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@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
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