Turkish RDVV low power problem

Maximus · Post by **Maximus** » Fri Feb 03, 2017 2:25 pm

Yes, I fitted 3.3k resistor after taking the picture and also fitted a heat sink on the final. Basically I'm only getting a very low signal from the oscillator. The pll is locking fairly quickly.

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Radio Garfield · Post by **Radio Garfield** » Fri Feb 03, 2017 2:59 pm

Maximus wrote: ↑Fri Feb 03, 2017 2:25 pm Yes, I fitted 3.3k resistor after taking the picture and also fitted a heat sink on the final. Basically I'm only getting a very low signal from the oscillator. The pll is locking fairly quickly.

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Measure the output power from the BFR96. It should be between 0,2 to 0,5W. Lets rule that out. After that we will go further.

And please verify is that oscillator and buffer working on correct frequency that You have set with the PLL. Display information LOCK don't necessarily means that PLL locking the frequency. We want to rule out the situation that transmitter goes out of lock and transmitting somewhere very far from set frequency and output stage is not matched to that frequency and give you very low signal. If You have f-meter then check it please.

Let us know.

Radio Garfield · Post by **Radio Garfield** » Fri Feb 03, 2017 8:18 pm

Albert H wrote: ↑Thu Feb 02, 2017 10:08 pm If you think about it, the 1kΩ and 680Ω are in series. That's (effectively) 1k68. The 100µ capacitor in series with the resistor is part of the PLL loop filter. The probable reason he broke the resistor into two parts was to give him a jumper where he needed one - without using a piece of wire. It's a PCB layout trick that I've employed from time to time.

Also, resistors in series or parallel is often a cheaper way of getting an unusual value - E48 resistors cost a hell of a lot more than a couple of E12! One VCO that I use a bit demands a 9p capacitor. I can buy 9p1 parts from some suppliers (or I can select from a pile of 10p and 8p2), but it's far easier, cheaper and less time-consuming just to put two 1% 18p caps in series.

Component selection is often a case of economics!

I never heard it can be done that way.

Thanks again Albert.

Maximus · Post by **Maximus** » Fri Feb 03, 2017 8:31 pm

Thanks Garfield. Will have a look when I get the chance.

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Maximus · Post by **Maximus** » Sun Feb 05, 2017 3:22 pm

Dug the scope out and think I've found the problem. It'd help if I fitted a regular bfr96 instead of the bfr96s version?

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Maximus · Post by **Maximus** » Sun Feb 05, 2017 3:57 pm

Ignore the last post it was an ordinary bfr96 that was fitted.
I did however fit a bfr91A. I don't think that would affect it.

It is definitely one of the two bfr transistors that are playing up. Given up for the day, it's getting cold outside.

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Maximus · Post by **Maximus** » Mon Feb 06, 2017 2:15 pm

All sorted now. The 1nf decoupling cap between the oscillator and bfr91 was open circuit.

Thank for your help everyone.

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Turkish RDVV low power problem

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Turkish RDVV low power problem

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