Re: LF: OPERA overload?

["Graham" <g8fzk@g8fzk.fsnet.co.uk>]

Lot  depends on the  RX Bob

 

That's a nice  set , looking  in the  book  , the  first  mixer LO drive  is   +23 dBm  200 mW  , compared to  the  Racal  Ra 1778  / Ra 6790gm  at  +37 to +39 dBm  5 to 8 watts   drive  , that  gives  a dynamic  range  ~ 120 dB ,   that puts a  question round the  large signal  handling   I run my  6790  with  no  pre-amp, clean  right  upto the  local  10Kw  mw  tx  , where  the  ra1778  with  pre-amp  takes a hit , same mixer  , but the  pre-amp over  loads ,  

 

SDR is the  way  out  of the  problem , digitise the  Ae signal .

 

G,

From: Bob Raide

Sent: Friday, December 20, 2013 5:54 PM

To: rsgb_lf_group@blacksheep.org

Subject: RE: LF: OPERA overload?

G et all;
Things have changed over this pasted year or so.  Many more new stations have come on and these newbies are running lower power and RXers that may not be up to what some of the veteran ops are using.  There really isn't allot of room for QRO in the 630 meter band-fortunately those of us that have been on awhile have authorization up above 500 kHz.  If I do any more QRO it will be above say 490 kHz [600 M band]-plenty of room up there-just announce a freq and folks will come up for you-20W ERP should be the limit at 630M-Bob
 

> From: g8fzk@g8fzk.fsnet.co.uk
> To: rsgb_lf_group@blacksheep.org
> Date: Fri, 20 Dec 2013 17:40:45 +0000
> Subject: Re: LF: OPERA overload?
>
> Jay,
>
> Just pulled these back from the psk-data base ,
>
> + 8 OPERA 0.477 20/12/2013 00:15 United States 1387498502 WE6XGR FN12LQ
> WD2XNS
> + 8 OPERA 0.477 20/12/2013 00:32 United States 1387499533 WE6XGR FN12LQ
> WD2XNS
>
> +8 is 5/6 db up on my signal over 25 miles range ,
>
> That's definitely one up from 'Cookie' more to Tall Boy , if Bob runs
> to double figures , then may be 'Grand Slam'
>
> The spectrum w/f has no link to the decode engine , but , yes under
> those conditions the noise floor is going to be much higher
>
> Can you generate a local signal 100% op4 , see if Bob will run the
> timer , give you 4 tx 8 rx window , that would give a value to the
> drop ?
>
> Use something like spec-lab to give a better view , the w/f in Op is
> only a indicator / tune aid , what happens to the noise floor , carrier
> on / off ?
>
> 73-G,
>
> --------------------------------------------------
> From: <jrusgrove@comcast.net>
> Sent: Friday, December 20, 2013 1:24 AM
> To: <rsgb_lf_group@blacksheep.org>
> Subject: LF: OPERA overload?
>
> > G
> >
> > I have to take issue with your earlier comments about OPERA being immune
> > to overload. Check out the
> > waterfall below. I'm looking for OP8 signals out west (UT and VE7) and
> > WE2XGR/6 running OP4 is
> > clearly desensing the OPERA software. Sensitivity can be seen returning to
> > normal between keyed
> > characters.
> >
> > The receiving setup is a 1000' BOG (beverage on ground) > Harris RF-590
> > receiver > Delta 44 sound
> > card. Receiver AGC is off and the received signal level is well below that
> > to cause gain compression
> > in the receiver. Likewise, the sound card is being operated well below
> > compression/clipping levels.
> >
> > Weak signals do not decode under these conditions ... same as with WSPR.
> >
> > Jay W1VD WD2XNS WE2XGR/2 WG2XRS/2
> >
> >
> >
> >
> >
>