SPID rotator - Standard or High Resolution?

I’m looking for a commercial rotator and specifically the SPID variant from RFHamstore - for my 2m prime focus solid dish antenna (for now, as I’m planning to “upgrade” to a 1,9m mesh one or possibly the 2.4m mesh variant).

The question is – do I need the standard version with the 0.5 degrees resolution (and lower cost) or the High Resolution one with the 0.1 degrees increments? The setup will be for L and S-Band observations.

So, do I need the extra fine resolution of 0.1 degrees… I’m guessing that I don’t, especially with a homemade antenna feed that will not be perfectly made and ideally positioned! It will be better to have a smaller diameter dish or a non dish antenna with a bigger lobe - but the 2m solid dish one is the one that I have now…

Furthermore, the standard versions are available with the Rot2Prog controllers but they are going to release the newest MD-03 controllers soon. I’m guessing that the newest MD-03 controllers are the way to go…

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An excuse to bust out my antenna slide rule :smile:

A 2.5 m dish at 2.5 GHz would have a half-power beamwidth of just over 3 degrees. One degree of pointing error is about 1/4 dB of pointing loss.

(found a virtual version! Antenna Virtual Slide Rule Calculators)

I’m not familiar enough with the SPID rotators to have a sense of the system-level pointing accuracy including backlash and such compared to the position feedback resolution. But, it seems like the 0.5deg resolution is sufficient for the application, especially if the cost differential would be more dB-effective by putting towards feed, LNA, or feedline upgrades.


Thanks for your answer Dan! Your antenna slide rule is amazing!