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doughboy
01-01-2012, 06:02 PM
Peak limiter for plate modulated rigs
Background
The three diode limter circuit below uses a keep-alive circuit instead of a tapped resistor, as in other negative peak limiter cicuits. This circuit provides a more constant load to the modulators and produces less distortion than other circuits.
Circuit Details
R1 = Plate Impedance of the RF Amplifier, power rating equals 1/20 of the modulator power.
C1 = 20-40 uF. C1 is not needed if the keep-alive power supply has a similar cap on its output.
Keep-alive power supply = 1/10 to 1/20 the B+ voltage, e.g. B+ = 1000 V, Keep-alive = 50 V. Current requirement is about 1/10 the current rating of the B+ supply.
D1 and D3 voltage ratings should be at least four times the B+ Voltage for a good safety factor. D1 and D3 current ratings are about 1/10 the DC plate current of the RF final amplifier.
D2 voltage ratings should be at least the B+ Voltage (preferably higher). D2 current rating should be three times the DC plate current of the RF final amplifier.
Maximum negative modulation is controlled by the Keep-alive power supply voltage. The voltage level should be made variable with a variac or suitable sized rheostat.

119

631
01-01-2012, 06:32 PM
Like anyone on this forum is going to know what to do with this information. LOL.

High Voltage Mobile NJ
01-02-2012, 02:08 AM
awsome Doughboy !! you explained the Three diode negative peak limiter circuit very easy . thank you so much .

rainmakersrepair
02-10-2016, 01:31 AM
Peak limiter for plate modulated rigs
Background
The three diode limter circuit below uses a keep-alive circuit instead of a tapped resistor, as in other negative peak limiter cicuits. This circuit provides a more constant load to the modulators and produces less distortion than other circuits.
Circuit Details
R1 = Plate Impedance of the RF Amplifier, power rating equals 1/20 of the modulator power.
C1 = 20-40 uF. C1 is not needed if the keep-alive power supply has a similar cap on its output.
Keep-alive power supply = 1/10 to 1/20 the B+ voltage, e.g. B+ = 1000 V, Keep-alive = 50 V. Current requirement is about 1/10 the current rating of the B+ supply.
D1 and D3 voltage ratings should be at least four times the B+ Voltage for a good safety factor. D1 and D3 current ratings are about 1/10 the DC plate current of the RF final amplifier.
D2 voltage ratings should be at least the B+ Voltage (preferably higher). D2 current rating should be three times the DC plate current of the RF final amplifier.
Maximum negative modulation is controlled by the Keep-alive power supply voltage. The voltage level should be made variable with a variac or suitable sized rheostat.

119




So are you using the circuit for a direct inject on like a cobra 29?

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doughboy
02-10-2016, 01:54 AM
This is for old tube rigs

ARCHBISHOP
02-17-2016, 04:20 PM
Thanks Doughboy there are a few vintage plate modulated rigs out there still in service. Plate modulated rigs CB or ham is the best way to in my humble opinion:300 (184): unless you go Flex or Anan with a broadcast processor and a big linear:OSMILEY:

tweakertweaker19
05-09-2021, 08:14 PM
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