QO-100 LNB Comparison

My downlink (DL) is realized by using an old 35cm off-set dish on my roof deck, something I mentioned before. On recommendation of an old friend, I bought a Venton EXL-S Rocket Single LNB. So far so good, this LNB served me on many contacts. Using the beacon feature of SDR-Console made it possible to have those contacts. However, during my tests using analogue equipment, drift from this particular LNB was noticeable.
I understood the Venton LNB is primarily useful with with POTY "dual band" feed, as it keeps the centre hole to a minimum. Fair enough. 

For my setup, I decided to use two separate dishes for UL and DL, hence, the size of the DL LNB is irrelevant to the UL feed geometry. As a matter of experimentation, I replaced the Venton LNB with an Octagon OSLO LNB in the 35cm DL dish setup. This LNB was purchased many years ago, when I was active on 3cm rain scatter and wanted to experiment a little bit with commodity gear. To my surprise, the Octagon LNB is a lot more stable, once at temperature. It also appears to be more sensitive than the Venton. Aperture is the name of the game here, I figure. Hmmm, maybe I should have used this LNB from the get-go and saved the few Euros by not buying the Venton LNB.

Still, there might be a use for the Venton LNB. As mentioned in my previous post, I am considering to use a single dish for DL and UL. With its smaller form-factor, the Venton Rocket might be the better choice when placed inside the UL feed helix in a single dish arrangement.

I will post my further experiment on this blog, so, stay tuned.

BTW, occasionally, you might be able to hear me on the transponder. Feel free to give my a call ;-)

QO-100 update

Not much to report, other than I shortened the RG-6 coax for the Up-Link. The length should be about 3.5m, however, I have not measured the length yet. In order to achieve the shorter transmission line, drilled a hole into a window frame relatively close to the UL dish. This allows the power amplifier to be indoors. 

By now, I made contacts in side-band from Brazil to Thailand. The occasional rag chew QSO confirmed that my signal is loud enough to not be difficult to listen to.

There is a plan of using the UL dish also for reception. The added gain in the DL might make it easier to operate with a full analogue setup. Although, the LNB being placed in the center of the feed-helix might compromise the UL signal. Something to experiment with...
Further down the line, I might acquire a larger off-set dish, e.g. 1m, mainly to add some gain to the UL.

QO-100 thoughts

The humble listener/follower of my station or posts might have experienced a certain lack of enthusiasm about operating on QO-100/ Please do not interpret much into this. The satellite is great. Probably the greatest any Oscars had ever been by this date.
However, once the setup is done, the fine tuning is somewhat frustrating.

What to look for?

Ideally, in my world, one would be going fully analogue, i.e. using only pure receivers and transmitters.
Does that justify the effort by the operators of the satellite? I don't think so!
Hence, we also should look into modern techniques, such as SDR.

Well, this is exactly the spot I am struggling with. I got the equipment for both, analogue down link and digital down link. I operated with the satellite using both. Concerning the up link, I an analogue only. 

What I used so far (RX - TX):

• RSP1a - FT817
• FT290R2 - FT790R2
• FT736R (RX+TX)

Any of the setups has advantages and disadvantages. 

For the time being, I am using the RSP1a - FT817 the most. However, I have a strong desire to move towards using the FT736R only.