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

Peter Markavage manualman at juno.com
Sun Nov 5 21:44:38 EST 2006

I've been using the SB-200 on AM since about the mid 90's. Still have the
same original tubes that were put in the unit in 1969. I can drive it
with the CE100V, 756PRO II, 706MKIIG, Johnson Ranger,  and even a
Lafayette HA-410(on 10 meters). I've never seen the tubes show any color.
I do use, in addition to the internal fan, an external fan as an exhaust
on the top of the unit. Output of the SB-200 is generally around 125
watts. I also made the "tuned input" component changes several years ago
in my SB-200 as per http://www.ne7x.com/sb200/heathkit-sb200.htm
It made a big difference when I run the Ranger and the 100V into the
SB-200 on 75 meters.

Pete, wa2cwa

On Sun, 5 Nov 2006 19:00:26 -0600 "John Coleman ARS WA5BXO"
<wa5bxo2006 at pctechref.com> writes:
>         I was going to comment earlier about the statement that this 
> Ranger
> would not hold it's on against the rice box with the SB200.  As Jim 
> pointed
> out there should not be but a DB or so difference if the ranger is 
> working
> properly and properly tuned.  I am curious as to what power his 
> ranger will
> put into dummy load and what the modulation looks like.  I think I 
> read in
> this thread about someone reducing the drive on the Ranger's grid.  
> That is
> a sure fire way to ruin the output tube (6146).  The single 6146 in 
> class C
> service as it is in the Ranger should have 2.5 to 3 milliamps of 
> drive on it
> at all times. Do not reduce the grid current drive to reduce power 
> on the
> Ranger.  If memory serves me right the 6146 is to be used at about 
> 65 watts
> plate input on AM plate modulation. It should be putting out between 
> 40 - 45
> watts carrier and develop about 180 watts PEP. (Could be a little 
> more with
> a good modulation XFMR)  That's only about 2-3 DBs below what the 
> SB200 will
> do as an AM linier when operated properly.  Now 3 DBs is not to be 
> taken
> lightly when the going is rough but if your going to do a lot of 
> work for a
> DB or 2 then put the work in the antenna or a bigger rig that will 
> get you
> 10 DB gain.
>         I have used the SB200 on AM and it does OK but I would not 
> want to
> do it for a long time.  Those tubes get real hot.  I use the SB200 
> as a
> driver for my big rig.  The input to the SB200 is about 5 - 10 watts 
> and the
> output of the SB200 is about 50 - 70 watts carrier this drives the 
> grid of
> my big class C plate modulated final.  But even using the SB200 to 
> put out
> 50 - 70 watts it get real hot and the tube show some color.  I think 
> the
> best thing I can do to increase the efficiency of the SB200 at low 
> power, is
> to reduce the plate voltage to about 1500 instead of 2500.  I added a 
> switch
> to the front panel of mine to increase the bias voltage making it 
> harder to
> drive.  I thought that this would decrease the conduction angle 
> enough to
> reduce the heat but the trouble is that the plate is still not 
> reaching
> saturation at the low power level so I figure that if I reduce the 
> plate
> supply voltage and increase the drive then I can come closer to the 
> non
> linear class C service for continuous CW and the efficiency will 
> surly
> increase.  The idea is to use the rice box rig at low power so it 
> will last
> a long time and have the SB200 to make up the slack. But I want it 
> to last a
> long time as well.  BJ and I like the flexibility of this type of 
> operation.
> That is to be able to flip some switches and use the SB200 as linier 
> on SSB
> as it was intended and then flip the switches back so as to lower 
> the output
> but raise the efficiency for continuous carrier operation as 
> required by the
> big class C final.  We have been operating it linearly with the 2500 
> volts
> supply and reducing the drive from the rice box carrier source but 
> it has
> always bothered me that it is so inefficient and those tubes show 
> color.  As
> I recall the PS in the SB200 is a voltage double type circuit 
> perhaps a
> little circuit change up with some HV switches might be in order 
> here?
> Any Ideas on this?
> John, WA5BXO
>     BTW the stock plate RF choke in the SB200 is NOT large enough on 
> 75 mtr
> and a lot of RF gets back into the PS causing weird AC modulation at 
> low
> carrier levels.  BJ and I thought it was the Filter Caps so we got 
> new ones.
> No help.  We found that the weird modulation on the output carrier 
> would
> come and go at different levels of drive at low power and only on 75 
> mtrs.
> We measured the DC at the POWER supply B+ point as it went through 
> the
> chassis to the plate choke and found some RF there and guess what 
> the RF was
> getting back to the diodes in the PS and modulating with the AC.  It 
> was
> real weird.  Placed a RF choke under the chassis and an extra RF 
> bypass
> cured the whole thing.
> 73, John, WA5BXO
> ______________________________________________________________
> AMRadio mailing list
> List Home: http://mailman.qth.net/mailman/listinfo/amradio
> Partner Website: http://www.amfone.net
> Help: http://mailman.qth.net/mmfaq.html
> Post: mailto:AMRadio at mailman.qth.net
ManualMan, now has available laminated credit card style "Quick Reference
Guides" and laminated "Mini-Manuals" for many of the current Icom,
Kenwood, and Yaesu HT's,mobiles, and HF rigs. Newly introduced heavy
steel HT stands are now available.

More information about the AMRadio mailing list

This page last updated 23 Feb 2018.