I am sure by now some of you have noticed that the bias pot is counter intuitive.
Anticlockwise increases the final bias current where as it should have been the
other way around. Cost me one IRF !
While new boards finals are being setup please remember this!
Farhan, next set you can consider changing this!
Cheers
--
Raj, VU2ZAP
Bangalore, India.
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It is quite simple to tell the difference between a birdie and an AM station in my analog vfo board.
The AM signals are very steady in tone compared to the birdies. I am not sure if this applies to the
raduino fed boards.
I also have the 199 birdie and a few more weaker ones between 7.1 and 7.3, will try and analyse
this after I am back in town tomorrow.
73
--
Raj, VU2ZAP
Bangalore, India.
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I am sure by now some of you have noticed that the bias pot is counter intuitive.
Anticlockwise increases the final bias current where as it should have been the
other way around. Cost me one IRF !
While new boards finals are being setup please remember this!
Farhan, next set you can consider changing this!
Cheers
--
Raj, vu2zap
Bengaluru, South India.
|
Re: interference from SW broadcasters above 7200
I recently switched over to the QRP Labs VFO, and notice that same birdie. After adding some hefty decoupling capacitors (2200uf) at the VFO and at the 7805 regulator, the birdie is significantly reduced and shouldn't cause any problems. YMMV. I suspect switching to RG174 for the signal injection will help as well, but I don't have any to try with.? --
Ryan Flowers KC7RYS?
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Re: Possible PA low output problem. Problem SOLVED
This is probably the best symptom to check. The 2N2219A is the driver for the final. The current flow through the emitter resistor determines not only the amount of drive,
but the amplifier class. If that 10 ohm resistor is being fried, either it is not a heavy-duty enough part, or it is being over-driven. Note that R136 provides the drive to the amplifier.
A proper procedure to check through would be:
Tools: a good DVM. a RF probe feeding a DC voltage to the DVM.
If you are replacing the IRF510, drop R136 and RV1 down to near zero. If not, adjust RV1 FROM ZERO for a drain current draw of an additional 100 ma. of current draw
for the whole rig. Note that RV1 adjusts the gate voltage; the increased drain current is an indirect effect. Note that at a gate voltage of 0-3v the drain current will be minimal,
and then increase quickly around 3v as the gate voltage is increased. At some point about 5v on the gate, there will be a sudden and very heavy current though the drain.
That is the avalanche region. If you hit that, you have gone too far. It is probably a good practice to put a 1/2A fuse temporarily in the drain supply line to limit
the current draw if you should hit the avalanche region; often, even that is not enough as the effect is sudden and catastrophic to the device if the current
is continuous. And every IRF510 is different. This can happen at ANY point! If it does around 3-4v on the gate, replace the unit with a better one.
Then, when you have decided that you are in the linear region of the IRF510, look to the driver. The 2N2219A should be only warm to the touch. The 10 ohm emitter resistor
should be cool and remain pretty much so, or heat to a bit warm. It should never be hot. The amplifier is operating Class A with the warmest feel (most current draw) to the resistor Measure the RF voltage at the top of RV1 when transmitting a more or less continuous tone. It should be in the region of 1-2v pk to pk. If not trace back and find out why. Usually that is somewhere in the mic drive. Gradually increase R136 while observing the power output into a 50 ohm dummy load. When you have about 5W output, stop. That is about right. Check your audio with a QSO and tweak the drive to make it right. Don't adjust too much. You may have to iterate some between R136 and RV1 to get an adequate result. But once you have hit an output region, further adjustments are small.
If you decide to use 24v at the drain of the IRF510, the procedure is about the same. Current draw will be different, of course, because you will be transmitting at a 10-20W level. But not that different! Never use anything over 14v in the main board. For one thing, power is applied continuously to the VFO and BFO, and these units have power limits. Even if you are using a DDS, Q8 and Q7 are still active. In fact, Q7 is usually the hottest area of the board, no matter what the BITX version.
john
AD5YE
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Re: Current draw and fusing
Mike:
Since the BITX is putting out about 6W on transmit, that means the current draw can be calculated. For DC power, P = E x I. Ordinarily, one can assume as a first rule of thumb that
the efficiency is around 40%. So the transmit current draw will be about 6W / .40 = 15W. The current draw will be 15 / 12 = 1.25A. Add another .25A for the "other than PA draw" and that gives a transmit current draw of about 1.5A. Receive power will be much less...one can get away with assuming about 5W. Note that the "quiescent current draw" adjustment is for .1-.2A in the PA, and about .2A in the rest of the rig.
A 4A fuse in the positive line would be more than enough. I am not sure why you would want to fuse the ground. The National Electric Code (and common sense) says that you should never provide any potential interruption to ground (or neutral). That is the power return and interrupting that leaves the rig at a voltage potential. If an operator provides a ground, then,,,well, you get the picture. Another thing, the IRF510 is a very fickle device. You should always use a fast-blow fuse and hope that it protects your final. A slo-blow fuse is guaranteed to destroy it if there is a sudden increase in current.
Note that AC power is completely different. That involves inductance and capacitance effects, SWR, and a whole lot of other things. Start with a good antenna and pay close attention to the SWR. Never transmit into a 3:1 SWR. Ideal is 1:1 but you can get away with 1.5:1. Commercial rigs usually have an automatic shutdown if a high SWR is detected. The BITX does not.
Be warned.
Hope this helps.
john
AD5YE
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Re: interference from SW broadcasters above 7200
The raduino output is to betaken using a snall coax like RG174. In case, loose wires with a? plug ius used,
?we do get local interference in places where there are radio stations in the 4.8 to5MHz . This is reported at Hyderabad (India) by vu3nep We need to prevent that induction. all the best ?sarma ?vu3zmv
On Sun, Feb 12, 2017 at 3:13 AM, Allard PE1NWL <pe1nwl@...> wrote: Touching the raduino crystal does indeed change the pitch of the tone of the birdies.
However, when I connect the antenna, and tune to a cw station, then the pitch also changes when I touch the crystal.
I think this is simply because the DDS output frequency is slightly changed when the crystal is touched.
So ANY received signal (birdies as well as 'true' signals) will be affected when the crystal is touched.
So i.m.o., the simple fact that the pitch of the birdie changes when the crystal is touched, does not necessarily mean that the birdie is coming from the crystal itself.
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Re: Possible PA low output problem. Problem SOLVED
On Sat, Feb 11, 2017 at 02:06 am, G4NQX wrote:
1n60 are a Schottky diode with similar specs to the others I mentioned but small glass package.
It's an old-time (hence the low "1N" number) point-contact germanium. I've heard those old germanium diodes (such as the 1N34) are pretty leaky. Will they work well in this application? 73, Todd K7TFC
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Re: Possible PA low output problem. Problem SOLVED
John Glad to ?hear about the success. Randy, K7AGE
On Sat, Feb 11, 2017 at 5:07 PM, John Smith via Groups.Io <johnlinux77@...> wrote: Jerry gave me the final clue to fully solving the problem. He told Randy in another thread about problem solving, that R136 is like a mic gain adjustment. I noticed in all pictures available, that pot was set exactly the same. So after changing the final PA and having to adjust the Bias lower for 100mA current draw, I thought this may need re-adjusting too. I kept saying that it doesn't seem to be generating a loud enough audio signal before sending it ?out to the final. So, I adjusted it while listening with the SW receiver and watching the watt meter until it was peaked with no audio distortion ever noticed, just no audio when turned all the way down clockwise. I couldn't wait, so I brought up the Sedona Arazona WebSDR station and actually heard my voice coming in from Oklahoma. I was running 20V on the PA. The signal was weak but audible and visible on the waterfall display. When I came down off the ceiling I did it again but couldn't hear it again. This is consistent with my CW signal monitoring. You know, band conditions between here and there right now, kinda of thing. 40M sure was busy at that time. ?Possible PA low output problem. Problem SOLVED!? Congratulations Tom, thanks Jerry, Randy helped too by asking Jerry the right question, and thank you everybody else except for the ex-parrot. I am surprised it worked that well with an antenna that had 4+ swr without the tuner, and 1.2:1 with a tuner I have noticed attenuates the signal both ways. I am probably going to put the original dipole back up and trim it for more than just CW.?
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Re: Possible PA low output problem. Problem SOLVED
Jerry gave me the final clue to fully solving the problem. He told Randy in another thread about problem solving, that R136 is like a mic gain adjustment. I noticed in all pictures available, that pot was set exactly the same. So after changing the final PA and having to adjust the Bias lower for 100mA current draw, I thought this may need re-adjusting too. I kept saying that it doesn't seem to be generating a loud enough audio signal before sending it ?out to the final. So, I adjusted it while listening with the SW receiver and watching the watt meter until it was peaked with no audio distortion ever noticed, just no audio when turned all the way down clockwise. I couldn't wait, so I brought up the Sedona Arazona WebSDR station and actually heard my voice coming in from Oklahoma. I was running 20V on the PA. The signal was weak but audible and visible on the waterfall display. When I came down off the ceiling I did it again but couldn't hear it again. This is consistent with my CW signal monitoring. You know, band conditions between here and there right now, kinda of thing. 40M sure was busy at that time. ?Possible PA low output problem. Problem SOLVED!? Congratulations Tom, thanks Jerry, Randy helped too by asking Jerry the right question, and thank you everybody else except for the ex-parrot. I am surprised it worked that well with an antenna that had 4+ swr without the tuner, and 1.2:1 with a tuner I have noticed attenuates the signal both ways. I am probably going to put the original dipole back up and trim it for more than just CW.?
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I received my kit but haven't started construction until I get the metal case. Does anyone know the power drawn during transmit with a bitx in normal 12-13vdc configuration? I'd like to fuse both power lines and try to figure out what size battery will give me 1-2 hours (at least) of field, portable use. Thanks
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Re: transmitting CW with Raduino Bitx40?
Here's something I tried. For my BITX40 with DDS I use a PC mic/phones headset. ?My keyer (K8+) has a sidetone that you can turn on/off. I use my FT-101E in CW mode as a monitor. ?I feed the BITX into my dummy load and tune it to a CW freq. Then I hold the PTT and tune the 101E and look for the carrier - somewhere near the BITX setting. I pull the phones plug out of BITX and listen through the speaker. ?I then place the headset mic on top of the sidetone speaker, start sending some CW and fine tune the 101E till I get a clear signal. It works great into the dummy load but I'm not game to try it on air. ?Am I really sending CW? Noel - VK2CAO
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Re: Testing VFO A, VFO B, RIT, USB, CW options in sketch code
On Fri, Feb 10, 2017 at 12:07 pm, Jerry Gaffke wrote: Currently that is crytal controlled, and involves hacking L5 and C103 I don't think I've seen a mod yet for USB. I had an Si5351 working on an Arduino, both backpacked to an LCD, so that's what I used in building mine. Buuut, It would be nice to use USB for digital might be nice.?
Would'ya just insert a BFO signal at the point where L5 joins, leaving Q10 and Q11 to amplify it?
Mike Y, KM5Z
Dallas, Texas
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Re: Bitx40 Circuit Diagnosis How To?
Note: I also removed c113 so that may have fixed the audio.
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Re: Bitx40 Circuit Diagnosis How To?
Q15 RX B: 0, E: 12.27, C: 0 Q15 TX B: 4.50, E: 11.71, C: 0.01 The above voltages were measured prior to heating up cold joint in R45. I have a simple RF probe kit, which is a capacitor, resistor and diode which is connected to a voltmeter.? It looks like it works as a rectifier and allows a voltage to be read from AC.? It is an older kit from the QRPp International Radio Club.? I have never used it.? Are these helpful? This is the RF Probe circuit: http://www.n5ese.com/rf_probe_schem.jpg
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Re: interference from SW broadcasters above 7200
Touching the raduino crystal does indeed change the pitch of the tone of the birdies.
However, when I connect the antenna, and tune to a cw station, then the pitch also changes when I touch the crystal.
I think this is simply because the DDS output frequency is slightly changed when the crystal is touched.
So ANY received signal (birdies as well as 'true' signals) will be affected when the crystal is touched.
So i.m.o., the simple fact that the pitch of the birdie changes when the crystal is touched, does not necessarily mean that the birdie is coming from the crystal itself.
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NOPE THE 9TH CKT COURT SAZS IT CAN BE ABOUT ANYTHING ? ? On 02/11/17, Ray Koster via Groups.Io<raykoster@...> wrote:? I am afraid it applies to the whole group...3000 posts since 26th Dec 2016!!!...There is not that many components on the two panels put together...someone should moderate this group and stop all these posts about unrelated items..SDR Kits..I thought it was about Bitx40 Kits!!!
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On Sat, Feb 11, 2017 at 11:56 am, Ray Koster wrote: someone should moderate this group and stop all these posts about unrelated items..SDR Kits..I thought it was about Bitx40 Kits!!!
Please reread the post you complain about. SDR Kits is the name of the outfit that makes one of the **VFOs** being used experimentally on the BitX40. That does not mean the group has been hijacked by SDR enthusiasts. By the way, according to its name, this group isn't about the BitX40, either. That's okay with me, because the world really doesn't need more than one group for the BitX family of scratch-built, kit-built, or semi-built transceivers.
Instead of asking someone else to eliminate the posts you don't want to read, why not just use the delete key? Todd K7TFC
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Re: interference from SW broadcasters above 7200
Is its can earthed? If not try earthing the crystal can. Regards Lawrence
On Sat, Feb 11, 2017 at 8:14 PM, philip yates <phil@...> wrote: Hi pitched tone, bang on 7.200, unplug the aerial and it is still there. At the moment my Bitx40 is just sitting on the bench, not in a case. Have just moved the Raduino and my finger made contact with some pads? on the rear of the pcb, the note changed, its the crystal that i made contact with.
Phil G7BZD
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If we get rid of oddball posts, we will not have any info on mods, tips, or tricks.? The kit was to be an inexpensive radio, for experimentation and learning.? That takes many forms.? It was made to be a starting point.? If the post doesn't seem relevant to you, just mark it as read and move on.
On Feb 11, 2017 2:16 PM, "ken barnes" < kenbarnesg8gti@...> wrote: i agree 110% with you ? ? ? ? ? KEN ? G6GTI
I am afraid it applies to the whole group...3000 posts since 26th Dec 2016!!!...There is not that many components on the two panels put together...someone should moderate this group and stop all these posts about unrelated items..SDR Kits..I thought it was about Bitx40 Kits!!!
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Raj vu2zap
Todd K7TFC
Allard PE1NWL