[TenTec] OCF antennas evolution

Fri Jul 12 10:55:38 EDT 2013

Let's say you are running a 80 meter dipole on 40 meters.  The impedance 
will be about 2500 ohms or higher.  Let's also say you are using 600 ohm 
ladder line.

Then by placing a 4:1 balun at the antenna, the 2500 ohms becomes 625 
ohms.  That means you have an excellent match on the 600 ohm ladder 
line.  You then match the 600 ohm line to the rig with a tuner.

The 4:1 balun in this case ends up with less loss than the 1:1 balun.

It all depends on what you are matching as to which one is better.

Carl Moreschi N4PY
121 Little Bell Dr.
Hays, NC 28635
www.n4py.com

On 7/12/2013 9:15 AM, Bob McGraw - K4TAX wrote:
> I commented recently where there is indeed a good application for 4:1
> balun usage. I think you have also indicated the correct use for 4:1
> baluns in some of your OFC antenna discussions. In most other cases,
> typically 1:1 ratios are preferable. I know that Jim , K9YC, has some
> good information and history on correct balun usage. To complicate the
> topic, there are current baluns and voltage baluns both in 1:1 and 4:1
> configurations as well as other ratio version. You are correct in that
> the topic is rather complex and there's widely varying opinions,
> approaches and results.
>
> In my case balun usage is in the 50 ohm to 50 ohm unbalanced to balanced
> configuration where a matched condition always exist. Thus being on the
> input of the tuner.
>
> 73
> Bob, K4TAX
>
>
> ----- Original Message ----- From: "Rick - DJ0IP / NJ0IP" <Rick at DJ0IP.de>
> To: "'Discussion of Ten-Tec Equipment'" <tentec at contesting.com>
> Sent: Friday, July 12, 2013 1:26 AM
> Subject: Re: [TenTec] OCF antennas evolution
>
>
>> Mike,
>>
>> I don't think anyone here is going to be able to explain to you in a
>> single
>> email why the 1:1 balun is better.
>> However I can show you how to learn about this in a systematic way, using
>> material from 4 of the experts in this field.
>> It will probably take you about 10 hours to do this, but then you will
>> know.
>> (otherwise, just take our word for it.)
>>
>> This is a 4 part training course:
>>
>> PART-1: View GM3SEK's online presentation on common mode current
>> problems,
>> especially the first half of it. View all of it but at this point, you
>> only
>> need to understand what all can be causing us problems. Ian's
>> presentation
>> is a good introduction to that. See:
>> http://www.ifwtech.co.uk/g3sek/in-prac/
>> (Note: it is a challenge just to bring the file up. You have to right
>> click
>> Ian's link and save the link to your computer. Then double-click the link
>> on your computer and it brings the PowerPoint file up.)
>>
>> PART-2: Read W7EL's excellent paper on "Baluns: What They Do and How They
>> Do It". These 8 pages will give you a good understanding of Baluns (which
>> Jim rightly called Chokes), and begin to answer your question. See:
>> http://www.eznec.com/Amateur/Articles/Baluns.pdf
>>
>> PART-3: View G3TXQ's excellent page on "Tuner Balun Ratios":
>> http://www.karinya.net/g3txq/tuner_balun/
>>
>> PART-4: Now that you have a fairly good understanding of all of this,
>> Read
>> K9YC's paper, "RFI-Ham". Although this is the most comprehensive paper, I
>> don't recommend beginning with this one. This is like the graduate
>> course.
>> It is 66 pages long, but it has everything in it. See:
>> http://audiosystemsgroup.com/RFI-Ham.pdf
>>
>> If you haven't a clue about all of this and view these resources in this
>> order, you will probably understand most of what Jim wrote, though if
>> you're
>> like me, you'll have to read it two or three times.
>>
>> SHORTCUT for your question, MIKE: Go straight to PART-3.
>>
>> However I recommend anyone asking this type of question, take the time to
>> work through all of this. It will be very beneficial.
>>
>> 73
>> Rick, DJ0IP
>>
>>
>> -----Original Message-----
>> From: TenTec [mailto:tentec-bounces at contesting.com] On Behalf Of Mike
>> Bryce
>> Sent: Friday, July 12, 2013 3:51 AM
>> To: Discussion of Ten-Tec Equipment
>> Subject: Re: [TenTec] OCF antennas evolution
>>
>> I quite aware that open line is generally considered lost less feed line.
>>
>> What threw me was the use of a 1:1 balun instead of a 4:1.
>>
>> That's the head scratcher.
>>
>> Mike wb8vge
>>
>> Sent from my iPhone
>>
>> On Jul 11, 2013, at 9:32 PM, k6jek <k6jek at comcast.net> wrote:
>>
>>> Mike,
>>>
>>> You're matching the antenna system, the antenna and the feed line. You
>> just can't separate the two. When the antenna impedance at a particular
>> frequency is different from the feed line characteristic impedance, the
>> impedance on the line is different every place on the line. You're
>> matching
>> whatever it happens to be at the shack end of the feed line.
>>>
>>> Losses are the reason to put the balun near the station instead of near
>> the antenna. Open wire line has much lower losses than coax under
>> conditions
>> of very high SWR. That's the reason we put up with the stuff which is a
>> royal pain in the arse, just so we can have a ridiculous SWR and not care
>> about it. And very high SWR is exactly what we have at almost all
>> frequencies when using a doublet as a multi-band antenna. The only reason
>> we can get away with such a thing is the low loss of open wire line.
>> So you
>> want to run that stuff as far as you can before switching to coax. As
>> long
>> as you can is ideally right into a balanced tuner, no balun at all.
>>>
>>> Jon
>>>
>>>
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