Re: Possible PA low output problem. Problem SOLVED
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Tom
Outstanding. I would just leave the dual diode out and make it like your other radio.
Did you notice that you had carrier without the mic plugged in? I have seen a couple of postings about having carrier without the mic.
Keep up the good work and reporting your findings.
Randy, K7AGE
On Wed, Feb 8, 2017 at 6:39 PM, tcmedlin1 via Groups.Io <tcmedlin1@...> wrote: Success ?!!!! ? I put the scope on both the working bitx40 and the low power radiuno again tonight.? Made comparisons. The bitx runs 7 watts and the radiuno would only do 1 w into a 50 ohm dummy load.? Both radios had a 1004 Hz tone injected at the mic. ?on the scope the AC signal was good up to the 2 diodes d-15 d-16. on the bitx. On the radiuno Farhan has replaced the two diodes with a single dual diode .? AC signal level look good going into both sides of the dual diode.? But coming out the dual diode, signal level was very very low and distorted. (all this time the receiver did seem to be receiving but not sure how well) I removed the dual diode and with a fluke DVM measured the front to back on each side. They were identical at 20 M ohms and 80K ohms.? So it appears that the dual diode tested ok with the meter.? I did not have any high speed diodes so I took 2 silicon diodes (typical voltage rectifiers) and soldered them in to replace the dual diode. The receiver came up and now the transmitter is putting out 5 watts. ? ? So changing these diodes cured the low 1 watt problem. Now I need to order a diode replacement.? Not sure I want to use the same diode number.? As I said this one checks good on dvm but does not work.? I may just order two seperate 1n4148s like the original board and install them. ? ?Farhan said that the new dual diode was pretty much matched on both sides so he took out the balance pot .? So maybe i would put in a balance pot and the old original diode replacements.? Are many people having this low power problem that have the radiuno with the dual surface mount diode? Tom ?W5KUB We will be announcing this breakthrough on our weekly ham show Amateur Radio Roundtable at 8 PMCT on Tues night.? Also if anyone from this group would like to be on the show and talk about the bitx we would love to have you.?
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