Topband: Choke Baluns etc
I think if I had a vertical with just a few Radials lying on the ground, I wouldn't use a Common Mode Choke either . . . to me, any RF on the outer of the coax would just mean it acts as another radial. I've actually NEVER had any issues with RF in the shack . . . I used Dipoles fed with co-ax on several bands for decades, without any Chokes at the feedpoint. However, in an effort to reduce Received Noise, I DID install decent Ferrite Choke Baluns on my 160m & 80m Dipoles about 4 years ago . . . however, it made no difference to anything ! (neither the noise level or the resonant frequency of the antennas) Here's something else that many people find surprising . . . At 3 different QTHs I have had over the decades, it wasn't possible to put up a Dipole for Top Band . . . so I had an End-Fed Half Wave. At all 3 locations the shack was in an attic room on the third floor . . . so the end of the 260ft of wire came into the attic window, straight to an ATU on the windowsill. The only ground I had was the Mains Wiring around the house, plus the central-heating system (copper pipes all over). Even running an Amplifier, I never had any RF Feedback issues . . . and those End-Fed Half Waves seemed to work just as well as the Dipoles I used at other QTHs. (I do, however, suspect that with all the RF Noise rubbish around these days that the noise level would be worse than a Dipole!) 73 Roger G3YRO _ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector
Re: Topband: choke/bleeder resistor on RXvertical?
Precisely, Peter! There was no DC path to ground on my inverted-L, because the tuner at the base was just two or three capacitors. A spark gap across the resistor will also discharge surge voltages from nearby lightning strikes. The tips of my homebrew shunt spark gap melted more than once from that. And that's why I use Ohmite Type OY resistors for that. 73, Mike www.w0btu.com On Sat, Dec 22, 2018, 10:55 AM Peter Bertini wrote: > A drain resistor would be advisable if there is no DC return path to > earth... if there is no inductor or resistance between the antenna and > earth it can develop wind or snow induced static voltage buildup, which can > lead to discharges that will cause noise in the receiver. Static voltages > can also damage any inline preamps between the vertical and receiver. > _ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector
Re: Topband: choke/bleeder resistor on RXvertical?
A drain resistor would be advisable if there is no DC return path to earth... if there is no inductor or resistance between the antenna and earth it can develop wind or snow induced static voltage buildup, which can lead to discharges that will cause noise in the receiver. Static voltages can also damage any inline preamps between the vertical and receiver. Pete _ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector
Re: Topband: choke/bleeder resistor on RXvertical?
Exactly. This has been discussed at length here in the past. Here are a couple of relevant threads: lists.contesting.com/archives//html/Topband/2018-12/msg00192.html lists.contesting.com/archives//html/Topband/2008-11/msg00162.html These are all I could find, after extensive searching. The archives search function here does not seem to work as well as in the past. 73, Mike www.w0btu.com On Wed, Dec 19, 2018, 12:30 PM Chuck Dietz wrote: > The choke bleeds off static charges that accumulate on the vertical. While > I have witnessed noise from huge static charging to a 32 foot vertical > mounted on the roof of the engineering building at Texas Tech in West > Texas, the choke does not bleed off “noise”. Noise is radio frequency > emissions from noise sources which can be local or distant. > > Chuck W5PR > > On Wed, Dec 19, 2018 at 12:19 PM Jamie WW3S wrote: > > > Since verticals are know to be "noisy" on receive, and a fix is a rf > choke > > or bleeder resistor to ground, anyone try that on short verticals used > for > > receive only to quiet some noise? > _ > Searchable Archives: http://www.contesting.com/_topband - Topband > Reflector > _ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector
Re: Topband: choke/bleeder resistor on RXvertical?
I put resistors (always 100k or more) across EVERY feedline - at the antenna. I keep a chart of what antenna has which value resistor. Two reasons for the chart.. if the resistor changes value, I can find it quickly. IF I drop a coax into a couple others, I can quickly determine which antenna is connected with which feeder. The resistors are all under 2 watt. Since I generally run qrp, the summertime "missing" resistor, leads me to believe "there went another strike".. and the discolored ones, make me believe that even at 2 watts, the wind static has power. Have a great day, Dale - WC7S in Wy "Actions speak louder than words" From: Topband on behalf of Gary - K7EK via Topband Sent: Friday, December 21, 2018 8:11 AM To: Mike Waters Cc: topband Subject: Re: Topband: choke/bleeder resistor on RXvertical? Question about the use of Ohmite bleeder resistors: What are the considerations relative to power rating in this application? Would a 2w OX or OY ceramic resistor survive extended use of full legal amateur power limit on such modes as RTTY, FT8, JT65A, SSTV, and various other high duty cycle digital modes, and AM voice, etc? Best regards, Gary, K7EK Sent from BlueMail On Dec 19, 2018, 13:08, at 13:08, Mike Waters wrote: >ALL my antennas have Ohmite OX or OY resistors from the antenna to >ground. >From 56k to a megohm or three. Doesn't everybody? :-) > >Ditto at dipole feedpoints. > >73, Mike >www.w0btu.com<http://www.w0btu.com> > >On Wed, Dec 19, 2018, 12:19 PM Jamie WW3S >wrote: > >> Since verticals are know to be "noisy" on receive, and a fix is a rf >choke >> or bleeder resistor to ground, anyone try that on short verticals >used for >> receive only to quiet some noise? >> _ >> Searchable Archives: http://www.contesting.com/_topband - Topband >> Reflector >> >_ >Searchable Archives: http://www.contesting.com/_topband - Topband >Reflector _ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector _ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector
Re: Topband: choke/bleeder resistor on RXvertical?
Question about the use of Ohmite bleeder resistors: What are the considerations relative to power rating in this application? Would a 2w OX or OY ceramic resistor survive extended use of full legal amateur power limit on such modes as RTTY, FT8, JT65A, SSTV, and various other high duty cycle digital modes, and AM voice, etc? Best regards, Gary, K7EK Sent from BlueMail On Dec 19, 2018, 13:08, at 13:08, Mike Waters wrote: >ALL my antennas have Ohmite OX or OY resistors from the antenna to >ground. >From 56k to a megohm or three. Doesn't everybody? :-) > >Ditto at dipole feedpoints. > >73, Mike >www.w0btu.com > >On Wed, Dec 19, 2018, 12:19 PM Jamie WW3S >wrote: > >> Since verticals are know to be "noisy" on receive, and a fix is a rf >choke >> or bleeder resistor to ground, anyone try that on short verticals >used for >> receive only to quiet some noise? >> _ >> Searchable Archives: http://www.contesting.com/_topband - Topband >> Reflector >> >_ >Searchable Archives: http://www.contesting.com/_topband - Topband >Reflector _ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector
Re: Topband: choke/bleeder resistor on RXvertical?
Noise is signal spread over a large bandwidth, We tune our receivers to a frequency to copy signals in a relatively narrow bandwidth. Nevertheless, there is some of that noise in that same bandwidth. How does placing a resistor or choke to ground reduce the noise while not reducing the signal at the same time? Wes N7WS On 12/19/2018 11:19 AM, Jamie WW3S wrote: Since verticals are know to be "noisy" on receive, and a fix is a rf choke or bleeder resistor to ground, anyone try that on short verticals used for receive only to quiet some noise? _ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector _ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector
Re: Topband: choke/bleeder resistor on RXvertical?
Hi Jamie, I assume you are referring to short RX verticals similar to those used in the Hi-Z and other arrays with a 20 to 25 ft vertical element. I have extensive experience with these and have the HiZ-8 on 160, the passive BSEF-8 array with 25 ft "umbrella" verticals on both 160 and 80 meters and also have the YCCC 9 vertical array. I have never experienced a situation where I believed there was a need for any type of choke or bleeder resistor to quiet noise. As Tree has pointed out with an active array such as the HiZ or YCCC-9 this may create issues with the array amplifiers After a proper installation to ensure good RF connections in the system and address any common mode noise condition that may exist, all of these are extremely quite at my QTH without the need for "bleeder" components. 73 Joel W5ZN On 2018-12-19 11:19, Jamie WW3S wrote: Since verticals are know to be "noisy" on receive, and a fix is a rf choke or bleeder resistor to ground, anyone try that on short verticals used for receive only to quiet some noise? _ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector _ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector
Re: Topband: choke/bleeder resistor on RXvertical?
ALL my antennas have Ohmite OX or OY resistors from the antenna to ground. >From 56k to a megohm or three. Doesn't everybody? :-) Ditto at dipole feedpoints. 73, Mike www.w0btu.com On Wed, Dec 19, 2018, 12:19 PM Jamie WW3S wrote: > Since verticals are know to be "noisy" on receive, and a fix is a rf choke > or bleeder resistor to ground, anyone try that on short verticals used for > receive only to quiet some noise? > _ > Searchable Archives: http://www.contesting.com/_topband - Topband > Reflector > _ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector
Re: Topband: choke/bleeder resistor on RXvertical?
thanks, makes sense.thats why I asked - Original Message - From: "Chuck Dietz" To: "Jamie WW3S" Cc: "Topband" Sent: Wednesday, December 19, 2018 1:29:40 PM Subject: Re: Topband: choke/bleeder resistor on RXvertical? The choke bleeds off static charges that accumulate on the vertical. While I have witnessed noise from huge static charging to a 32 foot vertical mounted on the roof of the engineering building at Texas Tech in West Texas, the choke does not bleed off “noise”. Noise is radio frequency emissions from noise sources which can be local or distant. Chuck W5PR On Wed, Dec 19, 2018 at 12:19 PM Jamie WW3S < w...@zoominternet.net > wrote: Since verticals are know to be "noisy" on receive, and a fix is a rf choke or bleeder resistor to ground, anyone try that on short verticals used for receive only to quiet some noise? _ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector _ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector
Re: Topband: choke/bleeder resistor on RXvertical?
At least for the Hi-Z verticals - you can measure a DC voltage when they are active on the antenna against ground. You would not want to short that to ground with a choke!! By having a voltage there - I think you can assume any static DC charges will be quickly dealt with. Essentially a resistor to ground is already there. Tree N6TR On Wed, Dec 19, 2018 at 10:30 AM Chuck Dietz wrote: > The choke bleeds off static charges that accumulate on the vertical. While > I have witnessed noise from huge static charging to a 32 foot vertical > mounted on the roof of the engineering building at Texas Tech in West > Texas, the choke does not bleed off “noise”. Noise is radio frequency > emissions from noise sources which can be local or distant. > > Chuck W5PR > > On Wed, Dec 19, 2018 at 12:19 PM Jamie WW3S wrote: > > > Since verticals are know to be "noisy" on receive, and a fix is a rf > choke > > or bleeder resistor to ground, anyone try that on short verticals used > for > > receive only to quiet some noise? > > _ > > Searchable Archives: http://www.contesting.com/_topband - Topband > > Reflector > > > _ > Searchable Archives: http://www.contesting.com/_topband - Topband > Reflector > _ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector
Re: Topband: choke/bleeder resistor on RXvertical?
The choke bleeds off static charges that accumulate on the vertical. While I have witnessed noise from huge static charging to a 32 foot vertical mounted on the roof of the engineering building at Texas Tech in West Texas, the choke does not bleed off “noise”. Noise is radio frequency emissions from noise sources which can be local or distant. Chuck W5PR On Wed, Dec 19, 2018 at 12:19 PM Jamie WW3S wrote: > Since verticals are know to be "noisy" on receive, and a fix is a rf choke > or bleeder resistor to ground, anyone try that on short verticals used for > receive only to quiet some noise? > _ > Searchable Archives: http://www.contesting.com/_topband - Topband > Reflector > _ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector
Topband: choke/bleeder resistor on RXvertical?
Since verticals are know to be "noisy" on receive, and a fix is a rf choke or bleeder resistor to ground, anyone try that on short verticals used for receive only to quiet some noise? _ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector
Re: Topband: Choke?
Jeff, If a choke at your shack makes *any* difference, then you need a better choke at the base of your inverted-L. 73, Mike www.w0btu.com On Wed, Jan 17, 2018 at 11:16 AM, Radio KH6O wrote: > I'll be erecting a 95-foot Inverted-L antenna. At the shack end of the > antenna, right before the insulator, I'll need to wrap the wire around > itself a few times so that it doesn't slip through the insulator. Because > the wire itself is insulated, is there any negative affect, such as a > choking action that might take place? > > 73, Jeff KH6O > _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: Choke?
Jeff, Et. Al., Rather than wrap the wire around the insulator opening or itself, how about a "split bolt" wire clamp with the saddle on the tension side? A good "mechanical knot". I can take photo of one if needed. Here is a website link: http://www.elecdirect.com/split-bolts-grounding-products/split-bolt-connectors/copper-alloy-2-conductors-16-str-8-str There is a larger one on the same "elecdirect dot com" page on the internet as well. GL & 73, George, K8GG > I'll be erecting a 95-foot Inverted-L antenna. At the shack end of the > antenna, right before the insulator, I'll need to wrap the wire around > itself a few times so that it doesn't slip through the insulator. Because > the wire itself is insulated, is there any negative affect, such as a > choking action that might take place? > > 73, Jeff KH6O > _ > Topband Reflector Archives - http://www.contesting.com/_topband > _ Topband Reflector Archives - http://www.contesting.com/_topband
Topband: Choke?
I'll be erecting a 95-foot Inverted-L antenna. At the shack end of the antenna, right before the insulator, I'll need to wrap the wire around itself a few times so that it doesn't slip through the insulator. Because the wire itself is insulated, is there any negative affect, such as a choking action that might take place? 73, Jeff KH6O _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: Choke material
Guy Olinger K2AV said: "Those chokes are of a material that is designed for audio frequencies. I can still remember the day's in my youth when I could hear the 15 kHz horizontal sweep frequency. I would not be using those for a frequency more than a hundred times the frequency they were designed for." Sorry, but I have to disagree. Those chokes are made for the horizontal and vertical frequencies, the horizontal being around 15 kHz. However it is a triangle wave. With the scan going across and then the fly back (steep part of the wave) coming back. The fly back part of the wave moves the scanning dot back much, much faster than the sweep part of the triangle wave that creates the line on the screen. If you were to check the timing on just the fly back part of the wave it would be much, much higher in frequency. So the cores would have to be suitable for a much higher frequency than 15 kHz. They would have to be suitable for the frequency of the steep part of the triangle wave. Hopefully I explained that in an understandable manner.. 73 Stan K8LL NW Ohio, USA 10-10# 76801 FP# 3255 100WattsAndAWire# 1939 Propagation is our master . . . but sometimes the master is cruel! _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: Choke material
Hello Guy, I don't disagree with this at all. The common-mode chokes I now use are K9YC's design, except for one still on the coax in the shack feeding a TX antenna. But I can personally testify that the TV deflection yoke cores I made were useful at much higher frequencies. For example, I made and installed common-mode chokes on 3 phase lines feeding some CNC equipment the last place I worked. IIRC, there were about 12 turns of 3x10 AWG THHN wound on it. They completely eliminated the RFI from a TIG welder in the same building, operating at some ISM frequency (probably 13 MHz). Having said that, I also installed some RF-rated Sangamo surplus mica caps (remember those? ;-) between the phases (and maybe to ground, too) on the equipment side of the choke. I never took the capacitors (IIRC .005 to .02 uF) out of the circuit to see what happened. Other times, they prevented RFI in my shack at frequencies above 160 meters. Just sayin'. Can't hurt to try them. 73, Mike www.w0btu.com On Fri, Sep 8, 2017 at 7:21 PM, Guy Olinger K2AV wrote: > Those chokes are of a material that is designed for audio frequencies. I > can still remember the day's in my youth when I could hear the 15 kHz > horizontal sweep frequency. > > I would not be using those for a frequency more than a hundred times the > frequency they were designed for. > > Use the #31 material for 1.8 Mhz. Go see K9YC's web page to see why. > > 73, Guy K2AV > > On Fri, Sep 8, 2017 at 3:30 PM, Mike Waters wrote: > >> Yes they are! I have used many of those ferrite cores for that purpose >> over >> the years. Wind as many turns of coax through them as possible. And make >> sure there is no gap between the halves. >> >> How they compare to stacked 2.4" 31 material toroids (which is what I've >> used the past few years), I can't say. >> >> 73, Mike >> www.w0btu.com >> >> On Fri, Sep 8, 2017 at 2:23 PM, Carol Richards wrote: >> >> > I have been cleaning out a shed with 50+ years of stuff. I found several >> > yoke cores from the TV sets made in the 60's. Are they usable for common >> > mode chokes? >> > >> _ >> Topband Reflector Archives - http://www.contesting.com/_topband >> > > _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: Choke material
Those chokes are of a material that is designed for audio frequencies. I can still remember the day's in my youth when I could hear the 15 kHz horizontal sweep frequency. I would not be using those for a frequency more than a hundred times the frequency they were designed for. Use the #31 material for 1.8 Mhz. Go see K9YC's web page to see why. 73, Guy K2AV On Fri, Sep 8, 2017 at 3:30 PM, Mike Waters wrote: > Yes they are! I have used many of those ferrite cores for that purpose over > the years. Wind as many turns of coax through them as possible. And make > sure there is no gap between the halves. > > How they compare to stacked 2.4" 31 material toroids (which is what I've > used the past few years), I can't say. > > 73, Mike > www.w0btu.com > > On Fri, Sep 8, 2017 at 2:23 PM, Carol Richards wrote: > > > I have been cleaning out a shed with 50+ years of stuff. I found several > > yoke cores from the TV sets made in the 60's. Are they usable for common > > mode chokes? > > > _ > Topband Reflector Archives - http://www.contesting.com/_topband > _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: Choke material
Yes they are! I have used many of those ferrite cores for that purpose over the years. Wind as many turns of coax through them as possible. And make sure there is no gap between the halves. How they compare to stacked 2.4" 31 material toroids (which is what I've used the past few years), I can't say. 73, Mike www.w0btu.com On Fri, Sep 8, 2017 at 2:23 PM, Carol Richards wrote: > I have been cleaning out a shed with 50+ years of stuff. I found several > yoke cores from the TV sets made in the 60's. Are they usable for common > mode chokes? > _ Topband Reflector Archives - http://www.contesting.com/_topband
Topband: Choke material
Hello all, I have been cleaning out a shed with 50+ years of stuff. I found several yoke cores from the TV sets made in the 60's. Are they usable for common mode chokes? Carol _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: Choke Construction Info Needed
My mistake. Now then, for lighting we don't really want much inductance between the antenna and ground. For a 100 kA strike rising in 2 us 1 MV is developed across 20 uH. Instead we want a sturdy spark gap of 1/32 inch connected directly from the feedpoint to the ground system. WX7G On Jul 26, 2012 4:23 PM, "Tom W8JI" wrote: > 30 watts is correct for 1500 watts in a 50 ohm system and a coil Q of 226. >> >> The power loss is 0.1 dB and the coil temp rise is around 20 deg C. >> > > No, it isn't. > > 1500 watts is 273 volts into 50 ohms. > > If Q is 226, and reactance 226 ohms, Rp is 51,077 ohms. 273 volts is 1.46 > watts heat. > > To get 30 watts of heat with 226 ohms reactance, Q would have down near > unity. No one makes a coil that bad. > > > > ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
Re: Topband: Choke Construction Info Needed
My Mistake: > To get 30 watts of heat with 226 ohms reactance, Q would have down near > unity. No one makes a coil that bad. I misplaced a decimal. Q would have to be near ten in the coil with 226 ohms reactance and 1500 watts to make 30W heat, not near 1. The other numbers are correct. A Q of ~200 is about 1.5 watts heat with 226 ohms reactance, so heat isn't the issue. SWR change is. ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
Re: Topband: Choke Construction Info Needed
> 30 watts is correct for 1500 watts in a 50 ohm system and a coil Q of 226. > > The power loss is 0.1 dB and the coil temp rise is around 20 deg C. No, it isn't. 1500 watts is 273 volts into 50 ohms. If Q is 226, and reactance 226 ohms, Rp is 51,077 ohms. 273 volts is 1.46 watts heat. To get 30 watts of heat with 226 ohms reactance, Q would have down near unity. No one makes a coil that bad. ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
Re: Topband: Choke Construction Info Needed
70 turns 2" diameter over 4" length would be 100 uH, and with an air core and #16 magnet wire would have a Q of about 200 or so. That's 1000 ohms impedance, a few hundred thousand ohms parallel resistance, and the dissipation would be less than 1 watt at 1500. Or 38 turns over 4 inches on a 4 inch form. You could use #12 wire Teflon insulated, and have a Q of maybe 300 or so. Again less than 1 watt heat out of 1500. Personally, I'd use #12 or 14 Teflon on some old PVC pipe. 73 Tom ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
Re: Topband: Choke Construction Info Needed
> That is only 226 Ohms at 1.8MHz and at 1500W will be dissipating about 30W > in a 50 Ohm system but Phil didnt say how he is feeding his tower which is > resonant well below 160M. That choke is probably too small and will change SWR, but thankfully reactance in reactances does not dissipate power. Reactance simply stores and returns energy. 226 ohms of resistance would be about 330 watts of heat at 1500 watts into 50 ohms (about 273 volts RMS). To find the heat, we would need to know inductor Q. If Q was 1, it would be 330 watts. A pure reactance is zero heat. Odds are the inductor Q would be in the hundreds, so dissipation would be negligible. 73 Tom ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
Re: Topband: Choke Construction Info Needed
30 watts is correct for 1500 watts in a 50 ohm system and a coil Q of 226. The power loss is 0.1 dB and the coil temp rise is around 20 deg C. WX7G On Jul 26, 2012 3:20 PM, "ZR" wrote: > ** > That is only 226 Ohms at 1.8MHz and at 1500W will be dissipating about 30W > in a 50 Ohm system but Phil didnt say how he is feeding his tower which is > resonant well below 160M. > > Yes it will work as well as survive a lot of energy at 35-50 Ohms compared > to a larger inductance 1A choke. > > Carl > KM1H > > - Original Message - > *From:* DAVID CUTHBERT > *To:* ZR > *Cc:* philcleme...@centurylink.net ; topband@contesting.com > *Sent:* Thursday, July 26, 2012 4:35 PM > *Subject:* Re: Topband: Choke Construction Info Needed > > 20 uH should be sufficient at the base of a 1/4 wave length vertical. > > #4 copper wire is used to connect towers to ground for direct strikes. > > Such an inductor can be close-wound with insulated #4 wire, diameter 8", 8 > turns. > > It should survive intact except for the insulation. > > Dave WX7G > On Jul 26, 2012 2:02 PM, "ZR" wrote: > >> It all depends upon how much survivability you want, nothing will survive >> a >> direct hit. Any 1.5 to 2.5 mH choke will suffice, just look at the safety >> choke in a commercial amp for the smallest choice. >> >> The big ones are often found in scrapped BCB transmitters and tuning units >> as well as show up at hamfests and on Fleabay as old military gear had >> various candidates. >> >> Carl >> KM1H >> >> >> - Original Message - >> From: "Phil Clements" >> To: >> Sent: Thursday, July 26, 2012 3:03 PM >> Subject: Topband: Choke Construction Info Needed >> >> >> >I need to construct a heavy-duty choke to be installed from the feed >> point >> > of my 160 meter vertical to ground, for static drain and for lightning >> > protection. How large does the wire, form, and inductance need to be? >> > >> > >> > >> > Thanks in advance for your expertize! >> > >> > >> > >> > (((73))) >> > >> > Phil, K5PC >> > >> > >> > >> > ___ >> > UR RST IS ... ... ..9 QSB QSB - hw? BK >> > >> > >> > - >> > No virus found in this message. >> > Checked by AVG - www.avg.com >> > Version: 10.0.1424 / Virus Database: 2437/5155 - Release Date: 07/25/12 >> > >> >> ___ >> UR RST IS ... ... ..9 QSB QSB - hw? BK >> > -- > > No virus found in this message. > Checked by AVG - www.avg.com > Version: 10.0.1424 / Virus Database: 2437/5155 - Release Date: 07/25/12 > > ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
Re: Topband: Choke Construction Info Needed
That is only 226 Ohms at 1.8MHz and at 1500W will be dissipating about 30W in a
50 Ohm system but Phil didnt say how he is feeding his tower which is resonant
well below 160M.
Yes it will work as well as survive a lot of energy at 35-50 Ohms compared to a
larger inductance 1A choke.
Carl
KM1H
- Original Message -
From: DAVID CUTHBERT
To: ZR
Cc: philcleme...@centurylink.net ; topband@contesting.com
Sent: Thursday, July 26, 2012 4:35 PM
Subject: Re: Topband: Choke Construction Info Needed
20 uH should be sufficient at the base of a 1/4 wave length vertical.
#4 copper wire is used to connect towers to ground for direct strikes.
Such an inductor can be close-wound with insulated #4 wire, diameter 8", 8
turns.
It should survive intact except for the insulation.
Dave WX7G
On Jul 26, 2012 2:02 PM, "ZR" wrote:
It all depends upon how much survivability you want, nothing will survive a
direct hit. Any 1.5 to 2.5 mH choke will suffice, just look at the safety
choke in a commercial amp for the smallest choice.
The big ones are often found in scrapped BCB transmitters and tuning units
as well as show up at hamfests and on Fleabay as old military gear had
various candidates.
Carl
KM1H
- Original Message -
From: "Phil Clements"
To:
Sent: Thursday, July 26, 2012 3:03 PM
Subject: Topband: Choke Construction Info Needed
>I need to construct a heavy-duty choke to be installed from the feed point
> of my 160 meter vertical to ground, for static drain and for lightning
> protection. How large does the wire, form, and inductance need to be?
>
>
>
> Thanks in advance for your expertize!
>
>
>
> (((73)))
>
> Phil, K5PC
>
>
>
> ___
> UR RST IS ... ... ..9 QSB QSB - hw? BK
>
>
> -
> No virus found in this message.
> Checked by AVG - www.avg.com
> Version: 10.0.1424 / Virus Database: 2437/5155 - Release Date: 07/25/12
>
___
UR RST IS ... ... ..9 QSB QSB - hw? BK
--
No virus found in this message.
Checked by AVG - www.avg.com
Version: 10.0.1424 / Virus Database: 2437/5155 - Release Date: 07/25/12
___
UR RST IS ... ... ..9 QSB QSB - hw? BK
Re: Topband: Choke Construction Info Needed
> > >I need to construct a heavy-duty choke to be installed from the feed point > > of my 160 meter vertical to ground, for static drain and for lightning > > protection. How large does the wire, form, and inductance need to be? > > Phil, > One method of dealing with this problem, particularly if one is using an FCP, where the IMPEDANCE is higher at the feedpoint than a resonant feed, is to go to ground with a 5 meg 10 watt resistor in parallel with a lawn mower non-resistance spark plug, gap set to 25 thousandths. The former keeps static drained, the latter gives a path for serious induced voltage. If you get a direct strike, everything at the bottom of the wire is toast, and #12 copper for the vertical is most likely evaporated. I can't think of anything doable that make survivability anything better than a pure fluke. Lightning around here turned the top 75 feet of a 120 foot tulip tree literally into toothpicks scattered over a 125 foot radius, welded conductors in buried cable 25 feet away. So you design for static and induced current/voltage. Feeding the base of a 160 vertical wire over radials with an ISOLATION transformer (not a balun) will give you the DC ground without letting in all the common mode current from the coax to the antenna. Wound after the fashion of the isolation transformer for an FCP, it will also keep an induced strike off the coax to the shack. 73, Guy. ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
Re: Topband: Choke Construction Info Needed
20 uH should be sufficient at the base of a 1/4 wave length vertical. #4 copper wire is used to connect towers to ground for direct strikes. Such an inductor can be close-wound with insulated #4 wire, diameter 8", 8 turns. It should survive intact except for the insulation. Dave WX7G On Jul 26, 2012 2:02 PM, "ZR" wrote: > It all depends upon how much survivability you want, nothing will survive a > direct hit. Any 1.5 to 2.5 mH choke will suffice, just look at the safety > choke in a commercial amp for the smallest choice. > > The big ones are often found in scrapped BCB transmitters and tuning units > as well as show up at hamfests and on Fleabay as old military gear had > various candidates. > > Carl > KM1H > > > - Original Message - > From: "Phil Clements" > To: > Sent: Thursday, July 26, 2012 3:03 PM > Subject: Topband: Choke Construction Info Needed > > > >I need to construct a heavy-duty choke to be installed from the feed point > > of my 160 meter vertical to ground, for static drain and for lightning > > protection. How large does the wire, form, and inductance need to be? > > > > > > > > Thanks in advance for your expertize! > > > > > > > > (((73))) > > > > Phil, K5PC > > > > > > > > ___ > > UR RST IS ... ... ..9 QSB QSB - hw? BK > > > > > > - > > No virus found in this message. > > Checked by AVG - www.avg.com > > Version: 10.0.1424 / Virus Database: 2437/5155 - Release Date: 07/25/12 > > > > ___ > UR RST IS ... ... ..9 QSB QSB - hw? BK > ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
Re: Topband: Choke Construction Info Needed
>I need to construct a heavy-duty choke to be installed from the feed point > of my 160 meter vertical to ground, for static drain and for lightning > protection. How large does the wire, form, and inductance need to be? Phil, This is like any shunt or series choke problem. The choke needs to be several times the impedance at the insertion point. In a case like this you don't want too much choke, which many people tend to do, because it: 1.) Can cause series resonance issues 2.) Reduces effectiveness of the system A general rule is a choke provides **about** 1000 ohms per 100 microhenries on 160 meters. With a 1/4 wave Marconi, a 50-100 microhenry choke would be provide more than enough impedance. With a half-wave end fed, the choke would have to be several hundred uH. The problem in this application is having the choke stand water, surge currents, and transmitter voltage. Most commercial BC tower chokes are solenoid construction with moderately heavy wire, almost like a plate choke for linear amplifiers but encapsulated. As a matter of fact, a standard high power amplifier plate choke would work pretty well. Like one of these: http://www.w8ji.com/rf_plate_choke.htm What this choke can do is prevent the antenna from trickle charging during wind or foul weather, if the antenna has no dc path to ground. What it will NOT do is prevent lightning damage from strikes within a few miles. If you want better protection, you could use a 1/4 wave stub, or heavy components in a parallel resonant circuit, with a spark gap to ground. I use pipes as gaps here on a 220-ft tower: http://www.w8ji.com/lifting_rohn_25g_45g_tower.htm That tower also has a 130 foot long horizontal tower that works as a "grounding stub". It allows me to access the tower with unlimited wires and cables without "shorting out" the tower to ground on 160, and it serves as a trickle drain. You could use 1/4 wave of shorted coax as a grounding stub on a 1/4 wave vertical. 73 Tom ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
Re: Topband: Choke Construction Info Needed
It all depends upon how much survivability you want, nothing will survive a direct hit. Any 1.5 to 2.5 mH choke will suffice, just look at the safety choke in a commercial amp for the smallest choice. The big ones are often found in scrapped BCB transmitters and tuning units as well as show up at hamfests and on Fleabay as old military gear had various candidates. Carl KM1H - Original Message - From: "Phil Clements" To: Sent: Thursday, July 26, 2012 3:03 PM Subject: Topband: Choke Construction Info Needed >I need to construct a heavy-duty choke to be installed from the feed point > of my 160 meter vertical to ground, for static drain and for lightning > protection. How large does the wire, form, and inductance need to be? > > > > Thanks in advance for your expertize! > > > > (((73))) > > Phil, K5PC > > > > ___ > UR RST IS ... ... ..9 QSB QSB - hw? BK > > > - > No virus found in this message. > Checked by AVG - www.avg.com > Version: 10.0.1424 / Virus Database: 2437/5155 - Release Date: 07/25/12 > ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
Topband: Choke Construction Info Needed
I need to construct a heavy-duty choke to be installed from the feed point of my 160 meter vertical to ground, for static drain and for lightning protection. How large does the wire, form, and inductance need to be? Thanks in advance for your expertize! (((73))) Phil, K5PC ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
