QRP balun query


Lloyd K3ESE
 

I've been a QRP op for decades, and never used a stand-alone balun. I used to use a ZM-2 to match portable antennas, which incorporate a balun. These days, I use a SOTAbeams Bandhopper linked dipole for portable ops, and there's an integral balun. For small rigs at the home QTH, I now use an Elecraft T1, which is unbalanced.

I recently built a QCX-mini, and for the first time, there's an issue: the sidetone is harsh and loud and scratchy, and my RBN results don't seem right, for the amount of power out (~5.7W).

Transmitting into a dummy load results in a sweet sidetone. The diagnosis seems to be I need a balun between the T1 tuner and my balanced feedline (both antennas are doublets fed with ladder line.)

After doing some reading, it seems as though a 1:1 current balun is what I need. Searching through providers of baluns, parts, kits, looking for plans, etc., it looks as though the kit offered by the QRPguys is my best bet/bang for the buck.

Opinions and ideas gratefully solicited.


Lloyd K3ESE
 

dang. someone pointed out that the QRPguys' balloons are voltage baluns. So, my search continues...


Tim N9PUZ
 

Perhaps this design...

http://www.n5ese.com/balun_1-1.htm

Tim N9PUZ

On 1/1/2021 9:28 PM, Lloyd K3ESE wrote:
dang. someone pointed out that the QRPguys' balloons are voltage baluns. So, my search continues...


n0sa@...
 

10 to 12 turns of RG174 on a FT-114-43 toroid core should do the job.
Larry
n0sa


W3BNO
 

Lloyd I build  baluns into all of my coax feeb lines. I also have a 1:1 current balun which is referred to as an isolator because it isolates the coax shield from the counter poise. This makes tuning verticals that use elevated radials much easier to tune. I make my 1:1 current baluns by wrapping 12 turns of rg174 through a FT140-43 core. I use the larger core to keep the bend radius of the coax at a reasonable level to minimize distortion of the foam dielectric. I believe the cores cost approximately $2.50 each from Diz at parts and kits. That's double the cost of the 114 cores but I look at the increased cost as insurance. Also don't try and make tight turns that conform to the core., just a loose wrap and use an abundance of wire ties to hold it all together. Before I started using these, it was all but impossible to tune my buddy stick, and some of my rigs that are sensitive to RF are now happy and work as they should. W3BNO


On Jan 2, 2021, at 8:57 AM, n0sa@... wrote:

10 to 12 turns of RG174 on a FT-114-43 toroid core should do the job.
Larry
n0sa


Lloyd K3ESE
 

Yep! I wrote to Diz, and he recommends ten turns of RG58 on a FT240 core, so that's gonna be the plan.


Johnny AC0BQ
 

I need to try one of these.
I’m glad you started this thread Lloyd.
72
Johnny ACØBQ 

On Sat, Jan 2, 2021 at 10:04 AM Lloyd K3ESE <llachow@...> wrote:
Yep! I wrote to Diz, and he recommends ten turns of RG58 on a FT240 core, so that's gonna be the plan.

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