[amsat-bb] Re: eggbeater rx performance MM
ka1rrw at yahoo.com
Sat May 30 07:04:12 PDT 2009
Let’s split your question into two parts
Car and House:
I have made literally hundreds of FM voice contacts with Mir and ISS from my car. I have also made hundreds of packet mail contacts with Mir.
On Mir the default power setting was 5 watts, into a Larsen Dual band Mobile antenna, mounted outside on the hull of Mir. The transceiver was either a Kenwood TM-733 or TM-V7A.
My car station was typically a 5/8 wave mono band 2-meter vertical, with a 45 watt class FM rig. I usually did not have the amps in the car since mobile amps are typically high maintenance.
ISS is running a similar setup. The transceiver is a Kenwood TM-D700, modified for three power settings, 5,10,25 (special mods). The ISS D700 has been programmed to default to 10 watts for voice and packet, unless changed by the crew, however every time the crew pushes a PM/function button, it forces the radio back to 10 watts.
The antenna is a Quad band system with 2, 440, patch for 1.2-2.4 Ghz. Gain is unknown, and must be assumed to be –3dBd for 2 meters.
So for beginners, LEO satellites, Running simple verticals and a 45+ watt class system and 0 dBd gain antennas is a good way to start from your car (parked or driving).
You will need to Pick your orbits in advance. I would usually only attempt orbits that were 45 degrees elevation or better from my Car.
For the more advances mobile users, try this Mobile EME array.
Other Car Tips:
Convert from RG-58 to LMR-240-UF or RG-213. The coax that usually comes with stock mobile antennas is too poor of quality to be used seriously.
Run Mono-band antennas for 2 and 440, get the highest Gain mono band (whip) antennas that will fit your mobile and garage. You may need a signal splitter since most rigs only have one SO-239 for 2/440.
Amps for your Car:
Get best antennas and coax first before using amps. In some States, we are limited to 50 watts on 440.
House Satellite Antennas:
It’s ok to start with a few simpler verticals or small beams to see if you like the satellite hobby.
If you do like Satellites and want to continue then you have two choices.
#1 Gradually build your antenna gain over several years,
1 Element 0 dBd
2 Elements 3dBd
4 Elements 6dBd
8 Elements 9 dBd
#2 you can jump in and buy a one of the 20+ element CP (circular polarized) 12-dBd class beams.
In many cases it maybe cheaper to go from 0 dBd to 12 dBd than buying lots of little antennas in-between. A CP style antenna system can be used for both Satellite and terrestrial DX.
Go with the most elements you can afford for a single boom.
20+ elements on 2-meters
40+ elements on 440
You can now get Flexible thick coax that will support an antenna Rotor.
Most people used RG-8 style coax, which is approximately 10 mm in diameter.
However you can now get flexible rotor grade coax which is approximately 15 mm in diameter, and has much lower loss than the best RG-8 style coax.
145 MHz 2.5 dB loss per 100 feet
438 MHz 4.5 dB loss per 100 feet
LMR 600 UltraFlex Rotor cable
145 MHz 1.1 dB loss per 100 feet
438 MHz 2.0 dB loss per 100 feet
As you can see, by switching from 10mm coax to 15mm coax you can reduce you loss by over 50%. The 15mm cables cost 2-3 times as much, however you will not have to worry about coax losses any more on Frequencies below 2 gig.
--- On Fri, 5/29/09, Eric Fort <eric.fort at gmail.com> wrote:
> From: Eric Fort <eric.fort at gmail.com>
> Subject: [amsat-bb] eggbeater rx performance
> To: "Amsat BB" <amsat-bb at amsat.org>
> Date: Friday, May 29, 2009, 9:17 PM
> I/m interested in the possibility of
> using oscars 27, 29, 50, 51, and 52
> without using rotors or directional antennas and maybe
> while mobile. Uplink
> seems not to be a problem as one can always QRO to a level
> where the
> satellite sees an apropriate signal level that is enough
> but without robing
> power from other transponder users. On recieve though
> you still gotta be
> able to hear 'em to work 'em. Is an eggbeater and a
> preamp enough to hear
> decently or is there another (better) way? Is working
> mobile and/or without
> directional antennas even practical? what's the best
> way to do it?
> Sent via AMSAT-BB at amsat.org.
> Opinions expressed are those of the author.
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