I can finally report a successful satellite QSO! Many thanks to all of you for your very useful feedback.
I ended up using my existing 2m/70cm 3el beam on the TV rotator with the addition of an SSB preamp for 70cm.
There are still a couple of limitations with my system. The first being that the antenna is fixed at a 0 degree elevation. I was able to work AO-51 from 7 degrees above the horizon, but lose it around 20 or so degrees elevation. While it's great that I can work it that far out, I'm losing out on the better passes with less path-loss.
The other downside is that even with two transceivers, I'm unable to work full-duplex. The two bands on the antenna use seperate elements and feed points, but share a boom. Transmitting on 2m completely overloads the front-end of the IC-7000. While full duplex would be useful, it's not absolutely necessary.
My primary goal is achieving reliable, repeatable communications (i.e. removing the luck from the equation as much as possible!). Hopefully I'll be able to reproduce yesterday's performance with my exising kit for a little while longer and consider how to add a permanent elevation and slightly longer booms.
Regards,
Scott NW2S
Congratulations to Scott, NW2S, on his recent successes in working satellites.
In reference to the stated problem:
The other downside is that even with two transceivers, I'm unable to work full-duplex. The two bands on the antenna use separate elements and feed points, but share a boom. Transmitting on 2m completely overloads the front-end of the IC-7000. While full duplex would be useful, it's not absolutely necessary.
May I mention some old ideas that could improve the "Mode-J" desense, which is a very common problem.
There are several ways to improve Mode-J desense.
1.) One is by using a combination of a "Mode-J Filter" on the 2-meter side, "MMf200-7" which attenuates harmonics outside the 2m band that can plague the 70cm receiving side, and a "PSF-432 Bandpass Filter" added on the 70cm UHF side. (I have several sets of these filters, which are obtainable from Spectrum International, Inc., Concord, MA, and they work very well!)
2.) Physical separation of antennas, but I don't recommend this often because it simply doesn't satisfy the needs of most users.
3.) By the inverted use of a "2m/70cm Diplexer" (commonly called duplexers now) connected in the UHF side, which has the common port connected to the UHF antenna, the 70cm port connected to the UHF radio input, and the 2-meter port connected to a small 50-ohm dummy load of some kind. (There used to be an example of this on the AMSAT site.)
Additional comments: A few other items could have some affect, such as proper grounding, the amount of uplink power used, circular polarization, and the use of high-quality coaxial transmission lines.
73, Charlie, N5TD Temple, Tx
participants (2)
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Charlie Schlieper -
Scott Wilson