[Heathkit] parasitic suppressor

[jeremy-ca]

There is no parallel LC circuit in a industry typical non resonant 
suppressor. What you have is a very small inductance that acts as a choke to 
VHF but passes HF with negligible loss.

The VHF energy is routed to the resistor which is the path of least 
resistance. The resistor then acts as a load and absorbs the parasitic.

Notice that the L portion is often different depending upon the tube used. 
Sweep tubes and old design ones such as the 811 and 572B oscillate in the 
low VHF region and have more turns than those that oscillate at higher VHF. 
The SB-220 3-500Z parasitic for example is right around 150 MHz based on 
many tests that I have run while the SB-200 572B is in the 75-80 MHz region.

Carl
KM1H


----- Original Message ----- 
From: <jhoyos at hoth.gcn.ou.edu>
To: <heathkit at mailman.qth.net>
Sent: Saturday, August 25, 2007 10:34 PM
Subject: [Heathkit] parasitic suppressor





A parasitic suppressor, as *most* of us are normally involved with,
creates a trap, (an L/C circuit piece), or block if you wish, that
simply stops the "undesired" frequencies from passing through the
finals, or the linear amplifier.

It can be accomplished by an inductor, (coil), wrapped around a carbon
resistor in the plate lead.

Other suppression methods are in the construction phase of an
amplification stage, for example:  Grounding the cathode in an amplifier
tube such as 572Bs or 813s.  Bypassing 'other' grids such as control
grid and screen grids with a high voltage disk ceramic capacitor from
pin to ground with ALMOST *NO* lead length.

Bob - N0DGN








If such a supprssor were an LC parallel circuit, its impedance were maximun
at the resonance frequency, so this frecuency would not be attenuated by
the PA because the LC circuit is in series with the anode.

I can not figure how the attenution is accomplished.

Tanks again.

Jorge
HK6BCC




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