[Amps] SB-200 input.

Jim Hargrave w5ifp at gvtc.com
Sat Jul 26 12:24:33 EDT 2014

The Dentron CM1,2 & U series of external input tuners are fixed broad 
band filters,
It uses a parallel circuit on 160m and PI-L on 80/40/20 with PI on 15/10.
The manual only specifies a "length" of RG-8 or equiv.

This works ok on my Clipperton-L (4x572B) when driven with an IC-735
However I get a better input SWR using the Internal tuner on my FT-920. 
Besides it is autotune.

Someone mentioned different cores. The CM uses T-94-2 on 160m, T68-2 on 
80/40/20/15m and air on 10m

Jim w5ifp at gvtc.com

On 7/26/2014 9:52 AM, Bill Turner wrote:
> One way to add a tuned input with little fuss is to place a "tee" 
> connector at the input of the SS amp and connect a parallel resonant 
> LC circuit at the tee. Make the LC circuit have a Q of between 3 to 5 
> at 50 ohms and you're in business. Use a variable cap such as an Arco 
> compression trimmer and tune for minimum SWR. This does not need to be 
> a pi network if you do not need any impedance transformation. If you 
> do need a pi network, it can still be done externally, but it gets a 
> bit more complicated.
> To multiband it, run a short piece of coax to a switch which selects a 
> separate LC circuit for each band. This is essentially what I have in 
> my homebrew 8877 amp, although the circuitry is inside the amp instead 
> of external to it. You might want two LC circuits on 80 and 160 to 
> cover the whole band, depending on the Q you choose.
> 73, Bill W6WRT
> _______________________________________________
> Amps mailing list
> Amps at contesting.com
> http://lists.contesting.com/mailman/listinfo/amps

More information about the Amps mailing list