Doesn't need to move that far. ?Typically it only needs to be shifted approx 6 kHz to the other side of the crystal filter's bandpass.? Eg LSB (as it is now) requires the filter's bandpass to be below the carrier crystal frequency. ?
USB requires the filter's bandpass to be above the carrier crystal frequency.?
Since it's easier to change the frequency of a single carrier crystal rather than the centre frequency of a ladder crystal filter that's what we do.?
So to get USB we need to move the carrier crystal DOWN by approx 6kHz. ?Fortunately shifting a 12 MHz crystal down this amount is fairly easy and you won't necessarily need a crystal of another frequency. ?You just put inductance in series with it to provide a VXO. ?Adding a second crystal in parallel makes shifting down easier but is probably not required. ?
73, Peter VK3YE
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Re: Sad reality of stock vfo
raj,
the varactors have a bad temperature coefficient. they contribute too.
- f
On Sun, Jan 1, 2017 at 11:52 AM, Raj vu2zap@... [BITX20] <BITX20@...> wrote:
?
NP0 capacitors for C94 95 96 WILL tackle the heat problem Farhan!
Happy new year!
Raj
>2. The culprit is heat. The RF amplifiers have significant current, there are three of them. The heat dissipates through the ground plane and heats up the VFO components. This heat would be missing if we used through hole components as those components are off the board.
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Re: It stopped transmitting
John,
Check if you have correct voltage at the TX and RX points. They come from
relay K1 - it could be faulty or not operating.
Good luck and Happy new year!
Raj vu2zap
At 31/12/2016, you wrote:
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?
Bill - I believe I did the same thing to my BITX40 as, now when I flip
the switch to transmit, it stays in the receive mode, but the frequency
shifts slightly. No sure if the relay switches or if I blew the PA final.
Receiver is fine, like your receive. I thought I may have left the radio
in transmit mode when I switched off the volume control pot
overnight? (as I had planned to keep the radio powered on) but now
believe that the issue may have resulted from using my TS-480 in transmit
to locate my BITX40 frequency. Have been hoping to see Farahan's
"troubleshooting the BITX40 transmitter" YouTube video, but I
guess it still is "in production." If you receive any feedback
on correcting your transmit side issues of the BITX40 could you please
share this information with me? I ordered the IFR510 and 2n2219a from
W8DIZ, but I hope to identify the issue before replacing the parts, if
their replacement is even required. 73? and tks. W4USF - John -
Lutz, FL.
Sent from my iPhone
On Dec 31, 2016, at 07:07, Bill Kittilson
bill@... [BITX20]
<BITX20@...
> wrote:
?
I managed to kill my bitx40. It was working great until I decided to tune
up the big rig. I can still receive. No power at all on transmit. I
replace the 510 transistor. Sill no output. The current does jump up to
over 1 amp when I switch to transmit.
Any idea what to look at next?
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Re: It stopped transmitting
Bill,
Check L6 and L7 and see if it is making contact with the solder on the board.
Check the relay K2, I seriously suspect that it could be faulty. Take the output from K2 pin 16 and ground to a (bnc) connector and check the TX out there with a power meter. If there is normal output then relay is suspect.. or not operating. When you
press PTT the relay should click, you should feel that with your finger. I have seen a lot of similar relays fail in my service
experience.
Cood luck and Happy new year!
Raj vu2zap
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At 31/12/2016, Bill Kittilson bill@... [BITX20] wrote:
I managed to kill my bitx40. It was working great until I decided to tune up the big rig. I can still receive. No power at all on transmit. I replace the 510 transistor. Sill no output. The current does jump up to over 1 amp when I switch to transmit.
Any idea what to look at next?
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Re: Sad reality of stock vfo
It is a complete, finished radio for $45!! Of course it is a compromise, and you have always been frank about the design issues.?
I am not complaining. I had fun putting this together, and I’m learning more from this one project than several years of other experiences. Just understanding the costs and compromises of the design decisions, and their effect on the final performance, has been a great lesson, and it is ongoing.
I will continue to explore, first the limits of changes to the analog vfo onboard, and then possible learn to build an outboard vfo.
I also look forward to the opportunity presented by the DDS VFO and learning about the Arduino architecture.
I find it hard to imagine a better way to spend $45 or $59 for an education.
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I will be frank. This design is a compromise. The VFO should have been on a separate board. I thought about it for a pretty long time. There was no cost difference. There was just one more board to hookup and wire up. In the end and after countless conversations with some co-builders, I decided to include the VCO on-board. I am still convinced that this was a better option than an outboard VFO for easy of use.
Here are some notes from my experimentation.
1. It is NOT about the capacitors. I build a two-tone oscillators using these caps that run at 14.000 and 14.200 MHz directly. They are so solid, I can't believe that it is a free running oscillator. 2. The culprit is heat. The RF amplifiers have significant current, there are three of them. The heat dissipates through the ground plane and heats up the VFO components. This heat would be missing if we used through hole components as those components are off the board. 3. The heat sensitivity is also due to it being a VCO. The varactor tuning couldn't be avoided as getting good quality capacitors is very tough these days.
If you'd still like to retain the analog tuning, do what bill suggests. Build an outboard VFO, shield it well and it will be rock stable.
- f
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Re: Sad reality of stock vfo
NP0 capacitors for C94 95 96 WILL tackle the heat problem Farhan!
Happy new year!
Raj
toggle quoted message
Show quoted text
2. The culprit is heat. The RF amplifiers have significant current, there are three of them. The heat dissipates through the ground plane and heats up the VFO components. This heat would be missing if we used through hole components as those components are off the board.
|
Re: Sad reality of stock vfo
I will be frank. This design is a compromise. The VFO should have been on a separate board. I thought about it for a pretty long time. There was no cost difference. There was just one more board to hookup and wire up. In the end and after countless conversations with some co-builders, I decided to include the VCO on-board. I am still convinced that this was a better option than an outboard VFO for easy of use.
Here are some notes from my experimentation.
1. It is NOT about the capacitors. I build a two-tone oscillators using these caps that run at 14.000 and 14.200 MHz directly. They are so solid, I can't believe that it is a free running oscillator. 2. The culprit is heat. The RF amplifiers have significant current, there are three of them. The heat dissipates through the ground plane and heats up the VFO components. This heat would be missing if we used through hole components as those components are off the board. 3. The heat sensitivity is also due to it being a VCO. The varactor tuning couldn't be avoided as getting good quality capacitors is very tough these days.
If you'd still like to retain the analog tuning, do what bill suggests. Build an outboard VFO, shield it well and it will be rock stable.
- f
On Sun, Jan 1, 2017 at 9:44 AM, Thomas Noel tnoel@... [BITX20] <BITX20@...> wrote:
?
John,
As I said - I knew from others’ experience that the stock design has some significant limitations. I just had no previous personal experience with such builds. I have read of quite a few design mods that offer improvement. The design is simple and easy to mod as Farhan intended. I built the stock design as a starting place for learning.?
I was surprised to see the drift so severe that it is hard to hold frequency during an “over”. I have made more than a dozen QSOs in less than two hours of operation. The operator on the other end even commented that I was drifting off frequency.
I would like to continue to experiment with the all-analog radio before moving to the DDS VFO.
Where exactly would you start? Replace the resistors as suggested by Farhan? They were included with my purchase. Which capacitors would you replace to stabilize the VFO, and change just the type, or change any of the values? My tuning range is just where I would want it now.
If anyone can give me a step-by-step attack plan in order of best anticipated return on effort, I would appreciate it a lot.
Thomas, That's not optimal behavior for that sort of design. It can do much better than that. I think you should revisit the traditional solutions for such problems and them implement them before moving on- NPO and styrene capacitors might be a start.
John KC9OJV
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Re: It stopped transmitting
Hi Kent,
Firmware version s1.02c is perfect! It is the latest version. In this version there was a change to eliminate audible clicks when the frequency changed.
I don't own a BITX40. On the QRP Labs VFO kit page there are a few connection details that were provided by Ashhar Farhan when he recommended the QRP Labs VFO kit for use with the BITX40. That's all I know!
73 Hans G0UPL? ?
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Re: Sad reality of stock vfo
John,
As I said - I knew from others’ experience that the stock design has some significant limitations. I just had no previous personal experience with such builds. I have read of quite a few design mods that offer improvement. The design is simple and easy to mod as Farhan intended. I built the stock design as a starting place for learning.?
I was surprised to see the drift so severe that it is hard to hold frequency during an “over”. I have made more than a dozen QSOs in less than two hours of operation. The operator on the other end even commented that I was drifting off frequency.
I would like to continue to experiment with the all-analog radio before moving to the DDS VFO.
Where exactly would you start? Replace the resistors as suggested by Farhan? They were included with my purchase. Which capacitors would you replace to stabilize the VFO, and change just the type, or change any of the values? My tuning range is just where I would want it now.
If anyone can give me a step-by-step attack plan in order of best anticipated return on effort, I would appreciate it a lot.
toggle quoted message
Show quoted text
Thomas, That's not optimal behavior for that sort of design. It can do much better than that. I think you should revisit the traditional solutions for such problems and them implement them before moving on- NPO and styrene capacitors might be a start.
John KC9OJV
|
Re: Sad reality of stock vfo
I can relate to this, and it's why I am switching to a digital VFO. Gluing down L4 was a *huge* improvement for my BITX40. The other thing is to have it in an enclosure that isn't drafty, so that the temperature stays roughly the same if possible. I'm still waiting for the VFO from QRP Labs to get here, but contacts ARE possible with the stock VFO. KC9OJV's suggestion is also a very good one, and were I not going digital, I'd be doing that next.
Ryan? KC7RYS
|
Re: Sad reality of stock vfo
Thomas, That's not optimal behavior for that sort of design. It can do much better than that. I think you should revisit the traditional solutions for such problems and them implement them before moving on- NPO and styrene capacitors might be a start.
John KC9OJV
|
I knowingly and with full understanding of the expected consequences built out my Bitx40 fully stock. Analog VFO, original resistors etc. All alignment went just as described in manual, and everything works just as advertised. The receiver is quite sensitive, and even without AGC it is easy to operate weak and strong stations. I have about 220kc of tuning range from 7.070 to 7.290.
The challenge is the VFO drift - even though I leave the set on all the time with volume turned down to silent, the drift is so severe that I must re-tune at least every 10-15 seconds during an attempted QSO or I drift so far off frequency that when I un-key - the other station is often gone, moved out of my passband. Never dreamed the drift would be this bad.
I have the replacement resistors for the VFO, and that will be next. I may try some of the other suggested changes just to further my own learning experience with this simple and elegant design.
But I have also ordered the DDS VFO parts!
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That's very philosophical and I like it! :-))
On Dec 31, 2016 7:20 PM, "ron van doremalen ronvandoremalen@... [BITX20]" < BITX20@...> wrote:
?
When shipped it will come
Sent from my iPhone
?
I ordered mine on the 25th. Payment shows up in PayPal, but no tracking info.
Rich
KC8MWG
?
Yep, tried aftership as well, no info.
73
Don Frasher AD7LL
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When shipped it will come
Sent from my iPhone
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?
I ordered mine on the 25th. Payment shows up in PayPal, but no tracking info.
Rich
KC8MWG
?
Yep, tried aftership as well, no info.
73
Don Frasher AD7LL
|
I ordered mine on the 25th. Payment shows up in PayPal, but no tracking info.
Rich KC8MWG
On Saturday, December 31, 2016 7:57 PM, "AD7LL donfrasher@... [BITX20]" <BITX20@...> wrote:
?
Yep, tried aftership as well, no info.
73 Don Frasher AD7LL
|
Ashhar, do the new ones use 70ma in recieve instead of 90ma because you have switched from100 to 220 resistors? Jerry aa1of
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Yep, tried aftership as well, no info.
73 Don Frasher AD7LL
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My experience was the same as most - I got initial tracking info from IndiaPost, but never heard again until it was on my doorstep.
Have Faith!
Tom kf7rsf
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I placed my order on 12-23, and I did get a tracking # via paypal. ?However, even if I enter it directly at Indiapost, google , or elswhere, I get no info received. ? ?Has anyone else had better luck?? ?or have they not actually shipped them yet?
73 Don Frasher AD7LL
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Aftership? Sometimes search again delivers an update
Sent from my iPhone
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?
I placed my order on 12-23, and I did get a tracking # via paypal. ?However, even if I enter it directly at Indiapost, google , or elswhere, I get no info received.
? ?Has anyone else had better luck?? ?or have they not actually shipped them yet?
73
Don Frasher AD7LL
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I ordered and paid for just the Raduino on 12/23 and haven't heard anything either, so I'm guessing we just wait. Joel? KB6QVI
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On Dec 31, 2016, at 4:19 PM, donfrasher@... [BITX20] < BITX20@...> wrote:
?
I placed my order on 12-23, and I did get a tracking # via paypal. ?However, even if I enter it directly at Indiapost, google , or elswhere, I get no info received. ? ?Has anyone else had better luck?? ?or have they not actually shipped them yet?
73 Don Frasher AD7LL
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Raj vu2zap
Joel Caulkins/N6ALT