HI Thanks to all that have responded regarding my quastion about Hi-Z or Apex loop antenna. 73 Rune LA7THA
> From: [email protected] > Subject: Topband Digest, Vol 130, Issue 2 > To: [email protected] > Date: Wed, 2 Oct 2013 12:00:10 -0400 > > Send Topband mailing list submissions to > [email protected] > > To subscribe or unsubscribe via the World Wide Web, visit > http://lists.contesting.com/mailman/listinfo/topband > or, via email, send a message with subject or body 'help' to > [email protected] > > You can reach the person managing the list at > [email protected] > > When replying, please edit your Subject line so it is more specific > than "Re: Contents of Topband digest..." > > > Today's Topics: > > 1. Re: Homebrew capacitors (Tom W8JI) > 2. Re: Homebrew capacitors (Mike Waters) > 3. 160m Inverted L High SWR (Bill Stewart) > 4. Re: 5/8 wavelength vertical is mo bettathanshorterversions?? > (Tom W8JI) > 5. Re: 160m Inverted L High SWR (Richard Karlquist) > 6. Re: 160m Inverted L High SWR (Grant Saviers) > 7. Hi-Z or Apex loop antenna (Rune ?ye) > > > ---------------------------------------------------------------------- > > Message: 1 > Date: Tue, 1 Oct 2013 12:10:06 -0400 > From: "Tom W8JI" <[email protected]> > To: <[email protected]> > Subject: Re: Topband: Homebrew capacitors > Message-ID: <CE57B4CC3DC04950A86FC1D21B7C3166@MAIN> > Content-Type: text/plain; format=flowed; charset="iso-8859-1"; > reply-type=original > > This post is worth reading and saving for homebrewers. Not nearly enough of > us understand capacitors this well. > > > > KK1L noted that there must be either an overlap or a gap in the sleeve > > that wraps the inner tube. A gap would create a "hot spot" where the > > breakdown voltage would be reduced, while an overlap could cause the > > inner tube to bind. This could be avoided if one could obtain > > dielectric tubing of the required dimensions or if one could "weld" > > the dielectric to seal the gap. I don't anticipate having a problem > > with the possibility of a small gap in my application, but two > > possible solutions to this condition come to mind. > > > > First, one could wrap the dielectric material twice around the inner > > conducting tube. While there would still be a gap, it would not be > > entirely an air gap, which would increase the breakdown voltage. Of > > course, one would also get 1/2 the capacitance per unit length, since > > the dielectric would be twice as thick - unless material half the > > original thickness could be obtained. > > > > Second, one could cut a slot down the length of the outer tube and > > center the gap in the dielectric material in the slot. In this way, > > the potential at the gap would be reduced according to the width of > > the slot. Here, again, the capacitance per unit length would be > > reduced, but less so than in the first solution. > > Other issues are any sharp points or edges in conductors will greatly reduce > breakdown voltage. This is often an operating time issue, because years of > cornoa will slowly eat away the dielectric. This is why some "capacitor" > stubs, even though apparently very conservative, will fail over time. I've > seen 50kV insulation fail at 5 kV just from having cornoa from a sharp edge. > > > > ------------------------------ > > Message: 2 > Date: Tue, 1 Oct 2013 12:25:06 -0500 > From: Mike Waters <[email protected]> > To: topband <[email protected]> > Subject: Re: Topband: Homebrew capacitors > Message-ID: > <ca+fxyxgfx4wkdtjvpjlfhkku+wvw19x9msc+zhna_hpzl4k...@mail.gmail.com> > Content-Type: text/plain; charset=ISO-8859-1 > > Good points, as usual, Tom. > > Corona --besides greatly reducing the breakdown voltage-- can also generate > ozone, which can gradually break down some dielectric materials. When I > worked at Owens-Illinois in Perrysburg Ohio in the late 70's, they used > large insulated conductors to feed 12 kV 3 phase from the substations into > the building. After a few years, ozone finally deteriorated the rubber > insulation to the point that it failed catastrophically. A spectacular arc, > explosion, and a lot of damage and downtime was the result. (Bob Wacke > WA8SHH probably remembers that.) Those HV cables are now made differently, > some with a static drain on the outer cover. > > 73, Mike > www.w0btu.com > > On Tue, Oct 1, 2013 at 11:10 AM, Tom W8JI <[email protected]> wrote: > > > ... years of corona will slowly eat away the dielectric... > > > > > ------------------------------ > > Message: 3 > Date: Tue, 1 Oct 2013 17:08:56 -0400 (EDT) > From: Bill Stewart <[email protected]> > To: [email protected] > Subject: Topband: 160m Inverted L High SWR > Message-ID: > <[email protected]> > Content-Type: text/plain; charset=utf-8 > > > Good afternoon all, > I just finished installing a new Inverted L. The previous one was > removed?because > a tree fell across a set of guys on my tower, which had to be taken down. The > new > Inverted L is strung up amongst a lot of tall (80 ft +) pine trees. The vert. > section is > abt 55 ft & the rest is nearly flat horizontal. Total length is 130 ft/6 in. > I am using a > 4 wire c-poise abt 9 ft high of which none are directly under the horiz. > section. > Each wire is abt 135 ft long. The min. SWR is abt 2.9:1 at 1833 khz. The SWR > curve is broad which looks odd to me. I am feeding it direct with a random > length of > 50 ohm coax. For these tests, I am using a TS-440S, which reduces power at > this > value of SWR (the internal tuner does not operate on 160). Normally, I would > run > vintage xmtrs, which load up ok. I will try it tonight to see if it gets out > of the yard. > ? > Any suggestions how I can get the SWR down below 2:1 so the?TS-440S will work > at > full power? I apologize if this subject has been discussed before. If so, > please point > me towards that info. > ? > Many thanks for any comments....73 de Bil l K4JYS > ? > > ------------------------------ > > Message: 4 > Date: Tue, 1 Oct 2013 18:03:49 -0400 > From: "Tom W8JI" <[email protected]> > To: <[email protected]> > Subject: Re: Topband: 5/8 wavelength vertical is mo > bettathanshorterversions?? > Message-ID: <5B579A7896514645A05FE436197AFEEF@MAIN> > Content-Type: text/plain; format=flowed; charset="iso-8859-1"; > reply-type=response > > >> Why would anyone use significantly more power to get a job done using a > >> low angle, when the same job could be done with a higher angle and less > >> power? > > > > ** If that higher angle has excessive path loss then the lower one stands > > a good chance of getting thru even though it starts at a launch loss > > disadvantage. > > That still makes absolutely no sense. The 5/8th wave is virtually never > better for overall operation, DX or not, and most of the time is a real > noticable dog. > > Why would someone use a "dog of an antenna" when that antenna costs more, > and has a poorer signal under almost any condition? > > > > ** It might to the few who feel that power rules are only for the other > > guy and working a new country, contest multiplier, or playing king of the > > hill, is the only goal that counts. > > Tubes with handles are readily available to those with something as small > > as an ALS-600, AL-80A/B, etc, as a driver. > > So let me see if I have this right. You think someone who wants to be loud > should intentionally uses a worse antenna just so they can run more power to > overcome the weakness they created by using the poor antenna. > > That makes no sense. > > > > > ------------------------------ > > Message: 5 > Date: Tue, 01 Oct 2013 15:14:12 -0700 > From: Richard Karlquist <[email protected]> > To: [email protected] > Subject: Re: Topband: 160m Inverted L High SWR > Message-ID: <[email protected]> > Content-Type: text/plain; charset=UTF-8; format=flowed > > On 2013-10-01 14:08, Bill Stewart wrote: > > Good afternoon all, > > > The vert. section is > > abt 55 ft & the rest is nearly flat horizontal. Total length is 130 > > ft/6 in. I am using a > > 4 wire c-poise abt 9 ft high of which none are directly under the > > horiz. section. > > Each wire is abt 135 ft long. The min. SWR is abt 2.9:1 at 1833 khz. > > The SWR > > This is exactly what you would expect. It corresponds to a drive > impedance > of something like 18 ohms, about right for a top loaded 55 foot > vertical. > > You will need to put a shunt capacitor of about 2400 pF across your > coax, > and then increase the length of the L until you get the resonance to > 1833 kHz. > > I currently have a top loaded 60 foot vertical and this is very similar > to my situation. You will find that after proper matching, the > bandwidth > is really quite narrow, indicating reasonable efficiency. > > You should probably add a common mode choke at the feedpoint if you > don't already have one. > > Rick N6RK > > > ------------------------------ > > Message: 6 > Date: Tue, 01 Oct 2013 15:21:10 -0700 > From: Grant Saviers <[email protected]> > To: Bill Stewart <[email protected]> > Cc: [email protected] > Subject: Re: Topband: 160m Inverted L High SWR > Message-ID: <[email protected]> > Content-Type: text/plain; charset=UTF-8; format=flowed > > In order of approximate decreasing importance: > > 1. the elevated radials should not be grounded anywhere. > 2. With elevated radials, you must have a good feedline choke at the > feedpoint, about 9 turns on a type 31 "big clamp-on", and that will > require RG58 or TFE RG174 if you run 1500 watts. > 3. My 160m T has about the same vertical dimensions but needed another > 80' total on the T top to resonate at 1835, or about 157' total wire. > Keep all wires more than 18" from paralleling the tree trunk and large > branches. Remember there are very high voltages at the top load wire ends. > 4. my feedpoint Z is 25 ohms (per EZNEC and VNWA measurements) and a 2:1 > balun brings the SWR to about 1.1 at 1835 with 6 x 125' radials at 10' > elevation > 5. I will add another 2 radials and probably a Hi Z choke for DC > grounding. I don't expect much change in the resonant F since radials 5 > & 6 had little effect. Check antennasbyn6lf.com for a lot of data about > elevated radials. > 6. series capacitors switched in series to the feedpoint with vacuum > relays or a motorized vacuum variable is planned per W8JI's suggestion > to be able to tune higher up the band. > > Grant KZ1W > Redmond, WA > > > On 10/1/2013 2:08 PM, Bill Stewart wrote: > > Good afternoon all, > > I just finished installing a new Inverted L. The previous one was removed > > because > > a tree fell across a set of guys on my tower, which had to be taken down. > > The new > > Inverted L is strung up amongst a lot of tall (80 ft +) pine trees. The > > vert. section is > > abt 55 ft & the rest is nearly flat horizontal. Total length is 130 ft/6 > > in. I am using a > > 4 wire c-poise abt 9 ft high of which none are directly under the horiz. > > section. > > Each wire is abt 135 ft long. The min. SWR is abt 2.9:1 at 1833 khz. The SWR > > curve is broad which looks odd to me. I am feeding it direct with a random > > length of > > 50 ohm coax. For these tests, I am using a TS-440S, which reduces power at > > this > > value of SWR (the internal tuner does not operate on 160). Normally, I > > would run > > vintage xmtrs, which load up ok. I will try it tonight to see if it gets > > out of the yard. > > > > Any suggestions how I can get the SWR down below 2:1 so the TS-440S will > > work at > > full power? I apologize if this subject has been discussed before. If so, > > please point > > me towards that info. > > > > Many thanks for any comments....73 de Bil l K4JYS > > > > _________________ > > Topband Reflector > > > > ------------------------------ > > Message: 7 > Date: Wed, 2 Oct 2013 06:16:57 +0000 > From: Rune ?ye <[email protected]> > To: "[email protected]" <[email protected]> > Subject: Topband: Hi-Z or Apex loop antenna > Message-ID: <[email protected]> > Content-Type: text/plain; charset="iso-8859-1" > > > I All, > I am moving in to a new qth in end of November and start to prepare my > antenna farm. My new land is around 3700 square meter so I should be able to > install some RX antenna for TB. > My new qth is around 20Km south of Oslo and are in a farmer land. I guess i > will be able to even install some 2-300 meter long beverage antenna if my > neighbor farmer allows me toJ. I have recently reading about HI-Z receiving > antenna (8 element version) last number of QST I found info about the new > Apex loop antenna. Is here anyone that has tried any of the two antennas? Are > they comparable? I am not afraid the size for an 8 element HI-Z or even the > Beverage antennas, I simply want to use the best antenna at present time. > (Well phased beverage antennas is probbably to big in that area) > > 73 Rune LA7THA > > ------------------------------ > > Subject: Digest Footer > > _______________________________________________ > Topband mailing list > [email protected] > http://lists.contesting.com/mailman/listinfo/topband > > > ------------------------------ > > End of Topband Digest, Vol 130, Issue 2 > *************************************** _________________ Topband Reflector
