Re: Ubitx average SSB output

Mike aka KC2WVB <rb5363@...>
 

Quick question. I think that what your doing is the following: Presumably the audio from the mic's audio line that carries the ac with a dc offset is first passed through a capacitor to block the dc and then used as input into a small preamp, perhaps an op-amp before anything else occurs. If so, then I imagine by changing the value of the named resistor you are increasing the gain associated with the op-amps behavior and consequently the audio's amplification above that of what otherwise occurs.

If my conjecture is near valid I am wondering if there is another way to do this such as by using a little stand alone pre-amp immediately after the microphone and prior to the assumed dc blocking filter. I only wonder because one could then control the gain and I do not have the right stuff for SMD removal or replacement.

On Fri, May 25, 2018, 8:30 AM iz oos <and2oosiz2@...> wrote:

I have changed just R63 so now it is 24 ohm (I added 2 ordinary 100ohms resistors in parallel) as suggested. I confirm it increases the average power to the right level given the stock mic element. Could it be further decreased, let's say 10 ohms?


Il 27/apr/2018 16:26, "Howard Fidel" <sonic1@...> ha scritto:
1K. Change one or the other, not both.


On 4/27/2018 10:14 AM, iz oos wrote:

If R63=24ohm what value should R65 be?


Il 27/apr/2018 16:03, "Skip Davis via Groups.Io" <skipnc9o=yahoo.com@groups.io> ha scritto:
Howard did you also change out R65 that was posted here too.
By the way the parts showed up here yesterday, thanks a lot. Now to find time to install them.

Skip Davis, NC9O 

On Apr 27, 2018, at 09:57, Howard Fidel <sonic1@...> wrote:

Yes. Change R63 to 24 ohms. The earlier rev boards had 100 ohms there, and V3 has 47. I put another 47 ohm resistor in parallel with the one on the board. Now I don't need to yell into the mic.

Howard WB2VXW


On 4/27/2018 3:22 AM, iz oos wrote:

I have checked SSB output for the Ubitx using a Softrock sdr receiver. The carrier is well aligned and the filter gives a very good shape. Whistling is gives full output with the stock mic element. The output seems clean but the average power during normal speech seems to me a bit low. Is there an easy way to increase it? 73, Franco




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