DV Scotland is an independent informal group of radio amateurs, mostly based in Scotland, who share a common interest in Digital / Analogue voice systems. ru-vid.com/show-UCdswor_tH5l_h8zGjqZ9c8g
you shouldn't have two peaks, you should be able to get both cavity peaks to become one, when they become one you have an even better peak. maybe try the coax lengths in between cavities and something was still wrong.
In the end, I sent the whole thing off to kgelectronics.com/ for alignment. I haven't gone back and looked at that test. That said, I recognize the patch cable I was using, and I know that's a pretty crappy cable. It's entirely possible it WAS WWV causing the issue.
Thank you sir! I just tuned a “Fingu” brand UHF (T-Band... yup.. you read that correctly) The public safety communications world LOVES President Donald J Trump! He cleaned up the Obama “spectrum giveaway” to his DemonCrat pals w/ the 2012 “stimulus crap” The duplexer is a BpBr rack mount unit and is supplied by /\/\otorola with their GTR8000 series repeaters. Nice device, but nothing seems as solid as the older gear. I don’t have an IFR anymore, so I used my Rigol DSA815TG. It’s a fairly cheap spectrum analyzer w/tracking generator. (Under $2k) Thanks for your videos... this one gave me the motivation to get some of my garage “pile-o- gear” tuned up and donated to the quite worthy volunteer fire/EMS world. 👍🏻
Hi Michael, have you tried to check your "Failsafe settings", like "Failsafe Minimum Distance in centimeters"? Had this set wrong once and the throttle has not come in as I was too close... Also, check your setting in "Advanced tuning" in "RTH and Landing Settings" and "Fixed Wing Navigation Settings" the "Loiter radius [cm]" - must be right. Mine is set for 100m, but beware it is in cm! So it must display 10000. I missed a zero once like this: "1000" and then it doesn't work... Good luck and let me know how you get on! Best Regards Mike
Mike, I think I had my nav_fw_bank_angle set too high. It was set to 50 during this flight. I believe that, along with a small loiter radius (nav_fw_loiter_radius = 5000) led to the failure. I increased my loiter radius to 10000 and reduced the bank_angle to 30, and didn't have subsequent problems.
Michael, I have struggled with cable lengths when tuning duplexers. After tuning a duplexer, if I change the two cables with different lengths, the IFR shows the tuning at different frequencies than first tuned. What is the correct cable lengths used to tune a cavity/duplexer. 300/f x VF x 1/2 wave length?
It was another wing more or less identical to the one I was chasing. It was a 3's battery and I ran it very very flat. I probably should have landed even before that chase began. Once they drop below about 10.5 volts they plummet.
Thanks Michael. I learned a lot until the part where you "diddled the knobs" then I spent 10 minutes rolling on the floor laughing and lost track of what we were doing. Otherwise very informative!
Nice video, There are a couple of things you should do to tune it better. Set the tracking generator to HIGH when checking the notch frequency. At that it will put out about - 3 db instead of -40 you are using . The duplexer will have over 80 db,more like 100 db of notch. You will not see that unless you go to the high output. You may only be getting 70 db of notch instead of 100 or more. Always use double shielded cables or better at those levels of signal. To tune the pass frequencies using a return loss bridge would be best, but if you do not have one you are fine with that part of the video.
Very cool with the sound and flying rubber-bits. That's 20.6 miles up, so 3x higher than commercial jets, more than double the height of the retired Concorde.
Michael that was a great explanation. Very well presented. Thanks for taking the time to do this. I believe I can use this to test mine out. Got to see if I can round up a uhf duplexer to try it on. Yes I have the homemade set but a commercial set will confirm I am doing it right. Thanks again my friend. 73. I am sure I will have more questions later So may shoot you an email. Buddy.
Thanks, Buddy. I'm glad I could give something back for you to look at. I've spent hours and hours learning from your videos. You da man! ;-) Please note, I'm no expert on duplexers. This is my first rodeo tuning one. I just noticed that the curves looked MUCH different from your home made duplexer test, so I wanted you to see what a commercial one looks like on the IFR. Enjoy and keep those great videos coming! Thanks & 73 - Mike
Thank you Michael. I now have the idea on how to start it. For the past hour I have been playing with my homemade duplexer. I do not have enough "Q" to notch the frequencies. So I need to trim my pick up inside the duplexer.. I can get a good define notch on each side but the isolation is terrible. I know what I have to do to make them better now. Thanks to your video got me on the right track. Going to see if I can locate a uhf duplexer commercial built to play with. Buddy
Fantastic stuff!!! Thanks to Jim NXZ for sharing with me. I was ready to help track her starting at Conesus NY. Now I know why we couldn't hear her. Next time we will :-) Best 73 de KB2RMC Tim
