[TowerTalk] Fwd: Fwd: Fwd: OWAs or Fans?

Mon Jun 20 20:32:32 EDT 2016

OK, this is how I am doing it:

1) My antenna tuner is isolated from ground. 2) the coax from the tuner to the radio is passing a choke. This render a balanced feed to the antenna feeder. I hope that clears that up a little. The technique was presented at a seminar at Boxboro some years ago.

So, answeres:

1) I have a 250 feet wire, fed 1/3 from one end in the air. Call it a Windom if you like.

2) The feed line is attached directly to the antenna.

3) The choke is (technically) at the ground end of the feed line.

4) The feed line is connected to the ground isolated antenna tuner. The isolation contribute to equal, balanced current in the feeder.

5) The choke is on the 50 ohm side of the tuner.

6) Yes, as the tuner is "acting" balanced. The tuner is, in reality unbalanced but as it doesn't have a return path to ground the high Z is by all means balanced.

7) The transceiver end of the coax has the shield grounded (to the shack shield. The shack shield is connected to the tower.)

I don't know if I explained it clearly but the tuner is "floating" from ground as the transceiver side is connected to the choke. That way the antenna side is balanced.

The tuner is homebuilt. It consist of a tuned circuit that is tapped for proper SWR. I have several of them. Each one covers about 3 - 1 in frequency. I am using four to cover 160 - 10 meter.

My question and interest is to get a CM choke next to the antenna so I can reduce the radiation from the feeder.

Hans - N2JFS

-----Original Message-----
From: Edward McCann <edwmccann at yahoo.com>
To: Hans Hammarquist <hanslg at aol.com>; towertalk <towertalk at contesting.com>
Cc: edward mccann <edwmccann at aol.com>
Sent: Mon, Jun 20, 2016 12:32 am
Subject: Re: [TowerTalk] Fwd:  Fwd: OWAs or Fans?

Hans:

Your initial inquiry asked about CM choke for open (and ladder line, I presume) feeder.

I passed on K9YC's counsel on the topic.

Your latest message has me a bit confused:

"I have a setup with the tuner isolated from ground and a CCM chock made of 50' of coax wound around a 4" PVC pipe. The chock is fairly wide band by NOT having an even pitch on the winding. The choke insure that there is no CM current entering the shack."

So, for clarity:

1. What antenna is in the air?
2. Is it fed with open wire feedline?
3. Where is your CM choke in the line?
4. From antenna, at you CM Choke,  do you connect one side of open wire to coax center conductor and other to ground?
5. Coming out of CM Choke, are you back to open wire feedline to tuner?
6. Is this open feedline hooked into balanced terminals of tuner?
7. Antenna side seems isolated from ground at tuner. But what about output side of tuner? Now coax, right, and transceiver chassis ( and therefore shield of coax) is now grounded. It is this not the case?

PS-what tuner are you using?

Thanks for clarification on this most interesting topic, i.e. A CM Choke for open feeder.

73,
Ed McCann
AG6CX

Are you using an open wire feed?

Sent from my iPhone

> On Jun 16, 2016, at 3:04 PM, Hans Hammarquist via TowerTalk <towertalk at contesting.com> wrote:
> 
> I am very fortuned not being surrounded by noise. Next door neighbor is 1000 feet away with no TV or any other RFI source and next neighbor is 1/2 mile away. Wonder if I can make a CM choke for an open feeder. Any idea?
> 
> 
> Hans - N2JFS
> 
> 
> 
> -----Original Message-----
> From: Jim Brown <jim at audiosystemsgroup.com>
> To: towertalk <towertalk at contesting.com>
> Sent: Thu, Jun 16, 2016 1:19 pm
> Subject: Re: [TowerTalk] Fwd: OWAs or Fans?
> 
>> On Thu,6/16/2016 7:26 AM, Hans Hammarquist via TowerTalk wrote:
>> Open wire feeders are simple to use if you know to address a few things
> 
> 
> The thing that it is NOT POSSIBLE to address is choking the feedline at 
> the feedpoint (that is, where it junctions the dipole). This makes the 
> antenna inherently noisy in most parts of the real world. Off-center-fed 
> antennas like Windoms are even worse in that regard.
> 
> This doesn't mean that they don't radiate -- that's NOT the issue. 
> There's nothing wrong with these antennas in concept, only that we as 
> hams are surrounded by RF noise sources.
> 
> 73, Jim K9YC
> 
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