开云体育

Ashar
Mazeltov on the awesome satellite work
Regards
73
Laurence Oberman

Charles French,

One way to find out... try it.? However use a good pot.? The shields go to one end of
the resistor and not to any ground near the pot and both shields are used at ground
where the pot was on the board.? Short leads and good lead dress keeping the two
shielded wires away from the board. The likely problem is RF feedback and oscillation

Me I'd dial it down as the sweet spot for passably decent IMD was found to be
around 2W anyway (for 80/40/20).

The current home brew radio I use with the 1208 is designed for it and the internal attenuator
was dialed down to 3db so all I needed the radio to deliver was about 3mW! Its dedicated to
the 1208.? Why?? Running the transverter and developing power to dump in resistors?resulted
in a power hungry system (nearly 40W in for about 10 out).? Doing a TRX specifically
for that lowered that to less than 26W (at 11W out) making it far more battery friendly.

Over the years I had my first Hb 20mSSB (3.5-4W),? WM20 (about 3w), and a TT505 Argonaut
(about 5W)? and all of them at one point or another drove the 1208 until I built a low low power
radio as a driver.? ?It iss a fun backup to my HF-6M (Eagle) and TT526 6n2 and five HB 6M
monoband radios.

Allison

Go Exseed Space!

We’re all watching on this monumental moment. wow 64 sats deployed all at once.


Lets go!!



Joe
kd2nfc

I had removed the "Extra" purple wire that is an ADC input often used for an S meter.? I assume that you have a v3 or v4 ubitx (I have the version 4).? You explained in one of your posts that the problem goes away when you ground the output connector on the uBitx with your hand.? That is pointing to the RF coming back on the shield of the coax.? Do you have a 1:1 balun on the dipole?? If not, again I would look to grounding and adding the balun.? MFJ or others make both baluns and full cut antennas.

Have you tried grounding the case?

If problems persist, I would also look at adding ferrites on the control lines from the encoder to the Raduino board.? That was one of the things I tried, again, helped but the grounding and ferrites on the feed to the antenna were the things that solved it for me.

I would also verify that you are not over driving the audio: I could reduce the problem by lowering my mic gain.? This also reduces the power out, so may be just a function of the correct frequency and power getting back to the nano.

Since all was well with the plastic case, I am still leaning towards the RF coming back down the coax brain, and surrounding the nano.? If there is unbalanced RF on the braid, putting the uBitx in case that is not grounded may not have helped.

From another post:

RF pickup is a bit unpredictable. Long wire, more pickup

ONLY if they use ADC in way I described as no push button board circuit on web.

Then, 0.1uF on ADC line and a good grounding point, short leads on the
Arduino board

ADC is mega ohm high impedence input. Can add
from push button long line
10k ohm series
0.1 uF to ground

Hi, and thanks for the informations. I would like to say that my antenna is an attic dipole for 40m and I use 50 ohms coax. What I didn't said in the beginning is that I disconnected the display and I used some wires to connect it to the Raduino. But the Raduino itself is still in the original socket. Can it be this happening because of the display wires ? And somebody mentioned above about a capacitor of 0.1uF in the ADC line... should I put this in paralel or in series with ADC line??

Is this kit still available or did I miss it?

Thanks,?
Scott

A two tone test will check for IMD (intermodulation distortion, google it!).
It does not check for spurs or harmonics, which are the primary issues with the stock uBitx.

IMD can make your signal sound bad, and cause interference to those operating nearby on frequency.
If you have bad IMD, you will probably be told about it.
The stock uBitx with the mike gain set to a reasonable level will have enough IMD to be
slightly alarming when looking for it with a spectrum analyzer.
But the IMD products are way down (50dB or so) once you get a couple khz away.?
And thus it's a legal transmission anywhere AM phone is legal (at least with respect to IMD).
When transmitting at 5 or 10 watts, the IMD is probably not perceptible to someone using an adjacent channel.

If you have bad spurs and/or harmonics, you will be interfering with operations
on totally different frequencies.
For example, when operating at 28mhz, there's a? spur at 45mhz-28mhz=17mhz.

This particular spur is due to the 2*45mhz second harmonic of the first IF?
mixing with the high side clk2 VFO.? The VFO is always at 45mhz+DialFreq.
In this case, the spur is at? 2*45mhz - (45mhz+28mhz) = 45mhz - 28mhz = 17mhz.?

We also have a spur at 12mhz, due to crosstalk within the si5351? from the BFO at clk0
into the VFO at clk2.? This 12mhz energy on clk2 goes through the mixer at T2 unmolested,
and continues on through the transmit power amp and the transmit low pass filters.

Harmonics are simple integer multiples of the operating frequency.
For example, when operating at 7mhz, we get harmonics at 2*7=14mhz and 3*7=21mhz.
The transmit low pass filters at L11 through L22 should take these harmonics out,
but the stock uBitx relays (and to some extent, the board placement and routing)?
allow the harmonics to sneak past the low pass filter.

Also, for various reasons, we have some carrier leakage, though not too bad.
This results in a not quite suppressed carrier riding along with our SSB signal,
sort of like an AM phone signal.? Not really much of an issue at 5 or 10 watts,
but it does make our signal a bit wider than it should be.

Spurs, harmonics, IMD, and residual carrier are why you should think twice
before?adding a linear amp to the uBitx.
Like any rig without ALC (automatic level control), increasing the mike gain
too much (or shouting into the mike) will result in IMD.

The Bitx40 has a much easier job with respect to spurs and harmonics.??
There is a 7mhz bandpass filter before the transmit power amp, which knocks out all those spurs.
And with only one transmit low pass filter there is?no easy path for harmonics to leak out.
With too much mike gain it will have IMD, and there is some carrier leakage,
but these are relatively minor issues.

Jerry, KE7ER

I AM VERY NEW TO THIS. I DO HAVE A WORKING uBITX HF RADIO TRANSCEIVER.

I DO NOT KNOW MUCH ABOUT PROGRAMMING.? I HAVE A QUESTION.

HOW DO I GET THE FILE OR FILES TO DECODE THE MD AND UCO FILE EXTENSIONS?

I NEED TO KNOW THIS AND WHICH FILES ACTUALLY GET DOWN LOADED TO THE

NANO?


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The problem is with your Mic connection!

Raj

I have a Bitx40 which was built from the kit and has been functioning rather well.

For no apparent reason the TX seems to have a problem (no TX)
I connected a RF meter to the radio and noted that when I key the mike the needle jumps and straight back down.
This indicated to me that some TX power has been supplied but not continuious.
Subsiquent keying of the ptt do not have any affect
I have changed the Mike , incase it was faulty. (and whistled in it too)
I also have a spare main board and I replaced it, with the problem persisting.

Any ideas on what further I can troubleshoot or test

i spent 4 hours on ians site and github. downloaded a dozen or so files, could not get anything going from there. i will builds my project some more then try again.i may be looking too hard. didnt understand the whole CEC thing.
thanks again,
DAVE N4LKN

With standard gain settings I would not suggest it stock on FT8 which is a 50% run time.
With a small fan blowing over the stock heatsinks the output transistors get hot on FT8 after 8 cycles

I have two ubitx and it takes a minimum of about a 2x sized from normal heat sink and small fan The easiest test is to put your finger against the transistor after running it.

That said I have about 3-4x heat sinks and a ducted fan over the finals on my other ubitx and run 20 volts through the finals without any heating of the transistors. Well I am sure that there is heat but it is being dissipated It shows 20 watts power output on a mfj meter.

On FT8 the digital power level control works pretty good for controlling the final modulation.

Antenna matching is real important too. Even a 1.4:1 makes a difference in heating.

Happens in every country. However if you feel hurt and you are convinced they did not act properly you may have the possibility to report this to other departments so they may see to investigate internally. Keep calm and ... them politely!

Warren discussed this in detail. TX IMD are quite bad, however it does not sound bad at all. Keep in mind it splatters if you shout into the mike. I will try the VOGAD add on, at least it should deliver an almost constant mic input.