[OKDXA] Feed Line Problems NOW BALUN RECOMMENDATIONS

Sat Apr 27 09:52:31 EDT 2013

Hi John,

Sorry for the delayed replay! The W2DU type of balun (lots of ferrite 
beads over the coax) is probably the easiest to get or make. If you 
decide to roll your own, get a coupe le of 2.4" #43 ferrite toroid 
cores, stack them together and wind as many turns of hefty parallel 
magnet wire (16 ga) in a single layer. Put this in an enclosure, seal it 
up, attach an SO-239 on either end, and have at it.

Or, go buy about 20 or so ferrite beads (77 is best, 43 will do) that 
will fit over the end of the coax (they make sizes that work with either 
RG-8, -8X or -58. Cut off the old connector, string them on, figure out 
how to keep them in place (silicon rubber will do if you find some big 
heat shrink to put over it), reattach the connector and you're done.

73,

Kim N5OP

On 4/21/2013 9:04 PM, John G. wrote:
> Hi Kim,
>
> You get to a question that I was getting ready to ask.  My only need 
> for a balun is to try to keep the RF off of the coax shield. 
> Originally I have a 4:1 voltage balun thinking I needed it for 
> impedance transforming, but that was before I knew as much about 
> antennas as I do today.  What is the best type of balun for this-the 
> one with the ferrite beads over a run of coax, or the one with the 
> wires running thru a torrid donut shaped device?
>
> 73 John AF5CC
> ----- Original Message ----- From: "Kim Elmore" 
> <cw_de_n5op at sbcglobal.net>
> To: "Oklahoma - DX news and information" <okdxa at mailman.qth.net>
> Sent: Sunday, April 21, 2013 3:46 PM
> Subject: Re: [OKDXA] Feed Line Problems NOW BALUN RECOMMENDATIONS
>
>
>> Do you need an impedance transformer as well as a balun? If all you 
>> need is a balun for coax, a 1:1 current balun (balances current 
>> rather than voltage) is probably what you want.  If you need an 
>> impedance transformation, you may want to use something purpose built 
>> for that.
>>
>> Array Solutions is a good bet: their stuff is pricey, but high 
>> quality. They have baluns for various transformation ratios: 1:1, 
>> 1.5:1, 2:1, 4:1, 6:1, 9:1, 12:1 and 16:1. They also carry an Unun in 
>> 1.5:1 and 4:1. DX Engineering is a another good source.
>>
>>
>>
>> Or, you can roll your own; they aren't hard to make. For 1:1 current 
>> baluns, a long string of ferrite beads on some coax, all sealed up, 
>> is always a good bet, though these can become inefficient under 
>> conditions of a large mismatch. In the end, since (ideally) you spend 
>> your time instead of your money, it's a matter of what you have the 
>> most to spare. Sometimes you spend just as much money PLUS your time, 
>> but there's still the knowledge gained, which you might not have 
>> gotten otherwise. If you roll your own and need an impedance 
>> transformer, I'd suggest a dedicated Sevick-type transmission-line 
>> transformer followed by a 1:1 current balun.
>>
>> 73,
>>
>> Kim N5OP
>>
>> On 4/21/2013 9:29 AM, John G. wrote:
>>> Thanks for the advice Roger.  Do you know what type of balun it was? 
>>> Also, since I am going to be getting a new current balun, any 
>>> recommendations as to brand? One that is built to last?  I am only 
>>> going to be running 100 watts
>>>
>>> 73 John AF5CC
>>> ----- Original Message ----- From: "Roger Simpson" <rksimpson1 at cox.net>
>>> To: <okdxa at mailman.qth.net>
>>> Sent: Sunday, April 21, 2013 1:38 PM
>>> Subject: [OKDXA] Feed Line Problems
>>>
>>>
>>>> I agree that the problem is likely a bad connection, bad coax,  
>>>> and/or relay contacts that have corrosion/dirt.
>>>>
>>>> The problem I had once with a balun was not actually the balun 
>>>> itself. It turned out to be the the wires from the balun were 
>>>> soldered to an SO-239 and the wire from the balun to the outside of 
>>>> the SO-239 was connected to a solder lug that was screwed down to 
>>>> the SO-239. In my case I took the balun out of the old case and 
>>>> built a new case for it out of some 2 inch PVC pipe with a couple 
>>>> of PVC pipe caps. Then I used a new SO-239 and soldered the wires 
>>>> from the balun to the new SO-239. This fixed my problem.
>>>>
>>>> The balun I am describing I originally bought back in the early 
>>>> 1980s. It was up for about ten years before it started giving me 
>>>> problems. I am still using the balun today on my 30m / 40m Inverted 
>>>> “V”. So the problem was not with the balun itself, but with a flaky 
>>>> connection. These flaky connections can definitely act differently 
>>>> on different bands. In some cases a flaky connection can look like 
>>>> a leaky diode on certain bands.
>>>>
>>>> These cases are so difficult to trace that I think it is easier to 
>>>> just replace stuff until the antenna works again. Also, these 
>>>> problems can be so flaky that they are intermittent. So you might 
>>>> think something is OK after checking and that have it to go back 
>>>> again later to its broken state.
>>>>
>>>> The way I isolated that the balun was the problem was that I 
>>>> replaced it. Once I knew that the problem was the balun I tore it 
>>>> apart to discover the corroded connection to the SO-239.
>>>>
>>>> 73  Roger   K5RKS
>>>>
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