What is being proposed is more like a legal limit flex radio. SDR goes a
long way in helping to forestall obsolesce.
On 5/3/12 11:52 PM, Roger (K8RI) wrote:
> On 5/3/2012 6:20 PM, W2XJ wrote:
>> A good portion of this has already been done. Check the HPSDR group.
>> Also look at the ADAT. The final hurdle is to do this at the legal limit.
> Viking had a legal limit transmitter (Invader 2000?) while Hallicrafters
> had a legal limit transceiver, the SR2000.
>
> I have a top of the line transceiver the Yaesu FTDX5000MP and what was a
> leading transceiver in its day, the Icom 756 Pro.
> I have an Emtron DX-2sp amp which is a legal limit amp that will run 24
> X 7 any mode and the Alpha 76 which was a nice amp for it's day. I even
> have reconditioned a hallicrafters HT-33B amp which was also considered
> to be one of the "good ones" back in its day. However, I didn't
> purchase the transmitters and amps at the same time. Far more hams are
> able to get one or the other even if they are top end, but not both at
> the same time. Yes there are hams who can plunk down ten grand for a
> state of the art, legal limit transceiver although they are a very small
> percent of the existing hams. That's no more than the cost of the top
> end Icom or Yaesu transceivers.
>
> This approach reminds me of the old "entertainment center" of the 60s
> and 70's with a stereo, TV, and record changer. As soon as the TV gave
> out or was outdated the entire system ended up out by the road even
> though the record change and stereo were still good. These things were
> big! Fairly expensive too. We think today's large screen TV are
> expensive. Back then a huge 21" CRT color TV cost over $4,000. They'd
> give two body builders hernias to move.
>
> 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.
> The more complex the piece of equipment the more likely it will have
> problems. Many of the transceivers suffer from teething problems, some
> times for years. Those ten to thirteen thousand transceivers are
> already being replaced by better equipment for roughly half the price.
> The manufacturers have to limit the features on some of these new
> transceivers to maintain the market for the expensive stuff, but as
> demand falls off the old, but expensive will fall by the wayside. OTOH
> they just go whole hog on the new ones because they expect to make more
> money selling a lot more of the rigs that run only half the cost of the
> ones they only sell a few of.
>
> 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.
>
> 73
>
> Roger (K8RI)
>
>> We did have transmitters back when AM was dominant. I fondly remember
>> the Viking 500 but I do not think such an approach is practical for
>> commercial production as not everyone can use a full limit TX and would
>> not pay for it.
>>
>> On 5/3/12 6:03 PM, Dan Mills wrote:
>>> On Thu, 2012-05-03 at 17:29 -0400, W2XJ wrote:
>>>> I agree. A complete transmitter would solve many technical issues and
>>>> depending on the implementation, could drastically improve performance.
>>>> Solid State broadcast transmitters that transmit digital carriers along
>>>> with analog and therefore must run in linear mode can achieve IMD under
>>>> -80 DBC using techniques most easily implemented in a composite unit.
>>>> For an I/Q interface, I think SDR has evolved to the point that Ethernet
>>>> is all that is required. Any control or tuning can use the same Ethernet
>>>> connection.
>>> I was thinking in terms of taking the data (possibly as ethernet frames)
>>> straight into a modest FPGA and then doing the upsample followed by
>>> cordic carrier generation thing in the gate array.
>>> Something like a very modest cyclone III should suffice I would have
>>> thought.
>>>
>>> Output could be either full on EER/PWM or partial EER with cartesian
>>> feedback via a high speed ADC with the loop closed right in the gate
>>> array.
>>>
>>> Regards, Dan.
>>>
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>>>
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>
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