conductor of ANY type leaving the house, including pipe, tubing, etc, besides RF and electrical connections. Failure to do so and you have the likes of one story already posted to this thread. This equation can be complicated by parallel conductors buried next to one another, etc, etc, but the principle remains the same. My son-in-law mistakenly left the neutral/safety ground leads ungrounded at an outbuilding that he ran power to. A lightning strike A QUARTER MILE AWAY in line with the power run put all the conduit in the building above ground (including the concrete floor), including the frame of the drill press he was using. He woke up five minutes later after being thrown 20 feet clear across the room. I think I was most fortunate not to have a death in the family that day. Takes far less than that to smoke a piece of electronic gear. 73 and stay safe, Guy. +++++++++++++++++++