To: <topband@contesting.com>
>Date: Wed, 12 Mar 1997 16:59:56 -0500 (EST)
>From: Lee Wells <leewells@lexmark.com>
>To: topband@contesting.com
>Subject: SUMMARY: Inverted L info (long)
>
>
>
>de Lee - KT4ZX
>
>
>Topbanders,
>
> Thanks for all of the input about the Inverted L questions.
>I ended up lengthening to 170 feet and feeding with a series cap
>over 4 elevated radials bent to fit the yard. It played VERY well
>in the 160 SSB contest (555 QSO's with 100 watts in 15 hours).
>
> Below is a summary of all the responses I received. I thought
>the info might be useful to others just getting involved with 160.
>
> 73's
> --Lee - KT4ZX
>
>
>---
>Lee Wells - KT4ZX
>leewells@lexmark.com
>
>
>
>
>===== My original note =====
>
>To: topband%contesting.com@interlock.lexmark.com
>Subject: TopBand: Inv-L vs HD special?
>
>I've just recently gotten on 160 with something resembling
>N5KO's "Home Depot Special." I'm thinking about modifying it to
>a more conventional inverted L and wanted to poll for ideas
>and thoughts on the subject.
>
>Since we don't have 100' sequoia's here in KY, the tip
>of the 1/4-wave vertical element is only about 70 feet in the
>air. So the "vertical" is below 45 degrees off the ground.
>I've got 4 1/4-wave radials (counterpoise?) run from about
>6 feet above ground at the base, going down to ground level
>as the go out into the yard. None of them are perfectly
>straight, a couple have to wrap around other objects for a few
>feet. One goes out 50 feet or so, then loops around some trees
>in one corner of the lot.
>
>The SWR is less than 1.5:1 from 1.80 to 1.91 MHz. The dip is currently
>at 1.835 with what appears to be 1:1. From what I've read, this seems
>fairly broad, so I'm guessing I have a lot of ground losses. The SWR did
>change from Sunday night to Monday night. It seemed to "shorten"...enough
>to move the dip up about 40 KHz. I didn't change anything though...the only
>noticable difference is that the ground was frozen last night, where
>it wasn't Sunday night.
>
>The antenna has managed to work a little DX over the past two nights (I just
>put it up Sunday). Last nights haul: IT9, DK6, F5, EA3 and VP2. I heard
>OK6, but he couldn't hear me. I received 559 on all of these, and it usually
>took the other guy a few trys to get my call. This feels like further proof
>of poor effeciency (ground loss). With only 100 watts, I can't afford to loose
>much!
>
>Here's what I'm thinking about doing:
>
>1) Make it into an Inverted-L. A second, nearby tree should
>hold the vertical up to about 60 feet or so, then run over
>horizontal to the current support.
>
>2) Lenghten the wire from 130' to about 170' and match with a
>series capacitor. From what I've read this should
>improve effeciency by moving the maximum current position
>up off the ground.
>
>3) Forget the long elevated radials, and put them on/in the
>ground. Also from what I read its a better trade to have
>more shorter radials (1/8 wave) than a few long ones. I'll
>probably put in 16-20 (1/8 wave) radials instead of the 4
>1/4-wave ones. And make them as straight as possible. Plus
>the elevated radials get in the way, especially when mowing season
>starts.
>
>4) Put up a couple two-wire beverages for receive. I'm not sure I
>can get to the full 580 feet (more like 400-500 ft range). Is
>this a problem??? Right now I can hear more than I can work so this
>isn't as critical as improving the transmit antenna. Also do
>these need to be perfectly straight, or can a slight bend around a tree
>be tolerated?
>
>So what do you think????? Am I on the right track??? Am I missing
>something? Any other ideas?
>
>Thanks in advance and 73's
> --Lee
>
>PS - I used wire with "purple insualtion" for the radials....does this
>add to the kharmic balabce???? :-) (Hey it was a little cheaper).
>
>---
>Lee Wells - KT4ZX
>leewells@lexmark.com
>
>
>
>=====================================================================
>
To: <topband@contesting.com>
>Date: Sat, 08 Feb 1997 16:16:54 -0500
>To: Lee Wells <leewells@sol.lpdev.prtdev.lexmark.com>
>From: Paul Pescitelli <k4uj%mindspring.com@interlock.lexmark.com>
>Subject: Re: TopBand: Inv-L vs HD special?
>
>
>>
>>1) Make it into an Inverted-L. A second, nearby tree should
>>hold the vertical up to about 60 feet or so, then run over
>>horizontal to the current support.
>>
>>2) Lenghten the wire from 130' to about 170' and match with a
>>series capacitor. From what I've read this should
>>improve effeciency by moving the maximum current position
>>up off the ground.
>>
>
>I would do the 2 above and you will have a pretty decent antenna.. Worked
>5x4f with mine last week. Work everything I can hear, (but that doesnt say
much)
>
>then do the one below... I wish I had room for 400-500 ft beverages. I would
>be in topband heaven...
>
>>4) Put up a couple two-wire beverages for receive. I'm not sure I
>>can get to the full 580 feet (more like 400-500 ft range). Is
>>this a problem??? Right now I can hear more than I can work so this
>>isn't as critical as improving the transmit antenna. Also do
>>these need to be perfectly straight, or can a slight bend around a tree
>>be tolerated?
>>
>
>slight bend is fine keep them about 7-12 feet off the ground and it will work
>great. (see on4un's book) We used a 420ft beverage in KP4 for the CQWW160CW
>and worked alot of EU off it. (it was pointed stateside, for lack of
>"natural" supports)
>
>Good Luck
>Paul K4UJ
>
>=====================================================================
>
>
>From: Rus Healy <rhealy%mdsroc.com@interlock.lexmark.com>
>To: "'Lee Wells'" <leewells@sol.lpdev.prtdev.lexmark.com>
>Subject: RE: TopBand: Inv-L vs HD special?
To: <topband@contesting.com>
>Date: Tue, 11 Feb 1997 16:17:11 -0500
>
>Lee,
>
>You'll have the best luck with this antenna if you make it an inverted =
>L, but leave the feed point elevated and stick with your four elevated =
>radials. The next incremental improvement comes from lengthening the =
>wire and adding series capacitance at the base of the vertical wire. As =
>you seem to understand, this raises the current maximum to a point =
>that's up the wire--1/4 wavelength from the open end. That's where most =
>of the radiation occurs. My antenna, which is just like this, kicks =
>butt. The vertical portion is only perhaps 50 feet high. In CQWW CW, I =
>worked 75 stations in 40 countries and 13 zones on 160. I was operating =
>all-band, so I spent about three hours total operating time on Top Band.
>
>Incidentally, I worked 9X5WW on 160 with one call over the weekend. That =
>was pretty cool! I do run 1 kW on 160, though.
>
>The 2:1 SWR bandwidth on my antenna (and N5KO's) is 70 or 80 kHz. That's =
>what you should see if the configuration is reasonably efficient.
>
>--73, Rus, NJ2L
>nj2l@mdsroc.com
>
>=====================================================================
>
>From: Rus Healy <rhealy%mdsroc.com@interlock.lexmark.com>
>To: "'Lee Wells'" <leewells@sol.lpdev.prtdev.lexmark.com>
>Subject: RE: TopBand: Inv-L vs HD special?
To: <topband@contesting.com>
>Date: Tue, 11 Feb 1997 16:54:00 -0500
>
>Lee,
>
>There's no problem bending radials to fit whatever shape is available. =
>In fact, you can bend them at right angles or into odd shapes. One of my =
>inverted L's radials is itself an L, making a 90 degree bend about 40 =
>feet from the feed point. I'd try to bring them straight into the feed =
>point for the first 40 or 50 feet, but otherwise run 'em anywhere you =
>can.
>
>Constant height isn't very important, but helps a lot for mowing, etc. I =
>support mine with electric fence insulators nailed to trees at about 10 =
>feet. Very fast to install, and robust, too. If the feed point winds up =
>being lower than 10 feet, slope the radials quickly up to 10 or 15 feet =
>and keep them at that height, plus or minus a bit, for the rest of their =
>run.
>
>Tuning the radials is a waste of time, in my opinion. Cut them to a =
>calculated 1/4 wavelength and tune the vertical wire alone for =
>resonance. N5KO and I both did that. You'll be fine. In fact, I'd bet =
>anyone a beer that you can't measure any electrical difference between =
>exactly resonant and close-to-resonant radials in this application.
>
>Always glad to help.
>
>--73, Rus, NJ2L
>
>nj2l@mdsroc.com
>
>=====================================================================
>
To: <topband@contesting.com>
>Date: Tue, 11 Feb 1997 17:03:36 -0500
>From: George.Guerin%kellogg.com@interlock.lexmark.com (George Guerin)
>To: Lee Wells <leewells@sol.lpdev.prtdev.lexmark.com>
>Subject: Re: TopBand: Inv-L vs HD special?
>
> Hi Lee,
>
> I vote for an Inverted L over a fair amount of radials. I have
> written a summary of feeding Inverted L antennas and would be happy to
> mail you a copy if you send me a business size SASE. Either a 128 or
> 160-170 foot style would work well.
>
> We used 160 foot length, with 80 up and 80 out over 32 radials about
> 80 ft long each on Curacao at PJ9Z a year ago in the CQWW160CW contest
> and did very well. The series capacitor was about 480 pfd from a 1000
> pfd 5 KV vacuum variable.
>
> If you go 70 up and 90 out you should do well with 400 - 450 pfd in
> series.
>
> The alternative is to make an L net at the base by making the length
> 135 feet (7 feet is about 2.1 uhy of a series inductor of an L-network
> tuner) and a shunt capacitor to ground. The value could be anywhere
> from 1000 to 2000 pfd shunt across the coax.
>
> I do not personally subscribe to only 4 elevated radials. ON4UN's
> book says about 30 radials about 1/8 wavelength is a reasonable
> compromise. Less is OK but more loss.
>
> Also the broad bandwidth makes me think of ground losses as a resistor
> soaking up RF power, giving you the bandwidth as a pseudo benefit!
>
> Hope this helps.
>
> George , K8GG
>
>=====================================================================
>
>
To: <topband@contesting.com>
>Date: Tue, 11 Feb 1997 17:39:33 +0000
>From: "Alfred J. Frugoli" <ke1fo%contesting.com@interlock.lexmark.com>
>To: Lee Wells <leewells@sol.lpdev.prtdev.lexmark.com>
>Subject: Re: TopBand: Inv-L vs HD special?
>
>> 4) Put up a couple two-wire beverages for receive. I'm not sure I
>> can get to the full 580 feet (more like 400-500 ft range). Is
>> this a problem??? Right now I can hear more than I can work so this
>> isn't as critical as improving the transmit antenna. Also do
>> these need to be perfectly straight, or can a slight bend around a tree
>> be tolerated?
>
>
>You might want to look into doing some kind of "2 slinky beverage",
>using the slinky beverage concept. I will have (within the week) an
>aritcle on my web page about the slinky beverage. Good luck.
>
>=====================================================================
>
>From: "Jon K. Jones" <jkjones%fn.net@interlock.lexmark.com>
>To: "'Lee Wells'" <leewells@sol.lpdev.prtdev.lexmark.com>
>Subject: RE: TopBand: Inv-L vs HD special?
To: <topband@contesting.com>
>Date: Tue, 11 Feb 1997 18:46:02 -0600
>
>Lee:
>Some comments from another 100w TopBand op.
>(I use a 1/4 wave balloon vertical)
>I found the efficiency of my vertical goes down
>fast as the angle of the wire goes below 45 degrees.
>An inverted L would be more efficient.
>Increasing the length to 170 feet would raise the
>feedpoint impedance - and improve efficiency some.
>Put down as many on the ground radials as you can.
>I found at the 100w level you probably do not need
>Beverages.
>73,
>Jon N0JK KS
>
>
>=====================================================================
>
To: <topband@contesting.com>
>Date: Tue, 11 Feb 1997 18:14:55 -0700
>From: Eric Gustafson <n7cl%sparx.mmsi.com@interlock.lexmark.com>
>To: leewells@sol.lpdev.prtdev.lexmark.com
>Subject: Re: TopBand: Inv-L vs HD special?
>
To: <topband@contesting.com>
>>Date: Tue, 11 Feb 1997 14:44:21 -0500 (EST)
>>From: Lee Wells <leewells@lexmark.com>
>
>
>Snip (brevity) ...
>
>>
>>The SWR is less than 1.5:1 from 1.80 to 1.91 MHz. The dip is currently
>>at 1.835 with what appears to be 1:1. From what I've read, this seems
>>fairly broad, so I'm guessing I have a lot of ground losses. The SWR did
>>change from Sunday night to Monday night. It seemed to "shorten"...enough
>>to move the dip up about 40 KHz. I didn't change anything though...the only
>>noticable difference is that the ground was frozen last night, where
>>it wasn't Sunday night.
>>
>
>I can shed light on this phenomenon. Frozen things are typically non
>conductive. When your ground froze, the conductivity of the frozen portion
>fell to near zero. If you doubt this, stick a couple of ohmmeter probes in
>a plastic ice tray with slightly salted tap water in it and put the tray in
>the freezer. If you didn't use enough salt to keep the water from
>freezing, then you can detect the exact time that freezing was complete by
>monitoring the measured resistance. Your antenna saw the distance between
>its phase center and the conductive portion of earth below it increase
>slightly.
>
>
>Snip (again) ...
>
>
>>3) Forget the long elevated radials, and put them on/in the
>>ground. Also from what I read its a better trade to have
>>more shorter radials (1/8 wave) than a few long ones. I'll
>>probably put in 16-20 (1/8 wave) radials instead of the 4
>>1/4-wave ones. And make them as straight as possible. Plus
>>the elevated radials get in the way, especially when mowing season
>>starts.
>>
>
>This is probably a good idea in this case. Figure out how long they _can_
>be. Then put in however many it takes to get the tip to tip distance
>between radials down to 0.03 wavelengths (about 26 for 1/8 wave radials).
>That will get you to the diminishing returns zone for radials of that
>length.
>
>
>Snip (some more) ...
>
>
>>
>>PS - I used wire with "purple insulation" for the radials....does this
>>add to the kharmic balabce???? :-) (Hey it was a little cheaper).
>>
>
>Yes, the K-balance will be much better. But purple is the royal color.
>And as you have already noted the (slightly) elevated purple radials are in
>fact a royal pain in the rear!
>
>
>73, Eric N7CL
>
>=====================================================================
>
To: <topband@contesting.com>
>Date: 12 Feb 97 06:31:39 EST
>From: "Robert g. Flory" <104117.3104%CompuServe.COM@interlock.lexmark.com>
>To: Lee Wells <leewells@sol.lpdev.prtdev.lexmark.com>
>Subject: Re: TopBand: Inv-L vs HD special?
>
>Lee,
>
>I think it will work better as an inverted L. Lengthening it will not make it
>work better as you want the maximum current in the vertical portion, not in the
>horizontal. If you could make the vertical part taller, then lengthening it
>might help.
>
>For a two-wire Beverage, the 450 ohm ladder line works nice and makes it easier
>to maintain the spacing between the wires. Then if you can't string it exactly
>straight it won't hurt it as much. 450 to 500 feet will work fine if you can't
>get more.
>
>Rob K2WI,an inverted L junky
>
>=====================================================================
>
>From: k0sd%juno.com@interlock.lexmark.com
>To: leewells@sol.lpdev.prtdev.lexmark.com
To: <topband@contesting.com>
>Date: Fri, 14 Feb 1997 14:04:06 PST
>Subject: Re: TopBand: Inv-L vs HD special?
>
>LEE,
> A couple remarks. It sounds like your elevated radials are too low
>for 160 m, they're already acting like buried radials. Your SWR curve
>also gives the same story.
> For the elevated radials to be effective on 160, they should be a min
>of 5 to 6 ft above ground. If they're in your way to walk under or
>mow, they may as well be on the ground. When you get them correct,
>you'll find the 4 elevated will behave as 120 buried radials, about same
>efficiency, impedance, ect.
> If you had them up, your SWR curve will come down to about 1.6:1,
>since your impedance will be about 25-35 ohms (whether you have 4 properly
elevated, or 120 quater-wave buried). Your SWR curve will be more
>like 2:1 from say 1820 to 1870.
> 73's de Stephen, K0SD in NC
> with 160 M vertical, and 4 on 80 in 4 square, and 4 on 40 in 4
>square, all elevated radials now.
>
>=====================================================================
>
>
--
FAQ on WWW: http://www.contesting.com/topband.html
Submissions: topband@contesting.com
Administrative requests: topband-REQUEST@contesting.com
Problems: owner-topband@contesting.com
Sponsored by: Akorn Access, Inc. & N4VJ / K4AAA
|