Topband: Elevated Radials Questions

Thu Dec 13 23:59:05 EST 2012

Sounds like really effective approaches!  I expect that the narrowing of the
BW as you added radials was because the additional radials were reducing the
losses of the system  and therefore raising the Q. Your 130 ft radials were
fairly close to 1/4 wave resonance on 160, I would think.  I agree with you
completely about building and measurement and testing to learn the real
answers to out  antenna question,

I do have antenna modeling software that I have used very successfully on my
160 inverted Ls and various multiband antennas, including "killer 5-band
quad (single feed line!) But I also take antenna analyzers, my trusty old
Millen grid-dip meter (that has retained remarkable calibration after so
MANY years) to measure what I've constructed. I'm not above taking a
receiver outdoors to "ride herd" on the grid-dip meter! When I was building
the 5-band quad after months of experimentation with the EZNEC programs and
carefully determining where the parasitic elements should resonate, I could
carefully put them on frequency with the dip-meter/receiver combination and
I could watch the driving-point impedance fall into line on each band as the
parasites were resonated where the model indicated.  I was rewarded with a
REMARKABLE "killer"  5-band antenna for 20-10 meters that was far and away
the BEST antenna that I've ever used!!  It took months of work with the
modeling program, and I learned many things about the interaction of quad
elements and developed my own means of suppressing and coping with those,
that, as  far as I know have never been really explored or published! I
suppose I should publish them some day! But I LEARNED SO MUCH!! And with
the quad I'd generally run barefoot at 100W frm the FT-1000 MP and generally
didn't wait much!! Of course, on 160, I generally turn on the 3-500
"afterburner" But  did work VK3 one morning with 100W to my inverted L! He
was CQ'n and I knew that a couple of other locals, including K4CIA were on
just a few KHz away, and I didn't have time to tune up the 3-500on 160, so I
just called him with what I had going at the moment!!

I should mention that I do a lot of antenna work professionally, but those
have been mostly embedded VHF and UHF antennas for electricity, gas and
water metering etc. Some other projects I have done in similar manner were a
40/30 GP for the KH1 dxpedition some  years back It was constructed from a
Radio-Shack push-up mast that we guyed, and a parallel 30 m wire and sets of
4 resonant radials for each band. We tuned and measured everyth in the
backyard of my friend, Jim, W4RS, who was up near Danville, Va at the time
We then disassembled, and packed and shipped to Howland Island by way of
Hawaii.  It was such a pleasure to be here on the receiving end in NC and
listen to  the big world-wide pile-ups on 40 and 30 fom  my home-brew
DXpedition antenna!!  Later I designed, modeled and built an 80/75 m "death
-ray" for Jim. It was 5 ground planes -one central driven element and four
parasitic ground plane elements  in a square around the driven element. The
parasites had shorted transmission lines of 450 ohm ladder that could be
shorted with relays and a control box in the station to switch the parasitic
ground planes from reflector to director tuning thereby enabling the array
to be steared in 8 directions aiund  the compass rose! It was a MONSTER!!  I
remember Jim calling an A61 who had a  HUGE EU pile- and on first call, the
A61 stopped and said "Who's the "radi0-sugar""  and Jim worked him handily!
I mention that one because all of the 80m ground planes had elevated
resonant radials!

So, experience teaches me that they are worth the effort! It's worth the
effort to do the modeling and measurement and testing when doing antenna
work! :)

Regards,

Charlie, K4OTV

-----Original Message-----
From: Topband [mailto:topband-bounces at contesting.com] On Behalf Of ZR
Sent: Thursday, December 13, 2012 8:51 PM
To: Grant Saviers; Dennis W0JX
Cc: topband at contesting.com
Subject: Re: Topband: Elevated Radials Questions

The only place Ive found tuned elevated radials being discussed so much is
on ham forums.

A bit over 20 years ago I installed a slanted wire 1/4 wave vertical for 160
coming off the top guy wire of a 160' tower and about 10' out.

Started with 4 radials of roughly 130', trimmed the radiator for best match
with zero reactance and measured the 2:1 bandwidth. Added 4 more radials and
the BW narrowed, added 8 more and it narrowed a bit more. Added another 16
and no change in BW so I assume the sweet spot is somewhere in the 20's at
this location and the radials starting at 12' and slowly sloping to 20' and
then thru tree branches. Just the way they were placed likely precludes any
chance of resonance. That antenna worked so well I added another, and used
nothing but coax phasing lines to switch directions or fire a figure 8
broadside. Cheap, simple and effective unless you like throwing away money
for a mailorder solution.

YMMV depending on ground effects and surrounding objects. OTOH I believe
people spend way too much time analyzing and relying on some questionable
answers and too little time doing some basic construction work and testing.

Carl
KM1H

----- Original Message ----- 

From: "Grant Saviers" <grants2 at pacbell.net>
To: "Dennis W0JX" <w0jx at yahoo.com>
Cc: <topband at contesting.com>
Sent: Thursday, December 13, 2012 5:27 PM
Subject: Re: Topband: Elevated Radials Questions

> Thanks for the comments and pointers.  The land around the antenna is 
> mixed grass and forested islands so on the ground radials would be 
> partially buried and partially on the surface.  Digging through the 
> trees and clearing the brush is not something I want to do. Also, 
> based on prior experience with verticals on metal roofs, I'm a real 
> fan of elevated radials.
>
> I am relying on the credibility of the N6LF QEX series for how 
> well/not well elevated radials will work (Mar - June 2012).  I realize 
> this work was all analysis with EZNEC PRO, but it seems to be the 
> similar to results of others I've read.  Googling "K5IU elevated 
> radials" I did find the 2008 N6LF article which has the experimental 
> data as well.  His analysis shows there isn't much difference in 
> losses with more than 4 radials between
> 0.15 and 0.27 wavelengths long.  I've heard conventional wisdom is to 
> tune radials for resonance, but the analysis for 4 or more radials 
> elevated > than a couple of feet seems to indicate it is a lot of work 
> for little benefit.
>
> I also found the 2005 thread "tuning elevated radials" on this 
> reflector quite informative.
>
> One thing that stands out is that I may be better off with more than 7 
> shorter than 130' radials.
>
> Grant KZ1W
>
>
> On 12/13/2012 12:06 PM, Dennis W0JX wrote:
>> Grant, you should consider putting in an additional 23 radials and 
>> put the radial system on or in the ground. This will eliminate any 
>> possible detuning by the big metal building and interaction with the RX 4
square.
>> You said that your vertical T will go up to 85 feet. However, by 
>> elevating the radials 10 feet, your effective vertical distance is 75 
>> feet which will allow you to shorten the top hat wires a bit. As an 
>> alternate, you could put down 1/8 wavelength radials on the ground 
>> but more of them and have a good system too.
>>
>> If you must go with an elevated radial system, I recommend that you 
>> read the articles by Dick Weber, K5IU, who strongly advocated 
>> elevated radials shorter or longer than 1/4 wavelength. If shorter, 
>> then the radials are loaded with a small coil. If longer, then they 
>> are tuned out with a capacitor. W5UN uses shortened elevated radials 
>> on his 160 meter 4 square with great results. They are about 70% of a
quarter-wave in length.
>>
>> 73, Dennis W0JX/8
>> Milan OH
>> _______________________________________________
>> Topband reflector - topband at contesting.com
>>
>
> _______________________________________________
> Topband reflector - topband at contesting.com
>
>
> -----
> No virus found in this message.
> Checked by AVG - www.avg.com
> Version: 10.0.1430 / Virus Database: 2634/5457 - Release Date: 
> 12/13/12
> 

_______________________________________________
Topband reflector - topband at contesting.com