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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