Re: Data transmission on 30 meters with PX3 problem

Posted by Bob McGraw - K4TAX on Sep 03, 2018; 1:37am
URL: http://elecraft.85.s1.nabble.com/Data-transmission-on-30-meters-with-PX3-problem-tp7644864p7644866.html

Here is another good information source on baluns and specifically the
type of material and how it performs under various conditions.

http://www.karinya.net/g3txq/chokes/

As it is said "I have no dog in this fight".

73
Bob, K4TAX




On 9/2/2018 8:28 PM, Bill Frantz wrote:

> This is one of the clearest explanations I have seen of the issue. Thanks Erik.
>
> 73 Bill AE6JV
>
> On 9/2/18 at 5:53 PM, [hidden email] (Erik Basilier) wrote:
>
>> As Jim K9YC has pointed out in his writeup on baluns etc, there is a
>> threshold effect when one applies a choke to reduce common mode current. The
>> current is determined by driving voltage and total (complex) series
>> impedance. The choke RF impedance will have a reactive as well as a
>> resistive component, and so does the circuit before the choke is applied.
>> The reactances may be of opposite signs and cancel out, in which case adding
>> the choke may actually make it easier for the common mode current to flow.
>> It is easy to think that one can add a marginal choke and look for a small
>> improvement as a reliable indication that a good choke will be worth the
>> investment or not. Wrong! Only then the choke tried has high enough
>> impedance to dominate the circuit can one judge whether whether adding
>> chokes helps. Also, adding the perfect choke near the antenna feed point is
>> not likely completely to eliminate common mode RF current at the rig end of
>> the cable. For common mode purposes, the perfect choke acts effectively to
>> disconnect the outside of the coax from the antenna, but that metal is still
>> there, close to the antenna, and it will be part of the antenna system as a
>> parasitic antenna element, affect the radiation pattern, and carry
>> substantial RF current.
>> 73,
>> Erik K7TV
> -----------------------------------------------------------------------
> Bill Frantz        | There's nothing so clear as  | Periwinkle
> [phone]      | a design you haven't written | 16345 Englewood Ave
> www.pwpconsult.com | down.    - Dean Tribble      | Los Gatos, CA 95032
>
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
> Message delivered to [hidden email]
>

______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[hidden email]

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html
Message delivered to [hidden email]