Increasing power

Place to come if youre having technical issues, including mic wiring

Moderator: stampman

Post Reply
stewartyboy01824
Good Buddy
Good Buddy
Posts: 28
Joined: Mon Mar 14, 2011 6:02 pm

Wed Nov 09, 2016 2:10 pm

Hi there,
Are you able to describe which knob to turn on the circuit board or the schematics on how to slightly increase the power on my president johnson 2 i bought from yourselves a while ago.
It only puts out 3 watts and hooked up to a 100 watt amplifier makes it only possible to transmit 45 watts.
I would like to turn my president johnson 2 upto 5 watts if possible to get the most out of my amplifier. Any help on how to do this at the printed circuit or a diagram of the schematics showing the correct dial to turn would be much appreciated.
Many thanks for your help and time.
Stewart.

stewartyboy01824
Good Buddy
Good Buddy
Posts: 28
Joined: Mon Mar 14, 2011 6:02 pm

Tue Nov 22, 2016 8:41 pm

Come on guys help me out here ☹


bobthetank
Good Buddy
Good Buddy
Posts: 21
Joined: Thu Sep 17, 2015 1:29 pm

Wed Jan 31, 2018 11:31 pm

Have you checked the RF power into a 50 ohm dummy load plug in via a wattage meter in your CB radio with amplifier disconnected completely,check if 4w then?
What is your VSWR like,without amplifier in line?

Check you have a good 13.8Volts DC at connector end of CB,low volts can cause radio to reduce RF power.
Ill assume you have a thick dc lead for your RF amplifier and enough current rated cables?
most cb stock are generally 3.5-3.8 watts from factory.

Also if its a car install,I would advise against using mag-mounts due to the poor earthing effect,use a drilled antenna in body work or gutter\boot mount thats grounded into vehicle,should this be your install.

reasons people wont post is its illegal using linear on cb band in UK and touchy subject.
I doubt you have even put a low pass filter on that amplifier to keep it harmonics clean?
if not I would advise if still continuing down this route to install on output of amplifier a High quality 100 Watt rated low pass filter ,to avoid "issues"
and possible interference to other users higher up in radio spectrum,its your risk at end of day.
Stick with well known branded names Kenwood,MFJ,etc
Even though frowned on and illegal in UK,I would rather have cb operators do the right thing,than the wrong thing and create more troubles and bad image.
Cab also speak to guys at Thunder-pole or other dealers to advise on products etc,only a phone call away!


Depending on linear RF amplifier some need 4w drive others require 10w drive,depends on make and model using?

Most Linear amplifiers are best not over driven due too duty cycle,harmonic cleanest and over heating esp if using FM mode.
As a rule of thumb 30-50w is more than ample for a 100W amp in FM mode
anymore is just a waste in heat and wont gain you much ie 3dB thats half an S-point between 50w and 100w.

an 1-S-Point to move needle on meter requires 6dB change for reference.
Most cb amplifiers rated 100w are not continuous rated at that power level,mainly for SSB operations,I wont go too technical on this for good reasons.

Depending on your install mobile or base,coax feeder quality\plugs and antenna are far more important area's often over looked!
Id use ECO flex mini ,RG-8X coax for mobile
and for base ops RG-213.Eco flex large or Westlake W100 coax options

Longer and higher the antenna on car\van better results
min 5ft length on car to get hold decent results,6-9ft for best results and range

If radio is in warranty and feel it is low power at 3W,then return it to dealer for resetting,without proper test equipment and Radio engineering skills
best not going inside and twiddling and get wrong pot adjustment!
Safest bet and will save you a lot of unforeseen troubles going inside radio blind.
Most dealers are pretty good if radio needs readjusting for your set up and keep your radio in warranty seals intact :wink:

I hope this information is of some use to you

All the best

Rob 73's

Post Reply