[TenTec] OT: Openwire Balanced Antenna Tuners (QST Test)

[Jim Brown]

On 2/17/2013 5:54 PM, Bob McGraw - K4TAX wrote:
> I'll take an air-wound inductor over a toroidal inductor any day, 
> space available.  The typical loss in an air-wound inductor is IR loss 
> where a toroidal has IR loss plus eddy current loss. 

That may be too broad a generalization.  While I haven't crunched the 
numbers for specific designs, I recently completed VNWA measurements of 
all the bandpass filter boxes I could get my hands on for 
multi-transmitter HF stations. Some use air-wound inductors, some do 
not. The filters having the lowest loss and the best performance are the 
W3NQN designs, both those sold by Array Solutions buit by W3NQN, and 
those  implemented by Bob, 5B4AGN, in his TXBPF kits. Those designs use 
two different mixes of powdered iron cores for the lower bands, and 
non-magnetic toroidal cores (essentially a PVC coil form) for 15 and 
10M.  The W3NQN designs also vary the wire size from one band to another.

My report, which includes photos of the filter sets and lots of measured 
data, is at

http://http://audiosystemsgroup.com/BandpassFilterSurvey.pdf

73, Jim K9YC