Greg,
There is a way to figure out how much power you are getting to your mode-L antenna. Times MIcrowave has a on-line calculator for many of the more popular cables. http://www.timesmicrowave.com/cgi-bin/calculate.pl
If you use the numbers for LMR-600 (3.056-dB/100-feet) in place of your 1/2-inch hardline you get: 60-feet of cable: Loss=1.8 dB Efficiency = .656
For RG-214 (8.472-dB/100 feet): 10-feet of cable: Loss=0.8 dB Efficiency = .823
add the loss in dB = 2.6 dB, or multiply the efficiencies = 0.54 So 10w x 0.54 = 5.4w This is a lot for AO-51.
Ain't math fun ;-) 73 Ed - KL7UW
At 02:22 PM 9/13/2008, Greg D. wrote:
Hi Robert,
The equipment is my receive side from my AO-40 setup, along with a newly acquired transmit side.
The receive side starts with a home made 3 3/4 turn helix in the bottom inch of a grapefruit juice can, which makes up the feed for a BBQ grill antenna that I lined with window screen in order to make it usable for circularly polarization. There's a Khune 2.4 ghz preamp (highly recommended!) attached to the feed, and a short cable to one of those infamous Drake downconverters. I modified the Drake in an unusual way, moving the local oscillator from whatever it was to 2100 mHz. That put AO-40's 2401.3xx mHz downlink in the middle of the Drake's design passband, and in a nice place between our 2m and 70cm bands so that I could use either as an uplink without interference. There's about 60' of Quad-shield RG-6 out the back of the Drake to the shack. where it terminates on a power injector connected to a multi-way Radio Shack RF (video) switch. The switch allows me to select our pre-Cable TV antenna (never throw anything away!) or the Drake as an input to an old ICOM R-7000! all-mode scanning receiver. The receiver is pretty deaf by many standards, and AO-40 was never more than an S1 or S2 on the meter, but it worked. (I've had AO-51 up to about S4 recently. Wow!)
The transmit side starts in the shack with an ICOM 1271A tranceiver that I picked up from a fellow Ham last year. I'd never been on 1.2 gHz before, so this was new territory. The tranceiver feeds a few feet of RG-8-like stuff (RG-214, I think) to get out of the shack, then there's about 60' of 1/2" hardline up to the roof, where it switches again to the RG-8-like stuff to go around the rotor and up to the antenna. The antenna is an 18 turn helix that I made from aluminum ground wire and wire ties. About 10 watts goes into the coax in the shack; not sure what makes it out the other end, but it's apparently quite sufficient for AO-51. I didn't have the 1.2 gHz equipment when AO-40 was working, so I don't know how well it would have worked on the higher altitude satellites.
The rotor assembly is home made; ham and tv-type rotors, run from a homebrew controller.
Pictures at http://home.wavecable.com/~ko6th, at the bottom of the page.
So, to answer your question, a lot of my getting on the microwave bands has been through stuff that I have built myself, with a few key components acquired opportunistically as they came around. From what I've seen recently, there are still downconverters to be had, as are the grill dishes, etc. Lots of folks have used the small 18" satellite TV dishes that many neighbors are giving away for free. The key is to be constantly hunting for stuff, designing and re-designing as you go, depending on what you can come up with.
Hope this helps. Good luck!
Greg KO6TH
CC: amsat-bb@amsat.org From: xunil@xunil.net To: ko6th_greg@hotmail.com Subject: Re: [amsat-bb] Re: Alone on L/S ON A0-51 Date: Sat, 13 Sep 2008 11:40:47 -0700
Hi Greg-
Too bad about the lonely pass. I haven't done a lot of research since I (recently) got back into working the birds, but from what I remember in the AO-40 days, my biggest problem working the microwave modes was finding equipment. I remember Down East made microwave gear but they were moving offices for what seemed like forever, and now it appears they're swamped with backlog and aren't able to fill new orders.
My question is, what L/S gear do you use, and where does one find microwave gear these days?
73, Robert KC0KNM
On Sep 12, 2008, at 8:45 PM, Greg D. wrote:
Hi Luc,
Well, I guess the other parts of this planet are a bit more active than out here on the coast... Really nice 50+ degree pass this evening, and again I was all alone on LS.
Greg KO6TH
From: lucleblanc6@videotron.ca To: amsat-bb@amsat.org Date: Fri, 12 Sep 2008 10:04:42 -0400 CC: eu-amsat@yahoogroups.com Subject: [amsat-bb] Re: Alone on L/S ON A0-51
On 11 Sep 2008 at 22:59, Greg D. wrote:
{snip}
P.S. Remember, AO-51 is in mode J-FM on the 'QRP' side (435.15/145.88) this week.
Also remember the main side is in LS. I had the whole bird to myself again tonight...
Greg KO6TH
Not quite VE3NPC,KD8CAO,WB8OTH,KC9ELU, and myself are there too when they are able to find the right uplink on L... But if i can succeed to have the uplink controlled by a PC L/S will be a greath mode +- path obstruction (Just hope they will put the sat in this mode again this winter)
BTW I don't know the extent of L/S mode operation in europe and in the rest of the world?
"-"
Luc Leblanc VE2DWE Skype VE2DWE www.qsl.net/ve2dwe WAC BASIC CW PHONE SATELLITE
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