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

Re: S-band receiving requirements



0.5 dB per N connector? Sounds like too much! I have measured a pair of BNcs
and a pair of N connectors all in a line at 1.5 GHz and I get less than 0.5
dB. I doubt that a single one is 0.5 dB. Maybe if you buy the radioshack
versions.

Pieter

----- Original Message -----
From: "guy lemke" <guy@com-pair.net>
To: "Jerry Pixton" <jpixton@shentel.net>; <amsat-bb@AMSAT.Org>
Sent: Sunday, May 20, 2001 13:48
Subject: Re: [amsat-bb] S-band receiving requirements


> You should figure in .5 Db per N connector if they are of good quality !!!
>
> Jerry Pixton wrote:
>
> > Mike and Gene,
> >
> > Ya, that coax ahead of the preamp/downconverer is all important. What is
> > the loss at 2400 Mhz of just a male/male N connector between the antenna
> > and converter  I have been using 0.25 db as a wag.
> >
> > If I have a helix antenna with 17 dBic, does that mean I should enter 14
> > into the spread sheet to cover the loss from circular to linear. Or
should
> > I be entering 20 since my antenna is really 3 db better than a linearly
> > polarized antenna?????  The antenna gain seems to be used on the data
sheet
> > to compute the transponder levels. Is the 3 db polarity loss embedded in
> > the "24" factor at the end of the equation?
> >
> > Jerry W6IHG
> >
> > At 08:17 AM 5/19/01 -0400, Mike73@aol.com wrote:
> > >In a message dated 5/18/01 8:40:08 PM Eastern Daylight Time,
> > >al7eb@ptialaska.net writes:
> > >
> > > >  Gene Marcus' spreadsheet is very useful for this process.
> > >
> > >I agree!!  A couple of pointers.....
> > >
> > >The very first coax loss number before the preamp is very important.
This
> > >really effects overall system noise. I calculated the 3 foot jumper
(RG-8) on
> > >my Meyers dish as -.36 dB at 2400 (yuk). Throw that number in the
spreadsheet
> > >and see what happens.
> > >
> > >Also, I asked Gene about the antenna gain. The number you input is dBi
> > >Linear. So to be accurate, if you're using a Meyers dish you should
subtract
> > >3 dB for the theoretical loss when going from linear to circular. So,
for a
> > >Meyers dish that was advertised as 25 dBi, you would input 22 dBi.
> > >
> > >I can see if I were to do any improvements to my system, I'd probably
attack
> > >the antenna. I already have a good low NF preamp. The changes I'd
contemplate
> > >would be to change the feed to circular and reduce the coax loss before
the
> > >preamp. To see the effect of these two changes, input .1 dB for first
coax
> > >loss and 25 dBi antenna gain in the spreadsheet and you'll see the
> > >improvement.
> > >
> > >Now back to cobbling together a 5668 uplink :-}
> > >
> > >73,
> > >Mike, N1JEZ
> > >AMSAT #29649
> > >Local Area Coordinator
> > >"A closed mouth gathers no feet."
> > >----
> > >Via the amsat-bb mailing list at AMSAT.ORG courtesy of AMSAT-NA.
> > >To unsubscribe, send "unsubscribe amsat-bb" to Majordomo@amsat.org
> >
> > ------------------------------------------
> > Dr. Jerry R. Pixton, PIXOS Designs LLC
> > http://www.pixos.com/designs/
> > jpixton@shentel.net
> > ------------------------------------------
> >
> > ----
> > Via the amsat-bb mailing list at AMSAT.ORG courtesy of AMSAT-NA.
> > To unsubscribe, send "unsubscribe amsat-bb" to Majordomo@amsat.org
>
> ----
> Via the amsat-bb mailing list at AMSAT.ORG courtesy of AMSAT-NA.
> To unsubscribe, send "unsubscribe amsat-bb" to Majordomo@amsat.org
>
----
Via the amsat-bb mailing list at AMSAT.ORG courtesy of AMSAT-NA.
To unsubscribe, send "unsubscribe amsat-bb" to Majordomo@amsat.org



AMSAT Top AMSAT Home