Inv L 80/40m Parallel Summary
MARIA
zs1afz@zs1ctc.ctech.ac.za
Thu, 21 Nov 96 16:59:38 -0200
Message-Id: 6574_zs1ctc
From: zs1afz@zs1ctc (MARIA)
To: towertalk@contesting.com
Hi Guys,
I hereby would like to thank you one and all for all the information
you have forwarded to me - I appreciate it VERY MUCH - I am sure that
I have included all the feedback in this summary, BUT please if I have
accidentally skipped someone ... please forgive - it definitely wasn't
on purpose!
Go well and THANKS AGAIN !!
73/88 Maria - zs1afz
********************************************************************************
******************************************************************************
To Date: Sat, 16 Nov 96 01:02:34 -0200
From: zs1afz@zs1ctc.ctech.ac.za (MARIA)
Subject: Inv L 80/40m Parallel
Hi Folks,
We are interested in installing an Inv L for 80m ......
Will it be possible to install an Inv L for 40m as well, the wire
thereof running parallel with the 80m Inv L's and fastened to the same
mast pole?
need the correct lengths of wire needed for the 80m and the
40m antennas?
We live near the coast and the soldering tends to come loose where
the radials are soldered to the screen. Any advice how we can improve
this situation?
Many thanks in advance for your help!
73/88 Maria - zs1afz@zs1ctc.ctech.ac.za
****************************************************************************
From: rlc@soho.ios.com
Please let me know what you find out. I am interetsed in a 160m/80m
version. Bob W2WG
Robert L. Carroll W2WG
Formerly AA2UV
rlc@mail.idt.net
****************************************************************************
From: K7LXC@aol.com
Subject: Re: Inv L 80/40m Parallel
In a message dated 96-11-15 20:30:18 EST, you write:
Hi, Maria --
> We live near the coast and the soldering tends to come loose where
>the radials are soldered to the screen. Any advice how we can improve
>this situation?
Use silver solder. It's better for outdoor use and silver oxide is a
conductor.
73, Steve K7LXC
*****************************************************************************
From: "Bruce Goldstein" <wa3afs@soli.inav.net>
COAXIAL INVERTED L Antenna:
Properties:
Scalable for different bands
Very broadbanded. SWR less than 2:1 across entire bands (depending
where you design the center frequency).
No antenna tuner needed
Construction:
1. Construct entire antenna out of coax (RG8X works the best as a
compromise between power handling and mechanical strength). RG8, RG58, or
RG59 are also acceptable.
2. Antenna is fed in opposite manner at base (Coax from shack center
conductor goes to shield of antenna and the shield from shack goes to
center conductor of antenna.
3. Coax of antenna is shorted at top end and also in one place in
antenna (See forumla to d the exact point 4. The more vertithe antenna the better. (My 40sions aust about vertical, my 80M version is looped over a tree (sort of like an
upside down I have had other antennas in my last QTH that went up about
60 feet and then horizontal to another tree.
I use bungy cords to take up the slack and allow for the wind to move
the trees around without undue stress on the antenna.
5. Radiequired. The more the better. The larger the
diameter, the less radials are required. The radials do not have to run
in straight lines. Because I do not like to make the effort to bury the
radials I run some of them along the house foundation and along fences.
Placing the radials above ground or under ground is optional. You
know when you have enough radials when the SWR is the same whether the
ground is wet or dry. I have had great results with between 8 and 20
radials. (I start with three and then like to watch the SWR change as I
add a few more at a time. I connect my radials to an alumunum plate with
stainless steel nuts and bolts. They seem to work ok.
Formulas (Fmhz is the center frequency of my favorite place on a band):
Total length of the antenna (in feet): 230/Fmhz
Short coax (measuring from bottom): 162.5/Fmhz
Radial length: 239.2/Fmhz
Good Luck and let me know if you have further questions and of course the
result!
73
Bruce WA3AFS
****************************************************************************
From: KF4HK@gnn.com (Jim Miller)
Marie; I will be happy to FAX copy of 40/80 or 80/160 dual Inverted
L, if u have access to fax machine, or good friend who has one.
73/88
Jim
kf4hk@gnn.com
Send country code also!
*****************************************************************************
From: "Chris R. Burger" <CRB@knersus.nanoteq.co.za>
> Will it be possible to install an Inv L for 40m as well, the wire
Ja.
> need the correct lengths of wire needed for the 80m and the
> 40m antennas?
Gebruik 71.3 / f, met f in MHz. Die antwoord is in m. Jy sal
miskien 'n bietjie moet sny.
> We live near the coast and the soldering tends to come loose where
> the radials are soldered to the screen. Any advice how we can improve
> this situation?
Gebruik krimpterminale op elke draad. Skroef dit met vlekvrye staal
aan 'n gegalvaniseerde plaat.
c
******************************************************************************
From: n4dw@juno.com (David A Wilson)
MARIA,
Several years ago, while living with my in-laws and job hunting, I wanted
to participate in Sweep Stakes, one of my favorite contests.
Since the QTH was not mine, I had to put up an antenna that would load
and work well at least on one band. I had enough aluminum tubing to
piece together 33 ft to make a monoband vertical for 40 meters. I also
had the base support from an old CB band vertical and enough wire to lay
out 4 radials approximately 3% longer than the 33 ft vertical part.
I drove a 5 ft mast into the ground about 3-1/2 ft, attached the CB base
and added the 33 ft of aluminum. I then attached the radials with
alligator clips so I could remove them easily in order to mow the grass.
When I attached coax between the antenna and rig, I found the SWR to be
unexceptable and quickly determined that the CB base had some kind of
inductive components burried in the plastic mount at the bottom. There
was a metal screw going through the outer aluminum tubing to the innards
of the base which I promptly removed.
Using a stainless hose clamp I attached the center conductor of my 50 ohm
coax to the base of the aluminum tubing and the shield was connected to
the grounded portion of the base.
With reasonable SWR (below 1.5:1) I now set to getting it as low as
possible at the low end of the band. I found that the SWR increased as
frequency increased, so I shortened the 33 ft slightly and at about 7025
reached almost a perfect 1:1 SWR. The radio played well and I was able
to work eurpoeans reasonably easily barefoot.
My effort in Sweepstakes resulted in over 600 QSOs and I was so pleased
with the antenna that I decided to toss a 66 ft piece of wire over a
nearby tree and attach the lower end of the 66 ft wire to the same point
that the coax feeds the vertical aluminum (again using an alligator
clip). The tree is far enough from the vertical that when the wire was
left to hang straight down it hit the ground about 12 feet away from the
vertical. Since the tree is only about 35 feet high, the extra wire at
the top was pulled towards the top of another 35 ft tree about 40 feet
directly away from the 40 mtr vertical.
Initially, when I wanted to operate 80 I would run out and clip the wire
to the feedpoint and when on 40 I would disconnect the wire and one of
the two 80 meter radials (66 ft * 1.03)(or 3% longer than the 66 ft) and
connect them together, pull them as far away from the 40 meter vertical
as I could. I was working on the theory that 132 ft of wire near the 40
vert would not be resonant and would not interfere with the operation of
the 40 meter vertical.
This setup worked very well for me even when I got lazy and quit
disconnecting and reconnecting the 80 meter L when I switched bands. So
well in fact that I was able to work 114 countries on 40 and 103
countries on 80 in 1995. My best DX on 80 was VQ9QM and 3Y0PI, both
worked while I was running barefoot.
I would suspect that the 40L & 80L you are thinking of putting up would
play reasonably well for you. Spend some time getting the 40 portion of
it tuned well before you put up the 80 portion. I would also suggest
that you don't run them parallel, but angle them apart a bit before
going horizontal.
I have since moved to a new QTH and put the combination back up here and
it still plays well for me. This year over 700 QSOs in Sweepstakes. I
find that if I can hear a station, I can usually work that station if I
have a fairly clear frequency when calling. Still barefoot! To show you
how well the dual antenna works, here is the summary from my CT log with
QSOs only from January 1995.
+Summary---------------------+
¦ Q Z C D ¦
¦ 160 1 1 1 0 ¦
¦ 80 463 27 114 14 ¦
¦ 40 589 30 145 26 ¦
¦ 30 139 26 113 7 ¦
¦ 20 288 29 93 18 ¦
¦ 17 96 22 88 7 ¦
¦ 15 201 21 70 11 ¦
¦ 12 13 11 12 0 ¦
¦ 10 30 8 16 0 ¦
¦ ALL 1820 175 652 83 ¦
¦ N4DW-CW ¦
+----------------------------+
+Summary---------------------+
¦ Q Z C D ¦
¦ 160 0 0 0 0 ¦
¦ 80 39 9 27 1 ¦
¦ 40 32 16 23 0 ¦
¦ 30 0 0 0 0 ¦
¦ 20 93 16 38 2 ¦
¦ 17 11 8 11 1 ¦
¦ 15 88 17 46 3 ¦
¦ 12 5 4 5 0 ¦
¦ 10 21 6 17 0 ¦
¦ ALL 289 76 167 7 ¦
¦ N4DW-SSB ¦
+----------------------------+
As you can see, I prefer CW so my dual antenna is cut and tuned for the
low ends of both bands. I do use an MFJ VERSA TUNER II, model MFJ-941D
and am able to tune the combination on all bands except 160 (no resonant
length for 160).
I am on the DXCC Honor Roll Mixed, Phone and CW and just could not be
without my radio and chasing DX. Without a permanent QTH of my own this
was the best choice for an antenna I could come up with. And it has
worked super for me for the past two years.
When the XYL (N1HEJ) & I finally get settled into our own place again,
that should be soon, I will probably keep using the 80 inverted L type
antenna, but the 40 meter vertical will probably be replaced with a KLM 3
ele monobander. I also have monobanders for 10, 15 & 20, but those will
take longer to put up. 40 is more important!!
Again, take thme to tune/prune both parts of the antenna for the
parts of the bands you wish to operate and it perform well for yo
73, Dave
n4dw@juno.com
David A. Wilson, N4DW
2977 Island Road
Blountville, TN 37617
*****************************************************************************
From: w5hvv@aeneas.net (Rod Fitz-Randolph)
Subject: Re: Inv L 80/40m Parallel
> We are interested in installing an Inv L for 80m ......
> Will it be possible to install an Inv L for 40m as well, the wire
>thereof running parallel with the 80m Inv L's and fastened to the same
>mast pole?
> need the correct lengths of wire needed for the 80m and the
>40m antennas?
Maria, you certainly can run them parallel. You can even feed them, at
the bottom of the 1/4 wave vertical section, at a common feed point.
There may be some interaction between them but it can be accommodated
by trimming to the proper resonance. I have used inverted "L"s with
very gratifying results. I notice a number of variations on the theme,
but the one I like the most is one that has a vertical element, 1/4 wave
long that starts at the ground, goes up vertically a quarter wavelength
and then a half wave length horizontal section. They work quite well.
I think you will be very pleased with them.
As for dimensions, the old 234/Fmhz=length in feet, works well for the
vertical section of it and the horizontal portion would be 468/Fmhz=
length in feet. I might suggest you make the horizontal portion just
a bit longer than the formula calls for and then trim to the frequency
you most use.
Good luck with the project. Please let me know how it comes out.
Rod Fitz-Randolph, W5HVV
Roderick M. Fitz-Randolph, W5HVV
79 Highland Hills Cove,
Jackson, TN 38305
(901) 661-9278 (Home Phone - after 10 AM & before 9 PM)
(901) 664-7539 (FAX Number - any time of day)
*****************************************************************************
Subject: L's
To: zs1afz@zs1ctc.ctech.ac.za
Message-Id: 01IBZIFDI0DE0
I have an L for 160 next to a vertical for 80. They are supported by the same
rope and separated by about 3 feet. I use fiberglass fence posts that are used
for electric fence (about 1/4 inch in diameter). They do interact a bit but
the 160 L is nonresonant and is tuned at the base with an L network. It will
work but expect the tuning to interact a bit.
Be glad to answer any more questions.
73 Dan
W8CAR
******************************************************************************
From: Wa
Message-Id: 961118_28155B
On Sun, 10 Nov 1996, MARIA wrote:
> Hi Walt,
> How I'd like to add that prefix to my list for WPX!!
If you are a WPX chaser, I would be glad to make a sked with you. Lets
not try it on a band as hard as 160m though! I often hear ZS at about
2000Z over my lunch hour while I am the club station at work. I could
make a sked with you on 20m SSB almost any weekday.
> Walt, many thanks for your reply and all the valuable information -
> I appreciate it very much!
> The radials however are a problem if we either bury or spun it on the
> ground. Firstly we will only just just be able to make a half circle of
> wire; but the most important thing of all is - we have 3 bullterrier dogs
> that dig everything up and if we spun the wire on the ground their toes
> hook onto the wire and then it is again the vet!
There is some interesting information about loaded radials in the ARRL
Antenna Compendium volume 3. The original work by Moxon, G6XN, appeared
in his book HF Antennas For All Locations. I cant vouch for the technique
(I have enough room for full size radials), but it looks interesting.
>The receiving loops with preamps I'd love to get
specs/measurements
> on that) sound very interesting - but again I a problem. The Kenwood
> TS-850s which I am using needs has nket for a rx antenna
> and we doant to mamod at this stage as the rig is still new.
Shps about 5-8 feet in diameter made from coax with a break in
the shield at top are common in the literature. I have not triem myself, but they are reported to be pretty good, but not as good as a
300 foot or longer Bee. , the Bege does not require a prea, the loop does.
As thoblem with the TS850S not having an external RX antenna port,
I know your quandry....I use the same rig. Short of modifying the 850
itself, the only option is to use a relay in the feedline to select either
the main TX antenna or an RX-only antenna. Place this relay between the
transceiver and the amplifier so that only 100w maximum could be put into
the RX antenna by mistake. Protecting any RX preamp or matching
transformer is a problem. I avoid this problem by using a Beverage (no
preamp) and very heavy duty 9:1 matching transformers which can take the
power without blowing up. Keying the extra relay is also a problem,
making QSK very difficult. I use a footswitch for solid control...watch
out about clipping dits if the relay is switched by the VOX circuit.
> We have been advised to use the Minooka Special Vertical antenna
> which is already installed but not connected as yet ... we are waiting
> for a matching unit from someone overseas who is building it for us -
> for the last 6 months now - to enable us to use the antenna on 160/80/40m)
> and then instead install an Inv L for 80m; to use one set of radials for
> both the antennas and to join the 2 feedlines ....I dont understand this
> joining of the two feedlines - can you perhaps explain it to me??)
> What do you think of the Minooka for 160 and Inv L for 80 - you think
> the setup will work better than only the Minooka with matching unit??
> Looking forward for some more advice from you ...
> Many thanks for helping me, Walt!
> 73/88 Maria - zs1afz
I am not really familiar with the Minooka Special antenna. I think that
was the precursor to the Battle Creek Special antenna, but I am not sure.
I am not a great fan of traps because of their loss, especially when you
need big values of inductance at high current portions of the antenna. I
dont think you can beat a 165 foot long inverted L with series matching
cap for simplicity or efficiency (you can fold the top section somewhat to
make it smaller if need be).
Good luck on topband. Email me for a sked on 20m.
73/88 Walt
------------------------------------------------------------------------
Walter Miller, AJ6T Saratoga, CA USA CM87
Reply to aj6t@sp.net
************************************************************************
From: w5hvv@aeneas.net (Rod Fitz-Randolph)
Subject: Re: Inv L 80/40m Parallel
> We are interested in installing an Inv L for 80m ......
> Will it be possible to install an Inv L for 40m as well, the wire
>thereof running parallel with the 80m Inv L's and fastened to the same
>mast pole?
> need the correct lengths of wire needed for the 80m and the
>40m antennas?
Maria, you certainly can run them parallel. You can even feed them, at
the bottom of the 1/4 wave vertical section, at a common feed point.
There may be some interaction between them but it can be accommodated
by trimming to the proper resonance. I have used inverted "L"s with
very gratifying results. I notice a number of variations on the theme,
but the one I like the most is one that has a vertical element, 1/4 wave
long that starts at the ground, goes up vertically a quarter wavelength
and then a half wave length horizontal section. They work quite well.
I think you will be very pleased with them.
As for dimensions, the old 234/Fmhz=length in feet, works well for the
vertical section of it and the horizontal portion would be 468/Fmhz=
length in feet. I might suggest you make the horizontal portion just
a bit longer than the formula calls for and then trim to the frequency
you most use.
Good luck with the project. Please let me know how it comes out.
Rod Fitz-Randolph, W5HVV
Roderick M. Fitz-Randolph, W5HVV
79 Highland Hills Cove,
Jackson, TN 38305
(901) 661-9278 (Home Phone - after 10 AM & before 9 PM)
(901) 664-7539 (FAX Number - any time of day)
END
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