[OKDXA] Feed Line Problems NOW BALUN RECOMMENDATIONS

[Kim Elmore]

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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