Gap challenger dx--ground plane ?
les
4ways
below the ant..
if so i can run north and south 25 feet but have only 33'ft lot and will
have to only place
10 ft ground wires west and east.will this make a problem?
i can also put a ground wire down 5 ft to the evetroft of the house.
any ideas.
will this ant.. work ok or should it be ground mounted?
what is the best hight?
ve4...@rac.ca
kingpop
gain.
Thomas R. Williams
According to GAP instructions, the Challenger can be elevated. However,
it is rather large and would present a mounting problem. In any case, it
should be guyed with braided dacron rope. The 3 - 25' counterpoise wires
are used to resonate the antenna on 40m. They should not be grounded, or
attached to any other metallic objects. Adding additional wires will not
improve results significantly. Removing them will deteriorate
performance drastically - on 40m only. I was told by GAP that the
antenna base should not be grounded. In fact, they knew of problems when
the insulating base filled with ground water and essentially grounded
the bottom of the antenna. I have never noticed any deterioration when
the base was in- or under- water. Recently the top of the base insulator
was under 6 inches of water and it still worked fine. My personal
experience shows that the antenna is great on 40 and 20m, OK on 10m, and
poor on 80 and 15m. Do you share the same results?
73,
Tom N2CU
kingpop
> According to GAP instructions, the Challenger can be elevated. However,
> it is rather large and would present a mounting problem. In any case, it
> should be guyed with braided dacron rope. The 3 - 25' counterpoise wires
> are used to resonate the antenna on 40m. They should not be grounded, or
> attached to any other metallic objects.
You forgot the part about having to keep the *counterpoise* wires 90
degrees to the antenna. A task that further encumbers a elevated
mount. As I said it's not worth the effort to elevate.
> Adding additional wires will not improve results significantly. Removing > them will deteriorate performance drastically - on 40m only.
This is almost a quote from their ads, and it's a well documented crock
here in the NG
> I was told by GAP that the
> antenna base should not be grounded. In fact, they knew of problems when
> the insulating base filled with ground water and essentially grounded
> the bottom of the antenna. I have never noticed any deterioration when
> the base was in- or under- water. Recently the top of the base insulator
> was under 6 inches of water and it still worked fine.
Down in South Fl., where GAP is located, during the rainy season the
water table would rise up in some places to ground level or just below.
During this time a antenna placed in the ground would lower is 40mt.
resonance to around 6.100Mhz. and the 20mt. band would stop functioning
all together. This may not be the case in your area due to a variance
in the water/soil conductivity
> My personal
> experience shows that the antenna is great on 40 and 20m, OK on 10m, and
> poor on 80 and 15m. Do you share the same results?
Yep, this is typical of how this eight band wonder plays. Good on two
bands (20&40) pretty much sucks on the rest. On 10 and 15 it has a high
angle of radiation because of it's electrical length on these bands. On
80 it's loaded with a very lossy coaxial stub. Hidden inside the center
section of the antenna is some 49' of coax that is used as a loading
device. This gives the antenna a great bandwidth but then all dummy
loads have great bandwidth!! 8~)
Thomas R. Williams
> > Adding additional wires will not improve results significantly. Removing > them will deteriorate performance drastically - on 40m only.
>
> This is almost a quote from their ads, and it's a well documented crock
> here in the NG
Well, not quite. This came from my personal conversation with George
Henf. Understanding that these are used to set the 40m resonance, and
are not acting as radials under a 1/4 wave vertical, I can accept this.
I've been reading this NG for some time, but haven't seen any comments
on this. Perhaps you can enlighten me with the results obtained when
adding more counterpoise wires. In the meantime, I'll follow the LXC
Prime Directive - When in doubt, do as the manufacturer says.
>On 10 and 15 it has a high
> angle of radiation because of it's electrical length on these bands.
I agree for 15m because it does use the entire length of the antenna.
However, on 10m it has a seperate radiating element (the rod that
extends vertically from the gap and parallel to the main tube). I
believe that this is 1/4 wavelength on 10m, so it shouldn't suffer the
high angle lobe.
> On 80 it's loaded with a very lossy coaxial stub. Hidden inside the center
> section of the antenna is some 49' of coax that is used as a loading
> device. This gives the antenna a great bandwidth but then all dummy
> loads have great bandwidth!! 8~)
Exactly, just like the thread about B&W broadband dipoles. Great SWR,
but no efficiency.
73,
Tom N2CU
Dick C
>
> just like the thread about B&W broadband dipoles. Great SWR,
> but no efficiency.
Don't write off the B&W T2FD or other terminated antennas.
They actually work very well and have for a long time been
widely used in applications where a broad range of
frequencies needed to be covered with a single antenna, or
where HF communications needed to be installed quickly,
perhaps by non-technically trained persons.
On every occasion that I have been involved in their use,
the small signal reduction experienced was not a factor in
completing the needed communication. The amount of reduced
signal could not be detected, although some loss was
undoubtedly experienced.
The T2FD has been widely used in military, commercial and
some Public Safety applications, including the Alaska State
Troopers, where long and medium range HF communications have
been routinely used. Nobody ever complained about their lack
of "efficency". I'm acqauinted with a former Alaska Trooper
who built, installed and used many of them.
The efficiency varies with the frequency in use - how well
the wire radiates at the particular frequency in use as
opposed to what percentage of the RF must be dissipated as
heat by the terminating resistor. Even a 50% loss would
cause only 3dB radiated power reduction, half an S-unit at
the recieve end of the circuit. An antenna tuner can help
maximize the power that is accepted by the antenna at some
frequencies.
And I doubt that anyone would say that a terminated rhombic
was not efficient.
A terminated antenna is always 100% more efficient than no
antenna at all. Like saying that CW, as inefficient as it
is, is much better than no communications at all.
Dick W0EX
Thomas R. Williams
So is loading a coathanger, but I wouldn't use it nor recommend it.
I am aware that many people have used this antenna and are satisfied
with its intended purpose. However, unless you were in one of those
special situations, you would be better off with an open wire fed
dipole. Most hams take great pains to squeak out every watt from their
system and throwing away half their power in a lossy antenna is
counterproductive. I doubt you'll find any QRP'ers using these antennas.
73,
Tom N2CU
ign...@num.ads.uga.edu
>> A terminated antenna is always 100% more efficient than no
>> antenna at all. Like saying that CW, as inefficient as it
>> is, is much better than no communications at all.
>>
>> Dick W0EX
>So is loading a coathanger, but I wouldn't use it nor recommend it. I am
>aware that many people have used this antenna and are satisfied with its
>intended purpose. However, unless you were in one of those special
>situations, you would be better off with an open wire fed dipole. Most
>hams take great pains to squeak out every watt from their system and
>throwing away half their power in a lossy antenna is counterproductive. I
>doubt you'll find any QRP'ers using these antennas. 73,
The loop antennas are often much quieter than dipoles, and T2FD has a
reputation of being very quiet. QSOs often depend not only on power but on
the ability to copy, especially on 30-160m. It is possibly that small
losses of T2FD are well componsated by lower noise and no-tune
characteristic. If you hear the DX first and don't have to tune to work
him, perhaps you can be ahead of the crowd. And if you hear lots of DX on
80 and 160m but can't work them, there is an incentive to set up a more
efficient antenna.
Just being a devil's advocate.
Ignacy, NO9E
kingpop
"Thomas R. Williams" wrote:
>
> Well, not quite. This came from my personal conversation with George
> Henf. Understanding that these are used to set the 40m resonance, and
> are not acting as radials under a 1/4 wave vertical, I can accept this.
> I've been reading this NG for some time, but haven't seen any comments
> on this. Perhaps you can enlighten me with the results obtained when
> adding more counterpoise wires. In the meantime, I'll follow the LXC
> Prime Directive - When in doubt, do as the manufacturer says.
This has all been hashed over many many times on the NG. Rather than
going over it all again try a search of GAP at dejanews.
> I
> believe that this is 1/4 wavelength on 10m, so it shouldn't suffer the
> high angle lobe.
Not true, the element you are referring to is not the only part of the
antenna that is active on 10mts. By the admission of their own
advertising the entire mast is active on all bands. I can remember old
advertising brochures that george had drawn current distribution graphs
for the different bands in. It clearly showed a full wave distributed
across the mast
Thomas R. Williams
You're right, Kingpop. Although my literature doesn't say the whole
antenna is active on each band, it does refer to the rods as "tuning
rods". Apparently the antenna functions as a center fed full wave dipole
on 10.
Thanks for the tip on searching dejanews.
73,
Tom N2CU
Thomas R. Williams
Yeah, a Beverage receives well, but doesn't work well on transmit ~8^)
I don't know about you, but hearing them, and not having them hear you
can get frustrating. Loud is good.
73,
Tom N2CU