[Elecraft] KX3 "Full" SDR

[dave]

Let me say that I calculate path losses the same way I did as an 
engineer at the phone co when calculating the losses in fiber optic 
systems - the path loss includes all losses between the TX and RX. 
This is the path the signal takes, hence this is the path loss. We 
must deliver a certain amount of energy to the RX. If it is in the 
path and it has loss, it becomes part of the path loss.

As best I can tell this is the same approach employed in VOACAP. There 
they call it system loss instead of path loss. But I believe it is the 
same quantity.

If you chose to define it differently that is fine.

And keep in mind that this does not include the gain of an amp or a 
beam. If you put those into the mix the RX noise level increases by 
several dB.

You can call the level by whatever term you prefer. -27 dBm, 2 
microwatts, S9+45. They are all the same. S9 is a reference point, so 
many dBm.

TX/RX makes no difference. It is a signal level we are talking about. 
A level of S9 is something many hams are familiar with. They can 
relate to S9+45 better than they can relate to 2 uW.

This is just like SWR = 2, return loss = 9.5 dB, voltage reflection 
coefficient = .33, power reflection coefficient = .11, they are all 
different ways of expressing the same thing. But far more hams know 
what SWR = 2 means than know what RL = 9.5 dB means.

And, yes, the wideband noise emitted by any of the Flex TX is excessive.

73 de dave
ab9ca/4



On 12/31/13 5:50 PM, Bruce Beford wrote:
> Dave, I agree with your math, except...
>
> Having a noise level of -27dBm delivered by the transmitter to the antenna
> system, does not mean the antenna has 100% radiation efficiency, yes?
>
> So -27dBm is 2 microwatts in transmitted noise to the antenna system, at
> this particular spacing, in a 500Hz bandwidth.
>
> You must make some allowances for not only path loss, but antenna efficiency
> on each end, yes?
>
> As I said, I am not trying to defend these performance (or lack thereof)
> claims. I just disagreed with the statement that the "Flex is transmitting
> wideband S9+45 noise"
>
> "S9+45dB" is a receive measurement, not a transmitter measurement. The Flex
> is sending 2 microwatts to the antenna at the frequency in question.
> Admittedly, that's too much, in many situations.
>
> Peace,
> Bruce N1RX
>
>
>
>
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:Elecraft at mailman.qth.net
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
>