75 meter hamstick vs low dipole
Buck
If I have a low dipole about 10 feet off the ground for 75 meters,
would it be better if I put a hamstick 75 meter vertical up and
connect the dipole wires to the ground side for a vertical?
Buck
N4PGW
--
73 for now
Buck, N4PGW
"Small - broadband - efficient: pick any two."
Cecil Moore
> If I have a low dipole about 10 feet off the ground for 75 meters,
> would it be better if I put a hamstick 75 meter vertical up and
> connect the dipole wires to the ground side for a vertical?
The low dipole is probably much more efficient than the
hamstick and most of the radiation is straight up which
is not necessarily a bad thing on 75m. Your question reminds
me of one on a clinical psychological test. "Would you rather
take one or two days to die an agonizing death?" :-)
--
73, Cecil http://www.w5dxp.com
nm...@wt.net
> If I have a low dipole about 10 feet off the ground for 75 meters,
> would it be better if I put a hamstick 75 meter vertical up and
> connect the dipole wires to the ground side for a vertical?
>
No.
Christopher Cox
I think the original post needs a couple of questions asked.
Agreed the low lying dipole is ideal for a NVIS antenna.
It would be interesting to see what kind of results would be had for
contacts greater than 600 miles between the two antenna's.
Chris
Michael Coslo
That Hamstick isn't going to be very efficient, so I guess it comes
down to whether or not the reduced efficiency of the dipole at the
desired DX angle allows for greater signal than the bad efficiency of
the Hamstick at all angles...
Suffice it to say that it probably isn't a very good option to run a
Hamstick setup at home when there are any other options available.
- 73 de Mike N3LI -
John Passaneau
news:fvf3qt$11gc$1...@f04n12.cac.psu.edu:
Your not going to gain anything from the swap. I've compared a full size
dipole to a hamstick dipole on 80m at the same hight. The dipole was
20db (about 3 S-units) better than the hamsticks. You will not gain
anything close to 20db by putting the hamstick dipole up higer. On 40m a
hamstick dipole is only about 10db worse than a full size dipole, better
still on the higher bands. And yes I'm talking about hamstick dipoles
using the right models for each band. On 80m the 2:1 SWR bandwidth is
about 60KHz, wider on 40m but still narrower than a dipole on all bands.
Ham stick dipoles seems attractive, but they fall into the better than
nothing class on the lower bands.
John Passaneau
Buck
<w3...@arrl.net> wrote:
>Michael Coslo <mj...@psu.edu> wrote in
>news:fvf3qt$11gc$1...@f04n12.cac.psu.edu:
>
>> Christopher Cox wrote:
>>> Cecil Moore wrote:
>>>> Buck wrote:
>>>>
>>>>> If I have a low dipole about 10 feet off the ground for 75 meters,
>>>>> would it be better if I put a hamstick 75 meter vertical up and
>>>>> connect the dipole wires to the ground side for a vertical?
John,
The idea I have is to make a vertical ground plane with the HamStick.
>Ham stick dipoles seems attractive, but they fall into the better than
>nothing class on the lower bands.
>
>John Passaneau
i fully understand that the HamStick is not a great antenna fro that
band, but how would the vertical ground plane made of a HamStick and
two full length radials compare to a dipole at the same 10 foot level?
what would the angle of radiation be like?
Cecil Moore
> what would the angle of radiation be like?
Probably about 25 degrees with -20dBi gain.
John Passaneau
news:uuqm14ppi85uan1f9...@4ax.com:
My suggestion would be to download the trial version of EZNEC and model a
7’ wire over ground. That is an easy model to do and will tell you what
the pattern will look like. As to the gain it will be just about the same
as my tests, about 20db down from a full size antenna. The reason is
hamsticks are very lossy on 80m and the bandwidth will still be about
60KHz. Anyway learning how to model antennas is a lot of fun and you can
try out a lot of different antennas easly. I can say from experance that
modeling works. Everything that I’ve carefuly modeled worked just like
the model.
John Passaneau
Dave Platt
Buck <usen...@lumpuckeroo.com> wrote:
>i fully understand that the HamStick is not a great antenna fro that
>band, but how would the vertical ground plane made of a HamStick and
>two full length radials compare to a dipole at the same 10 foot level?
I think it would compare badly to the dipole.
With the dipole, you'll have working in your favor the basic radiation
resistance of a dipole in free space, reduced by the proximity of the
dipole to the "reflector" (the lossy soil). Working against you,
will be the losses in the soil. It'll certainly be a cloudwarmer...
good for NVIS, not for DX as there will be little energy at a low
radiation angle.
If you short the dipole wires and use it as a two-wire sort-of-
elevated radial set, the radiation resistance of these wires will be
very close to zero - the far-field radiation from them will cancel out
almost entirely. You'll still have substantial losses in the soil, I
think, as the wires are only a small fraction of a wavelength above
the soil surface. The radiation resistance of the HamStick itself is
going to be quite low (an ohm or so??), and it certainly has a
substantial amount of loss resistance.
My SWAG is that by making this change, you might drop your radiation
efficiency from 25% (low dipole over lossy ground) to 5% or less
(lossy short vertical, over an inadequate radial network with
substantial ground losses). Don't trust these numbers!
>what would the angle of radiation be like?
Probably much like that of any other very-short monopole over a lossy
ground... pretty much omnidirectional, with a modest null pointing
straight up.
It *may* have more low-angle radiation in the pattern than the
low-dipole arrangement, but I think you'd lose most or all of the
pattern advantage due to the lower radiation efficiency.
--
Dave Platt <dpl...@radagast.org> AE6EO
Friends of Jade Warrior home page: http://www.radagast.org/jade-warrior
I do _not_ wish to receive unsolicited commercial email, and I will
boycott any company which has the gall to send me such ads!
Frank's
"Buck" <usen...@lumpuckeroo.com> wrote in message
news:2i7k14pdts0lgltr6...@4ax.com...
Assuming a 7 ft monopole, with a lumped element inductor
(located in the middle of the vertical) of Q = 500,
and 100 W input. The total radiated (sky wave) power is 1.4 W.
The gain is -12.7 dbi with a take-off angle of 23 degrees.
At resonance the input impedance is 14 ohms.
73,
Frank
Cecil Moore
> Assuming a 7 ft monopole, with a lumped element inductor
> (located in the middle of the vertical) of Q = 500,
> and 100 W input. The total radiated (sky wave) power is 1.4 W.
> The gain is -12.7 dbi with a take-off angle of 23 degrees.
> At resonance the input impedance is 14 ohms.
And the Q of a hamstick is probably a lot closer to 50
than to 500. Someone else reported the hamstick as -20 dBd.
Frank's
> than to 500. Someone else reported the hamstick as -20 dBd.
I would think it would be hard to design a coil with a Q of 50.
I tried to find a picture of a Hamstick to estimate the Q,
but no luck. Anyway, assuming the Q is 50, NEC returns
the following results:
Structure efficiency - 5%
Total radiated sky wave (with 100 W in) = 180 mW.
Input impedance - 112 ohms.
73,
Frank
Frank's
> Structure efficiency - 5%
> Total radiated sky wave (with 100 W in) = 180 mW.
> Input impedance - 112 ohms.
PS -- and the gain is -23 dbi at a 20 deg TOA.
Cecil Moore
> PS -- and the gain is -23 dbi at a 20 deg TOA.
Someone measured it at -20dBd so that may be
fairly accurate.
Buck
wrote:
>
>If I have a low dipole about 10 feet off the ground for 75 meters,
>would it be better if I put a hamstick 75 meter vertical up and
>connect the dipole wires to the ground side for a vertical?
>
>Buck
>N4PGW
In another forum, I was informed that the signal for the vertical was
very low at every angle compared to the dipole.
One of the things i was thinking about was if it would be beneficial
to add a good ground radial to the mobile whip on the car, once
parked. however, it is obvious that if one can raise, even 10 feet, a
full sized 1/2 wave dipole, it would produce much better results being
left in the dipole configuration.
Thank you to all who participated. (Even to the one who simply said
"NO"). that was a short, sweet and to the point answer. :)
73 for now
Buck
n4pgw
John Passaneau
some use in this discussion. I just realized that this thread is about a
low dipole compared to a vertical Hamstick antenna. I reported that I have
compared a Hamstick dipole to a full size dipole and that it was down 20db
from the full size dipole. I can also report on a Hamstick vertical
compared to a full size dipole on 80m. For some years I’ve been using a
phased vertical system as a receive antenna on the 80m SSB Dx window. It is
2 Hamstick’s spaced 1/16 wave apart and feed 90 degrees out of phase with a
relay system that lets me switch directions. As a receive antenna it works
very well. A friend that has a 900’plus beverage tells me that it compares
very well. For me it gives me about at 15db signal to noise advantage over
my transmit dipole. The front to back is also about 20db in the most
favorite direction. But here is the part that is germane to this thread.
The signal level compared to the dipole is still about 20db down. I don’t
care as receivers have a lot of extra gain and the increase in signal to
noise makes all the difference. I don’t have much of a ground system, just
4 10’ radials under each vertical but putting down a good ground will not
make up 20db, no way. The main advantage that a beverage has over this
antenna is that it will cover several ham bands and the Hamstick verticals
are only good for about 100Khz around the DX window but that is all I want
and it fits in my yard as the spacing is only about 30’.
So I can say that a phased hamstick vertical on 80m with a poor ground is
also about 20db down from a full size dipole at 40’.
John, W3JXP
Cecil Moore
> So I can say that a phased hamstick vertical on 80m with a poor ground is
> also about 20db down from a full size dipole at 40’.
It all makes good sense. The best 75m mobile antennas
are about 10 dB down from a 1/2WL dipole. The hamstick
is about 10 dB down from the best 75m mobile antennas.
nm...@wt.net
It's the lack of a decent radial system which makes me
look at it in a negative manner..
It's quite possible for the short vertical to outplay the
low dipole for DX, but... I don't see it happening with
only 2 radials and low to the ground.
The hamstick would actually work better mounted on a
vehicle than it would in that 2 radial scenario I bet.
So it's more the ground radial problem, rather than
the short radiator itself.
On 40m, my mobile outplays my 35-40 ft high dipole
to DX. But, I don't know if that would be the case with
two low radials, vs the usually better RF ground that
my vehicles provide.
With a low vertical on 80m, two radials ain't gonna
get it done as far as avoiding ground loss.
And the short vertical makes things even more critical.
For NVIS use, the low dipole would *smoke* the short
vertical with two radials. I've run low 80m dipoles 5-10 ft
off the ground when camping, and still had fairly
decent results to regional stations.
MK