ON4UN's Low Band DXing Free Download
Geraldine Ferraiz
I have space for a full-size dipole for 160 but I cannot get it up
very high, maybe 30 feet, higher than that only at great expense and
with great difficulty.I will likely put up a 160-meter dipole at 30 feet and feed it with
ladder line and a tuner, and use it for NVIS work on 160-40.For DX, though, I'm wondering if I will be happy with a vertical such
as the Voyager DX from Gap Antennas, or if I should bite the bullet
and go to the expense and difficulty of getting the dipole up 60-80
feet (which still won't be very high, compared with a wavelength, at
160 or 80).What's your advice?
Get a copy of ON4UN's low band DXing.Search the Topband archives Re: antennas.Measure/estimate your ground conductivity and permittivity and get
comfortable with a modeling program.And finally, experiment.I don't mean to be glib but there's really no quick answer to what
antenna you'd be happy with for DX on 40,80 and 160. 30 feet for a
horizontal antenna *is* too low, generally.Maybe someone can comment on the Voyager DX... I can't, specifically.
Verticals are good, short verticals are compromises and must be treated
with care.- - - - - - - - -This is what I use: can certainly work more 40&80m DX on this than on the 30 foot high,
100 foot long centerfed wire I used to use on those bands. As far as
160m goes, this is the first time I can work 160 DX at all... 73,
Dan
>What's your advice?Hi Rick,Choose your poison.A 30 foot high 160M dipole is a notable ground hugging air cooled
resistor. A GAP is probably worse.A combination of the two might be in order (which does NOT mean buy a
GAP to do this). Erect a 30 foot vertical and top load it with what
would have been the dipole.I will leave to others what could be done in higher bands (with one
word of advice, GAPs don't usually perform very well on their lowest
band(s), but have been to be reported as good verticals otherwise).73's
Richard Clark, KB7QHC
As someone has said get a copy of ON4UN's Low band dxing..
I would not particularly recommend the Gap Antenna for Low Bands.Than being said if you and put out a decent radial system for dx
Transmitting anyway I'd say you want some sort of vertical.Why not try a Inverted L. Try to get as much vertical as possible.
Base tune it with a matching network- The SGC line works well for that
application. you can read more about Inverted L's in Cebik's write up at: Luck
73, Dave Kc1di
Good morning, Richard.Actually, 30 feet is on the low side of "about right" on 160 and on
the high side of "about right" on 80, for NVIS work, of which I do a
lot. For DX, I agree that it's not of much use.And yet...My current antenna is an inverted V up about 35 feet in the center, 90
feet each leg, fed with ladder line. It started life as a
60-foot-high inverted V, full length for 160, in which configuration
it worked rather well. Then a storm came by and knocked a tree down
... well, I digress... :-(I had earlier put up the inverted V via one of those "expensive and
difficult" mechanisms I mentioned earlier (hired a 60-foot cherry
picker and operator). I couldn't do that again, so I hoisted what was
left of the antenna up to the top of my 35-foot tower, and trimmed the
legs so that they would stay within the property line. Kept the
ladder line feeder, and I tune it with an LDG RT-11 autotuner with the
LDG balun.I use that antenna on all bands including 160, with a Yaesu FT-817
running a cloud-burning 5 watts, and it works amazingly well for the
power level.But, as usual, I want more. :-)Thanks to you and others here for the feedback on the GAP. I REALLY
wasn't up for spending almost half a grand for a vertical.
I have a fairly high noise level around here on any of the horizontal
antennas I've tried.But, I have an MFJ-1026 "Deluxe Noise Canceling Signal Enhancer" :-)
that does an amazing job of cutting down the noise IF the noise is
primarily from one general direction (which seems to be the case
around here although I haven't been able to pinpoint it).That's one of the reasons I wanted to try some kind of a vertical and
see how that worked.I read somewhere that ground mounted verticals with radials on or
buried in the ground tend to be noisier. Is that true? That's one of
the reasons I was considering the GAP Voyager DX... doesn't require an
extensive radial system.
The T is better if he wants it to act like a DX vertical.
The L is ok, but if the horizontal wire is fairly long,
there will be a good bit of horizontal radiation.
This can be good for a mix of NVIS and DX, but
for DX only, the T is usually better. The T will have
an overhead null the same as a normal monopole.
I'd say most peoples L's on 160 have more horizontal
wire than vertical... :/ I know mine did. I could only
get mine about 45 ft vertical . That left 80-90 ft running
across the backyard. I often feed my coax fed dipoles
as a top hat vertical on 160 by shorting the coax, and
feeding as a vertical. At the moment I have a turnstile on
80m, and a dipole on 40. "6 legs total"
The 4 60 ft wires make a good "X" top hat..
MK
One is a a linear loaded 1/2 wave inverted L fed at the top of the L
rather than the base.Another is a top & bottomed hatted, bottom fed L.Neither design requires radials.Author includes theoretical radiation patterns & SWR curves.73Terry
W9EJO
> The L is ok, but if the horizontal wire is fairly long,
> there will be a good bit of horizontal radiation.
> This can be good for a mix of NVIS and DX, but
> for DX only, the T is usually better. The T will have
> an overhead null the same as a normal monopole.
You're right but I wasn't talking about the Inv-L above.
When I said "real vertical", I was talking about a
normal 1/4WL monopole. The T and the 1/4WL vertical
have about the same performance if the T's vertical
section is not too short.
Your sixtyvert antenna has me rethinking my vertical plans.I have a forty foot utility pole laying on the ground while I plan the
details for a taller vertical. In spite of my aversion to guys I think this pole is light enough to
be workable for me. My current vertical is a 45 foot wire off the
side of the tower tuned with an SGC-237. It seems to be working well
in spite of a minimal ground. It appears to me that the guy anchors
could be as simple as a few five gallon buckets of sand.I sure hate to pay that much shipping though!John Ferrell W8CCW
The Top-Band seems OK. On 160M I worked all states in one weeked last
winter (contest). But on 80m and 40m I have had very little luck
working anything. I suspect the trees are grabbing all the RF energy.Because the trees are virticle conductors I'm thinking that a
horozontal dipole might work better. I'll only be able to get it as
high as the tree tops. Maybe an average of 55ft high near the edge of
an east facing clift. Since I live on the West Coast this might give me
good coverage on the States on 40 and 80 meters for next falls Salmon
Run? What do you think?
Bob
AC7PN
For a long number of years I used a square loop antenna down low to the ground
on HF. It was not fed in the 'usual' place, at the mid-point on the horizontal
wire, either at the bottom of the square loop or on top. I chose to feed it
half way up one of the vertical sides so as to obtain the best results I could
from the vertical radiation for it. That so as to do the best job I could for
40 and 80 meter DX work without going after formal ground plane enhancement and
working the feed point against that, as in ground plane verticals with radials.
In the 40 meter case the lowest horizontal wire was about ten feet or so above
ground level. The actual loop was fed from a coax cable with the ground braid
of the coax tied directly to the loop wire, and the feed match as a gamma match
section using six inch open wire feed insulators for that, plus a series
capacitor made from a cut off piece of coax cable the braid connected to the
braid connect point end of the center wire of the feed coax and the inside coax
wire connected to the gamma match line section. I had pair of three element
quads made this way, with a pair of switched in or shorted wire stubs made from
the same six inch open wire feed lines which if shorted, made that loop a
director, and if opened, made it a reflector. They were supported at right
angles to each other so I had four-way aiming capability here.
You can laugh all you want, but about 270 countries on 40CW confirmed from it
wasn't too bad. And it placed way up there in the DX test single band entries
for a long time from W5 land, which isn't really the easiest place from which
to compete against the East and West coasts of the USA on low bands.
Yes, it was replaced by a four element phased vertical array, with elevated
tuned radials. Which is definitely noisier on receive. But it has the
advantage of being directionally switchable without going outside and getting
on a step ladder four times just to change the fire direction in the middle of
the night, or rain or .. even .. TRW's and twisters in this area of Texas. Of
which there were only twenty tornadoes on the ground in a single day just a
couple weeks ago right around here.
;)For years now I've wanted to build a low three element rotary vertically fed 40
meter quad to test this against the four square switched phased vertical array
I've used to romp the confirmed 40CW only card count to 321 now. That with
about a level 5 or 6 ground level quality here in sandy pine tree country. But
age, funds, want-to and other more important computer programming work in my
preference list have gotten in the way.
If I ever can get this done I'd dearly love to post the comparative figures on
a real-time real=workem romp! If it wouldn't be too much trouble for someone
interested in this, making a 40 meter wire loop is pretty easy. You only need
a pair of poles to support the top wire. I think you will be pleasantly
surprised how quiet it is and how effective it is, if vertically fed, for
working low band DX stations....
Mike - W5WQN