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15221Re: [perseus_SDR] Re: AOR7030 vs Perseus on You Tube

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  • Werner Karn
    Jul 1, 2011
      sorry, I should have made this more clear. You are right that in most cases the MW transmitters will show the strongest signals. In my case the strongest is showing -25dBm, so even summing up the total band will show no clipping on both antennas. 
      However, when transmitting myself with a close by antenna, the power level I can transmit without showing clipping is a difference of 12dB ( see below ) on the 2 antennas, i.e. with ALA1530 listening I can transmit with 50W without clipping at the same time, while with 1530S the limit is 3W. And without any difference ( i.e. compromising ) on the receiving results.

      2011/7/1 Alex Crow <alex@...>

      Are you saying you get the clip light on the Perseus above 2MHz with the attenuators off?

      Despite being in the middle of London I don't get this. Are you close to some big transmitters? I only see the clip light on on MW or below, usually 10dB att is enough to get rid of it, 20dB will never show clipping.



      On 01/07/11 22:06, Werner Karn wrote:
      I have an ALA1530 and an ALA1530S and have a noise level at 30 Mhz of
      -147dBm/Hz with ALA1530  and
      -135dBm/Hz with ALA1530S.
      As the receiver sensitivity is -153dBm/Hz, both Antennas are fully sufficient for use with Perseus. 
      In fact the higher amplifying version is limiting dynamic range when strong stations are present leading to earlier clipping.

      2011/7/1 Alex Crow <alex@...>

      I think it's probably down to the antennas and/or the input level to the RX. The chap that made the video made no indication of the settings on the AOR, so this is a just a guess - it may be of course that the splitter is dodgy or other factors are at play in the video.

      With a direct sampling RX you want as much signal going into the A/D as possible without clipping.

      A preamp (with preselection before it to limit intermod in the amp) or a "louder" antenna would probably put the Perseus back on top.

      I have a Wellbrook ALA1530S+, and I think with the Perseus it could do with another 6db gain once past as low as 7MHz or so, and 12db above 15MHz. With a longwire and a 1:6 or 1:9 balun sensitivity is higher but the longwire is *much* worse for local interference.

      I do wonder if the ALA330S with more gain on SW and less on MW and below would be better for higher SW freqs.

      It would be nice if the preamp on the Perseus was bypassable (without voiding warranty) with connections on the case so you could insert your own preamp after the preselection filters.



      On 01/07/11 16:06, DirkCL wrote:

      --- In perseus_SDR@yahoogroups.com, "iv3nwv" <nicopal@...> wrote:

      > Don't you find quite singular that your software is measuring in the
      > same bandwidth the power which is measured in the movie where it is > supposed that an antenna is connected to the receiver?
      > An efficient antenna should exhibit tens dBs of noise excess at that frequency. Why it doesn't? Is it a short one? Has any attenuator
      > placed between it and the receiver, was this due to a badly
      > isolated > or faulty antenna splitter either he took the movie just > during an exceptional day in which our galaxy didn't emit the noise we expect to receive from?

      Indeed very mysterious, Nico...

      As measured here with the settings as described by you:

      No antenna : -115 dBm
      PaoRDT miniwhip at 5m : -100 dBm
      Long Wire 25m at 10m : -90 dBm

      73 - Dirk

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