[hpsdr] New HPSDR card for VHF/UHF ?

[Marco IK1ODO -2]

At 12:31 06-09-10, Phil wrote:

>***** High Performance Software Defined Radio Discussion List *****
>...
>Is a VHF/UHF receiver with an overload at this level usable in Europe?

Another back-of -envelope calculation. I have a dear friend that has 
4x17el and 1kW, and he lives 40 km from my QTH (in line of sight).
The ERP is in the order of 200 kW, and the field at my QTH is -24.6 
dBm on an isotropic antenna. With my 17 dBi antenna and -1 dB cable I 
get -8.6 dBm at the RX input.
This is, unfortunately, quite a common situation in EU... when we 
point each other there is no way, the mutual interference is assured, 
expecially because of TX noise sidebands and RX reciprocal mixing. 
The required blocking dynamic range, assuming an SSB channel and 2 dB 
NF, should be 130 dB (-137 to -7 dBm), and the same for the transmitter!
Of course, all we know that analogic receivers have a gradual 
degradation, and we are used to it. I presume that contest users will 
not be very happy with a suddenly saturating ADC.
I will test it, however. I'm setting up a fixed station, where the 
antenna feeder (after an LNA) splits via a 3 dB splitter. One branch 
goes to an IC-910H (with all due switchings to allow transmission), 
the other goes to an high dynamic converter and then to a Perseus. I 
hope to get  some practical results (and figures) in next few months.

73 - Marco IK1ODO

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