How to best choke a receiver feedline

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I'm installing an active antenna.
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  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

Re: How to best choke a receiver feedline

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This is no antenna, it is a joke, a bad joke.

w.

Re: How to best choke a receiver feedline
On 11/16/2017 1:36 AM, Helmut Wabnig wrote:
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  Hmm, everyone has an opinion, is yours based on testing one?

Anyway, I found my problem was not the feedline. I started turning off  
breakers and one of them shut down the buzz. Two sources of buzz were on  
that breaker and outdoor light with IR sensor and my garage door opener.
I had a very minor buzz left, audible but didn't show up on the S meter.
That was cleared with an isolation transformer and lifting the ground wire.
  Now I can receive 200kHz beacons, AMBCB, 80 meters, 40 meters 10  
meters and 28 MHz CBer's. So it works, do I have anything to compare it  
to, not yet, but I'll be putting up a long wire soon.

                                            Mikek

   Btw, the antenna is quiet, without any chokes. I don't know if
running the coax inside the metal mast helped, the mostly underground
feed line probably did. Oh, I just realized I do have a choke at the  
bottom of the mast, just before the feed line goes into the ground. I'll  
remove that tomorrow and see if it's needed.

Re: How to best choke a receiver feedline
On 16/11/2017 07:36, Helmut Wabnig wrote:
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It is a perfectly acceptable active antenna, and works as well as any  
other short active antenna.

The comments about choking the feed-line are quite reasonable, it you  
have an antenna high up in the clear you don't want signals,  
particularly local noise, picked up on the feeder being fed to the receiver.

Jeff

Re: How to best choke a receiver feedline
Jeff wrote on 11/16/2017 5:16 AM:
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An acceptable choke can be a coil made of the feedline coax, correct?  My  
understanding is you have to match any magnetic material to the frequency in  
use while an air core doesn't have that complication.

--  

Rick C

Viewed the eclipse at Wintercrest Farms,
on the centerline of totality since 1998

Re: How to best choke a receiver feedline

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Depends on the frequency in question.

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True, but  at lower frequencies it is not possible to get enough  
inductance without a magnetic core of some sore in a reasonable size.

Jef

Re: How to best choke a receiver feedline
On 11/16/2017 1:36 AM, Helmut Wabnig wrote:
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  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

Re: How to best choke a receiver feedline
On Fri, 23 Feb 2018 15:34:17 -0600, in rec.radio.amateur.antenna you
wrote:

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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.

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.

There is always room for improvement,  
the best of all antennas does not exist :-)

OE8UWW

Re: How to best choke a receiver feedline
On 2/24/2018 3:22 AM, Helmut Wabnig wrote:
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  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.


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   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.

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  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.

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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

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Re: How to best choke a receiver feedline
On 2/24/2018 7:21 AM, amdx wrote:
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   I'll need to put a little more thought into the 1:9 balun issue.
  One reason I wanted a long wire is so I could experiment with
Crystal Radio. I'll need to figure out a way to switch from high  
impedance to low impedance balun fed.
                           Mikek

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