Re: Topband: 160 sloper readings
Hi Luke, No, no stretch in this stuff, I'm using WD-1A field telephone wire for the wire and it has a stainless core in each of the two wires. It's exceedingly tough stuff and for most intents it's almost impossible to break. I am in a few minutes heading out to make another 129' wire to put up though, maybe I somehow mistakenly made the other one the wrong length. 73, Gary KA1J > What wire have you used for the radiator? Could it have stretched? > > Luke VK3HJ > _ > Topband Reflector Archives - http://www.contesting.com/_topband > _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: 160 sloper readings
What wire have you used for the radiator? Could it have stretched? Luke VK3HJ _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: 160 sloper readings
Hi Guy, No tower here, can't have one. The antennas are all wire on or hanging from trees. The radials are in a forest, not anywhere I can leafblow them. 1/2 of the radials are in a tick infested marsh, the other 1/2 are on the tick infested bog/woods next to the marsh. I am 15 miles from Lyme, CT where Lyme disease was first noticed. Ground Zero for tick issues in New England... The 160 antenna used to be an inverted-L but that tree came down so now I use a spud gun to get the 160 on top of the nearest tall trees from the radial bed & it's right on the marsh line. I can't do another antenna, this one took a few years to construct & that when I had both legs, I'm now working with a prosthetic leg and going back into the bog isn't in the cards anymore unless my life depended on it. I used silver solder to solder the radials to the ring terminals which bolt to the radial plate, I used penatrox on each connection. Looking at the solder joints today they look essentially the same as when they were new. There is no place to run a new radial bed, AMTRAK is 75' from my property and as it is, the ends of my radials are 40' from AMTRAK, I can't move closer to the house or the radials will be under my Rx antennas. The Rx antenna is next to my neighbor's property. So... I have to deal with what I have and feel lucky to have what I've got. Short of buying another house and relocating, this is what I have to work with. I can't see anything antenna-wise that has fallen apart or suffered the ravages of time or salt water and I do see here & there some radials that are exposed and they all look to be intact, not chewed/dislodged. I made over 500 Q's on 160 running QRP in a contest earlier this year but with the apparent issues in resistance, I must have some issue sucking my signal. I just read a couple replies saying the MFJ 259B has issues on 160, it is old and it's definitely not state of the art. I remember being happy that I was getting a resonant SWR on 160 so something has changed. I'm changing the flexible coax to LMR-400 Ultra, the 7/8 hardline looks to read as deal with a dummy at the end. I'm out of guesses although maybe the leaves are an issue as you mentioned. All the radials have insulation on them and all the other bands seem to be working as expected, it's just 160 that has these issues. Always something... And thank you for the informative reply, I appreciate it. Gary KA1J > Hi, Gary. > > It is not clear from your description exactly how the "sloper" is fed, > where the radials are in relation to the tower, etc. > > Quite a few things could be responsible for a change like that. > > Not clearing the leaves off the ground over the radials will gradually > bury them and result in a slowly increasing feed R and loss. Clearing > the ground through each leaf fall period with a leaf blower usually > clears that up. You will note that in areas subject to seasonal > falling leaves, AM broadcast antennas have huge nicely mowed lawns > over their radials, and trees have been removed from the radial field. > That is not without cause or entirely for appearances. Buried bare > radials will behave differently over time than insulated radials laid > on top of the ground. > > The tower and all the wires running up it are HARD-coupled to the > sloper. It is possible to have more RF current in the tower and its > cabling than in the sloper wire. It is possible for the tower and its > cabling to be the major radiator/dissipator of the tower/sloper > *system*. > > Adding or removing cables on the tower, or changing the terminations > of conductors, if they are not all bonded (or capacitor-RF-bypassed) > to tower at top and bottom, will change the feed measurements. Exactly > how the measurement changes, and how much it changes, depends on > environment and grounding/blocking on those conductors. > > Adding/changing/removing yagi's, etc near the top of the tower will > change the "parasitic element" behavior of the tower as seen by the > sloper. > > Particularly if the ground is poor, simply having a rainy summer can > change the feed Z of the sloper. > > Deterioration of the radial conductors can raise the feed Z of the > sloper. > > Installing a new antenna/feedline or tower within a half-wavelength > radius or so can alter the feed Z of the sloper. > > Folks often throw up a wire from a brief description of an antenna, > and are happy if they can work QSO's. Considering how often time and > funds for ham projects are simply not available, I can hardly argue > with this, and I won't, having done the same myself, quite for cause. > I will note that getting on the air on 160 is one thing, and worrying > about the characteristics of a thinly engineered antenna, and that > over most of a decade, is quite another. > > The "time-lapse engineering" of the antenna may not have been > considered at erection time, and deterioration may have started
Re: Topband: 160 sloper readings
Hi, Gary. It is not clear from your description exactly how the "sloper" is fed, where the radials are in relation to the tower, etc. Quite a few things could be responsible for a change like that. Not clearing the leaves off the ground over the radials will gradually bury them and result in a slowly increasing feed R and loss. Clearing the ground through each leaf fall period with a leaf blower usually clears that up. You will note that in areas subject to seasonal falling leaves, AM broadcast antennas have huge nicely mowed lawns over their radials, and trees have been removed from the radial field. That is not without cause or entirely for appearances. Buried bare radials will behave differently over time than insulated radials laid on top of the ground. The tower and all the wires running up it are HARD-coupled to the sloper. It is possible to have more RF current in the tower and its cabling than in the sloper wire. It is possible for the tower and its cabling to be the major radiator/dissipator of the tower/sloper *system*. Adding or removing cables on the tower, or changing the terminations of conductors, if they are not all bonded (or capacitor-RF-bypassed) to tower at top and bottom, will change the feed measurements. Exactly how the measurement changes, and how much it changes, depends on environment and grounding/blocking on those conductors. Adding/changing/removing yagi's, etc near the top of the tower will change the "parasitic element" behavior of the tower as seen by the sloper. Particularly if the ground is poor, simply having a rainy summer can change the feed Z of the sloper. Deterioration of the radial conductors can raise the feed Z of the sloper. Installing a new antenna/feedline or tower within a half-wavelength radius or so can alter the feed Z of the sloper. Folks often throw up a wire from a brief description of an antenna, and are happy if they can work QSO's. Considering how often time and funds for ham projects are simply not available, I can hardly argue with this, and I won't, having done the same myself, quite for cause. I will note that getting on the air on 160 is one thing, and worrying about the characteristics of a thinly engineered antenna, and that over most of a decade, is quite another. The "time-lapse engineering" of the antenna may not have been considered at erection time, and deterioration may have started the day after the antenna's erection. It is unusual for a ham to have an academic grade recording of frequency sweeps and various measurements taken at routine intervals, along with dated notation of changes made to the antenna farm. It's not like a pilot's log or aircraft maintenance log which is required by law, and punishable if omitted. Almost *nobody* has this data, making explaining over-the-years-changes really difficult. Allowing leaves to accumulate may be highly preferable from an appearance or maintenance effort standpoint, but will gradually deteriorate TX antenna performance. This is an annual problem for those with BOGs in the woods. After two years, the bottom layer of leaves will have completely decomposed into soil or proto-soil, effectively burying the radial wires deeper. Six or seven years is worth half the years in inches further buried. This softer more permeable, sponge-like new layer will get criss-crossed with the grateful roots of anything growing in the woods. At the same time this adds more dielectric material inside the ad-hoc capacitor that is the sloper wire vs radials. If not increasing loss, the additional dielectric material has at minimum increased the feedline shunting capacitance of this ad-hoc capacitor, dropping the resonant frequency. Given everything above, it's not at all unusual that you would have experienced changes. Rather more it was guaranteed that you would experience changes. One of the blessings of elevated radials or an FCP is the 8 foot separation between constantly changing lossy ground and the system consisting of bottom of the vertical wire plus counterpoise. You may want to revisit the choice of 160 antenna. 73 and good luck, Guy K2AV On Sat, Aug 18, 2018 at 7:17 PM Gary Smith wrote: > Folks, > > I'm starting to get ready for the upcoming > winter frolics on 160. The 160 antenna is > a sloper and I have somewhere around 50 or > so 130' radials pretty much buried under > 6-7 years of leaves. When I went to the > remote coax switch & checked the readings > on the sloper with 10' of coax, I found > some readings with the old MFJ-259B that > concerns me. > > I thought I'd cut the Sloper at 129' long > for best SWR at 1.825 but I'm now reading > the lowest SWR at 1.737 MHz and the > impedance read 85. Going back to the shack > I read the antenna (with 360' of 7/8 50 > ohm commscope now in-between), and the > resistance drops to 55 but the SWR still > reads lowest around 1.737 > > It appears I need to shorten my antenna, > I'll have to work out the proper length > again but my concern is
Re: Topband: 160 sloper readings
Unless you have no BC stations for 200 miles distant, making measurements with an MFJ259 on 160m is going to give you unreliable readings. The overload threshold on that band is extreemly low. 73/jeff/ac0c alpha-charlie-zero-charlie www.ac0c.com On 18-Aug-18 6:10 PM, Gary Smith wrote: Folks, I'm starting to get ready for the upcoming winter frolics on 160. The 160 antenna is a sloper and I have somewhere around 50 or so 130' radials pretty much buried under 6-7 years of leaves. When I went to the remote coax switch & checked the readings on the sloper with 10' of coax, I found some readings with the old MFJ-259B that concerns me. I thought I'd cut the Sloper at 129' long for best SWR at 1.825 but I'm now reading the lowest SWR at 1.737 MHz and the impedance read 85. Going back to the shack I read the antenna (with 360' of 7/8 50 ohm commscope now in-between), and the resistance drops to 55 but the SWR still reads lowest around 1.737 It appears I need to shorten my antenna, I'll have to work out the proper length again but my concern is why at the feed point would I see 85 for the resistance at resonance. Suggestions on what might I give a look to when I go back out tomorrow? Thanks & 73, Gary KA1J _ Topband Reflector Archives - http://www.contesting.com/_topband _ Topband Reflector Archives - http://www.contesting.com/_topband
Topband: 160 sloper readings
Folks, I'm starting to get ready for the upcoming winter frolics on 160. The 160 antenna is a sloper and I have somewhere around 50 or so 130' radials pretty much buried under 6-7 years of leaves. When I went to the remote coax switch & checked the readings on the sloper with 10' of coax, I found some readings with the old MFJ-259B that concerns me. I thought I'd cut the Sloper at 129' long for best SWR at 1.825 but I'm now reading the lowest SWR at 1.737 MHz and the impedance read 85. Going back to the shack I read the antenna (with 360' of 7/8 50 ohm commscope now in-between), and the resistance drops to 55 but the SWR still reads lowest around 1.737 It appears I need to shorten my antenna, I'll have to work out the proper length again but my concern is why at the feed point would I see 85 for the resistance at resonance. Suggestions on what might I give a look to when I go back out tomorrow? Thanks & 73, Gary KA1J _ Topband Reflector Archives - http://www.contesting.com/_topband
