Hello Francesco,
The 437.024 transmitter antenna configuration on AO-16 is Left Hand Circular polarity (LHCP). The receiving antenna on the bird is a 1/4 wave vertical whip.
The fading is quite dramatic, which means the bird is spinning/tumbling, or some combination. We could never hear this before on AO-16 when it was transmitting its normal PSK signal, since we didn't hear the effect of fading on the uplink in this mode. Now we hear it, loud and clear!
It does take an uplink signal that is pretty close to on frequency (145.820). Adjusting for Doppler is helpful thing on the uplink.
Doppler on the 435 DSB downlink will make you love (or covet) a computer controlled VFO :)
It's so much fun to be a part of this NOW, on AO-16's 18th birthday---I vividly recall the launch and commissioning 18 years ago---THANKS to the folks that put them all together and got them in the air!!
73,
Mark N8MH AO-16 Command Team
Hello, I tried AO-16 too on one pass, noise level is high and also I noticed a very deep fading I could not compensate with H/V polarity switch. This is the only LEO I ever found difficult to access so far, I'm going to test other known sat to check my setup, maybe the problem is only here. I also found difficult to tune some stations, the audio never come good as if the modulation was distorted, I don't know if others had the same results. I've never had problems with linear sats however. I'll try again tomorrow.
73 Francesco IZ8DWF
Mark L. Hammond [N8MH]
Ye olde bird nerds,
I was sketching out some plans to rebuild my practically-failed Eggbeater antenna project for 70cm, as I am tired of cranking the rotator knob every pass and want to try out a good omni satellite antenna, which I can hang from the top limb of a tree 30 feet above my shack window (best option on my city lot).
My plan is to build on the K5OE Eggbeater II antenna. One thing that's always bugged me about these antennas is that most are implemented using a 93 ohm coaxial section to phase the loops. This is hard stuff to find, and though I know some hams say, "anything below 1.5 SWR is OK", I'm a perfectionist and want to try to polish it up.
The current antenna has a phasing section made out of two runs of RG-8X coax with the shields shorted and insulated, centers fed as a balanced 100 ohm (theoretical) matching section. It was difficult to build and I doubt its integrity because it's coiled up so tightly; I don't think that the foam core coax retains its impedance well when folded up in 1" PVC.
I was thinking about the feeding issues, then I recalled that one popular CP yagi antenna design is to space the horizontal and vertical elements 1/4 wavelength along the axis, and then feed them in phase. It then came to me that it may be possible to build an eggbeater with the two elements separated vertically by 1/4 free space wavelength, fed with simple half-wave coax sections to replicate the two loops' 100 ohm impedance into a simple coax tee. Polarity switching should be possible with a coax relay and a 1/2 wavelength delay line. Radials would be placed 1/4 wave apart as well, same spacing as the loops.
The advantages of this to me seem numerous. First of all, the free space quarter wavelength spacing is easier to accurately implement than a 1/4 wave phasing section using coaxial cable at 70cm, and the power/currents/etc split to the two antennas are more balanced as long as you build the 1/2 wave sections to equal lengths, leading to improved circularity skyward. You don't need to find rare coax for the phasing section, and instead of cramming several folded up or coiled runs of coax inside a narrow (for aesthetics) PVC tube, you only need to run two half-wavelength (or any multiple of half-wavelength) runs further down the mast, where the tee or relay could be ziptied.
So, that's my plan. If it makes sense, I'm going to give it a shot with 1/4" copper fridge tubing for the loops and some sort of sturdy wire (coathangers? heh) for the radials, using LMR240 coax for the two halfwave sections. If anybody has any input or comments, I'd love to hear them.
(P.S. If somebody's done this and I'm reinventing the wheel, please let me know. :) )
Matt KC4YLV
I've got oodles of RG-62 coax.... shoot me an address and a buck or two for postage & I'll send you a couple of feet....
George, KA3HSW
----- Original Message ----- From: "jonny 290" jonny290@gmail.com To: amsat-bb@amsat.org Sent: Wednesday, January 23, 2008 6:27 PM Subject: [amsat-bb] Thoughts on alternative eggbeater build/feeding
Ye olde bird nerds,
I was sketching out some plans to rebuild my practically-failed Eggbeater antenna project for 70cm, as I am tired of cranking the rotator knob every pass and want to try out a good omni satellite antenna, which I can hang from the top limb of a tree 30 feet above my shack window (best option on my city lot).
My plan is to build on the K5OE Eggbeater II antenna. One thing that's always bugged me about these antennas is that most are implemented using a 93 ohm coaxial section to phase the loops. This is hard stuff to find, and though I know some hams say, "anything below 1.5 SWR is OK", I'm a perfectionist and want to try to polish it up.
[snip]
Thanks for your thoughts Jonny. I am curious to see how that will work. I am in the process of totally rebuilding my station after 4 years qrt and am open to all the options. Egg Beater antennas are certainly on my list of things to build. I LOVE my long boom yagis, but the EB's would be fun to play with.
Chad kg0mw En-13
jonny 290 wrote:
Ye olde bird nerds,
I was sketching out some plans to rebuild my practically-failed Eggbeater antenna project for 70cm, as I am tired of cranking the rotator knob every pass and want to try out a good omni satellite antenna, which I can hang from the top limb of a tree 30 feet above my shack window (best option on my city lot).
My plan is to build on the K5OE Eggbeater II antenna. One thing that's always bugged me about these antennas is that most are implemented using a 93 ohm coaxial section to phase the loops. This is hard stuff to find, and though I know some hams say, "anything below 1.5 SWR is OK", I'm a perfectionist and want to try to polish it up.
The current antenna has a phasing section made out of two runs of RG-8X coax with the shields shorted and insulated, centers fed as a balanced 100 ohm (theoretical) matching section. It was difficult to build and I doubt its integrity because it's coiled up so tightly; I don't think that the foam core coax retains its impedance well when folded up in 1" PVC.
I was thinking about the feeding issues, then I recalled that one popular CP yagi antenna design is to space the horizontal and vertical elements 1/4 wavelength along the axis, and then feed them in phase. It then came to me that it may be possible to build an eggbeater with the two elements separated vertically by 1/4 free space wavelength, fed with simple half-wave coax sections to replicate the two loops' 100 ohm impedance into a simple coax tee. Polarity switching should be possible with a coax relay and a 1/2 wavelength delay line. Radials would be placed 1/4 wave apart as well, same spacing as the loops.
The advantages of this to me seem numerous. First of all, the free space quarter wavelength spacing is easier to accurately implement than a 1/4 wave phasing section using coaxial cable at 70cm, and the power/currents/etc split to the two antennas are more balanced as long as you build the 1/2 wave sections to equal lengths, leading to improved circularity skyward. You don't need to find rare coax for the phasing section, and instead of cramming several folded up or coiled runs of coax inside a narrow (for aesthetics) PVC tube, you only need to run two half-wavelength (or any multiple of half-wavelength) runs further down the mast, where the tee or relay could be ziptied.
So, that's my plan. If it makes sense, I'm going to give it a shot with 1/4" copper fridge tubing for the loops and some sort of sturdy wire (coathangers? heh) for the radials, using LMR240 coax for the two halfwave sections. If anybody has any input or comments, I'd love to hear them.
(P.S. If somebody's done this and I'm reinventing the wheel, please let me know. :) )
Matt KC4YLV
Sent via AMSAT-BB@amsat.org. Opinions expressed are those of the author. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb
participants (4)
-
Chad Phillips -
George Henry -
jonny 290 -
Mark L. Hammond