[AMRadio] Ranger... good news, bad news


Peter Markavage manualman at juno.com
Mon Nov 6 13:55:32 EST 2006


I see no reason to "dip and load" the SB-200 since it's a linear
amplifier.  When I do use the Ranger as a driver, at low power using my
screen voltage adjustable control, it's initially run into a dummy load
to get the approximate knob settings (dip and load, etc.) for the
frequency of interest. Then it's switched into the input of the SB-200.
SB-200 is tuned for maximum output while viewing an inline wattmeter. If
output power is above 125 watts, I just back down the screen control on
the Ranger and also check and/or adjust plate and load for resonance on
the Ranger(generally minor touching up).  You might also want to check
your input circuits on the SB-200. The tuned input on 75M for my SB-200
was centered around 10 MHz and on 10M, it was centered around 40MHz.
After diddling with the input capacitance values, I was able to get those
bands fairly close to where they should be. Check out the info on this
web site: http://www.ne7x.com/sb200/heathkit-sb200.htm

With the solid state rigs it's even easier. Push the button for AM, back
down on the RF drive, key down with the SB-200 and quickly tune for max.
On a good day, SB-200 "tune for max" can be done in less than 10 seconds.

FYI: Scope always hangs on the SB-200 output to watch for any perky RF or
audio anomolies.

Pete, wa2cwa

On Mon, 6 Nov 2006 10:21:46 -0600 "John E. Coleman (ARS WA5BXO)"
<wa5bxo2006 at pctechref.com> writes:
> Jack:
>         There should not be that much difference.  Perhaps the 
> Ranger is not
> putting out enough power because of a problem or its output is not 
> making it
> to the antenna.  There could be a problem on the pass through 
> circuitry of
> the SB200.  Try hooking the Ranger directly to the antenna not 
> passing it
> through the SB200 and don't forget to re-dip the plate on the ranger 
> after
> switching from SB200 to barefoot or vice-versa.  Of course if the 
> SB200 and
> ranger combo are putting out 200 - 300 watts then the setup is 
> wrong.  The
> output from the Ranger must be reduced until total output from the 
> SB200 is
> about 100 - 125 watts.  If you run too much carrier from the SB200 
> it will
> defiantly over heat and the output will be distorted.  Theoretically 
> the
> SB200 is capable of 1000 Watts PEP and theoretically it should be 
> capable of
> 250 watts carrier on AM.  But it would be bad news for the SB200 to 
> do that
> for any lengthy time.
> 
> Peter:
>         As for my SB200 with a carrier only output of 75 watts the 
> tubes
> will show a little color after ten minutes.  I would like to drive 
> the SB200
> harder and unload the output to dip the plate at a lower level but 
> there is
> not enough output capacitance on 75 meters to do this.  Perhaps a 
> switched
> in extra load capacitor would do the trick?
> 
>         Maybe it would be easier to just build a chassis with a pair 
> of
> 6146s or 807s running class C with 50 ohm dummy load at the control 
> grid
> instead of a tuned circuit and just have the plate circuit tuned.  I 
> may
> have just talked myself into something!!
> 
> John, WA5BXO



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