WA2ZKD

Here's the final pix of my notch filter I used to solve the severe AM overload I had. More info on it in a follow up post

a surefire solution at a decent price
https://www.ebay.com/itm/Lucent-GPS-40dB-High-Gain-Timing-Antenna-Lightning-Surge-Protection-Mount-Kit/323346523135?epid=10008077643&hash=item4b48f463ff:g:-yEAAOSwjkdZ81n5&_sacat=0&_nkw=40+gps+antenna&_from=R40&rt=nc&_trksid=m570.l1313&LH_TitleDesc=0

It seems like VOACAP and its online frontend variants have evolved as a Gold Standard for some. However, during my professional work I find that the answers are not always right with regards to MUF for the NVIS and NVIS+ paths I am interesting in. I find that REC533 may be a better model. Also, there's always debate as to what to use for SSN in any of those programs. Greg Hand, who wrote the latter variants of the xxxCAP programs says to use:

http://www.sws.bom.gov.au/Solar/1/6

The xxxCAP programs themselves may be downloaded here:

http://www.greg-hand.com/hf.html

It's hard to assess the user as Fremont CA station is the server and could be anyone who pointed it toward me.

https://wireless.vt.edu/symposiumarchives/2015_slides/document.pdf

My professional HF efforts are about 95% NVIS. It is not unusual to have multiple skywave components but also groundwave out 100's of KM. My work involves use of waveforms that accommodate doppler and multipath so operation is still possible but the TDoA scheme has no way to overcome that.

This tool helps with RX selection http://ve3sun.com/KiwiSDR/index.php?TXcall=CHU Ottawa&TXfrequency=3330am&TXlatitude=45.0753605&TXlongitude=-94.3082902&propagationTX=1

There been some discussion about antenna gain and coax loss but perhaps more important is can your antenna "see" the birds. In exploring different antenna types, I learned a few things:

• many people think GPS sats are geostationary which they are not (I never thought that BTW!)
• many people think that the constellation of sats in uniform around the Earth, it is not
• depending on where you live there may be few usable sats to your north or south, in my case the former.
• if your sat view is like mine or similar, avoid aiming into the "hole", see the graphic below from my kiwi
• you can preview your sat coverage on a cellphone using something like GPS Status (Android)
• there are sites that show the constellations such as https://in-the-sky.org/satmap_radar.php

This tool helps with RX selection http://ve3sun.com/KiwiSDR/index.php?TXcall=CHU Ottawa&TXfrequency=3330am&TXlatitude=45.0753605&TXlongitude=-94.3082902&propagationTX=1

this technique seems potentially useful for what we do

http://dxcluster.ha8tks.hu/hamgeocoding/