Sorry for off topic guys, but I recognized Josh from 20 years ago.? We had tcp/ip packet networks running on 2 meters.? Send me an email if you'd like to reminisce!

Jim Carpenter
wu1n@...

Hi Geoff,

Be sure the key contacts are very clean. My key will fail to operate the uBitx in CW mode if there is least imperfection. I installed the CEC software and that improved. It also has other features for CW that make it worthwhile. It is so easy to install that even *I* can do it.

I suspect that CW operation is an afterthought of the designers. Maybe not. I was wrong one time before ;)

73,

Bill KU8H

--
bark less - wag more

Hi ...why cant I get the tx/rx working on CW ????? I use the 4k7 pull up resistor as per drwg but when I press key the tx sends? R then back to receive ....if I leave the 4k7 out the tx goes into transmit sending R then flips back into rx and then tx again ...help !

On my yaesu I always set AGC to FAST for digital modes, AUTO for SSB.

Vince - K8ZW.

--
K8ZW

Non-operation?? I would check the wiring and integrity of solder connection.? If he is using Sunil's case and I/O circuit board - the latter is notorious for solder bridges.?

If encoder is not tuning smoothly - skipping frequencies with too big jumps - this strikes me as a bad encoder.? Of course obtaining a spare can aid debug.?

Curt

开云体育

I got 5 of these lately.? I used them with some code from the internet to change frequency on a RaduinoX.

Be sure to get the "Nuts" version shipped with the nuts!

These had serrated shafts and detents.

Mike, WA6ISP

A friend thinks he has a problem with the rotary encoder in his uBITX. Does anyone have the part number for it?

-- 
Mike Hagen, WA6ISP
10917 Bryant Street
Yucaipa, Ca. 92399
(909) 918-0058
PayPal ID  "MotDog@..."
Mike@...

开云体育

Fantastic. Thanks for your help Don.?

A friend thinks he has a problem with the rotary encoder in his uBITX. Does anyone have the part number for it?

--
73 Keith VE7GDH

Hi Daimon, I would suggest that you switch it out. With FT8 you will have several signals present within the pass band, some quite strong, others below the noise. Any strong signals that reduce your gain might push those weak signals (the interesting ones) down so low that they cannot be decoded. Just switch the AGC bias ( J1 on the kit, Q3 gate on home-brew version) to ground to disable it for your digital use. 73, Don

I have the ND6T / K5BCQ AGC kit to build and install and use my rig mainly for portable FT8 with a built in Raspberry Pi, with only occasional SSB use.

I don’t need the AGC for FT8, but if I install it, has anyone experienced negative impact on decodes?

I am thinking that if I set the jumpers to “short” (fast?) the. I might be OK, or should I have a switch to switch it in and out when using different modes?

thanks.

Daimon.
G4USI.

Hi Josh,

Very good points. I've been worrying a bit about the 120Mhz DAC, termination and signal length matching, especially as the DAC would most likely be connected through the mini PCI connector on the Arduino Vidor board. It may be possible to do without oversampling. Oversampling should provide an easier to clean up with the existing low pass filter signal. But, no oversampling may be OK. The tradeoff for oversampling vs more depth, on receive, could indeed be better with more depth. As nearby strong signals (such as a field day situation) could be in the bandpass of the roofing filter.?

Tom, wb6b

Very good. By the way, I do like your shroud and I appreciate your putting it up on Thingiverse.

Tom, wb6b

Hi,

?

I just received a Arduino MKR Vidor board. It is a higher powered Arduino with a medium sized FPGA included on the board.?

?

My thought was to add a fairly fast (around 120Mhz to allow oversampling) 10 or 12 bit DAC to supply the transmit signal directly to the low pass filter at Test Point 1. And use a 50Mhz 12 bit ADC (again to allow oversampling) for receive picking up the signal at test point 17.?

?

For receive this should be better than trying to push the ADC close to the antenna, as the digital receiver will then have a fairly cleaned up signal to work with and the signal frequency (12Mhz) is fairly moderate. In fact, if the frequency could be mixed down even lower, it might be possible to use fairly low speed ADCs.

?

Another advantage of the band pass filtering ahead of the ADC for receive is there should be no need for quadrature (I/Q) mixers, and dual ADCs, as the digital processing will not need to determine which signal frequencies are above and below the center frequency. (Internally, for SSB demodulation, depending on method, there could be I/Q processing. But that can all be handled in the FPGA).?

?

So the uBITX could be a really good starting point for the RF parts of a FPGA SDR transceiver. It's possible the specs for the ADC and DAC chips could be toned down a bit and reduce the costs further.?

?

Here are a couple of possible designs that could be used as a starting point.

?

Tom, wb6b

I choose to run the fan full time. The reason I run the fan while receiving is that it pulls heat out of the small heat sinks.

On my original ubitx, I run the finals at 20 volts and use it for digital. The heatsinks that I use on that radio weigh about 4x as much with a lot more finning. The fan is a regular 3" computer fan with a snug fitting shroud. I can run the transmitter at 20 watts into a dummy load in cw mode for an indefinite amount of time without making the transistors hot.

This set up is not as effective but it pull heat out of the heatsinks. I may well use larger heatsinks and design a different fan shroud.

Not planning on running a temp controlled fan nor just run it whilst the tx is on.

The power to the transmit wire is always connected so
there would have to be a relay to only apply power to
the relay when the PTT line is enabled. More complexity.


There are many schemes to make work what you suggest
which is essentially a good idea. Big rigs do this. Would
need a relay and a relay driver that is connected to the
PTT line. As the old saying goes, "It's doable."

On the other hand, drawing air out of a rig's box is the
best way since it is removing the hot air. But if the fan
is placed so air is forced into the box at the bottom, the
placement of the fan reduces the sound of the fan if the
box is elevated on feet, for example. In other words,
placement of the fan is an essential element in the noise
produced. Also, if the fan is mounted on rubber bushings,
the sound is not transmitted mechanically back into the
box. If the box is a hunk of iron, no problem but most of
them are small and light which invites some coupling
of the vibrations back into the box and makes the box
a soundboard for the noise. However, most sound is
acoustic and with mine, all I heard was wind noise and
this is why merely slowing down the fan is a way to
eliminate a lot of the sound. The exhausted air does
not need to be very high so slowing it down does what
is needed: Removing the hot air from the box. The
proper value of resistor is therefore a way to do this
and it's now something new or unique. Also, the fan
I used is essentially like the one suggested previously
only slightly larger. It was a 2-in fan measuring from
side to side.

Bob — KK5R

--------------------------------------------

I did some testing on my v4 board and found interesting correlation (though not able to verify mathematical accuracy):

The lower the signal at TP1 in CW transmit, the lower the output power.? This would have nothing to do with the LPFs either in the front end prior to the transmit amps, nor on the output.

This went on until above 14mhz, where the power starting dropping with out a decrease in level at TP1.

To me this suggests that there is something in the way that the design unbalances the first mixer to allow for the "bleed through" of the changed frequency of Clock#2.

I then used a constant tone through my mic for the ubitx using a signal generator connected to a powered speaker.? I kept the postion of the mic constant and changed the bands.? With this test, the 7.2mhz signal had more power than the 14.3mhz signal.? This suggests that the transmit power that others and I have been measuring is not indicative of the SSB power.

Again, this points to the CW process of unbalancing the first mixer has having side effects that impact power on some of the bands.

I should also note that the signal I measured with my scope was not at all sine wave clean in CW mode. It was almost square.? Would also explain the large amount of harmonics that I have measured with my inexpensive RF Explorer SA.

At this point I will be going back and coming up with a better way to inject a 1 or 2 tone audio signal into the uBitx to then measure the harmonics.??

Has anyone else seen this type of behavior?

73
Evan
AC9TU