Re: Topband: Best Outlet sttrip
This discussion is beginning to confuse me. I thought the issue being debated was the optimal way to provide surge protection to safeguard our radios from unexpected line transients, and not how to reduce hum in unbalanced audio circuits caused by ground loops or ground return currents. I believe the conventional wisdom is that both whole-house surge protectors and local surge protectors in combination provide the most effective safeguard. I'm afraid I don't understand how a surge protector that clips an, e.g., 1KV spike on a 120 VAC line can end up doing more damage than no protection all. I understand that the clipped current pulse returns through the ground line and will cause a voltage spike on the ground, and I also understand that other interconnected equipment connected to different grounds may potentially see part of the spike, but on balance that seems to me to be a less dire situation than having no protection at all. 73, Jim W8ZR Sent from my iPad > On Oct 8, 2013, at 19:06, Jim Brown wrote: > >> On 10/8/2013 2:42 PM, Tom W8JI wrote: >> the system should not be that sensitive to common mode issues on ports. > > Right. But first, we're not talking about common mode, we're talking about > chassis-to-chassis noise coupling into unbalanced interconnects, like > computers feeding radios, with or without various interfaces. And yes, > unbalanced interfaces are a lousy way to do it, but I don't know of a single > ham rig that has balanced interconnects for audio or accessories. > > So unless a ham wants to rebuild every rig and all accessory gear with > balanced interfaces, the simple power and bonding concepts I've outlined are > the lowest cost, most reliable, and a very robust solution. Yes, we could > add transformers, but transformers cost more, and shielded transformers cost > a LOT more. > > As Vice Chair of the AES Standards Committee Working Group on EMC, I was a > principal author of all AES Standards on the topic. It took a while to reach > a consensus, because some purists were unwilling to write Standards to work > with real world equipment. The path we took, and that the cool heads worked > very hard to achieve, was to write Standards defining the RIGHT ways to do > it, both inside and outside of equipment, but to define the right way to work > with vintage gear that was badly designed/built. Our first EMC Standard, > AES48, attacked the Pin One Problem, which was the most critical root cause, > both at baseband and at RF. We then wrote the protocols for balanced > interconnects, including the advice that when the cable shield needed to be > interrupted to prevent shield current, the interruption should always be at > the receiving end. This is counter-intuitive, but Bill Whitlock showed that > it is the only right way. > > The point of this digression is that there's no way in hell that hams are > going to replace our gear with stuff having balanced I/O for audio and > control, simply because it doesn't exist, and to assume that such gear will > exist in the foreseeable future is wildly unrealistic. Heck -- we can't every > get manufacturers to build gear without Pin One Problems. > > 73, Jim K9YC > _ > Topband Reflector _ Topband Reflector
Re: Topband: Best Outlet sttrip
Sent from my iPad > On Oct 8, 2013, at 19:06, Jim Brown wrote: > >> On 10/8/2013 2:42 PM, Tom W8JI wrote: >> the system should not be that sensitive to common mode issues on ports. > > Right. But first, we're not talking about common mode, we're talking about > chassis-to-chassis noise coupling into unbalanced interconnects, like > computers feeding radios, with or without various interfaces. And yes, > unbalanced interfaces are a lousy way to do it, but I don't know of a single > ham rig that has balanced interconnects for audio or accessories. > > So unless a ham wants to rebuild every rig and all accessory gear with > balanced interfaces, the simple power and bonding concepts I've outlined are > the lowest cost, most reliable, and a very robust solution. Yes, we could > add transformers, but transformers cost more, and shielded transformers cost > a LOT more. > > As Vice Chair of the AES Standards Committee Working Group on EMC, I was a > principal author of all AES Standards on the topic. It took a while to reach > a consensus, because some purists were unwilling to write Standards to work > with real world equipment. The path we took, and that the cool heads worked > very hard to achieve, was to write Standards defining the RIGHT ways to do > it, both inside and outside of equipment, but to define the right way to work > with vintage gear that was badly designed/built. Our first EMC Standard, > AES48, attacked the Pin One Problem, which was the most critical root cause, > both at baseband and at RF. We then wrote the protocols for balanced > interconnects, including the advice that when the cable shield needed to be > interrupted to prevent shield current, the interruption should always be at > the receiving end. This is counter-intuitive, but Bill Whitlock showed that > it is the only right way. > > The point of this digression is that there's no way in hell that hams are > going to replace our gear with stuff having balanced I/O for audio and > control, simply because it doesn't exist, and to assume that such gear will > exist in the foreseeable future is wildly unrealistic. Heck -- we can't every > get manufacturers to build gear without Pin One Problems. > > 73, Jim K9YC > _ > Topband Reflector _ Topband Reflector
Re: Topband: Best Outlet sttrip
FlexRadio equipment has balanced audio i/o 73 Peter -Original Message- From: Topband [mailto:topband-boun...@contesting.com] On Behalf Of Jim Brown And yes, unbalanced interfaces are a lousy way to do it, but I don't know of a single ham rig that has balanced interconnects for audio or accessories. _ Topband Reflector
Topband: 160M Vertical
Hello all, Plan on working at getting back on 160 after a few years of being off the air. I last used an Inv.L and beverage. A meager configuration but served me well. I've been looking for a decent substitute for the inv.L since the nice tall tree I used has been cut down. Has anyone tried a Cushcraft MA-160V? Glad to see the Topband reflector is still going. Probably the most knowledgeable group on the net. Thanks, jim/k2hn _ Topband Reflector
Re: Topband: Best Outlet sttrip
On 10/8/2013 2:42 PM, Tom W8JI wrote: the system should not be that sensitive to common mode issues on ports. Right. But first, we're not talking about common mode, we're talking about chassis-to-chassis noise coupling into unbalanced interconnects, like computers feeding radios, with or without various interfaces. And yes, unbalanced interfaces are a lousy way to do it, but I don't know of a single ham rig that has balanced interconnects for audio or accessories. So unless a ham wants to rebuild every rig and all accessory gear with balanced interfaces, the simple power and bonding concepts I've outlined are the lowest cost, most reliable, and a very robust solution. Yes, we could add transformers, but transformers cost more, and shielded transformers cost a LOT more. As Vice Chair of the AES Standards Committee Working Group on EMC, I was a principal author of all AES Standards on the topic. It took a while to reach a consensus, because some purists were unwilling to write Standards to work with real world equipment. The path we took, and that the cool heads worked very hard to achieve, was to write Standards defining the RIGHT ways to do it, both inside and outside of equipment, but to define the right way to work with vintage gear that was badly designed/built. Our first EMC Standard, AES48, attacked the Pin One Problem, which was the most critical root cause, both at baseband and at RF. We then wrote the protocols for balanced interconnects, including the advice that when the cable shield needed to be interrupted to prevent shield current, the interruption should always be at the receiving end. This is counter-intuitive, but Bill Whitlock showed that it is the only right way. The point of this digression is that there's no way in hell that hams are going to replace our gear with stuff having balanced I/O for audio and control, simply because it doesn't exist, and to assume that such gear will exist in the foreseeable future is wildly unrealistic. Heck -- we can't every get manufacturers to build gear without Pin One Problems. 73, Jim K9YC _ Topband Reflector
Re: Topband: Best Outlet sttrip
Hi Jim, MOV from phase to green wire dumps current onto green, IZ drop on green back to the panel raises potential of that chassis. It has a low voltage (signal cable) to another box, plugged into another MOV strip at a different location, more current on green, probably not the same, probably not the same IZ drop. The difference appears on the low voltage interconnection and fries I/O for that interconnection. Same issue happens if the interconnection is to equipment with a different ground connection. I've seen MANY reports from engineers of destructive failures in small wired Ethernet systems in homes and small offices with no radios or towers involved. Likewise, large audio and video systems with equipment at widely separated locations have this issue. I worked in that field for many years, and we solved it by using series-mode protection on branch circuits. I understand your concern now, but that problem is really rooted in a design issue with the equipment. The system should not be that sensitive to common mode issues on ports. It is foolish or poor planning to think, by simply not clamping a distant line for surges, we somehow protect poorly designed input systems. A design sensitive to common mode places a burden on everyone else in the world to protect the poorly protected or designed ports. It's like saying "I'm going to do a bad job, so watch out for me". It is like the unrealistic dream that unbalanced audio lines from chassis-to-chassis, grounded at each chassis, is a good system and that all that needs to be done is be sure that all of the world's chassis are at virtually zero potential to each other. That just sets everyone up for problems. It is unrealistic to expect every piece of gear and system to ensure all non-clustered pieces of gear are at the exact same chassis potential. If something as simple as a MOV clamp causes a problem, you can bet the same gear will have problems from dozens of other causes. I suspect the real root of this is cheapness, where they want to avoid isolation and protection on the port and pass the blame or burden off on the rest of the world. MOVs are fine IF the bonding of grounds and equipment is properly done, and if everything is at a single outlet. I have long advocated a scheme for AC power in shacks whereby all power comes from outlets that share the same green wire, or from outlets whose green wires are bonded together. Likewise, I have long advocated a scheme whereby every equipment chassis is bonded to every other chassis by short fat copper, and to station ground, and to all other grounds. That works well both for lightning protection and for the prevention of noise coupled by leakage currents into unbalanced interconnects, and into Pin One Problems. That's true, and that's good advice. Although proper grounding for lighting belongs at the entrance and not on the desk. Now, when we make a signal interconnect between gear plugged into different outlets, we have different IR drops due both to differences in the relative strength of the harmonics on those outlets, and to the lengths of the green wires, and the difference is the familiar power line "buzz" that we have long called "ground loops." I prefer to call it what it is -- noise coupled by leakage current -- because we can now understand the mechanism, and knowing the mechanism, know how to prevent it. The easiest way to prevent it, because there are dozens of causes, is to not have port designs sensitive to common mode. In broadcasting, we would have nearly been taken out and put in front of the firing squad for running audio lines with shields grounded at each end, or unbalanced low level lines between equipment that was not on the same rack when the shield was grounded at each end. Sometimes we need to rethink the point of ingress, and not make the rest of the world responsible for our cheapness or lack of planning. :) 73 Tom _ Topband Reflector
Re: Topband: W8ji ATR-10 design 160M?
Sorry I need to add some thing I left out. The ATR-10 modification I am using is without the series capacitor sorta speak. The MFJ 989B is fed into a tap on the coil. Cause of the T network on the tuner There is series capacitance on the input to the external components. So the external components is an inductive L network with a cap from the antenna going to ground. 100pF seams to give the MFJ 989B a bit more tuning range than the 250pF cap. Jim K9TF On Tue, Oct 8, 2013 at 12:56 PM, Jim GM wrote: > Tom W8JI made some measurements back in 1997 on the ATR-15 when it first > came out. Not sure how this will print out. > > * > * > > *The ATR-15 measures as follows for load R and loss on 1.8 MHz: > 12.5 ohms 21.8%(27.8%) > 25 ohms 16.5% (22.9) > 50 ohms 10.6% (11.0) > 100 ohms 8.9% (10.7) > 200 ohms 8.1% (10.4) > 400 ohms 7.4% (10.1) > 800 ohms 6.9% (8.8%)* > > > Doubling the value of C cuts low impedance losses in half. I put 500 pF > air variable caps in the ATR-15 and the 12.5 ohm loss was 13.1 percent. > > I don't even come close to the MFJ-989 results they published. I > measured the values (they are the ones in brackets above) for the 989 > using both an HP 4191A analyzer and a Harris RF voltmeter, as well as > confirmed on meters. > > > My question is where in the tee match was the extra capacitance installed? > was it going to ground? > > N4XM commented in 1997 on the MFJ 989 review. > > >*>>T network tuners (like the 989, Xmatch, Vectronics, Tucker, * > >*>>Murch, etc) handle the least power on 160 and with capacitive* > >*>>reactance low resistance loads. T network tuners handle MORE * > >*>>power into higher resistance loads or loads with some amount * > >*>>of inductive reactance. * > > > w8JI comments > > >*L network tuners (like the Ten-Tec, Nye Viking, etc) handle more* > >*power into impedances near 50 ohms, but often do a poor job * > >*matching reactive or very low impedance loads on low frequencies. > >(Sometimes* > >*these tuners are called Pi-networks, even though* > >*they do not really function as a pi except perhaps on 15 or ten* > >*meters) * > >** > >*In a T network tuner, maximum efficiency and power handling * > >*generally occurs when maximum and equal amounts of * > >*capacitance are used in the capacitors, and the least amount of* > >*inductance is used. This is true even though many other settings* > >*will produce a low SWR.* > > > > I later read more archives. What came up was the ATR-30 How beefy it was. > What the plate spacing on this tuners capacitors? I would think on a > short antenna like mine it is not enough. > > So back to the ATR-10. The W8JI design with variable taps seams to handle > high power with nor arcing problems. > I just do not know why this is working for me. Can some one please > explain this to me I am confused? All this reading > requires a younger mind. > > Jim K9TF > > On Sat, Oct 5, 2013 at 1:54 PM, Jim GM wrote: > >> >> My antenna is a 99 foot inverted L for 160M with 95 short radials 2000 >> feet of wire. >> >> What I am trying now is W8JI suggested modification design to improve the >> ATR-10 design by taps on the coil for adjustment. Works well. >> http://www.w8ji.com/antenna_tuners.htm >> >> Had my MFJ-989B at the feed point, I had to add a capacitor to ground >> 250pf so it could work. Inductance was at max farthest away from ground. >> Voltage was so high at 300 watts in, the 0.125 meshed plate spacing arced >> over, it has a T network and I had expected this to happen. >> http://www.mfjenterprises.com/support/MFJ-989B/MFJ-989B.pdf I run 500 >> watts. >> >> What I was looking at is removing the coil and the input would be at the >> top of C1. I made a test with QRP using 2 small spaced caps taken out of an >> MFJ-901A. Works well. Because of the high voltage situation would there be >> an issue with this and I need to go to a 0.25 inch spacing between plates? >> Vacuum variables are out of my price range. >> >> ATR-10 with W8JI modifications is a high pass tuner or is it? Removal of >> the coil would make this a low pass circuit. Besides that on 160M which one >> would be more efficient, and off the top of your head what would be the >> percentages? If you had my make do with what I have setup, what tuning >> network would you use? >> >> Does any one have an email address for MFJ Service department? I have >> the wrong one. I sent my MFJ 998RT to their Service department, the High >> voltage that was developed with 300 watts pretty much done it in. The >> ATR-10 W8JI redesign has greatly reduce the High voltage that I was seeing >> with out the inductor. >> >> -- >> Jim K9TF >> > > > > -- > Jim K9TF > -- Jim K9TF _ Topband Reflector
Re: Topband: W8ji ATR-10 design 160M?
Tom W8JI made some measurements back in 1997 on the ATR-15 when it first came out. Not sure how this will print out. * * *The ATR-15 measures as follows for load R and loss on 1.8 MHz: 12.5 ohms 21.8%(27.8%) 25 ohms 16.5% (22.9) 50 ohms 10.6% (11.0) 100 ohms 8.9% (10.7) 200 ohms 8.1% (10.4) 400 ohms 7.4% (10.1) 800 ohms 6.9% (8.8%)* Doubling the value of C cuts low impedance losses in half. I put 500 pF air variable caps in the ATR-15 and the 12.5 ohm loss was 13.1 percent. I don't even come close to the MFJ-989 results they published. I measured the values (they are the ones in brackets above) for the 989 using both an HP 4191A analyzer and a Harris RF voltmeter, as well as confirmed on meters. My question is where in the tee match was the extra capacitance installed? was it going to ground? N4XM commented in 1997 on the MFJ 989 review. >*>>T network tuners (like the 989, Xmatch, Vectronics, Tucker, * >*>>Murch, etc) handle the least power on 160 and with capacitive* >*>>reactance low resistance loads. T network tuners handle MORE * >*>>power into higher resistance loads or loads with some amount * >*>>of inductive reactance. * w8JI comments >*L network tuners (like the Ten-Tec, Nye Viking, etc) handle more* >*power into impedances near 50 ohms, but often do a poor job * >*matching reactive or very low impedance loads on low frequencies. (Sometimes* >*these tuners are called Pi-networks, even though* >*they do not really function as a pi except perhaps on 15 or ten* >*meters) * >** >*In a T network tuner, maximum efficiency and power handling * >*generally occurs when maximum and equal amounts of * >*capacitance are used in the capacitors, and the least amount of* >*inductance is used. This is true even though many other settings* >*will produce a low SWR.* I later read more archives. What came up was the ATR-30 How beefy it was. What the plate spacing on this tuners capacitors? I would think on a short antenna like mine it is not enough. So back to the ATR-10. The W8JI design with variable taps seams to handle high power with nor arcing problems. I just do not know why this is working for me. Can some one please explain this to me I am confused? All this reading requires a younger mind. Jim K9TF On Sat, Oct 5, 2013 at 1:54 PM, Jim GM wrote: > > My antenna is a 99 foot inverted L for 160M with 95 short radials 2000 > feet of wire. > > What I am trying now is W8JI suggested modification design to improve the > ATR-10 design by taps on the coil for adjustment. Works well. > http://www.w8ji.com/antenna_tuners.htm > > Had my MFJ-989B at the feed point, I had to add a capacitor to ground > 250pf so it could work. Inductance was at max farthest away from ground. > Voltage was so high at 300 watts in, the 0.125 meshed plate spacing arced > over, it has a T network and I had expected this to happen. > http://www.mfjenterprises.com/support/MFJ-989B/MFJ-989B.pdf I run 500 > watts. > > What I was looking at is removing the coil and the input would be at the > top of C1. I made a test with QRP using 2 small spaced caps taken out of an > MFJ-901A. Works well. Because of the high voltage situation would there be > an issue with this and I need to go to a 0.25 inch spacing between plates? > Vacuum variables are out of my price range. > > ATR-10 with W8JI modifications is a high pass tuner or is it? Removal of > the coil would make this a low pass circuit. Besides that on 160M which one > would be more efficient, and off the top of your head what would be the > percentages? If you had my make do with what I have setup, what tuning > network would you use? > > Does any one have an email address for MFJ Service department? I have the > wrong one. I sent my MFJ 998RT to their Service department, the High > voltage that was developed with 300 watts pretty much done it in. The > ATR-10 W8JI redesign has greatly reduce the High voltage that I was seeing > with out the inductor. > > -- > Jim K9TF > -- Jim K9TF _ Topband Reflector
Re: Topband: Best Outlet sttrip
On 10/8/2013 8:11 AM, Tom W8JI wrote: Why would that be true? I can't understand any mechanism that would consistantly increase damage because an MOV protected stip is added. MOV from phase to green wire dumps current onto green, IZ drop on green back to the panel raises potential of that chassis. It has a low voltage (signal cable) to another box, plugged into another MOV strip at a different location, more current on green, probably not the same, probably not the same IZ drop. The difference appears on the low voltage interconnection and fries I/O for that interconnection. Same issue happens if the interconnection is to equipment with a different ground connection. I've seen MANY reports from engineers of destructive failures in small wired Ethernet systems in homes and small offices with no radios or towers involved. Likewise, large audio and video systems with equipment at widely separated locations have this issue. I worked in that field for many years, and we solved it by using series-mode protection on branch circuits. MOVs are fine IF the bonding of grounds and equipment is properly done, and if everything is at a single outlet. I have long advocated a scheme for AC power in shacks whereby all power comes from outlets that share the same green wire, or from outlets whose green wires are bonded together. Likewise, I have long advocated a scheme whereby every equipment chassis is bonded to every other chassis by short fat copper, and to station ground, and to all other grounds. That works well both for lightning protection and for the prevention of noise coupled by leakage currents into unbalanced interconnects, and into Pin One Problems. The mechanism for the leakage current side of it is quite similar. We know that the AC line is full of the harmonics of 60 Hz because current is drawn by capacitor-input supplies in pulses at the peaks of the cycle, and that the triplen harmonics add both in the neutral and in the ground of 3-phase systems. Few of us have 3-phase in our homes, but a LOT of power distro to us uses "high-leg delta" on the street to feed us. High leg delta is 240V delta, where one side of the delta has a center-tapped transformer to feed single phase customers, and 3-phase customers get all three phases. These single phase customers have no neutral, so much of their harmonic current shows up on our neutral. In our homes, we have equipment with intentional capacitors (line filters) and stray capacitance (mostly transformers mounted to the chassis) between line and neutral, and between line and green. This capacitance dumps the line voltage, including the harmonics present in the voltage waveform, onto the neutral, increasing linearly with frequency. So when we stick a scope between the two ends of a green wire, we see those harmonics. Now, when we make a signal interconnect between gear plugged into different outlets, we have different IR drops due both to differences in the relative strength of the harmonics on those outlets, and to the lengths of the green wires, and the difference is the familiar power line "buzz" that we have long called "ground loops." I prefer to call it what it is -- noise coupled by leakage current -- because we can now understand the mechanism, and knowing the mechanism, know how to prevent it. With unbalanced interconnects, this buzz is added to the signal. And if the gear has Pin One Problems, it's also coupled into gear by that mechanism. The power distro scheme (same green wire, or bonded outlet boxes) typically reduces the buzz by 20 dB (by taking the drop in the long green wires to the panel out of the equation). Bonding the gear is typically good for another 20-30 dB. 73, Jim K9YC _ Topband Reflector
Re: Topband: Best Outlet sttrip
Most branded outlet strips have MOVs for "surge suppression." MOVs on branch circuits are well known to CAUSE destructive failure of equipment powered from these outlets when there are interconnections between that equipment and equipment powered from other outlets. The only good place for MOVs is at the service entraince (that is, where power enters your home). Hi Jim, Why would that be true? I can't understand any mechanism that would consistantly increase damage because an MOV protected stip is added. The function and wiring of MOV's is to clamp all three conductors together during a surge. The proper fix is to make sure common equipment has a common feedpoint. Not to eliminate protection in the hopes reducing protection also reduces common mode currents between isolated feeds! I'll certainly continue to use MOV's and MOV strips on all of my equipment. 73 Tom _ Topband Reflector
Re: Topband: Best Outlet sttrip
On 10/6/2013 7:04 AM, Dan Bookwalter wrote: I am in need of a couple outlet strips for the shack , what is the best option out there that is not overly expensive Most branded outlet strips have MOVs for "surge suppression." MOVs on branch circuits are well known to CAUSE destructive failure of equipment powered from these outlets when there are interconnections between that equipment and equipment powered from other outlets. The only good place for MOVs is at the service entraince (that is, where power enters your home). The "best" outlet strip is something we can all easily build with parts from Home Depot or Lowe's. We need duplex outlets, gangable steel backboxes, some wire, and a coverplate. Don't buy the cheap duplex outlets for a buck apiece, buy the better ones. 73, Jim K9YC _ Topband Reflector
Re: Topband: Outdoor cable trunking - opinions pse
Recently St. Croix was wired across the 27 mile length with yellow tubular fiber conduit designed for direct burial. When the huge truck mounted cable reels had tails of 20 and 30 feet left over I picked them up and plan to use them under the lawn for my feedlines. They are 2" ID so they should be able to take all the RG-6 I run to Beverages that the field rats like to chew into. I have even though of trying to split them with a skill saw for an easier application but sort of gave up that idea and prefer to leave them whole. Putting through a #14 solid THNN wire is no problem for a pull wire and cutting off the F-connectors that run to the torioid decoupling bank at the shack is not any big deal. Herb Schoenbohm, KV4FZ On 10/8/2013 9:25 AM, Ashton Lee wrote: I have pretty different needs on a mountain top in Western Colorado… I need to shield my cables from pack rats who will chew on it. I use very inexpensive irrigation tubing which is made for in ground lawn sprinkling systems. This can be buried or tied in runs above ground. On Oct 8, 2013, at 5:58 AM, "Shoppa, Tim" wrote: _ Topband Reflector
Re: Topband: Outdoor cable trunking - opinions pse
Lightning strikes aren't common round here, and if there is one it's more likely to damage the trees or the house. I don't want anyone to get the impression the lightning damage I get comes from lighting hitting my cables. The damage I get is from ground loop currents that flow through the cables. The current opens the shield inside the cable by melting the foil and the shield. The better the grounded, the worse the problem becomes. The most unreliable cables I have are the cables out to the elements in my eight circle, because it has 6 or 8 buried radials at each vertical. I used to lose a cable or two every year. I fixed it by plowing in a number 8 wire out from the hub to each vertical, and using a 50 foot coil of small cheap coax in a sacrificial choke where the feed for the eight circle branches off the 1500 foot or so long trunk bundle. Damage to shields has nothing at all to do with direct strikes, but rather ground loop currents in the earth when lightning hits within several hundred feet of the cable at any point. The better the cables are grounded, the worse this type of problem becomes. _ Topband Reflector
Re: Topband: Outdoor cable trunking - opinions pse
I have pretty different needs on a mountain top in Western Colorado… I need to shield my cables from pack rats who will chew on it. I use very inexpensive irrigation tubing which is made for in ground lawn sprinkling systems. This can be buried or tied in runs above ground. On Oct 8, 2013, at 5:58 AM, "Shoppa, Tim" wrote: > I think the British word "trunking" is what we in the US would call "cable > tray", metal trays with removable metal lids. > > Cable tray is very nice for cable management. Solid bottom galvanized cable > tray, the kind specified by standards where I work, is hard to justify in > cost until dozens of cables are laid in it and total cost of wire management > over decades starts becoming important. > > While cable tray lids offer some shielding to 60Hz and audio frequencies, it > is markedly inferior to well fitted metallic conduit for RF shielding. > > I've seen cable tray used inside the shack for cable management in some nicer > ham station pictures. It would be very hard to justify the substantial cost > for a long cable tray run between shack and antennas. > > Tim N3QE > > - Original Message - > From: Dave G4GED [mailto:radiodave.g4...@tiscali.co.uk] > Sent: Tuesday, October 08, 2013 03:17 AM > To: topband@contesting.com > Subject: Topband: Outdoor cable trunking - opinions pse > > Hi all, > > I want to re-run all my TX and RX antenna feeders through trunking > (detachable lid type), fixed along the bottom of a new 200ft timber fence. > This will give protection and future flexibility that burying or closed > conduit methods wont. > > The question is...to use galvanised steel or PVC? > > I'm favouring steel because when earthed, I believe it will give extra > noise screening for the RX feeders but are there any down sides such as > "oven effects" in hot summer sun or "diode effects" between lids and > sections, or any other problems? > > PVC is a bit cheaper but wont offer the extra screening. > > Does anyone have any relative experience please? > > Thanks in advance. > Dave G4GED > > _ > Topband Reflector > _ > Topband Reflector > _ Topband Reflector
Re: Topband: Outdoor cable trunking - opinions pse
On 08/10/2013 08:17, Dave G4GED wrote: Does anyone have any relative experience please? The plastic trunking I tried became a home for various wildlife. While it kept the rain off the cables, it did make them thoroughly unpleasant to handle. I now use little gutter brackets, screwed to the fenceposts, and hook the cable in those. It keeps stuff off the ground, makes access easy, and has not been a problem (so far, anyway). Lightning strikes aren't common round here, and if there is one it's more likely to damage the trees or the house. 73 Keith _ Topband Reflector
Re: Topband: Outdoor cable trunking - opinions pse
I think the British word "trunking" is what we in the US would call "cable tray", metal trays with removable metal lids. Cable tray is very nice for cable management. Solid bottom galvanized cable tray, the kind specified by standards where I work, is hard to justify in cost until dozens of cables are laid in it and total cost of wire management over decades starts becoming important. While cable tray lids offer some shielding to 60Hz and audio frequencies, it is markedly inferior to well fitted metallic conduit for RF shielding. I've seen cable tray used inside the shack for cable management in some nicer ham station pictures. It would be very hard to justify the substantial cost for a long cable tray run between shack and antennas. Tim N3QE - Original Message - From: Dave G4GED [mailto:radiodave.g4...@tiscali.co.uk] Sent: Tuesday, October 08, 2013 03:17 AM To: topband@contesting.com Subject: Topband: Outdoor cable trunking - opinions pse Hi all, I want to re-run all my TX and RX antenna feeders through trunking (detachable lid type), fixed along the bottom of a new 200ft timber fence. This will give protection and future flexibility that burying or closed conduit methods wont. The question is...to use galvanised steel or PVC? I'm favouring steel because when earthed, I believe it will give extra noise screening for the RX feeders but are there any down sides such as "oven effects" in hot summer sun or "diode effects" between lids and sections, or any other problems? PVC is a bit cheaper but wont offer the extra screening. Does anyone have any relative experience please? Thanks in advance. Dave G4GED _ Topband Reflector _ Topband Reflector
Re: Topband: Outdoor cable trunking - opinions pse
The question is...to use galvanised steel or PVC? I'm favouring steel because when earthed, I believe it will give extra noise screening for the RX feeders but are there any down sides such as "oven effects" in hot summer sun or "diode effects" between lids and sections, or any other problems? Once shielding (just like when common mode suppression) goes beyond a certain point as a ratio to levels inside the cable, any additional shielding is useless. The sole exception is lightning or another sudden severe unusual excitation. I looked at all this with common cable types I planned on using (dual shield with braid and foil). Unless fields exciting the cable were beyond the levels caused by my own transmitters into a dipole above and parallel the cable, any additional shielding was useless. The test for common mode is more involved than just open circuiting the cable or terminating it, but with normal "non-exceptional" cables nearly all CM issues would come from coupling in at a gap in the system, either at plastic boxes that are absent large backplanes between shields, or poor shield connections at a connector or connector. PVC is a bit cheaper but wont offer the extra screening. Does anyone have any relative experience please? Metal conduit, with proper grounding, will improve lightning survivability a great deal if you are blowing shields out in storms somewhere out in the middle of the runs. Of course there are other ways to reduce shield damage, but a metallic pipe forms an effective bypass for high CM currents that might melt the cable shield. It can or will improve shielding from the outside along the run, but I can't imagine a case where that is an issue unless your cable runs past a high power transmitter antenna or your receive antenna levels are near thermal noise floor limits in feedline conductors. It does not mitigate CM noise or end-damage, however. The same or more current and voltage will exist at the ends. Unless running past in-band very high level noise sources, or past something causing lightning to enter the shield, I think is a waste of worry, time, and money. Tom _ Topband Reflector
Topband: Outdoor cable trunking - opinions pse
Hi all, I want to re-run all my TX and RX antenna feeders through trunking (detachable lid type), fixed along the bottom of a new 200ft timber fence. This will give protection and future flexibility that burying or closed conduit methods wont. The question is...to use galvanised steel or PVC? I'm favouring steel because when earthed, I believe it will give extra noise screening for the RX feeders but are there any down sides such as "oven effects" in hot summer sun or "diode effects" between lids and sections, or any other problems? PVC is a bit cheaper but wont offer the extra screening. Does anyone have any relative experience please? Thanks in advance. Dave G4GED _ Topband Reflector
