Well this video helps a whole lot. Thanks for making it.
I was consulting this transponder passband table I made while watching the video:
In your video it definitely looks like the passband is shifted in your video. Paul Stoetzer, N8HM told me he thought it was less sensitive on the edges, and this shows that too, which makes it harder for me to decide where it begins and ends, as it gradually drops off. I'm not sure it's exactly -5KHz/+25KHz, but it definitely looks off. If you had a waterfall that would help too.
Has anyone else seen this?
73, John Brier KG4AKV
On Sat, Jan 8, 2022 at 12:31 PM Herb Sims [email protected] wrote:
My fig is a Yaesu FT-847.
Here is a video I shot of the most recent pass showing how, if you use their published Uplink and Downlink frequencies (which you supplied in another post https://www.amsat.org/wordpress/wp-...Amateur_Radio_Satellite_Users_Manual_V...) then the BPF for the uplink of +/15KHz is most definitely skewed to -5kH/+25KHz. As I walk the uplink (with matched offset for the downlink) you can hear my signal roll-off at -5KHz and again at +25KHz.
Do NOT use the larger frequency boxes as those are Doppler CORRECTED - you will be looking at the frequency above the Doppler shifted values (much smaller font) for the TRUE uplink frequency.
Now assuming their documentation is wrong (i.e. the value of the center of the passband) then if you assume the CENTER of the passband to be 145.880 (UP 10KHz on the uplink) and 435.170 (again DOWN on the frequency) THEN you will have +/-15KHz passband.
I think my math is correct on the change of uplink and downlink CENTER frequencies.
What radio are you using? You're the only one who has remarked about this. I really think you just have some settings wrong. Can you set it to normal/non-inverted? Maybe the display is backwards.
On Fri, Jan 7, 2022 at 9:59 PM Herb Sims [email protected] wrote:
Working HO-113 right now....The bandpass is most definitely -5/+25KHz....a simple "walk up/down" of the transmitter shows the roll-off very easily.
On 1/7/22, 4:30 PM, "John Brier" [email protected] wrote:
Did you see my response to you on QRZ? https://forums.qrz.com/index.php?threads/observations-of-ho-113-formerly-known-as-cas-9-formerly-known-as-xw-3.794829/#post-6067512 It sounds like you had Mac Doppler in normal/non-inverted mode but XW-3, like almost all linear sats (except AO-7 when it is in the 10 meter uplink mode) are reverse/inverted. The -5/+25 KHz you mentioned equals 30 KHz, the width of the passband, so it really sounds like that was your issue. I'm going to remove reference to this non-symmetrical passband issue from my article if you can confirm that's what caused the problem. 73, John Brier KG4AKV