[amsat-bb] new sats and 23cm
ko6th.greg at gmail.com
Thu Aug 6 00:46:40 UTC 2015
I also have 10w on 23cm from my Yaesu FT-736R, and a reasonable beam on the rotor. At least, it worked quite well through the recent LEOs.
How much EIRP are we expected to need for tthis one?
On August 5, 2015 5:52:06 AM PDT, David <dwarnberg at verizon.net> wrote:
>Zach, all... thanks very much for all the replies, it does give me some
>things to ponder... I do realize the add on 23cm module for the
>IC-9100 has only 10 watts output.. so it seems to limit my options or
>add more cost to the final setup...
>Again thanks everyone for the replies, as par for the course you guys
>are very helpful
>From: Zach Leffke [mailto:zleffke at vt.edu]
>Sent: Wednesday, August 05, 2015 1:20 AM
>Cc: amsat-bb at amsat.org
>Subject: Re: [amsat-bb] new sats and 23cm
>Sorry, typo... G/T doesn't make sense since uplink only band....please
>substitute 'affect G/T' with 'affect overall link budgets' in my
>Apologies, its late and I need sleep.
>On Aug 5, 2015 1:12 AM, Zach Leffke <zleffke at vt.edu> wrote:
>> Directive Systems and engineering has loop yagis specifically for the
>amateur satellite service in this band. It is what we will be using in
>the Virginia Tech ground station. No feedback yet on performance
>(we're not up yet) but they look very well made and the folks at the
>company are fantastic and they have a great reputation with their
>antennas at microwave and up. They are fairly compact and lightweight
>as well and could likely be added to a G5500 style setup with ease and
>minimal additional strain on the motors.
>> I'm not aware of any omnis for this band off the top of my head, but
>being that it is an uplink only allocation, lack of gain and increased
>path loss could be made up for with power (bearing in mind the recent
>threads on proper uplink power levels). Consider though that there is
>about 18.8dB and 9.7dB of additional path loss over VHF and UHF
>respectively. Assuming similar rx gains and noise performance on the
>bird at 23cm, as well as atmo/iono losses, that additional loss will
>have to be overcome on the ground, either with increased antenna gains,
>or with increased power. Given that the 9100 makes about 10W on 23cm,
>it may be time for a decision. a) 23cm module plus fairly beefy amp
>plus homebrew omni, or b) 23cm module plus rotator system plus well
>built (and factory tuned) yagi.
>> Personally, I'd recommend option b with rotator plus beam plus lower
>power, mainly because antenna gain is easy/cheap at 23cm and PAs can be
>expensive/tricky at 23cm, but I have access to existing rotator
>systems which bias my opinions.
>> My two cents....
>> Also it might be interesting to see some more rigorous analysis and
>antenna designs for 23cm (omnis and beams). Maybe comparisons of
>various omnis and various beams and how they affect G/T (imagine a cute
>little lindenblad or turnstyle or eggbeater for 23cm and how physically
>small it would be compared to what we are used to at VHF/UHF, it would
>be roughly a third of the size of its UHF equivalent!). Once we can get
>some details from the Fox engineering crew or Ops crew on the expected
>performance of the uplink receiver on 23cm, could make for a good
>article or two for the Journal (especially the bit on 'microwave omnis'
>and their feasibility, I'm sure the eng/ops crew has or will have a
>solid handle on the overall receiver performance and link budgets).
>> -Zach, KJ4QLP
>> On Aug 4, 2015 11:32 AM, David <dwarnberg at verizon.net> wrote:
>> > I see lots of talk about some new sats going up that will be
>> > so I have some questions.. first let me explain what I have setup
>> > currently.
>> > 1) Icom IC-9100 (23cm module not added yet)
>> > 2) M2 eggbeaters (70cm and 2m) with preamps
>> > So I am contemplating adding the 23cm add on for the 9100 but
>> > perplexed about an antenna. suggestions?
>> > Thanks
>> > David, KK4QOE
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>Sent via AMSAT-BB at amsat.org. AMSAT-NA makes this open forum available
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