Topband: Topband Digest, Vol 259, Issue 14

[Tom Boucher]

Sorry Jim K9YC but it is incorrect to say that a loading coil at the base
of an antenna, which is less than a quarter wave, will affect the high
current point of the antenna. Assuming the coil is pure L with no
distributed C, the current exiting the coil will be the same as that
entering it. It is simply another way of matching the antenna to the
feeder. However I'm sure you are right to say it's more convenient to
accept the slight loss in the feeder and to tune it in the shack.

I think it was W8JI who went to great lengths with two thermocouple RF
ammeters to prove the currents were the same at the top and bottom of his
mobile antenna loading coil.

73,
Tom G3OLB

On Sun, 28 Jul 2024 at 05:03, <topband-request at contesting.com> wrote:

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> Today's Topics:
>
>    1. Quarter wave sloper ? (jim.thom jim.thom at telus.net)
>    2. Re: Quarter wave sloper ? (Felipe J. Hern?ndez)
>    3. Re: Quarter wave sloper ? (Gene Smar)
>    4. Re: Quarter wave sloper ? (jim.thom jim.thom at telus.net)
>    5. Re: Quarter wave sloper ? (Gene Smar)
>    6. Re: Quarter wave sloper ? (Tree)
>    7. Re: Quarter wave sloper ? (Rick Kunath)
>    8. Re: Quarter wave sloper ? (Rick Kunath)
>    9. WG: AW:  Quarter wave sloper ? (dj7ww at t-online.de)
>   10. Re: Quarter wave sloper ? (Felipe J. Hern?ndez)
>   11. Re: Quarter wave sloper ? (Jim Brown)
>   12. Re: Quarter wave sloper ? (Jim Brown)
>   13. Re: Quarter wave sloper ? (jim.thom jim.thom at telus.net)
>   14. Re: Quarter wave sloper ? (Jim Brown)
>
>
> ----------------------------------------------------------------------
>
> Message: 1
> Date: Sat, 27 Jul 2024 12:47:51 -0700
> From: "jim.thom jim.thom at telus.net" <jim.thom at telus.net>
> To: topband at contesting.com
> Subject: Topband: Quarter wave sloper ?
> Message-ID:
>         <
> CAB4ZMgu5-mK94Mjy9KhpmF_A-1Kyg5Px6fULXb1k2MVQOfmMLA at mail.gmail.com>
> Content-Type: text/plain; charset="UTF-8"
>
> Has anyone had success with a 160m,  1/4 wave sloper....hanging off a 90'
> tower, with a 40m yagi just above the top of the tower ?
>
>
> ------------------------------
>
> Message: 2
> Date: Sat, 27 Jul 2024 15:50:23 -0400
> From: Felipe J. Hern?ndez <np4zet at gmail.com>
> To: "jim.thom jim.thom at telus.net" <jim.thom at telus.net>
> Cc: topband at contesting.com
> Subject: Re: Topband: Quarter wave sloper ?
> Message-ID:
>         <CAOSq5+u3rjangyiZSvVtp9A=
> 4WaLcJa6xmWO6vr5f5jmqiD1ag at mail.gmail.com>
> Content-Type: text/plain; charset="UTF-8"
>
> Yes, is a great performer, don?t waste your time with inv v or sloping
> dipoles, is a little trickier to tune but it?s a fantastic radiator.
>
> Felipe
> Np4z
>
> On Sat, Jul 27, 2024 at 3:48?PM jim.thom jim.thom at telus.net <
> jim.thom at telus.net> wrote:
>
> > Has anyone had success with a 160m,  1/4 wave sloper....hanging off a 90'
> > tower, with a 40m yagi just above the top of the tower ?
> > _________________
> > Searchable Archives: http://www.contesting.com/_topband - Topband
> > Reflector
> >
>
>
> ------------------------------
>
> Message: 3
> Date: Sat, 27 Jul 2024 20:35:24 +0000 (UTC)
> From: Gene Smar <ersmar at verizon.net>
> To: "jim.thom jim.thom at telus.net" <jim.thom at telus.net>,
>         <topband at contesting.com>
> Subject: Re: Topband: Quarter wave sloper ?
> Message-ID: <10192229.543199.1722112524283 at mail.yahoo.com>
> Content-Type: text/plain; charset=UTF-8
>
> Not exactly, but close. I installed an 80M 1/4 wave sloper (a/k/a
> half-sloper) wire off my 64 foot tower at 50 feet. Above the wire at 66
> feet is a? Bencher Skyhawk tribander where I shorted all the parasitic
> elements to the boom for extra top-hat loading. The sloper seems to be
> pretty broadbanded and I can work into the Canadian maritime provinces and
> UK and western Europe pretty regularly from Maryland with 100 Watts.
> FWIW.
> 73 de?Gene Smar AD3F?
>
> Sent from my Radio Shack TRS-80 model 100 laptop
>
>   On Sat, Jul 27, 2024 at 3:48 PM, jim.thom jim.thom at telus.net<
> jim.thom at telus.net> wrote:   Has anyone had success with a 160m,? 1/4
> wave sloper....hanging off a 90'
> tower, with a 40m yagi just above the top of the tower ?
> _________________
> Searchable Archives: http://www.contesting.com/_topband - Topband
> Reflector
>
>
>
> ------------------------------
>
> Message: 4
> Date: Sat, 27 Jul 2024 13:36:57 -0700
> From: "jim.thom jim.thom at telus.net" <jim.thom at telus.net>
> To: Felipe J. Hern?ndez <np4zet at gmail.com>
> Cc: topband at contesting.com
> Subject: Re: Topband: Quarter wave sloper ?
> Message-ID:
>         <CAB4ZMgv4ySL076WQ1dYapA5fOODeX28QOHD=
> 21Kx+7szEh1eJg at mail.gmail.com>
> Content-Type: text/plain; charset="UTF-8"
>
> Tnx for the quick response.
>
> Is a CM choke required at the feedpoint ?
> If  I can't fit the entire required length of wire,(I think I can get aprx
> 110-120')  can I insert a small coil at the feedpoint ?  Perhaps relay
> switched, to obtain 2 x segments.
> I'm toying with the idea of using the 75m rotary dipole at the top of the
> mast as a possible RX ant for 160m....might be worth a try at least. The CM
> choke at the 75m rotary dipole has 10.5 k Z on 160m.   I have zero room for
> dedicated 160m RX ants. My corner lot is only 89' wide x 115' deep.
> Monster house next door.  I have a power line running down the side street,
> on my side.
>
> Jim  VE7RF
>
> On Sat, Jul 27, 2024 at 12:50?PM Felipe J. Hern?ndez <np4zet at gmail.com>
> wrote:
>
> > Yes, is a great performer, don?t waste your time with inv v or sloping
> > dipoles, is a little trickier to tune but it?s a fantastic radiator.
> >
> > Felipe
> > Np4z
> >
> > On Sat, Jul 27, 2024 at 3:48?PM jim.thom jim.thom at telus.net <
> > jim.thom at telus.net> wrote:
> >
> >> Has anyone had success with a 160m,  1/4 wave sloper....hanging off a
> 90'
> >> tower, with a 40m yagi just above the top of the tower ?
> >> _________________
> >> Searchable Archives: http://www.contesting.com/_topband - Topband
> >> Reflector
> >>
> >
>
>
> ------------------------------
>
> Message: 5
> Date: Sat, 27 Jul 2024 20:45:31 +0000 (UTC)
> From: Gene Smar <ersmar at verizon.net>
> To: jim.thom at telus.net,  Felipe J. Hern?ndez <np4zet at gmail.com>
> Cc: topband at contesting.com
> Subject: Re: Topband: Quarter wave sloper ?
> Message-ID: <1470642773.544844.1722113131546 at mail.yahoo.com>
> Content-Type: text/plain; charset=UTF-8
>
> I don't have a choke on the sloper feedline, but I did run the coax inside
> the Trylon tower legs into a steel box at the base where the antenna switch
> is. I'd often thought about shortening the wire for 60M and installing a
> loading coil and shorting relay at the coax/wire junction for 80M
> operation, but haven't convinced myself to go through the trouble.?
> 73 de?Gene Smar AD3F?
>
> Sent from my Radio Shack TRS-80 model 100 laptop
>
>   On Sat, Jul 27, 2024 at 4:37 PM, jim.thom jim.thom at telus.net<
> jim.thom at telus.net> wrote:   Tnx for the quick response.
>
> Is a CM choke required at the feedpoint ?
> If? I can't fit the entire required length of wire,(I think I can get aprx
> 110-120')? can I insert a small coil at the feedpoint ?? Perhaps relay
> switched, to obtain 2 x segments.
> I'm toying with the idea of using the 75m rotary dipole at the top of the
> mast as a possible RX ant for 160m....might be worth a try at least. The CM
> choke at the 75m rotary dipole has 10.5 k Z on 160m.? I have zero room for
> dedicated 160m RX ants. My corner lot is only 89' wide x 115' deep.
> Monster house next door.? I have a power line running down the side street,
> on my side.
>
> Jim? VE7RF
>
> On Sat, Jul 27, 2024 at 12:50?PM Felipe J. Hern?ndez <np4zet at gmail.com>
> wrote:
>
> > Yes, is a great performer, don?t waste your time with inv v or sloping
> > dipoles, is a little trickier to tune but it?s a fantastic radiator.
> >
> > Felipe
> > Np4z
> >
> > On Sat, Jul 27, 2024 at 3:48?PM jim.thom jim.thom at telus.net <
> > jim.thom at telus.net> wrote:
> >
> >> Has anyone had success with a 160m,? 1/4 wave sloper....hanging off a
> 90'
> >> tower, with a 40m yagi just above the top of the tower ?
> >> _________________
> >> Searchable Archives: http://www.contesting.com/_topband - Topband
> >> Reflector
> >>
> >
> _________________
> Searchable Archives: http://www.contesting.com/_topband - Topband
> Reflector
>
>
>
> ------------------------------
>
> Message: 6
> Date: Sat, 27 Jul 2024 14:13:22 -0700
> From: Tree <tree at kkn.net>
> To: 160 <topband at contesting.com>
> Subject: Re: Topband: Quarter wave sloper ?
> Message-ID:
>         <
> CAKF9HhYr1mU2BeRraRE+UpwoAtwQbRNbKQQtGR_Z5YgOg9PThQ at mail.gmail.com>
> Content-Type: text/plain; charset="UTF-8"
>
> For a quarter wave sloper - assuming the coax goes down to the ground and
> runs down the ground some, it should exhibit pretty much the same impedance
> at the shield as the grounded tower is showing - which for a 90 foot feed
> point will be pretty high and hopefully the impedance looking up at your
> top loading is much lower.  Therefore, you would have no reason to put a
> balun on the feedpoint.
>
> If your tower was close to a half wavelength long (assuming grounded at the
> bottom) - then you would need a choke not only on the coax - but one on the
> tower as well (probably best implemented with a tuned section of tower
> below the feedpoint limiting current flow at the base of the tower).
>
> Hopefully - the 40M yagi has the elements connected to the boom.
>
> Tree N6TR
>
> On Sat, Jul 27, 2024 at 1:45?PM Gene Smar via Topband <
> topband at contesting.com> wrote:
>
> > I don't have a choke on the sloper feedline, but I did run the coax
> inside
> > the Trylon tower legs into a steel box at the base where the antenna
> switch
> > is. I'd often thought about shortening the wire for 60M and installing a
> > loading coil and shorting relay at the coax/wire junction for 80M
> > operation, but haven't convinced myself to go through the trouble.
> > 73 de Gene Smar AD3F
> >
> > Sent from my Radio Shack TRS-80 model 100 laptop
> >
> >   On Sat, Jul 27, 2024 at 4:37 PM, jim.thom jim.thom at telus.net<
> > jim.thom at telus.net> wrote:   Tnx for the quick response.
> >
> > Is a CM choke required at the feedpoint ?
> > If  I can't fit the entire required length of wire,(I think I can get
> aprx
> > 110-120')  can I insert a small coil at the feedpoint ?  Perhaps relay
> > switched, to obtain 2 x segments.
> > I'm toying with the idea of using the 75m rotary dipole at the top of the
> > mast as a possible RX ant for 160m....might be worth a try at least. The
> CM
> > choke at the 75m rotary dipole has 10.5 k Z on 160m.  I have zero room
> for
> > dedicated 160m RX ants. My corner lot is only 89' wide x 115' deep.
> > Monster house next door.  I have a power line running down the side
> street,
> > on my side.
> >
> > Jim  VE7RF
> >
> > On Sat, Jul 27, 2024 at 12:50?PM Felipe J. Hern?ndez <np4zet at gmail.com>
> > wrote:
> >
> > > Yes, is a great performer, don?t waste your time with inv v or sloping
> > > dipoles, is a little trickier to tune but it?s a fantastic radiator.
> > >
> > > Felipe
> > > Np4z
> > >
> > > On Sat, Jul 27, 2024 at 3:48?PM jim.thom jim.thom at telus.net <
> > > jim.thom at telus.net> wrote:
> > >
> > >> Has anyone had success with a 160m,  1/4 wave sloper....hanging off a
> > 90'
> > >> tower, with a 40m yagi just above the top of the tower ?
> > >> _________________
> > >> 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
> >
>
>
> ------------------------------
>
> Message: 7
> Date: Sat, 27 Jul 2024 17:04:58 -0400
> From: Rick Kunath <k9ao at yahoo.com>
> To: "jim.thom jim.thom at telus.net" <jim.thom at telus.net>, Felipe J.
>         Hern?ndez <np4zet at gmail.com>
> Cc: topband at contesting.com
> Subject: Re: Topband: Quarter wave sloper ?
> Message-ID: <0f201a28-5ab3-4ddd-b6f7-8ee774fb9f85 at yahoo.com>
> Content-Type: text/plain; charset=UTF-8; format=flowed
>
> Jim,
>
> On your sloper and the 2x segments idea for wider bandwidth, have you
> thought about just running 2 separate sloper wires with one slightly
> longer than the other in a fan arrangement? You could trim those lengths
> from ground level to get the resonances where you wanted them. Hold
> those apart a very short distance at the ground end, sort of like the
> fan dipole antenna. That would eliminate any relay at the tower top.
>
> As to receive antennas, It might be worth putting up a LoG antenna (Loop
> on Ground - https://www.kk5jy.net/LoG/) with 30-feet per side
> dimensions. I have one and it can work wonders sometimes. That's right
> on the grass and after a few weeks it just disappears. I also use a
> 10-foot by 30-foot flag antenna, and it's fed at the bottom corner and
> un-terminated. I phase that against the LoG or another flag to null down
> noise and even atmospheric noise can be nulled as long as it is not all
> coming from many directions or many wave angles.
>
> A few thoughts for you...
>
> Rick Kunath, K9AO
>
>
>
> ------------------------------
>
> Message: 8
> Date: Sat, 27 Jul 2024 17:12:30 -0400
> From: Rick Kunath <k9ao at yahoo.com>
> To: "jim.thom jim.thom at telus.net" <jim.thom at telus.net>, Felipe J.
>         Hern?ndez <np4zet at gmail.com>
> Cc: topband at contesting.com
> Subject: Re: Topband: Quarter wave sloper ?
> Message-ID: <420c66b0-1a33-41ff-a9d6-0ec4cef96668 at yahoo.com>
> Content-Type: text/plain; charset=UTF-8; format=flowed
>
> Jim, I forgot to mention that 90 or 100 feet is plenty of separation for
> a phased flag array made of two un-terminated flags mounted vertically
>
> I made a cheap water drill to mount mine and PVC pipe goes into the
> ground like butter and cements tight almost immediately. I droverr a 1
> 1/2 x 10-foot PVC pipe 5-feet into the ground and then a couopling and
> another 10-foot section on top. That's enough to get the bottom wire of
> the flag at about 4 feet from the ground and it works well. But as a
> note, paint the top pipe black before you put it up to make it disappear
> from view. White shows up pretty well. Black doesn't.//The bottom part
> and the coupling is easy enough to reach to paint from the ground. /
> /
> If you wanted to you could terminate the bottom corner opposite the
> feedpoint, either adjusting that and then making up a fixed resistor
> pack or using a VACTROL to make it remote adjustable, but I find my
> ability to move the null where I want it is great without the
> termination and loss of bi-directionality and the additional 30 dB loss
> with termination so you need a preamp at each loop. Unterminated you
> don't need the preamp./
> /
> Rick Kunath, K9AO
>
> ------------------------------
>
> Message: 9
> Date: Sat, 27 Jul 2024 23:45:37 +0200 (CEST)
> From: "dj7ww at t-online.de" <dj7ww at t-online.de>
> To: "topband at contesting.com" <topband at contesting.com>
> Subject: Topband: WG: AW:  Quarter wave sloper ?
> Message-ID:
>         <
> 1722116737804.1613816.b2ae55c657edecbd20fae133cdedaa9a98c3023e at spica.telekom.de
> >
>
> Content-Type: text/plain; charset="utf-8"
>
>
> Yes, I use one.
> Dropped from 37 meters and fed 25m from the tower against 90 ground
> radials.
> At 38m is my 3 element fullsize for 40m and at 45m a 5 element for 20m.
>
> The sloper does very well, also on receive., I resonate with a motor
> driven  shortening variable C across the whole band..
>
> 73
> Peter, DJ7WW
>
>
>
> -----Original-Nachricht-----
> Betreff: Topband: Quarter wave sloper ?
> Datum: 2024-07-27T21:48:25+0200
> Von: "jim.thom jim.thom at telus.net" <jim.thom at telus.net>
> An: "topband at contesting.com" <topband at contesting.com>
>
> Has anyone had success with a 160m,  1/4 wave sloper....hanging off a 90'
> tower, with a 40m yagi just above the top of the tower ?
> _________________
> Searchable Archives: http://www.contesting.com/_topband - Topband
> Reflector
> ?
>
>
>
> ------------------------------
>
> Message: 10
> Date: Sat, 27 Jul 2024 17:57:55 -0400
> From: Felipe J. Hern?ndez <np4zet at gmail.com>
> To: "jim.thom jim.thom at telus.net" <jim.thom at telus.net>
> Cc: topband at contesting.com
> Subject: Re: Topband: Quarter wave sloper ?
> Message-ID:
>         <CAOSq5+tPAfqvEU339JFDhjiusmN9uOs-x6XOcX5Q_=_
> AZXPZ7w at mail.gmail.com>
> Content-Type: text/plain; charset="UTF-8"
>
> In my case I have a 1:1 balun one leg to the antenna and the other to the
> tower, it?s simple and it works
>
> On Sat, Jul 27, 2024 at 4:37?PM jim.thom jim.thom at telus.net <
> jim.thom at telus.net> wrote:
>
> > Tnx for the quick response.
> >
> > Is a CM choke required at the feedpoint ?
> > If  I can't fit the entire required length of wire,(I think I can get
> aprx
> > 110-120')  can I insert a small coil at the feedpoint ?  Perhaps relay
> > switched, to obtain 2 x segments.
> > I'm toying with the idea of using the 75m rotary dipole at the top of the
> > mast as a possible RX ant for 160m....might be worth a try at least. The
> CM
> > choke at the 75m rotary dipole has 10.5 k Z on 160m.   I have zero room
> for
> > dedicated 160m RX ants. My corner lot is only 89' wide x 115' deep.
> > Monster house next door.  I have a power line running down the side
> street,
> > on my side.
> >
> > Jim  VE7RF
> >
> > On Sat, Jul 27, 2024 at 12:50?PM Felipe J. Hern?ndez <np4zet at gmail.com>
> > wrote:
> >
> >> Yes, is a great performer, don?t waste your time with inv v or sloping
> >> dipoles, is a little trickier to tune but it?s a fantastic radiator.
> >>
> >> Felipe
> >> Np4z
> >>
> >> On Sat, Jul 27, 2024 at 3:48?PM jim.thom jim.thom at telus.net <
> >> jim.thom at telus.net> wrote:
> >>
> >>> Has anyone had success with a 160m,  1/4 wave sloper....hanging off a
> 90'
> >>> tower, with a 40m yagi just above the top of the tower ?
> >>> _________________
> >>> Searchable Archives: http://www.contesting.com/_topband - Topband
> >>> Reflector
> >>>
> >>
>
>
> ------------------------------
>
> Message: 11
> Date: Sat, 27 Jul 2024 15:10:10 -0700
> From: Jim Brown <jim at audiosystemsgroup.com>
> To: topband at contesting.com
> Subject: Re: Topband: Quarter wave sloper ?
> Message-ID:
>         <9c28a25d-824c-403b-a0e1-0c5d8a0686e7 at audiosystemsgroup.com>
> Content-Type: text/plain; charset=UTF-8; format=flowed
>
> On 7/27/2024 12:47 PM, jim.thom jim.thom at telus.net wrote:
> > Has anyone had success with a 160m,  1/4 wave sloper....hanging off a 90'
> > tower, with a 40m yagi just above the top of the tower ?
>
> Yes, I've successfully used a sloping wire, suspended from a piece of
> large PVC conduit running horizontally through the tower at the top. I
> feed it against radials at the bottom, about 20 ft off the ground. N6BT,
> who has done a lot with verticals and elevated radials on 160, told me
> that they need to be near that height for reasonable efficiency. I've
> also added a dozen or so on-ground radials to the tower, which causes in
> to act as a passive reflector, yielding a few dB gain in the direction
> of the slope.
>
> An important piece of advice -- if your sloper is shorter than a quarter
> wave, do NOT add a loading coil, just feed it with a decent RG-213/RG8
> size coax and tune it in the shack. Loss is quite low in that size coax
> on 160, but the feedpoint is a high current point, which makes it an
> important part of the antenna; a loading coil at that point eliminates
> part of the high-current, making the antenna a bit less efficient.
>
> 73, Jim K9YC
>
>
>
>
> ------------------------------
>
> Message: 12
> Date: Sat, 27 Jul 2024 15:13:14 -0700
> From: Jim Brown <jim at audiosystemsgroup.com>
> To: topband at contesting.com
> Subject: Re: Topband: Quarter wave sloper ?
> Message-ID:
>         <8e2598d2-b742-45d3-a72d-cda4e603e2ab at audiosystemsgroup.com>
> Content-Type: text/plain; charset=UTF-8; format=flowed
>
> On 7/27/2024 1:36 PM, jim.thom jim.thom at telus.net wrote:
> > Is a CM choke required at the feedpoint ?
>
> It CAN make the antenna a bit quieter on RX, and prevents the feedline
> from acting as a radial, which could put RF in your shack if your
> bonding is poor.
>
> 73, Jim K9YC
>
>
>
> ------------------------------
>
> Message: 13
> Date: Sat, 27 Jul 2024 18:59:31 -0700
> From: "jim.thom jim.thom at telus.net" <jim.thom at telus.net>
> To: topband at contesting.com
> Subject: Re: Topband: Quarter wave sloper ?
> Message-ID:
>         <CAB4ZMgsVnEPhLsAHGA9d+V7=
> w-b8uLvXKn+3J1sDPTJsRj2sFQ at mail.gmail.com>
> Content-Type: text/plain; charset="UTF-8"
>
> Quarter wave sloper ?
>
> Just to be xtal clear, when I said 1/4 wave sloper,  I meant coax run up to
> nearly the top of the tower, with braid to tower.....and hot side of coax
> to the 1/4 wave sloping wire.  Bottom of the sloping wire has the
> insulator....and 6' off the grnd.    NO radials anywhere.  Base of tower
> has 3 x 8' deep grnd rods, all cad welded below grnd, then 2 ga wire to
> each tower leg.  Another 2 ga bare copper wire runs from base of tower to a
> 4th grnd rod outside basement window..... then more 2 ga ( insulated
> RW-90)..to SPG alum plate just inside the basement.
>
> The 3 x els of the modified F12  340N (40m yagi)  are INSULATED from the
> 35' boom.  Both the REF and the DIR  have a pair of vac relays and a flat
> strap coil inside a nema box (one at each end of boom) to provide for 4 x
> tuning segments.  Insulator between the inner 40m ele halves.  Both halves
> are insulated from the boom.   The Driven ele also has a plastic nema box,
> and also a center insulator, but this time has TWO flat strap coils, and
> FOUR vac relays, 2 per coil, to provide for 7 x segments.  All 8 x vac
> relays operate independently.  Driven ele is mounted 6' up the mast.
>  Equal spacing from DE to each parasitic ele.
>
> I have used 1/4 wave slopers in the past...but 75m only.  Same deal, coax
> to top of tower, braid to top of tower, and hot side of coax  to 1/4 wave
> sloping wire. Yagi just above top of tower.
>
> Jim   VE7RF
>
> On Sat, Jul 27, 2024 at 12:47?PM jim.thom jim.thom at telus.net <
> jim.thom at telus.net> wrote:
>
> > Has anyone had success with a 160m,  1/4 wave sloper....hanging off a 90'
> > tower, with a 40m yagi just above the top of the tower ?
> >
>
>
> ------------------------------
>
> Message: 14
> Date: Sat, 27 Jul 2024 21:03:05 -0700
> From: Jim Brown <jim at audiosystemsgroup.com>
> To: topband at contesting.com
> Subject: Re: Topband: Quarter wave sloper ?
> Message-ID:
>         <2a375da9-336d-4739-9c57-c2072c2a0a1d at audiosystemsgroup.com>
> Content-Type: text/plain; charset=UTF-8; format=flowed
>
> On 7/27/2024 6:59 PM, jim.thom jim.thom at telus.net wrote:
> > Quarter wave sloper ?
> >
> > Just to be xtal clear, when I said 1/4 wave sloper,
>
> Yes, and that's been a popular way to do it. I chose another, and
> described it. It is, indeed, a quarter wave, and it slopes.
>
> BTW -- those rods under the tower are an effective earth connection for
> lightning. But they are NOT a low-impedance path for RF, simply because
> the earth is a big resistor.
>
> The only function of an earth connection for transmitting antennas is
> lightning protection. The earth is a big resistor. The functions of
> radials are 1) to SCREEN (shield) the field produced by the antenna from
> lossy earth; and 2) to provide a low resistance path for the antenna's
> return current. A counterpoise provides only the second function.
>
> N6LF has been publishing some excellent work on radial systems,
> describing an interactive research process wherein he models various
> conditions, then built and measured them extensively, revising his model
> or modeling different variables, depending what he learned in the
> measurements, and so on. It is excellent engineering, and has given me
> many new understandings/insights of why radial systems behave the way
> they do. Many of us consider it the most important work on LF antennas
> in fifty years.
>
> https://www.antennasbyn6lf.com/
>
> The 2009 series on ground systems and the 2012 series on elevated radial
> systems are the material I find so worthwhile. Grab them and settle in
> with a nice Scotch.
>
> 73, Jim K9YC
>
>
>
>
>
> ------------------------------
>
> Subject: Digest Footer
>
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> ------------------------------
>
> End of Topband Digest, Vol 259, Issue 14
> ****************************************
>