Beautiful work Gordon! Very impressive.
73
toggle quoted message
Show quoted text
On May 23, 2025, at 6:10?AM, Gordon Gibby KX4Z via groups.io <docvacuumtubes@...> wrote:
?
I have now gotten an elevation system working very well using a linear actuator (12V) from Amazon.? ?Also created crossed yagi's to allow for circular polarization.? ? Using "J" half-folded dipole driven elements has turned out very well.? ? The impedances of these driven elements wasn't as large as I had expected (they are dragged downward in impedance by the influence of the nearby reflector and director).? ?However a very fortunate outcome was that the impedance of putting each crossed yagi in parallel with the other resulted in nice combined impedance.? ?I chose to use short feedlines that (corrected for velocity factor) were 1/2 wavelength, for the purpose of allowing me to use a nanoVNA to try and estimate the actual feed point impedance.? ?It worked!
?
Putting the yagis in parallel using a BNC T-connector resulted in an almost perfect SWR on my 70cm set and tolerable on the 2meter set.? ??
?
Here is a photo of the final antenna, with the booms and yagi's now implemented in standard 3/4 inch Schedule 40 PVC from Home Depot:
?
?
I'm still very very new at all of this, but I have now been able send and receive AX.25 (packet) to the ISS very easily on 2 meters.? ?This is an APRS digipeater, so acts a little differently than normal digipeaters I'm familiar with.? ? ?I'm still working on figuring out the best software with which to approach it -- there are LOTS of users so it is a big crowded!
?
Working my way back up to attempting the LINEAR satellites.? ?In the meantime, I have now worked out how to control the rotators remotely over WIFI using a raspberry pi to run the rotctld.? ?That will be for another post here.
?
So far the Yagi's seem to be working amazingly well for the homebrew way that i built them!? (the box on the base is just for stability weighting)
?
Gordon KX4Z
?
