Re: Topband: Band Report
N4KG used to say "160 is never good 2 nights in a row". 73, Larry K4AB On Tue, Dec 18, 2018 at 11:54 AM Don Kirk wrote: > As a followup to my previous post about great band conditions early Monday > morning, the band this morning (Tuesday) was back to its typical self if > not a little worse from here in the Midwest USA. European stations peaking > 25 dB above my noise floor early Monday morning were lucky to be peaking 5 > dB above my noise floor this morning (which is much more the norm). I > would call what we experienced Sunday night / Monday morning one of those > rare special days (magic days). I sometimes notice a day each side of the > magic days where propagation is a little better than normal, but this > morning was not one of them here in the Midwest. What Sunday night / > Monday morning shows is that you must check the band everyday or you have a > great chance of missing one of those very special moments where the band is > red hot. > > Just FYI, > Don (wd8dsb) > > On Mon, Dec 17, 2018 at 6:20 PM Don Kirk wrote: > > > Hi Dave and Gang, > > > > This morning I was on from 0600 to around 0730 UTC and the band was in > > great condition into Europe from the Midwest (but lots of QSB), and at > the > > same time I heard KH6 really pounding in strong. I typically call > > conditions like this morning as one of those special days that occurs > only > > a handful of times a year on 160 meters. Stations like DL5AXX and SM5EDX > > were at times peaking 25 to 30 dB above my noise floor, but there were > lots > > of smaller stations easily workable which is an indicator of very good > > conditions. > > > > Here is a link to a recording of DL5AXX that I made this morning: > > https://www.youtube.com/watch?v=bEqLKMjG7L8 > > > > 73, > > Don (wd8dsb) > > > > > > > _ > Searchable Archives: http://www.contesting.com/_topband - Topband > Reflector > _ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector
Topband: Weatherproofing F-type connectors
I'm in the process of installing a receive 4 square for 160 using F type connectors and high quality flooded RG-6. Do these things need additional weatherproofing? As I recall all the many cable TV installations I have had over the decades, done by major cable and satellite companies, none have been weatherproofed. If its good enough for those guys, at those frequencies, shouldn't it be good for us at 1.8 MHz? 73, Larry K4AB _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: 160 Shunt-Fed Tower Readings
TU, Charlie on a great explaination for us non-engineers! The topband reflector is a great resource for guys like me trying to understand this band, even after decades in the hobby. And yes, I'm working on the Beverages, as we speak! Thanks, again! 73, Larry K4AB On 12/10/14, Charlie Cunningham wrote: > Hi, again, Larry, > > Well, first of all the shunt feed, being a shorted transmission line, < 1/4 > wavelength in extent, would present an inductive resent at the feed point > that you are correctly cancelling with the 1000 pF series variable > capacitor. You missed ever so slightly and you are showing a series > reactance of j5.6 ohms! Trivially small and negligible!! DON'T bother > trying > to improve it!! You would pick up more reactance than that by just > changing > frequency a few kilohertz!! It's PERFECT! The 15893 pF is the equivalent > series capacitance that would produce -j5.6 ohms of capacitive reactance - > so the message is that the equivalent series capacitance is NEGLIGIBILY > LARGE!! (LARGE is GOOD!) If you had measured at a frequency where the > reactance cancellatio was exact and perfect, the driving point impedance > would be pure real, with 0 reactance that would correspond to infinite > capacitance or 0 inductance. > > The real part of your driving point impedance is 59.5 ohms real, resulting > in a VSWR od 1.23:1!! So near a "perfect match" that you won't improve it > significantly, even if you did an AWFUL LOT of work to make a trivially > small change in the tap point of your wire cage!! The mismatch loss at > 1.23:1 VSWR is essentially 0, and the excess loss in a feedline operating > at 1.23:1 VSWR is essentially 0, and the loss in even a very long run of > coax would be essentially equal to the "flat' loss - that is: the loss in a > "flat" line operated at 1:1 VSWR. > > So, Larry, you've done a GREAT job on your TX antenna. And do keep in mind > that you have 24 feet of boom up there that's top-loading that 94' of Rohn > 25! Just congratulate yourself on a job well done, and ENJOY!! If you want > to worki on topband antennas - work on Beverages or terminated loop receive > antennas to help you HEAR better! > > Great job! Have fun and enjoy! > > BTW - I AM an RF engineer and I have spent q lot of my career designing and > measuring antennas > > 73, > Charlie, K4OTV > > > > -Original Message- > From: Topband [mailto:topband-boun...@contesting.com] On Behalf Of Larry > K4AB > Sent: Wednesday, December 10, 2014 6:14 PM > To: Charlie Cunningham > Cc: topband@contesting.com > Subject: Re: Topband: 160 Shunt-Fed Tower Readings > " line >>Why do you feel a need to improve it? > > Thanks for the response, Charlie! > > I'm concerned about a few things: > > 1) I'm thinking the antenna is electrically too short. After all, the Yagi > at the top really isn't adding too much top loading. And I'm thinking > adding a couple of top loading wires connected to the tower might be > beneficial. > > 2) What exactly is the analyzer telling me when it says C:15893pF? > I'm far from an engineer, but something tells me that's way high. Or is > it? > > 73, > Larry K4AB > > > On 12/10/14, Charlie Cunningham wrote: >> From your description and your measured data, Larry, I don't see how >> you could improve the antenna noticeably! Why do you feel a need to >> improve it? >> I appears to be resonant, well-matched and it appears to have an >> excellent ground image system! I think you might be kidding yourself >> if you change anything! As the old adage says n "If it ain't broke >> -don't fix it"! >> >> 73, >> Charlie, K4OTV >> >> -Original Message- >> From: Topband [mailto:topband-boun...@contesting.com] On Behalf Of >> Larry K4AB >> Sent: Wednesday, December 10, 2014 2:41 PM >> To: topband@contesting.com >> Subject: Topband: 160 Shunt-Fed Tower Readings >> >> The antenna is a 94' Rohn 25, with a Force 12 24'boom Delta 6BA on top. >> Note >> that the elements are insulated from the boom. The base of the tower >> is grounded. >> >> 73 radials are attached to the base ranging in length from 130'-250'. >> 15,000 feet of radials, average length of ~200'. >> >> It is fed through a series 1000pF 10KV Jennings vacuum variable. >> The shunt is a 4 wire cage about 3" in diameter and attached at ~45' >> level. It is spaced about 3' from the tower. >> >> Here are the readings I get from a RigExpert AA-30 at the feedpoint: >> >> 1.830 kHz >> Series model: lZI: 59.7 Ohms >> R:59.5 Ohms >> SWR: 1.23 >> X:5.6 Ohms >> C: 15893 pF >> >> What are these reading telling me,and how can I improve the antenna? >> >> Thanks, in advance! >> >> 73, >> Larry K4AB >> _ >> Topband Reflector Archives - http://www.contesting.com/_topband >> >> > _ > Topband Reflector Archives - http://www.contesting.com/_topband > > _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: 160 Shunt-Fed Tower Readings
>I would like to know how you can get 15893pf from a 1000pf capacitor. That >has to be a mis-read value there...gary maybe rounded off to 159pf?? That's a great question. Where is the analyzer actually getting that reading? 73, Larry K4AB On 12/10/14, Tom W8JI wrote: >> I'm concerned about a few things: >> >> 1) I'm thinking the antenna is electrically too short. After all, the >> Yagi at the top really isn't adding too much top loading. And I'm >> thinking >> adding a couple of top loading wires connected to the tower >> might be beneficial. > > If you run any power, you will likely start to have problems with arcing at > > the Yagi antenna elements where they cross the boom. > > This is because of the poor insulation, and because of the high voltage at > the boom when on 160. > > The cure for that is to ground the elements to the boom though air coil > inductors. Just five or ten uH would work OK, and not upset the antenna > operation. This would also add 160 top loading. > > >> 2) What exactly is the analyzer telling me when it says C:15893pF? >> I'm far from an engineer, but something tells me that's way high. Or is >> it? > > It is meaningless. It just means you are measuring almost where the antenna > > is resonant. > > 73 Tom > > _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: 160 Shunt-Fed Tower Readings
>Why do you feel a need to improve it? Thanks for the response, Charlie! I'm concerned about a few things: 1) I'm thinking the antenna is electrically too short. After all, the Yagi at the top really isn't adding too much top loading. And I'm thinking adding a couple of top loading wires connected to the tower might be beneficial. 2) What exactly is the analyzer telling me when it says C:15893pF? I'm far from an engineer, but something tells me that's way high. Or is it? 73, Larry K4AB On 12/10/14, Charlie Cunningham wrote: > From your description and your measured data, Larry, I don't see how you > could improve the antenna noticeably! Why do you feel a need to improve > it? > I appears to be resonant, well-matched and it appears to have an > excellent > ground image system! I think you might be kidding yourself if you change > anything! As the old adage says n "If it ain't broke -don't fix it"! > > 73, > Charlie, K4OTV > > -----Original Message- > From: Topband [mailto:topband-boun...@contesting.com] On Behalf Of Larry > K4AB > Sent: Wednesday, December 10, 2014 2:41 PM > To: topband@contesting.com > Subject: Topband: 160 Shunt-Fed Tower Readings > > The antenna is a 94' Rohn 25, with a Force 12 24'boom Delta 6BA on top. > Note > that the elements are insulated from the boom. The base of the tower is > grounded. > > 73 radials are attached to the base ranging in length from 130'-250'. > 15,000 feet of radials, average length of ~200'. > > It is fed through a series 1000pF 10KV Jennings vacuum variable. > The shunt is a 4 wire cage about 3" in diameter and attached at ~45' > level. It is spaced about 3' from the tower. > > Here are the readings I get from a RigExpert AA-30 at the feedpoint: > > 1.830 kHz > Series model: lZI: 59.7 Ohms > R:59.5 Ohms > SWR: 1.23 > X:5.6 Ohms > C: 15893 pF > > What are these reading telling me,and how can I improve the antenna? > > Thanks, in advance! > > 73, > Larry K4AB > _ > Topband Reflector Archives - http://www.contesting.com/_topband > > _ Topband Reflector Archives - http://www.contesting.com/_topband
Topband: 160 Shunt-Fed Tower Readings
The antenna is a 94' Rohn 25, with a Force 12 24'boom Delta 6BA on top. Note that the elements are insulated from the boom. The base of the tower is grounded. 73 radials are attached to the base ranging in length from 130'-250'. 15,000 feet of radials, average length of ~200'. It is fed through a series 1000pF 10KV Jennings vacuum variable. The shunt is a 4 wire cage about 3" in diameter and attached at ~45' level. It is spaced about 3' from the tower. Here are the readings I get from a RigExpert AA-30 at the feedpoint: 1.830 kHz Series model: lZI: 59.7 Ohms R:59.5 Ohms SWR: 1.23 X:5.6 Ohms C: 15893 pF What are these reading telling me,and how can I improve the antenna? Thanks, in advance! 73, Larry K4AB _ Topband Reflector Archives - http://www.contesting.com/_topband
