On 2/24/2018 3:22 AM, Helmut Wabnig wrote:
On Fri, 23 Feb 2018 15:34:17 -0600, in rec.radio.amateur.antenna you
wrote:
On 11/16/2017 1:36 AM, Helmut Wabnig wrote:
On Thu, 9 Nov 2017 15:23:15 -0600, amdx wrote:
I'm installing an active antenna.
https://www.ebay.com/itm/MiniWhip-Ac...72.m2749.l2649
The seller discusses choking the feedline to prevent it
from adding signal.
How do I best accomplish this.
I don't have any beads, I do have loads if ferrite potcores and some
toroids.
The antenna will be up 24ft, last 4 feet is pvc, the first 20 ft is
steel.
Will it help to run the coax inside the mast?
About 75 ft of the coax is run underground and then about 7 feet up to
the radio.
I plan to choke it at both ends.
Mikek
This is no antenna, it is a joke, a bad joke.
w.
Helmut,
I got my long wire up. 16ft high sloping up to 50ft high.
It's 132 ft long plus another 16ft down and 4 more ft into the house.
I tested from 211kHz to 1600kHz because that's what the antenna switch
on my the radio allows.*
My active antenna is better at 211kHz and much less noisy, at 325KkHz
the signal strength is about equal, but still the active antenna has
less noise.
In the lower half of the AM band the long wire is equal or 1 S unit
higher in signal strength.
In the upper half of the AM band it is about 2 S units higher signal
strength.
The long wire is always noisier. The Active antenna is preferable.
In fact the active antenna has less noise on every band where I tested,
5MHz, 10MHz and 15MHz.
I still want to hook up an external antenna switch and test it at night,
but right now, the active antenna is clearly the winner.
I'm not in a particularly noisy area. In the middle of the AM band,
1025kHz (mid afternoon),
I have 1 S unit on the active antenna and 3.5 S units on the Long wire.
* I have an Icom R71a, the radio has two antenna inputs, a UHF connector
input and a long wire input.
The antenna input is manually switchable up to 1600kHz and then radio
takes over and only the UHF antenna connector is used.
Hmm, for some reason my unit switches at 1598Khz.
Mikek
I wonder what exactly you are doing.
Where is the active antenna placed?
I would put it outside, a few meters away from the house
in a free space and use shielded cable for connections.
I put the active antenna about 30ft from the house, up 24ft.
The coax is buried in PVC from the antenna base to the house.
The last 4ft at the top of the metal mast is pvc pipe, and the coax
runs inside the steel mast.
Your long wire antenna is end fed, that means, it is unsymmetric,
if I understand you correctly. And the wire goes unshielded
into your house. This is the second worst scenario one could imagine,
the worst being no antenna at all. End fed antennas should have a 1:9
balun at the end and connected via coax.
That's a good point, although, my radio is made to accept a long wire
antenna.
I do think the change is worth doing, that will allow me to use a coax
switch to make it easier to compare antennas on all bands. Rather than
just AM, that the antenna switch on the radio allows.
I did some night time testing last night and found the long wire has
directional characteristics that help eliminate co-channel interference.
The active, being omni picks up stations from all directions,
making it less desirable at night when the atmosphere allows more
signals to arrive.
There is always room for improvement,
After I get the 1:9 balun put up, I have an antenna phasing unit that
I'll be able to experiment with and help eliminate co-channel interference.
the best of all antennas does not exist :-)
Nope that's right. At one time I had a rotatable Flag with a variable
termination, that was quiet and directional even on the AM band.
Mikek
OE8UWW