Re[2]: TopBand: QST Antenna Tuner Review

[Paul D. Schrader]

I bet all that paralleling and unparalleling as you change frequencies and bands
 is really fun stuff.  Wonder why they aren't around anymore?  73 Paul N4XM




>     I know they are no longer made, but the TenTec Models 229 and 238 
>     tuners are not all bad.  Being L-network tuners, they cover a very 
>     wide range.  They have an internal 500 pf 2 KV air variable capacitor 
>     and padding in four steps of 440 pfd, so the internal capacitors can 
>     have a total value from 40 to 2260 pfd.  Also both models have an 
>     external terminal for another 1000 pfd parallel padder for 160 meters 
>     which raises the total shunt capacitance up to 3360 pfd!
>     
>     The roller inductor is good quality and covers 20+ uhy.
>     
>     So, although QST cannot review it, these models make sense, and have 
>     the ability to be used effectively on 10 through 160 meters.
>     
>     There is a Collins model 180-U reversible L network tuner in a smaller 
>     box that is about the same, but only up to about 10 uhy and 1500 pfd.  
>     Using a coaxial T on the capacitor side, another 1000 or 1500 pfd can 
>     be paralleled across the internal capacitor.  They were rated, by the 
>     military, for 500 watts SSB and RTTY, and have been used for a KW by 
>     hams.  The model 180-S has a vacuum variable of similar construction, 
>     but uses plugs and jacks to add capacitive padders, instead of a 
>     ceramic rotary switch like the 108-U and TenTec models.
>     
>     I am also reminded that someone made a "Unique Wire Tuner"  It had a 
>     series capacitor and shunt inductor L-network inside.  It could be 
>     rewired to shunt capacitor and series inductor, if one is willing to 
>     add capacitance externally across the internal 2 KV air variable, it 
>     would work OK on 160 as well.  The current in the coil would be the 
>     limiting factor.  It should be good for 500+ watts.
>     
>     Hope this helps.
>     
>     73         George          K8GG


--
FAQ on WWW:               http://www.contesting.com/topband.html
Submissions:              topband@contesting.com
Administrative requests:  topband-REQUEST@contesting.com
Problems:                 owner-topband@contesting.com
Sponsored by:             Akorn Access, Inc. & N4VJ / K4AAA