[TenTec] TenTec 228 ATU - update

[Dr. Gerald N. Johnson]

On Sat, 2008-06-28 at 18:30 +0800, Marinus Loewensteijn wrote:
> Found a construction description of a 1:9 unun with a FT114-61 toroid that 
> spans several bands. Will try this setup with a low pass L-C matching network 
> since it will have very low losses.

But not zero losses. That toroid will survive 100 watts, but not 1.5 KW.

> Don't know how long the link will stay current 
> but here it is (it is in German but the pics will give enough information).
> 
> http://www.technik.ba-ravensburg.de/~lau/beverage-unun/beverage-unun.html
> 
> The backup plan will be to build an S-Match and then use a Guanella 4:1 output
> unun for matching the lowest impedances. According to some information the 
> losses in properly build Guanella are low and it can handle up to a 1:5 SWR.
> 
> 73, Marinus, ZL2ML
> 
Switching in a low to medium Z output transformer can take care of low
feed Z antennas, nothing new there, is especially handy when feeding
short loaded verticals.

Maybe for your loads, you want an output transformer wound to have a tap
for 12.5 ohms (4:1 from the 50 ohm winding),  no transformer for 50 ohm
load, and 1:4 for the 200 ohm load region. It would have 3 or four
winding. I might be lazy and make it with four windings in quad filar,
just enough turns so that two windings in series gives the right winding
for 50 ohms. Then the connection between those two windings is the 12.5
ohm load point. The other two windings in series and connected to the 50
ohm input gives a 200 ohm load point at the extreme and a 9 * 12.5 or
112.5 ohm load tap. More winding taps can give more load values to
minimize the impedance ratio of the tuner and so give it the best chance
for low loss and broad bandwidth. However the minor losses of this
output transformer may be more than that of an L, Pi, or T match
covering that load range made with large low loss parts.

73, Jerry, K0CQ