The RX-320 and the Pegasus/Jupiter are conceptually very
similar, but there are some really quite significant
differences circuit-wise.
The RX-320's analog signal path is this:
1. Antenna.
2. Single fixed low pass filter (first IF rejection).
3. 1st mixer (pair J310's).
4. 45 MHz roofing filter.
5. BF998 gain stage
6. Diode ring 2nd mixer (MMSD914's).
7. 455 kHz filter.
8. 2x MMBT3904 gain stage.
9. Diode ring 3rd mixer (MMSD914's).
10 AD1847 CODEC.
The Pegasus/Jupiter (probably) analog signal path is this
(ignoring the TX items):
1. Antenna.
2. Band switched bandpass filters.
3. 1st mixer (pair J310's).
4. 45 MHz roofing filter.
5. BF998 gain stage
6. Diode ring 2nd mixer (BAT68_04's).
7. 455 kHz filter.
8. 2x MMBT3904 gain stage (with IF gain adjustment).
9. Diode ring 3rd mixer (MMSD914's).
10 AD1847 CODEC.
Also the RX 320 has no provision for RF gain or attenuation
in the signal path like the Pegasus/Jupiter do (which is
really unfortunate). I find that to make the RX-320 truly
listenable on 80M with a dipole during noisy summer band
conditions I need put between 15 and 20 dB of attenuation in
front of the antenna input. Once I do that it really is quite
pleasant to listen to.
Duane
N9DG
--- Kevin Purcell <kevinpurcell@pobox.com> wrote:
> I really would have though the Jupiter would be better --
> it probably
> is in real life with better preselection/LPF. The
> intercepts for the
> RX320 are not very impressive.
>
> ARRL RX320 review:
>
> Minimum discernible signal (Noise floor), 500 Hz filter
> Frequency
> 1.0 MHz -117 dBm
> 3.5 MHz -133 dBm
> 14 MHz -134 dBm
> Blocking dynamic range, 500 Hz filter
> 3.5 MHz 111 dB*
> 14 MHz 109 dB*
> Two-tone, third order IMD dynamic range, 500 Hz filter
> 3.5 MHz 84 dB*
> 14 MHz 82 dB*
> Third-order intercept
> 3.5 MHz -7.4 dBm
> 14 MHz -10.7 dBm
> Second-order intercept
> -29 dBm
>
> ARRL Jupiter review:
>
> SSB/CW sensitivity, 3 kHz bandwidth, 10 dB S/N: 0.35 μV.
> Noise floor
> (MDS), 525 Hz bandwidth:
> 1.0 MHz â??121 dBm
> 3.5 MHz â??127 dBm
> 14 MHz â??135 dBm
> Blocking dynamic range: Not specified.
> Blocking dynamic range, 525 Hz filter:
> 3.5 MHz 113 dB
> 14 MHz 123 dB*
> Two-tone, third-order IMD dynamic range: Not specified.
> Two-tone, third-order IMD dynamic range, 525 Hz filter:
> 3.5 MHz 87 dB
> 14 MHz 85 dB*
> Third-order intercept: claimed +10 dBm.
> 3.5 MHz +11 dBm
> 14 MHz +7.3 dBm
> Second-order intercept: Not specified.
> Second-order intercept: +53.6 dBm.
>
> * == Measurement was noise-limited at the value indicated.
>
____________________________________________________________________________________
Looking for a deal? Find great prices on flights and hotels with Yahoo!
FareChase.
http://farechase.yahoo.com/
_______________________________________________
TenTec mailing list
TenTec@contesting.com
http://lists.contesting.com/mailman/listinfo/tentec
|