[Date Prev][Date Next][Thread Prev][Thread Next] - [Date Index][Thread Index][Author Index]

Re: so35

Bob and group,

I'm not arguing either Bob, but trying to quell big station bashing
which for some reason you seem to be a standard bearer.  I guess at this
point we talk the same talk, but I still take issue with your basic
premise.  Sometimes practicality outweighs the calculator, and reality
dissolves the theory.

Bob Bruninga wrote:
> Mike took issue with my comment that 5 watts will do for most all LEO's
> and listed all the reasons for running more power and high gain antennas
> in order to guarantee success.

I never said run more power to assure success, ever.  However, most
stations with marginal downlink antennas HAVE to run more power than
would be necessary if they could hear well, just to be able to hear
their own signal.  So in this regard, a station which hears well can
lower their power output to a lower EIRP than the gator station.  Those
pundits calling the big stations gator stations don't understand the
term.  A gator station can't hear, so yells.  Every big station I've
ever worked hears quite well.

> All he said is true, but that was not my point.  For each such station
> that "guarantees" its own success, that station is doing it at the expense
> of others in most cases.  This is OK.  If one has an urgent comm
> requirment, then I defend his use of higher power.

I guess your basic argument again is that a big station guarantees its
own success by running excessive power at the expense of others.  Not
the case at all.  Again, if you can hear the downlink better, it takes
less power to hear your own signal.  Why is there any contention here? 
I assert that all stations should hear better than they transmit.  We'd
all be better off in the long run.  Unfortunately, the opposite is true
with many marginally equipped operators.  

I can give you a good test for the viability of your station.  If you
can hear the noise floor on FO-29, you've arrived.  A well equipped,
experienced operator can adjust the downlink polarity sense without even
hearing a signal or keying the rig.  In my experience, polarity sense is
more critical on FO-29 than any other bird.  For whatever reason, it
changes polarity several times in a pass.  The well equipped station
will adjust downlink and uplink sense until they match and keep their
power output constant.  A station with fixed polarity sense will
compensate during those flip flops by increasing power.  Been there. 
Seen it.  Which station is guaranteeing their own success by increasing

> My point was that there is a nominal ERP that will work under nominal
> conditions.  Do the link calculations and  THrow in a 3 dB polarization
> missmatch and another 6 dB margin.  That ERP should allow everyone to get
> into the bird *most* of the time in the absence of collisions.  If you
> dont get in under these conditions, then the channel is too busy and the
> only ones who will are the ones that do so at others expense.
It is apparent your APRS mindset is at work here.  It is easy for a
digital link to rebroadcast redundant packets to fill in.  It gets
tiresome when carrying on a QSO to keep repeating your last
transmission.  This happens regularly in QSO with stations without the
ability to adjust to changing conditions.  The big station will
anticipate the polarity change and switch the sense accordingly.

You state that the polarization mismatch penalty is 3 db.  Only if you
are using a linear antenna.  If you have a RHCP antenna receiving a LHCP
signal, in theory the penalty is infinite.  In reality, the penalty is
somewhere around 20 db.  Many factors will make that penalty vary. 
Seldom is a signal truly circular, but some component of elliptical. 
Multipathing will also lessen the theoretical infinite penalty.  Feed a
6 fold power increase to maintain your signal into your link budget, or
do it the efficient way and throw in switchable sense. 

With all due respect Bob, I appreciate all your efforts for the amateur
community.  You will go down in history as one of our best and a legend
at that.  I have been reading all the posts bashing the "big stations," 
and had to say something.  There are discourteous operators at all
levels of our hobby.  Just because a person has assembled a top notch
station does not relegate them to ranks of villainy. 

Use your cane pole and sit in one place and hope for the fish to come
by, or learn to fly fish and fish the entire stream.  God I'm glad we
all get to make choices.

73, Mike

    |                              .  / ^  _ \  . 
    |                              |\| (o)(o) |/|
    ^    ---   * -----------------.OOOo--oo--oOOO.------------------- *
   |||   | |   * Mike Gilchrist - KF4FDJ ..... AMSAT Area Coordinator *
   |X|   | |   * P.O. Box 763 ................ AMSAT  member   #31884 *
   [X]~~~|k|   * Fort Myers, FL  33902 ....... ARRL  member  #1781549 *
  /   \  |f|   * http://www.gate.net/~seven77  telephone 941.772.7907 *
 |     | |4|   * kf4fdj@amsat.org ............................ EL96ap *
 |  P  | |f|   * I.S. Professional ..... CNA .... Computer Consultant *
 |  3  |=|d|   *   AO10, AO27, FO20, FO29, RS13, RS15, MIR, E Layer   *
 |  D  | |j|   *    Bringing Oscar demos to the Lee County Schools.   *
 |_____|=| |   * * * * * * * * * * * * * *  * * * * * * * * * * * * * *
  /*X*\  | |   *  Black holes were created when God divided by zero.  *
                                  .oooO   (   ) 
                                  (   )    ) / 
                                   \ (    (_/ 
Via the amsat-bb mailing list at AMSAT.ORG courtesy of AMSAT-NA.
To unsubscribe, send "unsubscribe amsat-bb" to Majordomo@amsat.org