On Tue, 19 Sep 2006 14:31:52 -0700, Frank Gilliland
wrote:
+++
+++Enough of that cheap one-board crap..... this amp is MODULAR!
+++
+++Modular design allows easy repair and modification, as well as ease of
+++construction and interchangeability between different amps. It also
+++allows seperation of functions both electronically and physically. The
+++modules include:
+++
+++* Input module. Includes variable attenuator and dummy load which
+++provides adjustment of input power without 'tweaking' anything inside
+++the radio.
+++
*************
An attenuator on the input is nice. I am not sure a variable one is
needed. By variable a multistep attenuator with four to six different
values of attenuation would be a sufficient. A capability to switch
the input drive to a internal du mmy load would nice luxury item but
not necessary.
+++* Control module. Board that controls keying, bias & cooling fan.
+++
+++* Sensor module. Board with circuits that take measurements from
+++various locations throughout the amp and sends them to a meter. Meter
+++function selection can be by rotory switch or by LCD display simply by
+++swapping the board (module). Meter functions may include:
+++
*****************
Man talk about monitoring circuits. Nice thing to have on a high tier
amp. In reality most of these are great for development and early
testing. Actual production would cause product cost to sky rocket.
+++ - RF input power, Fwd
+++ - RF input power, Ref (for matching amp input to radio output)
************
Redundant circuitry since most modern tranceivers todday have some
form a SWR bridge incorparated into the transmitter. Would be more
needed if the run of coax from the transceiver to the amp were rather
long.
+++ - Base current
****************
If you are into monitoring everything, I would add a monitor of base
bias voltage also.
+++ - Emitter voltage, (RMS)
+++ - Emitter voltage, (peak)
+++ - Emitter current
+++ - RF output power, Fwd (RMS)
+++ - RF output power, Fwd (Peak)
+++ - RF output power, Fwd (Peak & hold)
+++ - RF output power, Ref
+++ - AF input (Ext. mod. function, AM only, see below)
+++ - DC supply voltage, amp
+++ - DC supply voltage, radio
+++ - DC supply current, amp
+++ - DC supply current, radio
+++
+++* Power Amplifier Module. The module will consist of the amplifier
+++circuit, heat sink and cooling fan, constructed inside an enclosed
+++sub-chassis designed for forced-air cooling. Flying in the face of
+++convention, the power amplifier circuit will -not- be mounted on a PC
+++board. Instead, the components will be chassis-wired with heavy-guage
+++copper, except for the transistors which will be wired with strips of
+++copper sheet having rounded edges and corners. This allows easy repair
+++and modification, as well as more secure and robust connections.
+++Circuit will be an ultra-linear, broadband, AB push-pull design
+++(details at a later date).
+++
****************
AIr dielectric striplines are nice for the power transistors. They do
introduce some memchanical issues. Great if you are in the 2KW or more
output range. In the 100 to 250 watt range 2 ounce copper laminate
would be quite sufficient. If varying dielectric constants are an
issue then a use of teflon laminate would be preferable over that of
FR4/FR5 laminates. Even alumina ceramics would offer a more stable
dielectrtic for the striplines.
Most of the low level, low current components do not require "dead
bug" style mounting. Laminates will do nicely. If you really want to
go whole hog on the striplines then why not take the copper strips and
either silver or gold plate them. Word of caution on gold over copper.
Nickel is not a good conductor of RF. Nickel is usually plated onto
copper to give gold a hard surface to plate to. Plating gold directly
onto copper requires a much thicker plating so that the copper will
not leach through the gold.
+++* Output module. Includes matching network and output connector, the
+++type of which depends on the desired output method: balanced or
+++unbalanced. The reason is that an unbalanced output is fine for mobile
+++amps where the amp is mounted to an adequate RF ground, but that is
+++rarely the case with base amps. So an option is provided for balanced
+++output; the line can then be run to a point where a good RF ground can
+++be found (e.g, a ground rod right outside the window) where it is
+++coupled to a coax with a balun, or simply run balanced right to the
+++antenna. The user now has these choices and they are built right into
+++the amp!
+++
+++* Power supply module (optional). Power transistors that are designed
+++for higher voltage are more linear and -much- more reliable than those
+++designed to operate on 12-14 volts. This switching power supply bumps
+++up the voltage to 28 or 50 VDC and allows the use of such transistors.
+++
+++
+++Additional features:
+++
+++* An external modulation function can be included, allowing the amp to
+++function as a Class C modulator. Audio input is via a terminal strip
+++on the back and fed from a common 8-ohm audio amplifier. The base bias
+++is then adjusted (with a screwdriver through a hole in front panel) to
+++Class C operation for higher efficiency. This works only in AM mode.
+++There is no provision for audio filtering, so hi-fi (wideband) AM is
+++possible if desired.
+++
*********************
Man after designing such a high tier amp, you adjust the bias through
a panel hole with a screwdriver? Will you supply the gold plated
screwdriver? I can understand why no band limiting filter designed in
since most CBers would bypass that anyway. Th en again, ,a hightier
amp as this would be nice to include it to show CBers what a nice
thing to hear band limited audio on the desired channel and not 20
channels away.
+++* Connections for remote operation:
+++ - Key ground
+++ - Key on ground
+++ - Key on high (=+5VDC)
+++ - Key function select 1 (amp in/out)
+++ - Key function select 2 (key auto/manual)
+++ - Key function select 3 (AM/SSB)
+++
+++
+++I am open to any comments or suggestions, provided they are limited in
+++scope to the design concept and desired features.
+++
+++
+++
***********
Oh well what the heck
james