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Re: S-band receiving requirements



Hi Guy,

You can get as defensive as you want, but maybe you should not be buying
those crummy connectors. I deal with N connectors every day and I don't rely
on what others say. I do all the measurements myself. I have the latest
model HP8753ES 3 GHz network analyzer on my bench and I have never seen
losses that high. If you are getting 0.5 dB, your connectors can be rated as
"radioshack" quality.

Pieter Ibelings
 N4IP



----- Original Message -----
From: "guy lemke" <guy@com-pair.net>
To: "Pieter Ibelings" <elpieter@hotmail.com>; <amsat-bb@AMSAT.Org>
Sent: Sunday, May 20, 2001 14:12
Subject: Re: [amsat-bb] S-band receiving requirements


> I don't think so!!! I work with 2.4 Ghz every day at the company I work
for and
> we use times microwave and I have talked to their engineers many times and
they
> have told us that this is what we should expect... So believe what you
would
> like but this is still my answer to the question.
>
>         Guy Lemke
>         KD6MTU
>
> Pieter Ibelings wrote:
>
> > 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
> > >
> > > ----
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> > >
>
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