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Re: LPF toroids
Thanks John 73 Ken On Thu, Feb 9, 2017 at 6:31 PM, John Backo via Groups.Io <iam74@...> wrote: Ken: |
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Re: Click on keying ptt
You are shorting out one of the input resistors and increasing Vcc on the input darlington pair.
This is not a good idea, since it increases the current drain and heat generated. Pin 2 is for "Bypass" and is meant to go to ground through a capacitor to filter out line noise. Your method upsets the voltage balance of the internal transistors. Interesting idea though... The best solution is probably a FET mute such as that commonly found to mute CW receive during key down. It should be at the input and might have to be somewhat heftier than a 2N7000 (which is commonly used) but I think a BS170 should handle it. john AD5YE |
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Re: Possible PA low output problem. Problem SOLVED
The Vishay datasheet for BAT54 diodes lists the BAT54S SOT-23.
It has a marking "L44". Note that the common output of this diode pair is where the old pot went (between the diodes). If using separate diodes, some rearrangement might have to be made. john AD5YE |
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Re: LPF toroids
Ken:
They are T-37-6 toroids. Toroids are classified by their diameter and their color. Hence, T50-2 toroids would be 1/2 inch across and color red, usually used in a frequency range below 30m. The usual colors for RF are red (type 2). yellow (type 6) and white (type 7). Beware of toroids that are yellow with a white side. They are common in switching power supplies. These are #26 material and are meant for low frequency switching. Note that this nomenclature applies to powdered metal toroids. Ferrite toroids are different. Generally they are all black or grey. The same size nomenclature applies but they a totally different mix. Usual ones in Rf are FT-37-43 and FT-37-61. The "FT" stands for "Ferrite Toroid". FT's are usually used in broadband transformers and mixers. check out the Amidon site for more information. john AD5YE |
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Re: Possible PA low output problem. Problem SOLVED
My Q13 seems fine with voltages in-line with Randy's voltage chart. I haven't checked everything yet. From much earlier posts about Q13, it was one of the first things I checked. I am still awaiting conformation from Tom on the part location and part number IL440. It's possible he's wrong. Really need others to confirm and comment. But if it's true I am gonna throw that wrong part into the sun!
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Re: Click on keying ptt
OK, I've done some experiments today:
1. connect a jumper wire between pin 7 and pin 4 (GND) - the audio was almost completely muted, but not 100%. 2. connect the jumper between pin 7 and pin 6 (+Vcc) - now the audio was muted completely! So I'd guess this feature allows for a very elegant way to mute the audio during transmit - in fact much nicer than the way it's done in the current design (interrupt the input signal with relay K2). Now I still need to find a way to somehow use the 12V at "TX" (from relay K1) for applying +Vcc to pin 7. Would it be safe to connect "TX" via 100 ohms to pin 7? In that case pin 7 would be at +Vcc during transmit, however at the same time pin 6 would then not be connected to the supply anymore (because it is connected to "RX"). I'm not sure if that would hurt the LM386. Any ideas or other suggestions? 73, Allard |
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Re: Possible PA low output problem. Problem SOLVED
Don't assume low power out is due to a bad diode pair. The two issues at Q13 mentioned below can both cause a "Possible PA low output problem" that would be indistinguishable from a bad diode pair in the modulator. ?Also could be a a damaged IRF510, perhaps from driving a high SWR load with 20v on the drain, or setting the bias control beyond 100ma quiescent. ?Or the microphone connector got shorted out. ?Or transformer wires shorted or broken. ?Or about half the remaining parts in the rig experiencing some sort of failure. On Thu, Feb 9, 2017 at 12:19 pm, Jerry Gaffke wrote:
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Re: transmitting CW with Raduino Bitx40?
Has anyone implemented CW using the information contained in the comments of the latest Raduino sketch from . I have been trying to determine which Arduino input pin he is using for the CW key, from lines 103-116 of the sketch it looks like it should be "D5". Not sure how you change the mode to CW in the sketch. There is also mention of adding an NPN transistor and resistor connected to the PTT in lines 322-330. This new sketch is supposed to key the TX when you start sending CW and keeps the TX keyed until CW has stopped for a number of seconds. The comments also mention how to implement dual VFO's and RIT. Apparently the CW sidetone is also being fed to the mic input to generate the CW signal. AL |
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Re: transmitting CW with Raduino Bitx40?
Correction: We have to move the BFO up in frequency to get the BFO into the crystal filter passband on a stock Bitx40. ?This follows from the discussion in post 21810 Jerry On Fri, Jan 27, 2017 at 09:48 pm, Jerry Gaffke wrote: First off we have to move the BFO down in frequency by a khz or so, such that it is in the crystal filter passband. ? |
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Re: SDR kits VFO
Are you using an offset in the SDR VFO? 73 Ken On Thu, Feb 9, 2017 at 2:33 PM, Marc Jones via Groups.Io <gw0wvl@...> wrote: Hi Ken, I've tried it all and more with this SDR kits VFO, None of it works . |
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Re: Possible PA low output problem. Problem SOLVED
Regarding post 19730, there's a couple issues a bit further down that we need to keep track of. 1) ?Q13 is dissipating an awful lot of heat for a Sot23, may need to adjust the emitter resistor there. 2) ?Having your Bitx40 hooked up to an antenna while some nearby antenna is transmitting at high power can blow Q13, may need Raj's dual diode plus lamp fix. On Thu, Feb 9, 2017 at 12:04 pm, Jerry Gaffke wrote:
post 19730 ? |
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Re: Possible PA low output problem. Problem SOLVED
You'll never see BAT54 printed on a SOT23, that wouldn't fit. ?So they choose an arbitrary 2 or 3 ?character code to distinguish it from all the other SOT23 products they make. ?But there are far more SOT23 types than there are codes, and different manufacturers that build BAT54's will choose different codes. ?We've seen this before on the 2n3904 transistors, read post 19730. ?The ohmmeter readings taken of the bad part suggest that it really is a dual diode. My guess is that the correct part is getting stuffed, but at least one slipped by QC at the factory, got damaged when soldering it down, or by excessive current now that the 100 ohm pot has been removed. ?If it is excessive current, perhaps adding a resistor in series with C106 would fix it. ?Adding back R106 if it isn't needed for establishing modulator balance would best be avoided. ?Not yet clear if this dual diode was a problem on more than one unit. Jerry, KE7ER On Thu, Feb 9, 2017 at 11:23 am, John Smith wrote:
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Re: SDR kits VFO
Do you have a scope? If you do, set VFO to 5 MHZ. Scope the VFO signal at T2 with a x10 probe. You're going to need a signal around 1.4 v peak to peak. 73 Ken On Thu, Feb 9, 2017 at 2:33 PM, Marc Jones via Groups.Io <gw0wvl@...> wrote: Hi Ken, I've tried it all and more with this SDR kits VFO, None of it works . |
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Re: SDR kits VFO
Jack Purdum
Dollar to a donut it involves little more than changing a variable from unsigned long to signed long. Jack, W8TEE From: Jerry Gaffke via Groups.Io <jgaffke@...> To: [email protected] Sent: Thursday, February 9, 2017 2:47 PM Subject: Re: [BITX20] SDR kits VFO You are correct, and the SDR Kits VFO can probably do this. ?I don't have one, but the SDR Kits VFO apparently doesn't know about negative offsets, so as you tune up from 7mhz, the SDR Kits display will show the frequency decreasing. ?That's fine if you are ok doing the subtraction in your head or on a hand calculator, but a bit inconvenient. Example: ? 7.000mhz ssb is mixed with 5.000mhz vfo to create 12mhz IF 7.200mhz ssb is mixed with 4.800mhz vfo to create 12mhz IF For the receive frequency to go up from 7.000 to 7.200, the VFO must go down from 5.000 to 4.800. The SDR Kits VFO doesn't know how to subtract, so it will show a frequency that is decreasing. At least, nobody here has yet figured out how to make it subtract. Jerry, KE7ER On Thu, Feb 9, 2017 at 10:55 am, ron van doremalen wrote: The only thing you need to inject in the BITX40 is thus a 4.8-5.0 signal. ?
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Re: SDR kits VFO
You are correct, and the SDR Kits VFO can probably do this. ?I don't have one, but the SDR Kits VFO apparently doesn't know about negative offsets, so as you tune up from 7mhz, the SDR Kits display will show the frequency decreasing. ?That's fine if you are ok doing the subtraction in your head or on a hand calculator, but a bit inconvenient. Example: ? 7.000mhz ssb is mixed with 5.000mhz vfo to create 12mhz IF 7.200mhz ssb is mixed with 4.800mhz vfo to create 12mhz IF For the receive frequency to go up from 7.000 to 7.200, the VFO must go down from 5.000 to 4.800. The SDR Kits VFO doesn't know how to subtract, so it will show a frequency that is decreasing. At least, nobody here has yet figured out how to make it subtract. Jerry, KE7ER On Thu, Feb 9, 2017 at 10:55 am, ron van doremalen wrote: The only thing you need to inject in the BITX40 is thus a 4.8-5.0 signal. ? |
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Re: SDR kits VFO
Hi Ken, I've tried it all and more with this SDR kits VFO, None of it works .
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Regards? Marc ?'Gw0wvl'...
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Re: SDR kits VFO
All Someone should ask SDR Kits to modify their firmware to allow the negative offset. The QRP Labs VFO kit didn't support negative IF offset either but when I learned of the people wanting to use it for the BITX40 I made the necessary firmware enhancement. I know SDR Kits owner very well, he's a good friend of mine - and I'm sure he would be helpful! 73 Hans G0UPL |
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Re: Possible PA low output problem. Problem SOLVED
This will be my first hack. ?Could you write a small commentary on what you actually did in the order you did things, Apart from removing things and stuffing in replacements and adding components are there other connections you need to make? ?It all makes sense to me but I would appreciate a bit more detail. Thank you. Noel |
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Re: SDR kits VFO
There are two ways to get 7.0 - 7.2 MHZ(This RF). BFO is fixed at 11.998600 MHZ(approx). BFO - RF = 11.998600 - 7.0 - ?= 4.9986 to 4.7986? or BFO + RF = 11.998600 + 7.0 = 18.998600 to 19.198600 73 Ken VA3ABN On Thu, Feb 9, 2017 at 1:55 PM, ron van doremalen <ronvandoremalen@...> wrote: Jerry, |
Allard PE1NWL
Marc Jones