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On Tue, November 27, 2018 8:56 pm, Mike Lichtman via Groups.Io wrote:
>

> Chuck,
> Just a thought — did you ground the two final heat sinks in any? way? (like
> to a metal case). They should be floating.? 73 Mike KF6KXG
>
>
>
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They have a insulator and plastic type shoulder washer on the screws aand
a little larger heat sink but tested before applying power each time
before applying power, the one bias pot messing a leg is the only bad
component i have found, will mayb replace and order new 510s ,,, little
done in with this thing for the moment, thanks for the thoughts
73 chuck

AndyH,

Don't know if the clock signals are interfering with reception, but some
noise is interfering with my scope measurements of the low level RX
signal path.? With no antenna and high audio, can hear a tone in the
background and significant microphonics from the ubitx board.? Not so
noticeable with antenna and signals.?? No encoder ticks...

To help explain the difficulty presented when trying to trace RX signals
through the chain, see the attached image. ? Hard to get a lock with
counter on the "noise" - jittering.? Sometimes, for some TPs, seems to
be in the 50 MHz range. It may be something other than clock signal...(?).

I downloaded the MAR-3+SM graphs.? They do show gain at 3 different
currents, but only down to 28 ma.? Was wondering about even lower
currents.?? ...But it seems to work, bringing the gain way down as the
current approaches zero (actually the device voltage of 5). ? Was mainly
wondering about linearity and IP3 at the very low supply currents.

Since my first Nano died, I am using Jim's raduino clone.?? FWIW, the
original Raduino began to work when I tried the good Nano in it. ? Now
have 2 working mother boards and one working nano.

Woody? -?? KZ4AK



On 11/27/2018 20:16, AndyH wrote:

If you've got so much clock signal floating around that you have
trouble receiving, you might want to find the problem.? My radio is
dead quiet with no antenna attached, as is my BITX40.? I can sometimes
hear ticks from the rotary encoder without an antenna, but that's it.

What sort of raduino-like-object are you using?
_._,_._,_
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The preamp performance and biasing will be affected by the impedance of the power supply feeding the phantom power as well as the amplitude of the input signal and the phantom supply voltage. The circuit was designed with the Icom mic circuit in mind which has 8V with about a 1.2K impedance.? The mic cartridge I used was spec'ed at -55dB I didn't attempt to measure distortion other than listening to the transmit audio through headphones using the monitor feature of the Icom transceiver to determine that audio was not noticeably distorted.? Over the air other stations commented that my audio sounded very clean and natural.

The audio sounded clean to my ear with the biasing shown but no attempt was made to optimize it for other radios or microphone cartridges knowing that there is not a universal standard for phantom mic power or microphone response.? ?

If the input is driven hard enough to push the 2N3904 into saturation on positive input peaks the negative output waveform would be clipped.? That asymmetry would be seen if the biasing of the base was slightly high and if the input was being driven at a higher level than a typical dynamic microphone cartridge produces.? It all comes down to a number of variables in both the radio and the microphone so biasing might need to be adjusted to optimize for a particular radio and microphone combination.??

It should also be noted that if the alternate circuit (no phantom mic power available) is used, a resistor will be needed in series with a regulated supply voltage to raise its impedance or the preamp will not operate in its linear region.? Since there are a multitude of potential suppy voltages available in transceivers? the correct resistance value will vary but most likely fall in the 1K to 2K range for most radios.

73 - Paul - K8PD
?

What are the components Q942 and Q952 for? These were missing from my factory assembled board. The main problem I am having is each time I power up the receive works ok etc, but the second I hit the cw or ptt key the finals blow, drain shows grounded.. Three times in a row now, first time i thought there might have been a shorted wire when mounting board, no and blew a second time, check for shorted land etc. and the land from power in to the finals was burnt into, fixed with small jumper, repalce finals for third time and checked for shorts etc. best i can. made a temp fuse by using a one strand of small copper wire to postive connection and it burnt almost on contact, tried again and the receicer works as before? but also just as before the finals went, saw what i thought was la little some from maybe a bias pot not sure, just pulled the finals again.? Just about to give up on the project but maybe some of you could give me some thoughts , advice , help anything at this point.... :)

chuck

Looking at:

and?
Looks like there is a Falcon 9 going up in the next day.

Nov. 28 Falcon 9 ? Spaceflight SSO-A

Launch time: 1831:47 GMT (1:31:47 p.m. EST; 10:31:47 a.m. PST)

Launch site: SLC-4E, Vandenberg Air Force Base, California

All the best.

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