[Amps] Why are we building amps rather then transmitters? (Tubes vs. Solid State)

[W2XJ]

Dan

I agree generally and in principle. There may be a few different ways to
do this which is well worth discussing.

I am not sure how I got misquoted below.

On 5/4/12 9:34 AM, Dan Mills wrote:
>  On Thu, 2012-05-03 at 23:52 -0400, Roger (K8RI) wrote:
>>  On 5/3/2012 6:20 PM, W2XJ wrote:
>>  When we combine the transmitter or transceiver with the amp we now have
>>  a very sophisticated amp that has just had its MTBF most likely cut in half.
>>  If you follow the Icom and Yaesu reflectors you will find that these top
>>  end transceivers are not trouble free and they are very complex pieces
>>  of equipment.
>  I was only advocating the transmitter being integrated (and only part of
>  it at that!), adding the RF signal generation and I/Q modulator to the
>  amp housing seems to be to be fairly trivial small signal electronics if
>  the amp is simple minded, or something more if the amp is trying to be
>  clever, but look at what it does to the other box:
>
>  It removes the heat from the 100W PA.
>  It removes now redundant LPF networks and their associated relays (not
>  exactly a trouble free area!).
>  It removes the 100W PA (so making more space for a better RX).
>  Probably the fan can go.
>  As the 'amp' is now a transmitter, that stupid gain limitation the FCC
>  impose on amplifiers goes out the window so we do not need to make 100W,
>  then attenuate it to 15W before driving a 20db gain power stage.
>
>  Note that if the input to the exciter is an I/Q pair of reasonable
>  bandwidth, then that power section can operate any mode nearly
>  trivially, dependent only on what the DSP in the front end can produce
>  as the I/Q pair.
>
>  Back in the day, separate transmitters were sold because the transceiver
>  as we know it did not really exist, then the transceiver as a package
>  became the go to option because much of the (then) expensive signal
>  processing path could be shared between transmit and receive and sharing
>  things like the VFO was a operational convenience.
>
>  My contention is that the sand has now advanced enough to make the low
>  level modulator and RF stages of a transmitter an almost irrelevant part
>  of the cost of a rig (never mind an amp), so if it allows the amp to
>  play it smarter it surely makes sense to provide the signals from the
>  basic radio to allow an external modulator/amp to work with input as
>  something other then 100W or RF power.
>  A 100W packaged radio would require an extra connector to support this
>  style of operation as well as a menu option to turn off  its internal
>  transmit path, and it might be that the internal 100W transmit path
>  could be an optional module....
>
>
>>  I do like the idea of amps that can be integrated *with* the
>>  transceivers so they operate as if they were part of the transceiver,
>>  but physically seperate so  they don't have to be purchased at the same
>>  time and neither piece of equipment depends on the reliability of the
>>  other. In this case the amp doesn't have to be driven by the output, but
>>  from a much lower power intermediate stage.
>  I am advocating forgoing the RF drive to the amp and sending it a
>  baseband pair and data about what frequency to translate it to.
>
>  RF as input to an 'amp' has only downsides as far as I can see given
>  that generating the RF inside the 'amp' is so nearly trivial these
>  days.
>
>  73, Dan (M0HCN)
>
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