Re: Bitx40 review (video)
The blue RV1 is the bias set for the IRF. The drive is set by the preset
R136 before the driver transistor.
At 17/12/2016, you wrote:
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?
Another nice video Peter.? Thanks.?? In your comment on
the pot in the RF amp stage, I think you made the same mistake that I
did: assuming that that pot was for setting the IRF-510 bias (as was the
case in all earlier BITX circuits).?? But take a look at the
schematic:? The bias is set by a regulator chip (smart move Farhan!)
and that pot just sets the RF level going to the driver (thus allowing
VK3YE to go QRPpppppppppppp from the beach!). 73? Bill
On Saturday, December 17, 2016 1:59
AM, "parkerp@... [BITX20]"
wrote:
?
There's not much in it that most people here won't already know, but a
video review I've just uploaded could still be of interest.
|
Re: Damage to SMT version bitx40 from nearby transmitter
Thomas,
I would recommend you do both. The diodes may not take the all power from
your other antenna.
Yes the two diodes in parallel are connected between pin 12 of k1 and
ground. Both diodes should be
connected in opposite polarity. The line marking the cathode of one
should go to ground and
the other diode's cathode should got to pin 12 (Rx antenna line). This
will limit the voltage to
less than one volt and that wont damage the Rx.
The bulb is useful for preventing the diodes from blowing up by
dissipating excess incoming power.
I used to run a 10M packet bbs link and another antenna was for my base
HF. When one transmitted
the other rig lamp used to glow.
You can check the power received by connecting a QRP power meter on the
40M antenna and
the other port of the meter to a dummy load. You will find out? how
much power is picked up by the
40M antenna when you transmit on the main winlink antenna.
I forget a lot too @ 60! The doctor asked to visit again when I start to
forget my XYLs name!
Cheers
Raj
vu2zap
At 17/12/2016, you wrote:
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?
Raj,
Thank you for the response. You confirm my fear that the danger of damage
is real and present.
I am very much a beginner at this sort of work. I have excellent
mechanical and soldering skills, but know little of circuit elements
beyond what was required for my license.
I believe you have offered two possible ways to mitigate the risk -
either the diodes OR the incandescent bulb. Correct?
If I choose the diodes in parallel, I assume one lead of each goes to pin
12 of K1 relay. Does the other lead of each go to ground? Or where? Be
gentle please!
If I choose the miniature bulb, does that bulb function as a sacrificial
element like a gas discharge arrestor cartridge? Or is it able to absorb
and limit the voltage? I can do either, and it seems you are saying the
second option is better.
I?�?m learning as fast as I can!
Thomas W Noel
KF7RSF
On Dec 16, 2016, at 9:07 PM, Raj
vu2zap@... [BITX20]
<BITX20@...
> wrote:
Thomas,
At pin 12 of K1 relay solder 2 4148 diodes in parallel but in opposite
polarity. This will limit the receiver from getting high RF voltage.
Also if you cut the track between K1 pin 12 and K2 pin 14 and insert a
12v 60 or 40 ma miniature incandescent bulb it would be better. This is
common protection method in commercial transceivers and amps. This track
seems to be on the component side.
cheaper still!
73 Raj vu2zap
At 17/12/2016, you wrote:
?
How likely is this to happen? Bitx40 connected to 40M resonant antenna
perpendicular to another antenna with a 100W transceiver running a
Winlink gateway.
I fully expect front-end overload and nasty noises, but will the coupling
cause actual damage> I would like to leave the bitx40 running but
volume minimized to lessen drift during warm-up period.
Currently I leave it running but antenna dis-connected, but it is only a
matter to time until my feeble brain forgets.
Thomas W Noel
KF7RSF
|
Re: Bitx40 review (video)
Another nice video Peter.? Thanks.?? In your comment on the pot in the RF amp stage, I think you made the same mistake that I did: assuming that that pot was for setting the IRF-510 bias (as was the case in all earlier BITX circuits).?? But take a look at the schematic:? The bias is set by a regulator chip (smart move Farhan!) and that pot just sets the RF level going to the driver (thus allowing VK3YE to go QRPpppppppppppp from the beach!). 73? Bill
On Saturday, December 17, 2016 1:59 AM, "parkerp@... [BITX20]" wrote:
?
There's not much in it that most people here won't already know, but a video review I've just uploaded could still be of interest.?
| | | | | | Reviewing the BITX40 7 MHz 7 watt transceiver module available from http://www.hfsigs.com Modifications at http://bitxhacks.blogspot.com.au/ There ... | | | | Preview by Yahoo | | |
?
|
There's not much in it that most people here won't already know, but a video review I've just uploaded could still be of interest.? | | | | | | Reviewing the BITX40 7 MHz 7 watt transceiver module available from http://www.hfsigs.com Modifications at http://bitxhacks.blogspot.com.au/ There ... | | | | Preview by Yahoo | | | ?
|
Re: Damage to SMT version bitx40 from nearby transmitter
Raj,
Thank you for the response. You confirm my fear that the danger of damage is real and present.
I am very much a beginner at this sort of work. I have excellent mechanical and soldering skills, but know little of circuit elements beyond what was required for my license.
I believe you have offered two possible ways to mitigate the risk - either the diodes OR the incandescent bulb. Correct?
If I choose the diodes in parallel, I assume one lead of each goes to pin 12 of K1 relay. Does the other lead of each go to ground? Or where? Be gentle please!
If I choose the miniature bulb, does that bulb function as a sacrificial element like a gas discharge arrestor cartridge? Or is it able to absorb and limit the voltage? I can do either, and it seems you are saying the second option is better.
I’m learning as fast as I can!
toggle quoted message
Show quoted text
Thomas,
At pin 12 of K1 relay solder 2 4148 diodes in parallel but in opposite polarity. This will limit the receiver from getting high RF voltage.?
Also if you cut the track between K1 pin 12 and K2 pin 14 and insert a 12v 60 or 40 ma miniature incandescent bulb it would be better. This is common protection method in commercial transceivers and amps. This track seems to be on the component side.
?
cheaper still!
?
73 Raj vu2zap
At 17/12/2016, you wrote:
??
How likely is this to happen? Bitx40 connected to 40M resonant antenna perpendicular to another antenna with a 100W transceiver running a Winlink gateway.
I fully expect front-end overload and nasty noises, but will the coupling cause actual damage> I would like to leave the bitx40 running but volume minimized to lessen drift during warm-up period.
Currently I leave it running but antenna dis-connected, but it is only a matter to time until my feeble brain forgets.
Thomas W Noel
KF7RSF
|
Re: Damage to SMT version bitx40 from nearby transmitter
Thomas,
At pin 12 of K1 relay solder 2 4148 diodes in parallel but in opposite
polarity. This will limit the receiver from getting high RF voltage.
Also if you cut the track between K1 pin 12 and K2 pin 14 and insert a
12v 60 or 40 ma miniature incandescent bulb it would be better. This is
common protection method in commercial transceivers and amps. This track
seems to be on the component side.
cheaper still!
73 Raj vu2zap
At 17/12/2016, you wrote:
toggle quoted message
Show quoted text
?
How likely is this to happen? Bitx40 connected to 40M resonant antenna
perpendicular to another antenna with a 100W transceiver running a
Winlink gateway.
I fully expect front-end overload and nasty noises, but will the coupling
cause actual damage> I would like to leave the bitx40 running but
volume minimized to lessen drift during warm-up period.
Currently I leave it running but antenna dis-connected, but it is only a
matter to time until my feeble brain forgets.
Thomas W Noel
KF7RSF
|
Not really. I would guess the confusion arises because there are two different inversions happening. The first is what you experienced with the DDS -- the frequency span is the same but TUNING is inverted. That is mostly tradition as we ordinarily count going up in frequency as we turn the dial clockwise. In the case of the BITX40, if the VFO tunes from 4.7 MHz to 5 MHz, then the RF tunes from 7.3 MHz to 7.0 MHz. So to get a "proper" tuning we actually have to reverse or "invert" the VFO signal. That is what you have actually described in your rig. The second type is much more subtle. If one thinks of sidebands, the USB extends lower audio frequencies from the carrier outward UP in frequency, and the LSB does the reverse, i.e., the higher audio frequencies are DOWN in frequency. Merely shifting the USB to the LSB area will invert the audio; now the upper audio frequencies are nearer the carrier and the lower ones further away. That is not the way we hear things. How then does one decode USB on LSB side (or vice versa)? Clearly some other mechanism has to happen which also inverts the effect of the LSB into one of an USB (ibid). Then the phases will be correct and the original audio will reappear. This is not a simple problem. Most of the traditional 9 MHz IF and 5 MHz VFO rigs (the 20/60m rigs) did not have this problem. Generally if the filter were a lattice filter, they used both a USB and LSB crystal and adjusted the BFO frequency to either sideband; That is, they use dual BFO frequencies. They also used (as does Farhan in his 20/40 rig) dual bandpass filters to accommodate each of the different sidebands. This practice continues; some BITX rigs use the same mechanism even though they do not use lattice filters (they generally use Cohn filters). With the advent of the sharp bandpass crystal filter rigs (such as the BITX) this did not work any more and there is ONE BFO frequency. Note that the modulating frequency on transmit is the IF. The received modulated frequency is the RF. The VFO is passive and merely adds or subtracts enough to produce either an RF output or IF input. So where can sideband inversion of the second type take place? In the mixer. Note that the IF is the actual modulated RF signal on transmit. ? "The resulting upper and lower sidebands each contain both of the
modulating frequency components. The upper-sideband components consist
of the sum of each modulating frequency plus the carrier frequency, and
no inversion takes place. The lower-sideband components consist of the
carrier frequency minus each of the modulating frequencies, and they
become inverted. Inversion occurs in any frequency-translating process
when the mixing frequency is higher than the signal frequency and the
difference products are selected in the output circuit. This principle
can be used for sideband switching in both transmitters and receivers,
since by this means an upper-sideband signal is converted to a
lower-sideband signal or vice versa." Source:SSB - QRZ Israel HAM radio portal.htm Since our mixing frequency is the VFO? (5 MHz), and the output is the RF (7 MHz), no inversion of the second kind takes place. But there is another product (VFO + IF) where it does because the IF is greater than the VFO (-IF + VFO). This product is suppressed by the final BPF. Consider that BPF. It is critical. It keeps out non-40m frequencies from the receiver, and also suppresses non-40m signals from the transmitter, including out-going inversion products. I know this is confusing. I wonder all the time if I have gotten it right. The math is somewhat complex. Hope this helps anyway. john AD5YE ---In BITX20@..., <chase8043@...> wrote : Hi John
I had a chance to try some testing with sideband inversion.
BFO = 11.9986 MHZ and VFO = 4.8486 MHZ this gives me a starting frequency of 7.15 MHZ(RF = BFO - VFO). Set the encoder to increase frequency in CW direction. But this to increase VFO or decreasing RF. So I switched it so RF goes up in CW direction.
I usually listen in on a net at 7.163 MHZ. To tune in the voice I had to increase RF. So I find that LSB is on the wrong side of the (non-existent) carrier.
Is this the sideband inversion?
73
Ken VA3ABN
On Thu, Dec 8, 2016 at 11:56 PM, iam74@... [BITX20] <BITX20@...> wrote:
?Think of it this way: VFO - IF = RF. Does this result in sideband inversion? (hint: -IF + VFO. It it positive or negative?) Why don't you try it and see what happens. If you get nothing but garble, then the answer is "no...it does not.
If the results are clear signals, then you must decide if the LSB is being inverted, or is it truly USB. Remember that the ordinary condition by convention is that the LSB on 20m is garble or non-existent. Therefore you must hear USB inverted to LSB or true USB for intelligibility. Be aware of AM; test your results through several different QSOs.
Actually, it doesn't matter which it is -- as long as communication takes place.
john
AD5YE
---In BITX20@..., <chase8043@...> wrote : Opps. Not? 18.998600 - 4.998600 = 14.0. Should be 25.998600 - 11.988600 = 14 or is this the wrong sideband?
73 Ken
|
Damage to SMT version bitx40 from nearby transmitter
How likely is this to happen? Bitx40 connected to 40M resonant antenna perpendicular to another antenna with a 100W transceiver running a Winlink gateway.
I fully expect front-end overload and nasty noises, but will the coupling cause actual damage> I would like to leave the bitx40 running but volume minimized to lessen drift during warm-up period.
Currently I leave it running but antenna dis-connected, but it is only a matter to time until my feeble brain forgets.
|
Re: Pop in speaker on key-up
Trip - KT4WO
The infamous BITX-Click has been well documented on this forum, but it was mostly
some time ago.?
There is a capacitor that couples the receive audio from the BFO mixer and another
capacitor that couples the microphone amplifier to the BFO mixer.? In Rx mode and in
Tx mode these capacitors get charged to different voltages.? When you change modes
these capacitors take on different voltages.? This causes a click when going from Tx
to Rx mode, and a 20 ms carrier burst when going from Rx to Tx mode.?
There have been several methods suggested to alleviate this situation, but basically
the situation is something that most will live with as a trade-off for simplicity and low
cost.? Once you have an antenna connected the receive-mode click should be less
noticeable.? 0.1 mfd across your speaker terminals might help minimize the click.?
Some of the early BITX20 and BITX17 builders resorted to using a relay to switch
microphone and speaker circuits as a way to eliminate this situation.? That too is
documented in the forum.
It is possible to make an LTSpice simulation that documents this situation, and that
might lead to simulator experimentation to come up with a solution to the problem.
In fact, any of the BITX circuit sub-sections can be ran in LTSpice as a means for
providing better understanding how they work and to trial proposed modifications
without having to melt solder.
Arv? K7HKL
_._
On Fri, Dec 16, 2016 at 4:05 PM, kt4wo67@... [BITX20] <BITX20@...> wrote:
?
Just to the controls hooked up...for testing. Upon key up I get a loud "pop" in the speaker.
I searched the group and didn't see this issue.?
Ideas??
Trip - KT4WO
kt4wo67@...
|
Re: Pop in speaker on key-up
Trip et al,
It has been discussed before. Search for “PTT noise” or PTT transient”. Cause and solutions both simple (ignore it) and complex (Multi-transistor multi-relay switching schemes to cut the power during the crossover) have been described. Some of the discussion far predates the new SMT Bitx40 from India.
I have it with all cleaned up and in a fully shielded enclosure.
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?
Trip,
I found that while I had my board sprawled all over my bench that the click on Xmit was real loud with all my cables crossing each other, when I got the wiring cleaned up and separated and the power output cable replaced by a piece of RG-174 coax it's hardly noticeable anymore. Joel Caulkins?KB6QVI
?
Just to the controls hooked up...for testing. Upon key up I get a loud "pop" in the speaker.
I searched the group and didn't see this issue.?
Ideas??
Trip - KT4WO
kt4wo67@...
|
Re: Pop in speaker on key-up
Trip,
I found that while I had my board sprawled all over my bench that the click on Xmit was real loud with all my cables crossing each other, when I got the wiring cleaned up and separated and the power output cable replaced by a piece of RG-174 coax it's hardly noticeable anymore. Joel Caulkins?KB6QVI
toggle quoted message
Show quoted text
On Dec 16, 2016, at 3:05 PM, kt4wo67@... [BITX20] < BITX20@...> wrote:
?
Just to the controls hooked up...for testing. Upon key up I get a loud "pop" in the speaker.
I searched the group and didn't see this issue.?
Ideas??
Trip - KT4WO
kt4wo67@...
|
Just to the controls hooked up...for testing. Upon key up I get a loud "pop" in the speaker. I searched the group and didn't see this issue.? Ideas?? Trip - KT4WO kt4wo67@...
|
There is an excellent and easy to remember rule of thumb on sideband inversion.? Explained here:
On Thursday, December 15, 2016 9:52 PM, "Ken Chase chase8043@... [BITX20]" wrote:
?
Hi John
I had a chance to try some testing with sideband inversion.
BFO = 11.9986 MHZ and VFO = 4.8486 MHZ this gives me a starting frequency of 7.15 MHZ(RF = BFO - VFO). Set the encoder to increase frequency in CW direction. But this to increase VFO or decreasing RF. So I switched it so RF goes up in CW direction.
I usually listen in on a net at 7.163 MHZ. To tune in the voice I had to increase RF. So I find that LSB is on the wrong side of the (non-existent) carrier.
Is this the sideband inversion?
73
Ken VA3ABN
On Thu, Dec 8, 2016 at 11:56 PM, iam74@... [BITX20] <BITX20@...> wrote:
?
Think of it this way: VFO - IF = RF. Does this result in sideband inversion? (hint: -IF + VFO. It it positive or negative?) Why don't you try it and see what happens. If you get nothing but garble, then the answer is "no...it does not.
If the results are clear signals, then you must decide if the LSB is being inverted, or is it truly USB. Remember that the ordinary condition by convention is that the LSB on 20m is garble or non-existent. Therefore you must hear USB inverted to LSB or true USB for intelligibility. Be aware of AM; test your results through several different QSOs.
Actually, it doesn't matter which it is -- as long as communication takes place.
john
AD5YE
---In BITX20@..., wrote : Opps. Not? 18.998600 - 4.998600 = 14.0. Should be 25.998600 - 11.988600 = 14 or is this the wrong sideband?
73 Ken
|
Hi John
I had a chance to try some testing with sideband inversion.
BFO = 11.9986 MHZ and VFO = 4.8486 MHZ this gives me a starting frequency of 7.15 MHZ(RF = BFO - VFO). Set the encoder to increase frequency in CW direction. But this to increase VFO or decreasing RF. So I switched it so RF goes up in CW direction.
I usually listen in on a net at 7.163 MHZ. To tune in the voice I had to increase RF. So I find that LSB is on the wrong side of the (non-existent) carrier.
Is this the sideband inversion?
73
Ken VA3ABN
On Thu, Dec 8, 2016 at 11:56 PM, iam74@... [BITX20] <BITX20@...> wrote:
?
Think of it this way: VFO - IF = RF. Does this result in sideband inversion? (hint: -IF + VFO. It it positive or negative?) Why don't you try it and see what happens. If you get nothing but garble, then the answer is "no...it does not.
If the results are clear signals, then you must decide if the LSB is being inverted, or is it truly USB. Remember that the ordinary condition by convention is that the LSB on 20m is garble or non-existent. Therefore you must hear USB inverted to LSB or true USB for intelligibility. Be aware of AM; test your results through several different QSOs.
Actually, it doesn't matter which it is -- as long as communication takes place.
john
AD5YE
---In BITX20@..., wrote : Opps. Not? 18.998600 - 4.998600 = 14.0. Should be 25.998600 - 11.988600 = 14 or is this the wrong sideband?
73 Ken
|
Re: BitX40 Spectrum Output
Sure I'll do it now. Thanks.
Tom
|
Re: BitX40 Spectrum Output
tom,?
i couldn't find the other file. can you put them both under a folder with your callsign?
- f
On Thu, Dec 15, 2016 at 5:26 AM, thomasinaz@... [BITX20] <BITX20@...> wrote:
?
Hi everyone,
I'm going to upload 2 pics into the file section if someone is able to look at them for me. I have two signal approx 500-700k away from the tuned freg and less than 20dbm difference in output with the mic keyed and no audio. Not sure if something is coupling to the antenna leads or what.
The signal to the far left is the vfo which is set from 4.7 to 4.9 MHz.
Thanks for any help in advance.
Tom w7amh
|
New file uploaded to BITX20
Hello,
This email message is a notification to let you know that
a file has been uploaded to the Files area of the BITX20
group.
File : /BitX40 Spectrum Output/ssh.bmp
Uploaded by : tom_hurst@... <thomasinaz@...>
Description :
You can access this file at the URL:
To learn more about file sharing for your group, please visit:
Regards,
tom_hurst@... <thomasinaz@...>
|
New file uploaded to BITX20
Hello,
This email message is a notification to let you know that
a file has been uploaded to the Files area of the BITX20
group.
File : /BitX40 Spectrum Output/ssl.bmp
Uploaded by : tom_hurst@... <thomasinaz@...>
Description :
You can access this file at the URL:
To learn more about file sharing for your group, please visit:
Regards,
tom_hurst@... <thomasinaz@...>
|
Hi everyone,
I'm going to upload 2 pics into the file section if someone is able to look at them for me. I have two signal approx 500-700k away from the tuned freg and less than 20dbm difference in output with the mic keyed and no audio. Not sure if something is coupling to the antenna leads or what.
The signal to the far left is the vfo which is set from 4.7 to 4.9 MHz.
Thanks for any help in advance.
Tom w7amh
|
?
On W5KUB (facebook) there is also the sketch. Not sure if attaching to this mail is the way to go.
?
Ron – PA3FAT
?
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Van: BITX20@... [mailto:BITX20@...]
Verzonden: 14 December, 2016 03:37
Aan: BITX20@...
Onderwerp: Re: [BITX20] Re: Bitx Drift
?
?
Is there a schematic and write up on this VFO anywhere? It sure looks like a neat project. Thanks for posting it. ?
?
?
Would this solve your problems:
Working with W5KUB, Tom Medlin, last days to get the Arduin/SI5351 to work.
Still needs some work but no more drift.
Ron – PA3FAT
I have 100 NP0 caps for 1000pF and 150 pf. ?these are surface mount.? I would be happy to send some to anybody to try.? Just send a SASE to me (I am good
on QRZ.com).? Note that I had a bit of difficulty with my mod, so your milage may vary. ?
all true, but i store my toroids in air. when the radio is cookin', i'd bet that a toroid parked in the middle of the top ( i.e. the side with the warm
resistors attached and the side where they would radiate from) of that board is warmer than one parked on the bottom side. sounds like a test worthy hypothesis... and, true or not, would that be a factor in VFO stability??
and while i have ordered npo caps, and have considered changing and moving the inductor, currently my indian made bitx and i are at opposite ends of a
continent... so, sadly, i can only conjecture at this point. but it would be fun to actually measure and see if it makes any significant difference. i.e. does it really help to move the toroid to the bottom of the board?
?
|
Raj vu2zap
Joel Caulkins/N6ALT