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Re: S-band receiving requirements



Guy, Pieter, etal:

Not wanting to argue with you, but I have made my own loss measurements up
to 1 GHz and find <0.1 dB.  In otherwords the loss is too small to measure.
 I regularly check loss through coax relays and cables, and 0.2 dB is
common for a microwave relay.  To be conservative maybe 0.2 dB per
connector, but not 0.5 dB at 2.4G.  Now maybe the engineers were talking
about 24G or higher.  N-connectors are not good above about 10 to 14 GHz.

But if you are into "dB pinching" then convert all your equipment to sma's.
:-)

Ed

>From: guy lemke <guy@com-pair.net>
>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
>> >
>> > ----
>> > Via the amsat-bb mailing list at AMSAT.ORG courtesy of AMSAT-NA.
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>> >
>
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