VK-JOE wrote:Do you still have the 100D?
Yes. In fact recently I spent several weeks using it in lieu of my 8000DLE because the 8000 needed repair.
I have been using the "loan" 100D I have - I can’t fault it - has very sensitive receiver - is there a review somewhere on the improvements in "performance” a 7000DLE MK II has over the 100D? - ignoring ascetics and jumper conveniences of cause.
In terms of receiver performance there is almost no practical difference between any of the 16-bit models from the Hermes to the Andromeda. The receiver schematics are nearly identical, and literally are identical in every important way. The minor differences in board layout do very slightly affect the noise floor and phase noise performance. You can measure a few dB here or there on the test bench, but since normal band noise far outweighs internal noise sources these things are mostly undetectable in normal operation. The one major difference that occurred with the advent of the first Orion MKII board in the first version of the 7000 was a change from a 20dB gain ADC LNA to an LNA in the same parts series but with 14dB gain. That definitely helped the ultimate noise floor by 2 or 3dB, but again it takes very good band conditions to notice this.
Obviously the 14-bit receivers (10E, 100B) do not perform as well, but your 100D is not in that category.
On the transmit side again certain improvements were made that increased TX noise and phase noise performance. This is harder to notice, obviously, especially after your signal has gone across any part of the ionosphere. However it is particularly helpful at low drive levels. More specifically, prior to the Orion MKII, the drive level was controlled exclusively by varying the reference voltage of the DAC. Now the output of the DAC goes to a step attenuator with implements gross drive control, with fine steps still being accomplished by varying the DAC reference voltage. This allows the DAC output to remain at a much higher SNR.
The biggest, and quite significant, difference between the 100D and succeeding models (200D and up), involves PureSignal performance. The original 100D, with either the Rev. 15 or 16 RF board, did not use an internal coupler for PureSignal feedback. Instead the internal crosstalk performance during full duplex operations was so bad that the crosstalk itself was used to implement PureSignal feedback! When an external coupler was used for PureSignal, feedback-to-crosstalk levels were still quite bad internally, resulting in less than optimum PureSignal performance. Many of us, myself included, modified our 100D units to use a high quality external RF switch to solve this problem. See also: http://www.w1aex.com/anan/anan.html#relay