[amsat-bb] Re: beginner question re: uplink power
n3tl at bellsouth.net
Sun Oct 19 11:05:32 PDT 2008
Paul and all,
I would be curious to hear from anyone currently using verticals with preamps as their primary receive antennas. I have hesitated to respond to your initial post, Paul, because (1) I am very new to the satellites; (2) as a result, my personal experience with antennas involves only the Arrow handheld antenna, the eFactor 0-gain omni antenna, the Elk dual-band log periodic an MFJ mag-mount dual-band vertical for my vehicle, and HT-specific antennas (Pryme AL800, MFJ 1715 and 1717, etc.); and (3) my other knowledge regarding using omni antennas for satellite work is limited to what I have read here and elsewhere on the Internet.
All of that being said, I believe I would opt for something other than a vertical - even with preamps - as my prime base-station antennas for the satellies. I haven't yet built one of the Ramsey preamps, but I intend to as the weather turns cool here in North Georgia and I spend more time inside. I am curious about its ability to improve reception for me with the sFactor, which is an outstanding transmit antenna for reaching the satellites - based on my experiences with it. I also logged more than a dozen contacts involving AO-27, AO-51 and SO-50 using the eFactor with an HT as a handheld antenna. My personal experience suggests that a preamp would help it on the UHF receive side a great deal, although it honestly exceeded my expectations - given the physical size of the UHF part of the antenna.
The N3TL handheld station has worked 46 states, VE1-2-3-4-5-6-8-9, Mexico, Venezuela, Barbados and marimtime mobile stations all on 5 watts' rf out or less. It also has worked 20 states, Ontario, Mexico and Venezuela on .05-watt (50 milliwatts) on the same set of 2 AA Duracell batteries. For the sake of perspective, I made my first-ever satellite contact on June 28th of this year - less than 4 months ago.
>From here, output power isn't the issue. I believe your money and time will be best-invested in optimizing the receive side of your satellite station.
Best of luck with it, and 73,
Tim - N3TL
AMSAT Member No. 36820
Athens, Ga. - EM84ha
-------------- Original message from Edward Cole <kl7uw at acsalaska.net>: --------------
> At 09:30 PM 10/18/2008, 12.01 wrote:
> >I have a beginner question. I am in the process of setting up my first
> >satellite station. My initial investment is minimal and I have chosen
> >to start out with a pair of 2m and 70cm omni antennas on the roof. To
> >help out a bit I am also adding a mast mount preamp on each antenna. To
> >protect the preamps they will be switched out of line by a RF sense
> >switch (one for each amp). For reference the two preamps and the pair
> >of RF switches are all made by Ramsey (I know there are better preamps,
> >but not available in my current budget). I am keeping this initial
> >adventure limited to the LEOs (and ISS, etc.).
> >_The question: _ When I assemble the RF switches I must choose a RF
> >range for the switch to work within. The range is determined by the
> >choice of a specific resistor. The default three ranges suggested are
> >0-10 watts, 10-30 watts, and 30-100 watts. I would be able to change
> >the range later but it would require removing the unit from the mast.
> >So... not having any experience (yet),_ what uplink power range is
> >recommend for non-gain antennas?_ Is there one range that should cover
> >the LEOs? If not, how much should I expect the required uplink power
> >needs to vary across various satellites? Is it different for each band?
> >I have read that it is always best to never be louder than the beacon
> >and that's fine. I'm just needing to know where to start off my
> >hardware choices.
> >Thanks in advance for any help from you folks with the know-how. I look
> >forward to a qso with you.
> >.paul ac0z
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> I'm surprised that you have had only one reply. I am not QRV on the
> Leos so my advise is not as good as what you might get. My
> "understanding" is that one can work most of the Leos with power
> <10w. This is IF the stations on the bird also comply by not using
> more power than is needed. If a "power war" ensues to try to capture
> the satellite then running low power may be less effective to "break in".
> But seeing that so many folks run HT's that typically are 5w, I think
> you might chose the lowest range as long as your equipment output
> matches. You have to consider that you will have no antenna gain
> using omni-directional antennas so uplink RF power needs are
> affected, accordingly. NOW if some experienced sat op will add their
> input on this subject you should have the info you need.
> I wonder if the Ramsey preamps allow for "hard" switching. That is
> by separate control line that the radio PTT controls. Then You have
> no issue with RF power and would run the units with the RF sense
> disabled. I should state that "many" (dare I say most) experienced
> VHFers that run high power (>100w) use hard-wired switching. I know
> of NO eme stations that use RF sense control lines.
> PS: when my standard AO-10/13/40 ground station is re-installed I
> will have available 5-60w with 16.5 dBc UHF uplink (all-mode).
> 73, Ed - KL7UW BP40iq, 6m - 3cm
> 144-EME: FT-847, mgf-1801, 4x-xp20, 185w
> 1296-EME: DEMI-Xvtr, 0.30 dBNF, 4.9m dish, 60W
> http://www.kl7uw.com AK VHF-Up Group
> NA Rep. for DUBUS: dubususa at hotmail.com
> Sent via AMSAT-BB at amsat.org. Opinions expressed are those of the author.
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