Building the Antenna Analyzer: can you use 50 ohm resisters instead of 51 ohm ones??

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You can try also this lib, it's focused on small size and optimizations for MCU operations

73 CO7WT.

Thanks for all the great suggestions. Looks like I have the Etherkit library version 2.01 so I updated to 2.10. This makes a noticeable improvement to around 2.5ms but I can't duplicate Don's results of 735us. I don't understand how our results could vary so widely. Could it be frequency dependent? I am switching back and forth between 7.030Mhz and 11.946Mhz.

So then I followed one of Jerry's (KE7ER) suggestions and modified my sketch to use his?si5351bx code. That was really easy to do and?si5351bx_setfreq()?took about 2ms to execute. Not bad - at 30WPM that is about 5% of the morse element length.?

Here is an ADDED BONUS.... I think Jerry wrote that code to save code space and wow did it ever. Using his code instead of the Si5351 library cut my code size from 22.4K (72%) down to 12.4K (40%). That is awesome! Thank you Jerry!! Even if I eventually decide to use two outputs for this I will stay with the si5351bx code for the code size reduction.
73, Jerry, W0PWE

-- 
73 CO7WT, Pavel.

I'm certainly interested in a group collaboration.? Much better to have a pool of talent working on this together rather than plugging away at it on my own.

As far as goals are concerned, I'll toss this list out as a starting point for discussion:

General goals:
- uses GitHub for sharing and file distribution
- Initial code supports CW and SSB on multiple bands
- Supports Si5351
- Add various digital modes over time
- Code support for rotary encoders
- Code supports use of both external keypad/switches and external USB keyboard
- Code supports both standard Pi HDMI display output and optional non-HDMI LCD displays
- S-meter support via ADC on HAT
- Display code shows frequency, S-Meter, mode (CW/USB/LSB/etc)

PC board 'HAT' requirements:
- Works with any Pi that uses the standard 40-pin Pi GPIO connector
- Stackable, allowing user to use multiple HATs if desired.? For example, this would allow a user could use add a sound card HAT rather than a USB sound card dongle
- On board 5V/3.3V power supply generation from 12-15V input supply with connector for external power switch (something the Pi's lack)
- Si5351, perhaps on a small daughter-card to allow user to select chip version that best suites them
- Support for external non-HDMI LCD display for those that want a cheaper or smaller display
- Support for external switches/keypads
- Support for 4 or more ADC channels
- On board Relay drivers for BitX 12V/24V power, TX/RX, M1/M2, etc.??
- On board Relay drivers for multi-band BPFs/LPFs.? User can populate PCB for multi-band support or leave off relay driver components for single band support

Optional and/or Future Hardware/Software Features
- Tone generation for tuning/debugging
- Touch screen support
- Real Time Clock (RTC) support
- GPS support (perhaps including grid locator support)
- Digital volume control using either USB Keyboard or additional push-buttons or rotary encoder
- Built in antenna analyzer (perhaps based on W8TEE design, but using Pi for control)
- Support for both Si5351 and DDS
- Built in frequency meter
- Quadrature support for SDR

Notes:

1) Since the various Raspberry Pi models only have 1-2 USB ports (not including the micro-USB input power-only connector), any enclosure should probably include room for an optional small 4 port USB Hub.

2) Although the Raspberry Pi has excellent interrupt support, its interrupt latency can be highly variable.? Any feature requiring precision timing-critial interrupts may have to be handled by a small microcontroller/Arduino.??

3) Depending on proximity/shielding/etc, user may have to disable WiFi and/or Bluetooth on the Pi while using it to drive the BitX/uBitX to limit noise.

Thanks,

Carl, K0MWC

I'm confused... ?one selection on the switch routes power out of the device to an external step up module and back in? ?Why not build the boost circuit into the case? ?Or failing that, have it select a separate input for 24v (6s li-ion or similar)?

Mike's right, the LM386 can oscillate when the volume pot is set for minimum volume.
The fix is to insert a resistor, any value between 1k and 10k, between the volume pot pin 2 and the LM386 pin 3.

Also, R111 at 100 ohms limits current into the LM386, this can clip audio peaks.
Can fix this be adding a 10 ohm resistor in parallel.with R111.

I believe both of the above come from posts Raj has made to this forum.

I have no idea where the "2 places on the LM386" are that Mike is putting his 10uF caps.

Jerry, KE7ER

Thanks for all the quick responses. Good information and leads to a solid plan.

73, Peter,
ve3poa

True, but the 26-pin GPIO connector has been retired by the Raspberry Pi organization.? All the newer Pi boards use the 40-pin GPIO connector.? Plus the 40-pin GPIO gives you the expanded I/Os, which is part of the point in going with the Pi (better performance, gobs of memory, more I/Os).?

73
Carl - K0MWC



?

It should work right out of the box, once you have followed the wireup instructions from hfsigs.com.
If it doesn't, check all those coils for cold solder joints, broken wires, and shorts, as that seems to be
the primary source of trouble on these rigs.
Check out the receiver first, but will take a halfway decent antenna to get any signals since gain is
kept low to avoid overload when using a "real" antenna.
Avoid feeding the rig more than 12v, I'd recommend using a 1A fuse into the main rig,
and a 2A fuse into the IRF510. ?If you don't have an RF wattmeter,?
use a 2w 50ohm resistor as a dummy load,?it should get hot when transmitting?
while yelling into the mike. ?Better yet, build a diode RF?detector, and measure?
the RF voltage across the dummy load.
With the original firmware, the operating frequency may jump around a hundred hz or so,
enough that I wouldn't want to put it on the air.
So once you think the rig is working, next step is to figure out how to download Allard's code:
? ??
I suggest you just add the function button, and avoid the other mods till you know the rig is working well.

Here's a couple other mods to consider:
??/g/BITX20/message/33933

Some insist that everyone avoid any chance of the 2'd harmonic not meeting the letter of the law.
It's good to add that 100pf C0G/NP0/SiverMica cap to?the output low pass filter, rated for at least 100v.

The typical 100w ssb transmission may well have a 2'd harmonic that's 10db worse than our 5w bitx40.
FCC regs state that we should use "the minimum transmitter power necessary to carry out the desired communications".
Ignoring that directive (as many operators do) seems a far greater sin. ?

Q15 can be blown by several volts at the base if your bitx40 is hooked up to an antenna while a nearby rig
is dumping 100w into some other antenna. ?If that's in your future you should do the double-diode mod.?
?
Good luck!

Jerry, KE7ER

Hi Peter, several of us in the Barrie WAX Group have our BITX40v3 on the air now.
One mod that really helps is to use a 10 turn pot for tuning (the single turn that is included is just too touchy when tuning).
Allard PE1NWL makes one of the better firmware upgrades and that is the one we all use: ??
Be sure to install the two push buttons for Function and for Fine Tune (this gives 1 Hz tuning resolution) in Allard's sketch.
Take a look at Minimum BITX40v3 Hacks at ?
There are a number of useful links in the TCA article 'BITX40v3 - an Affordable and Fun "Kit" Transceiver' in the September/October issue.

73, AL? VE3RRD

That's exactly where I am. I have not yet had time to dig into this any further. I am planning on writing an Arduino sketch that switches between two different output frequencies, so that I can follow along with the scope to see what's happening. The problem with?the sandwich construction is that it's really hard to get to the different points in the circuit where "stuff happens".

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Yes, Just build it stock, don't hook up transmitter power.

Get Rec working first.? Get tunning working with Pot and or modifications with Sketch and 10T pot.

Figure out a box and where everything needs to go.? I used a Jameco metal box, a little to small but nice.

Might next work on Audio amp.? Like putting a resistor to the pot for noise at near zero volume.

I went to 16 Ohm 4" (Big) speaker from an 8 Ohm 2" speaker.? That and 10uF caps on the 2 places on LM386

made my audio MUCH better.? My advise is to use a 16 Ohm speaker.

Go from there.

Mike, WA6ISP

Hello group,

I've had my Bitx for a while and am just starting to put it together. I've been reading this list off and on but now so much has happened with the mods I almost don't know where to start.

I thought of just build it see what happens and search for answers as issues come up but maybe that's not the best way as it sees that there are a lot of interesting and necessary mods out there.? Any suggestions as to an appropriate approach??

Thanks and 73, Peter?
ve3poa?

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

I am getting the Min SWR: 5.00? at Freq: -3117200 message using a dummy load or any antenna.? I have tried using both antenna inputs using plain wire and tiny coax, all with the same results.? Any help would be appreciated.

Thanks,
Glenn? WU3Z

My first guess would be poor performance on 20m is due to the board layout around the IRF510.
So maybe replace those parts with a final built ugly style on a small piece of copper clad FR4,
then glue or solder that board in place.?
IRF510 source lead should go directly to the ground plane, as short as possible.
Perhaps add a 10 ohm resistor in series with the gate to avoid oscillations.
Allison recommends clipping the drain lead from the IRF510 and soldering any drain connection
directly to the tab, that keeps the AC at the drain from coupling into the gate. ?
And of course, give it a good heat sink.

Let us know what you find out.

Jerry

Hello group,

I've had my Bitx for a while and am just starting to put it together. I've been reading this list off and on but now so much has happened with the mods I almost don't know where to start.

I thought of just build it see what happens and search for answers as issues come up but maybe that's not the best way as it sees that there are a lot of interesting and necessary mods out there.? Any suggestions as to an appropriate approach??

Thanks and 73, Peter?
ve3poa?

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This is sort of early, but I'd like to use the BITX40 to help more people in our local ARES group get on HF (many of them were VHF-only) -- and in the longer run I think they are going to need a bit more power.? ?I have filters waiting for me at home to try and add another band or two the rig (already ran it at very low power on 80, just enough to reach my WINLINK RMS on the other side of the house) ---? ?

AC2CZ/VE2 's 50-watt dual IRF-510 amplifier caught my eye, particularly because he put in some protection circuitry after lots of experience with the system....and I'm going to try a printed circuit board of his design:

?

,_

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I'm doing multi-band as well, with modular filters. So far it works great on 80 and 40 (and presumably 60 once I build the filter!) but on 20, output is reduced from 5-7w to about 1w. I'm definitely interested in hearing others experiences. The receiver is definitely not deaf on 20m, as I've used it on 20m after cranking the bias WAY up on the PA (and dealing with the subsequent heat) but it seems like there's some other issue. The IRF510 works fine at 14mhz AFAIK. Input is welcome.



--
Ryan Flowers W7RLF

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?<-- Learn how to go digital on the BITX40