HI
Thanks to all that have responded regarding my quastion about Hi-Z or Apex loop
antenna.
73 Rune LA7THA
> From: topband-request@contesting.com
> Subject: Topband Digest, Vol 130, Issue 2
> To: topband@contesting.com
> Date: Wed, 2 Oct 2013 12:00:10 -0400
>
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> 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" <w8ji@w8ji.com>
> To: <topband@contesting.com>
> 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 <mikewate@gmail.com>
> To: topband <topband@contesting.com>
> Subject: Re: Topband: Homebrew capacitors
> Message-ID:
> <CA+FxYXgfX4wkdTjVpjLfhKku+wvW19x9mSc+zHNa_hPzL4Kr9A@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 <w8ji@w8ji.com> 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 <cwopr@embarqmail.com>
> To: topband@contesting.com
> Subject: Topband: 160m Inverted L High SWR
> Message-ID:
> <438809017.16709736.1380661735999.JavaMail.root@embarqmail.com>
> 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" <w8ji@w8ji.com>
> To: <topband@contesting.com>
> 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 <richard@karlquist.com>
> To: topband@contesting.com
> Subject: Re: Topband: 160m Inverted L High SWR
> Message-ID: <2d0e22f5785d1c944743ceaa2e22d87e@sonic.net>
> 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 <grants2@pacbell.net>
> To: Bill Stewart <cwopr@embarqmail.com>
> Cc: topband@contesting.com
> Subject: Re: Topband: 160m Inverted L High SWR
> Message-ID: <524B4AD6.3030501@pacbell.net>
> 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 <runeegil@hotmail.com>
> To: "topband@contesting.com" <topband@contesting.com>
> Subject: Topband: Hi-Z or Apex loop antenna
> Message-ID: <DUB126-W87F89769EE6A7471BC8489C4160@phx.gbl>
> 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
>
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> ------------------------------
>
> End of Topband Digest, Vol 130, Issue 2
> ***************************************
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Topband Reflector
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