hello, im from Argentina country...sorry my inglish is a bit bad i build this transmitter----it is currently giving 11 watts
I want to use only 13.8 volts -- to modulate I am using a TDA2003 amplifier and a transformer 5:1 ratio.
the transformer is 80 turns primary and 400 turn secondary..----all in a core of approximately 6x6 cm or similar to 12v 1amp transformer box.
I know that the SWR power meter can not show modulation....but I watched videos on youtube and I know how the needle should move when a person is talking...say heeeeelooooooo and the needle goes up.
well ... the problem is ...I hear myself very well but people say that I have "low audio". the needle moves backwards in my swr power meter!and it moves very little aproximately 10% I tried to change the amplifier by the tda1554q (22watts) and it improved but only a little
It's hard to tell what's going on without an oscilloscope but it sounds like positive modulation is simply topping out and unable to push the IRF510 far enough to get equal positive, and negative peaks. I'd suspect either your modulation transformer is saturating and unable to drive the current harder into the positive range or your MOSFET is simply unable to push the full 44 watts (11 watts carrier) for 100% modulation. I'm not even sure if that circuit is capable of 40+ watts continuous so 10-11 watts may be asking a bit much when modulated. If I were you I'd back off the power a bit and try to achieve 100% modulation and see where that lands you for carrier power and work up from there. Also check your power supply closely and monitor average voltage on modulation peaks to make sure it's not bottoming out from large current drain.
Post by HighMountainRadio on Apr 19, 2018 7:34:59 GMT -6
Greetings hfwaves !
I concur with the information and excellent advice given by Kage ! I absolutely agree with his analysis of your situation ! It is normal, in this situation, for you to be seeing your SWR/Power Meter display a 'drop' as you are witnessing.
Best wishes and welcome to the forum ! Thank you for joining us here as a new member of our great community that Kage has so generously provided us the opportunity to enjoy ! We look forward to your future participation here and you will find many, very technically proficient members here, more than willing to assist you with your questions !
73... Spooky...
"Knowledge Is Always Made More Valuable By Sharing It With Others !" Always Remember To Be Kind ! True Greatness Often Has Very Humble Beginnings ! Help A Kid Out Today ! *** High Mountain Radio *** "Broadcasting From Somewhere High In The Remote Appalachian Mountains"
I did a test...lower the power of the carrier to 6 watts(lowering the voltage in the drain, before the modulation transformer) ....and everything remains the same (
I think I'm going to have to get an oscilloscope
maybe I'm modulating correctly and my swr power can not notice-- I have an SDR, I have to look for a plugin that seems to measure the amount of modulation.
I am confused ..... what difference is there between these two videos? look at the power meter in both cases
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