I heard Tom (VE3THR) for a moment or two, but the noise level is AWFUL!
--
John - WA2FZW

You got it! I do recommend the 3 position SPDT on-off-on switch idea, though, for the front panel control. Otherwise, Kees included those shorting plugs for you. You're Welcome! 73, Don

I have a spare stock Raduino. Email me....

73 Nick VK4PLN

I'm calling CQ on 7277 but have a S9 noise level here, so not sure I'll hear anything!
--
John - WA2FZW

Just so I got this, the 3 pin connector replaces the coax connections so the only other connections are the +5 Volts and the twisted pair from the volume control?? Looks like a very elegant solution!? I like being able to mount the board securely.

Thanks!

UBITX_CEC_Vxxxxx_16P.hex? : It is the LCD equipped with uBITX. Default LCD, 16x02 Parallel LCD This is the one you need

Sorry I cant help anymore as it works fine for me.

I did this of course.
I checked the box in the Ubit Manager on the PC, pressed encode and reuploadet it. Turned the radio off and on again. No change :-/

Thanks for sharing Mike. I found that most of my 2N7002's had about 10 pF output capacitance, the specs show up to 30 pF. Still not bad compared. I found that I got about 23 dB maximum attenuation with the shunt connection. Did you make a quantitive measurement? Hard to tell much from the audio clip but it sounded much like my first circuit (simple shunt). Makes for an easy mod, though! My next step was just to hang another 2N7002 across the output of first IF which added another 15 dB or so. The series element made the big difference, though. 73, Don

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Just to elaborate a bit: if you look at the datasheets for the different FETs above you can see that the output capacitance varies a lot from large size fets to small size fets. If the output capacitance is too high, you loose control over the AGC shunting effect / series resistance effect since ther will be lower isolation due to the capacitance.

You need to run Ubitx Manager on your PC.

Philip G7JUR

Hello everybody,

I just installed ND6Ts AGC Circuit and wanted to turn on the S-Meter in the firmware according to the instructions on
KD8CECs Homepage.
However I just can't get it on the display.

Whatever I selection of options I choose,? the only things i get on my standard 16x02 Parallel Display is

VFO A, VFO B, Mode, and tuning steps. I can change which VFO is shown first (toggling) or switch on (and off) rotation,
but I am not able to get my callsign or the S-Meter on the display.

The S-Meter signal is there - i checked it in the setup, ADC Pin7 gets read and a reasonable value is shown.

Am i doing something wrong? I thought first I may have accidently uploaded the 16x04 P Firmeware and reuploaded again -
this was not the case.

However according to the pictures (http://www.hamskey.com/2018/05/setting-smeter-to-ubitx-with-cec.html) there must be a way.

Any help would be appreciated.

Sascha, DL5SMB

I believe there is an nonlinearity problem on some of the newer V4 uBitx radios (the one with transistors in the final audio amp). Two of my radios had this problem.
The problem is that the two diodes in the final amp doesn't make a voltage drop that is larger than the drop over the BJT B-C junction drops, so there will be a crossover distortion problem.

I did a mod: cut the trace between the diodes. Soldere in a 500 ohm pot paralelled with the a 125 ohm resistor. I adjusted the pot from a low value and increased the resistance until the nonlinearity disappeared by listening to a moderately strong cw signal. I checked the lower transistor so it didnt become too warn from the quiescent current.

73s

The uBitx is prone to overload if there are strong signals. I have done some tests with an analog AGC detector and different FET shunts on the RX line after the relay before the first mixer.

I used a similar detector circuit as other people have published here. However, I used a BC548 as an audio amplifier instead as this is a very common bipolar transistor that is highly available with a high Hfe. The Hfe is approx 200x on the B series . The gain was set to approx? 200 in a common emitter amplifier. I take the signal from before the volume control. (Be aware that the volume control pot affects the impedance a bit so the level changes even if you tap on the hot side of the audio pot ... ). The detector is two 1N4148 diodes. There is a 1uF capacitor and a 1Meg resistor to set the first order RC circuit constant.

I tried with different FETs I had laying on the shack. Since this fet is used as a is a RF shunt circuit, it is not possible to use a JFET directly since JFETs are depletion mode.

By using an enhancement mode N channel Mosfet the RF shunt presents a high impedance to the AGC amplifier / recitifier. However, the output capacitance of the RF shunt Mosfet is a bit critial. I tried with a FQP30N06L (output capacitance in the 300pF range) and a IRLIZ44N (output capacitance in the 400pF range). Those presents a too low Z to the RF path since XC = 1/(2*pi*f*C). This is around 28ohm at 14 MHz, which will cause attenuation when the AGC is not active.
Instead I used a BSS138L N mosfet that I took of a level converter board I had laying around (I cut the board in four with the SMD part on to ease soldering). I soldered the mosfet controlled RF shunt directly to the relay pin and to ground on the back side of the uBitx circuit board instead of going in on the top side of the board as some other have reported on this forum. See pic.

Shunt mosfet for RF AGC:


The AGC seems to work well even with just one shunt element.




Testing with and without AGC:

Bill, The trace cut is shown under the manual . You are correct with the destinations but that trace between them needs to be separated anyway and this is a convenient way to do it. The AGC board is designed so that if you use a 3-pin right-angle header instead of the 2-pin shown, you can plug the board right in. Instead of bending the middle pin to meet the traces like the others do, drill a hole through to the ground plane on the underside just large enough to accept the diameter of the pin and bend the pin over to go through it. Scrape the coating off of the area around the pin there and solder it for an excellent ground return. Between the glue holding the new header to the board, the mechanical support of the new hole, and the three solder connections it becomes nice and sturdy. If you placed that connector carefully, the new board will plug right in with enough clearance to the other parts. Bring over your twisted pair from the volume control (or the plug), and your +5 volts (like the green wire from Raduino pin 3 and decide how you would like to select your AGC release timing.
Otherwise, bring those two coaxial cable center conductors to their respective "In" and "out" holes, their shields to the center hole between, and jumper between points #1 and #2 as shown.

My best advice is to take your time. Plan a lot, Work slowly. You want to make the experience last, right? Like taking a vacation. A person doesn't want it to be over quickly!
73, Don

I'd like to build a uBitx completely from scratch. I've been looking at the circuit diagram and I cant figure out how to wire up the raduino. How would one make a raduino from scratch and wire it to a uBitx? I'd preferably like to be able to build it on a proto board. Would it be doable for someone with pretty good experience in wiring pcbs and proto-boards to build a uBitx from scratch on a proto board. If not does anyone have pcb designs for the uBitx and the raduino. And does anyone have a list of everything I would need to purchase to build a uBitx. I don't want to ask to much but if anyone has built a uBitx from scratch and has files and such that would be great. Thanks a lot, in advance.

Between the microR2 and the miniR2, yes, they listen easy.
The most noticeable property is listening to a pile up, rather than a mis of heterodynes
and noise you hear what sounds like a busy restaurant with everyone talking.? Its then
up to the ear to pick it apart.

The closest I have to the Drake is the Atlas 210X, it was a single conversion HF IF?
solid state radio when that was becoming common.? Its twist is no RF amp.? If we
get past the VFO drift some suffered it was a very clean radio to listen to on a busy
band.? I was lucky to find two of them in functional condition missing things like Mic
and power connector and needing some minor fixes.? One is fully restored and
includes a few engineering fixes from back when and its a very nice, compact for
a 100W radio, and yet a very simple radio.

I've worked on Drake R4Cs and TR4s and they are very good but there are a set
of mods for them that make it an amazing radio.? The one feature was the PTO being
good and stable.? ? Yes, people mod radios even then!? Adding new technology
and knowledge to make a good radio better.

How a radio sounds and feel is why some radios I have get used more.? IT's that?
intangible better.

Allison

I installed my 12v auxiliary cooling fan in my uBITX earlier today to replace the unseemly box fan I had propped up over my open cased radio.? After I installed it and dialed in the temps I fired up WSJT-X to see if there was any performance changes with the fan on, well, lo and behold I discovered that I have a "remote digital fan on indicator" on all bands so I'm assuming it's getting in via the audio circuit not RF side.? It also turns off when the fan does.? Perfect, I think I'll leave it.

Behold: