Date   
Re: Cooling fan Shroud

Bob Lunsford <nocrud222@...>
 

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

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

On Thu, 1/17/19, Tom, wb6b <wb6b@...> wrote:

Subject: Re: [BITX20] Cooling fan Shroud
To: BITX20@groups.io
Date: Thursday, January 17, 2019, 9:02 PM

Another easy solution is
to simply run the fan from the 12V transmit power, assuming
that is not what you are already doing. No reason to run the
fan while receiving.

Tom,
wb6b

Re: Cooling fan Shroud

_Dave_ K0MBT
 

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.

Wild and crazy uBITX, Arduino FPGA idea. #arduino #ubitx #sdr #fpga

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.

 

http://k6jca.blogspot.com/2017/02/an-fpga-sdr-hf-transceiver-part-1.html

https://www.tapr.org/pdf/DCC2010-FPGA-BasedTransceiver-KD6OZH.pdf

Tom, wb6b

 

Re: Cooling fan Shroud

Tom, wb6b
 

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

Tom, wb6b

Re: Wild and crazy uBITX, Arduino FPGA idea. #arduino #ubitx #sdr #fpga

Joshua Blanton
 

Hello Tom,

I think that's a very interesting idea - a couple of thoughts that might be useful (or not) - you may already be well aware of these:

1) 120MHz signaling can be hard to wire, especially in wide parallel buses - this may be difficult to wire without signal integrity errors, unless you're laying out a board for the task.  12-bit sampling just increases the number of lines you're trying to keep synchronized.  Modern FPGAs shouldn't have an issue running I/O at 120MHz, but you will probably need terminated signal paths and matched cable lengths to ensure data transport

2) Your dynamic range will be limited by the 10- or 12-bit sample depth; oversampling can help, but it might be more effective to get a 14- or 16-bit ADC at a slower clock rate than to oversample at a lower depth.  It's been a while since I've looked at the math; I'm sure several people on the list are smarter than me about this!  If you incorporate AGC, this should help considerably (but close-in signals will still affect your dynamic range, obviously).  I might even consider sub-sampling, although I don't know if you can get ADCs (significantly better than 16-bit, for reasonable cost) that would support 12MHz sub-sampling...

Very, very interesting - I've been thinking about building just such a configuration (at least single-conversion, and then sampling at an HF IF with a fast ADC) for a while, but I'm not really a hardware guy - and I would feel compelled to lay out the ADC and FPGA portion, at minimum, and sounds tedious.  I've seen high-speed FPGA designs, and I know that I'm not competent to lay them out :-)

Anyway, good luck - I'd love to hear about the project, if you proceed!

Josh, KB8NYP

On Thu, Jan 17, 2019 at 10:11 PM Tom, wb6b <wb6b@...> wrote:

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.

 

http://k6jca.blogspot.com/2017/02/an-fpga-sdr-hf-transceiver-part-1.html

https://www.tapr.org/pdf/DCC2010-FPGA-BasedTransceiver-KD6OZH.pdf

Tom, wb6b


Re: Wild and crazy uBITX, Arduino FPGA idea. #arduino #ubitx #sdr #fpga

Tom, wb6b
 

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

Re: Unexpected measurements

jim
 

Have not seen this -exactly- but ..all my testing was in ssb mode

DK7IH has a simple two-tone  test oscillator (copied below)  I add  2 switches to turn off each oscillator (to test for maximum warp) ...Tho he calls it a wien bridge, its really a phase-shift oscillator ...inject into mike input

Jim


On Thursday, January 17, 2019, 6:04:52 PM PST, Evan Hand <elhandjr@...> wrote:


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



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

AGC and FT8

Daimon Tilley <daimontilley@...>
 

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.

Re: AGC and FT8

Don, ND6T
 

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

rotary encoder

Keith VE7GDH
 

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

Re: AGC and FT8

Daimon Tilley <daimontilley@...>
 

Fantastic. Thanks for your help Don. 



On 18 Jan 2019, at 15:18, Don, ND6T via Groups.Io <nd6t_6@...> wrote:

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

Re: rotary encoder

Michael Hagen
 

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


https://www.ebay.com/itm/5X-EC-11-Rotary-Encoder-Digital-Potentiometer-20mm-Knurled-Shaft-with-Switch-USA/382671052600?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2057872.m2749.l2649

On 1/18/2019 8:33 AM, Keith VE7GDH wrote:
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@...

Re: rotary encoder

Curt
 

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

Re: rotary encoder

Arv Evans
 

It is possible to test the mechanical switch type rotary encoders by using a pair of resistors and
LEDs to show the outputs as the knob is turned slowly.  Connect a 1500 ohm resistor from +5
to the LED and the LED cathode to an encoder output.  If you use two resistors and two LEDs
you can see the quadrature output states. 

Arv
_._


On Fri, Jan 18, 2019 at 9:33 AM Keith VE7GDH <ve7gdh@...> wrote:
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



Re: AGC and FT8

Vince Vielhaber
 

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

Vince - K8ZW.

On 01/18/2019 05:41 AM, Daimon Tilley wrote:
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.

CW operation on microBITX

geoffg3wzp@...
 

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 !

Re: CW operation on microBITX

Bill Cromwell
 

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

On 1/18/19 2:24 PM, geoffg3wzp@... wrote:
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 !
--
bark less - wag more

Re: Wild and crazy uBITX, Arduino FPGA idea. #arduino #ubitx #sdr #fpga

WU1N
 

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@...

Re: rotary encoder

Wayne Leake
 

 I bought a bunch of the plain switches, with the threaded shaft casing, plus nuts and washers.
 Also bought 2 or 3 mounted on boards with resistors where called for.
 I figure to replace the pot with them, just need to get the coding set for that.
 It is a good idea to test some of these things.
 I bought two ten turn pots, plus have one that came with a BITX20 parts kit for the boards that Sunil sells.
 And, it turns out that one of the pots I bought is bad. No connection between any of the 3 connectors, period.
 Now I don't know who i bought it from.
 I'll take note of how to test the switches..

 Wayne WA2YNE
 still trying in West Texas.

Adding uv meter .board and leads to ubitx

will.benn@...
 

Hi my name is Will put together ubitx radio kit .Found the audio very low .can  you suggest an add on amp .also bought uv meter kit along with made up board  and leads as recommended by F6HOY.the problem .I have no idea how to connect to the main board of the radio.can any one help 73 Will