I've been looking at getting setup to use those oscars over which one can actually communicate via sound, spoken words, voice, etc. in real time. I have little to no interest in listening to/for things that simply take bandwidth to go beep beep or even send telemetry. I'm not really interested in packet either. (there's enough terrestrial APRS coverage that I really have no need for APRS sat coverage either.) So given what is presently or soon will be operational, are there any transponders (fm or linear/ssb) that I would be unable to work with 2 M2 eggbeater antennas (1 each for 2M & 70cm) and a TS-2000X multimode radio, possibly with the addition of a good low noise preamp for each band? does anything on orbit or planned really require the use of directional high gain antennas and a rotator to use effectively, or should the above be expected to be suitable for sat work for the foreseeable future given my interests?
(yes, I know many sats can be worked with an HT and directional antenna. I've done it. Now I'm looking to put something together that I can simply sit down and use, does not require doing a strange dance across the yard or a public park and having to explain to PD that I'm not a terrorist trying to contact space aliens...., and basically points and tunes itself over the period of a given pass with only minor if any adjustment other than keying and unkeying the mic.... eventually I'd like to possibly adapt this to mobile operation for use while driving. What operating would I NEED rotors and directional antennas?)
Thanks,
Eric AF6EP
Modest yagis are more effective than eggbeaters ... Computer-controlled yagis with an elevation rotator is an "ideal" setup for many.
You will receive some excellent suggestions from those with more elaborate systems than mine
Clint K6LCS
Sent from my iPod touch.
This raises the question of where, when, and why are rotors and directional gain antennas required and/or necessary. sure,it's preferable not to be radiating power in a direction not directed to the transponder but I'm more so inquiring about the limiting factors here. If I make the assumption that I have 100W or even 1000W at the antenna feedpoint,I likely can generate enough EIRP to reach the sat with full quieting (or is getting enough EIRP a problem here?) likely more of the issue is one of effective rx sensitivity and system noise figure, along with sufficient rx antenna gain to hear the down link. It would be helpful for someone to demonstrate the required up link and down link link budgets and how they apply here. where if at all is a setup with rotators and directional antennas required to work current or expected sats and when can a modest station with sufficient uplink power and excelent rx sensitivity/selectivity be expected to get the job done?
Thanks,
Eric, AF6EP
On Mon, Mar 23, 2015 at 10:54 PM, Clint Bradford [email protected] wrote:
Modest yagis are more effective than eggbeaters ... Computer-controlled yagis with an elevation rotator is an "ideal" setup for many.
You will receive some excellent suggestions from those with more elaborate systems than mine
Clint K6LCS
Sent from my iPod touch.
Eric,
100W EIRP is, in most cases, more than enough - and is generally the most power recommended to be used on any of the linear transponders. Of course, if your path to the satellite is blocked by trees, this calculation may change.
Let's look at the link budget for what is probably the worst case downlink - for SO-50 at the horizon.
SO-50 TX +24 dBm TX Antenna Gain 0 dB Path Loss -155 dB RX Antenna Gain +10 dB
-121 dBm
This is probably just below usability at the horizon for most receivers, even assuming you have zero feedline loss, so you'd need to add more antenna gain or a preamp. If you're beaming through a tree, subtract at least 10 dB from that signal strength. Polarization mismatch can also affect the signal you receive with periodic fading if you do not have switchable V/H or RHCP/LHCP polarization.
For a real world example, my portable station - an Arrow antenna, 6 ft of LMR-240, High Sierra Microwave preamps for both 2m and 70cm, and 2 FT-817s - can hear and work all the satellites to the horizon (when I'm sufficiently clear of obstructions and in a low noise area). Sometimes I could use more transmit power - maybe 10 or 20 watts, but the five watts does it in most cases. On Saturday morning, I worked SP3QDM on FO-29, at a range of 6,913 km from here in Washington, DC, using this portable setup (https://twitter.com/PRStoetzer/status/551437882205171712), so it definitely does not take large antennas or high transmit power.
73,
Paul Stoetzer, N8HM Washington, DC (FM18lv)
On Tue, Mar 24, 2015 at 4:57 AM, Eric Fort [email protected] wrote:
This raises the question of where, when, and why are rotors and directional gain antennas required and/or necessary. sure,it's preferable not to be radiating power in a direction not directed to the transponder but I'm more so inquiring about the limiting factors here. If I make the assumption that I have 100W or even 1000W at the antenna feedpoint,I likely can generate enough EIRP to reach the sat with full quieting (or is getting enough EIRP a problem here?) likely more of the issue is one of effective rx sensitivity and system noise figure, along with sufficient rx antenna gain to hear the down link. It would be helpful for someone to demonstrate the required up link and down link link budgets and how they apply here. where if at all is a setup with rotators and directional antennas required to work current or expected sats and when can a modest station with sufficient uplink power and excelent rx sensitivity/selectivity be expected to get the job done?
Thanks,
Eric, AF6EP
On Mon, Mar 23, 2015 at 10:54 PM, Clint Bradford [email protected] wrote:
Modest yagis are more effective than eggbeaters ... Computer-controlled yagis with an elevation rotator is an "ideal" setup for many.
You will receive some excellent suggestions from those with more elaborate systems than mine
Clint K6LCS
Sent from my iPod touch.
Sent via [email protected]. AMSAT-NA makes this open forum available to all interested persons worldwide without requiring membership. Opinions expressed are solely those of the author, and do not reflect the official views of AMSAT-NA. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb
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Clint Bradford -
Eric Fort -
Paul Stoetzer