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Re: It stopped transmitting
On the contrary.
These? are voltage devices, not current devices. If you put enough voltage on the gate, it will go into avalanche mode and destroy the device within milliseconds. Always start with noting the gate voltage, and NEVER exceed 5v. DC.? Even this is questionable since there is a lot of variance in these devices and the gate voltage is not a fixed amount. As to AC voltage, mostly you are looking for the instantaneous quantity. That can and will easily exceed 5v. But it must never remain there for more than a microsecond or two for the reasons above. The 50 ma. figure is an assumption that this will put the device in the more or less "safe" zone. That is not guaranteed. With your device, 50 ma. gives you a gate voltage of ~3.5v, but that is not fixed. Every IRF510 (every switching MOSFET for that matter) is different. If the average "good" voltage is about 3.5-4.0v, then about half will be lower than that; half slightly more than that, but never more than 5v or so. john AD5YE ---In BITX20@..., <socijalizam1@...> wrote : you must look the current ,about 50ma (witahout input signal) ..voltage is not imporant but in my case is 3,4v on gate irf 510 |
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Re: It stopped transmitting
Yes, you monitor current into the final when setting the IRF510's bias. ?Ashhar's "Wire Up" notes suggest setting the bias for 100ma. ?Just be aware that (as I read the datasheet) the current goes from almost zero to 10 Amps over about 1/5'th of the 5v range available to that pot, and 10a*12v = 120 Watts is enough to blow the top of that IRF510 across the room. ?A fuse of some sort might be a good idea, though will cost you about as much as the IRF510.
On the other hand, I'm not seeing many reports here of people blowing the final, so I'm probably getting a little carried away. Regarding whether the IRF510's can run reliably at 24v for higher power: > Good thing they never saw this: > ? ? Note that he's running all those IRF510's with 40v on the drain. That design is very aggressive, and not just in the choice of drain voltage. So my take is that his IRF510's blew at about 41v. Jerry, KE7ER ---In BITX20@..., <socijalizam1@...> wrote : you must look the current ,about 50ma (witahout input signal) ..voltage is not imporant but in my case is 3,4v on gate irf 510 |
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Re: Si5351 VFO - Low Pass?
开云体育Spurious responses caused by the odd-order harmonics inherent in a square-wave local oscillator are relatively easy to eliminate with front-end filtering. What is much more difficult to eliminate is the intermodulation distortion caused by having the mixer diodes only partially conducting for a significant proportion of a cycle - that's what happens if you use a sine-wave local oscillator.Steve G3TXQ |
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Re: Si5351 VFO - Low Pass?
Whether a LPF at the VFO frequency lowers your noise level may or may not be noticeable, however the Si5351 outputs Square waves that are inherently high in harmonic energy which is why you need a LPF. The mixer should be mixing ONLY the signal we want and not all of the harmonics being generated, so, in the end you may not notice anything different with your ears, but I'm going to include a LPF because it's the proper way to do it and it's easy. Nobody is saying that it wont work without one. Also there are many commercially designed VFO's driving diode ring mixers with sine wave outputs that perform perfectly, I've built many of them including simple Collpits Crystal oscillators, they work perfectly. YMMV.
Joel KB6QVI |
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Re: It stopped transmitting
Indeed.
From fig 1 on page 3 of the Vishay datasheet, the IRF510 might have a drain current of around 10 Amps at a Vgs of 5 Volts. ?That's sucking 10*12 = 120 Watts from a 12 Volt supply, and all that power is has to go somewhere. ?Drain current approaches zero at a Vgs of 4 volts, so adjusting RV1 will be touchy. ?Also check fig 3, shows that with Vgs at 4.5v, the drain current doubles as temps go from 25C to 175C, so we could have thermal runaway. ?It would be very easy to blow an IRF510 when twiddling that RV1 pot. ?Page 2 says Vgs(th) is between 2 and 4 volts. ?So I'm pretty sure the voltage at the IRF510 gate will have to be higher than 1-2 volts. I plan to put at least a fuse, or perhaps a minismdc075f/24-2?polyswitch, in-line?with the power connector into PA-PWR1. ?And perhaps a thermal sensor on the IRF510 heat sink that clamps the IRF510 gate bias to ground if the temperature exceeds 80C or so. As mentioned previously, the IRF510 was designed for use on stuff like automobile turn signal blinkers. A fun quote from ? ? "In talking to International Rectifier, they were floored to find out QRPers were using them at 7MHz or higher." Good thing they never saw this: ? ?? Jerry, KE7ER ---In BITX20@..., <iam74@...> wrote : What is the voltage at the base of the IRF510? It should be about 1-2v. Anything above 5v or so will blow it up. These devices are very touchy. ? |
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Re: Si5351 VFO - Low Pass?
P.S. I meant to also mention, I agree with those who said that a squarewave is ideally better for a diode ring mixer. I think that theoretically the diode ring mixer should be more noisy with a sinewave drive, than squarewave. I think if there is noise its source is probably elsewhere... On Fri, Jan 6, 2017 at 11:25 PM, Hans Summers <hans.summers@...> wrote:
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Re: Si5351 VFO - Low Pass?
I agree with Jerry I don't think any detectable extra noise will be caused by the Si5351A. If you have noise it is likely coming in from elsewhere - such as the processor for example. (By the way I have not heard of anyone reporting the QRP Labs VFO is noisy, I think the earlier comments about noise were from an SI5351A in a different system). It would be quite nice to have some more specific details, everything so far was a bit vague. Fact is, when you use the analogue VFO built on the BITX40 board, everything is close by. When you pipe in an external VFO then unless you are careful, you have introduced much longer wire lengths, and opportunity for ground loops etc. All of these can help pick up noise. As far as I can tell a lot of ground loop elimination is as much black magic as it is science. Easy things to try are to put an inductor in series with the supply voltage to digital circuits, with a decoupling capacitor either side. That's a Low Pass Filter and keeps RF out of the supply lines. A lot of times if there is interference from digital circuits, this helps a lot. I agree also, the 40m LPF is not the right one to use, because the VFO is at 5MHz not 7MHz. We have a 60m LPF which would be suitable .? 73 Hans G0UPL |
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Re: the arrival
Billy Shepherd
10 days total
From: BITX20@... [mailto:BITX20@...] Sent: Friday, January 06, 2017 3:10 PM To: BITX20@... Subject: Re: [BITX20] the arrival 10 business days (Mon-Fri)? Or 10 days total? Rich KC8MWG On Friday, January 6, 2017 3:07 PM, "Billy Shepherd billy.shepherd@... [BITX20]" <BITX20@...> wrote: Took 10 days from the point that it was “put in a bag”…also was not able to track it after that…just showed up 10 days later. From: BITX20@... [mailto:BITX20@...] Sent: Friday, January 06, 2017 3:03 PM To: BITX20@... Subject: Re: [BITX20] the arrival Checked the India Post tracking on mine today. Looks like it was shipped on Monday, and arrived (and subsequently put into a bag in Mumbai) yesterday morning (Mumbai time). Next destination is ISC New York. We'll see how long customs holds onto it once the plane arrives. I am simply hoping it arrives before the Straits Area Amateur Radio Club, which I belong to, meets on the 17th, as I want to try to drum up some interest in this as an affordable club project. Rich KC8MWG On Friday, January 6, 2017 2:26 PM, "Billy Shepherd billy.shepherd@... [BITX20]" <BITX20@...> wrote: After a week I emailed HF Signals to see if they received my order. They emailed back immediately and advised it would ship in next 24 hrs and it did. From: BITX20@... [mailto:BITX20@...] Sent: Thursday, January 05, 2017 6:21 AM To: BITX20@... Subject: Re: [BITX20] the arrival Mark, Me too, same day, haven't heard a thing. Joel Caulkins KB6QVI On Jan 4, 2017, at 9:27 PM, 'Mark W' k3mrk1@...<mailto:k3mrk1@...> [BITX20] <BITX20@...<mailto:BITX20@...>> wrote: I ordered the upgrade on 12/23 and haven’t heard a thing yet. Mark K3MRK From: BITX20@...<mailto:BITX20@...> [mailto:BITX20@...] Sent: Wednesday, January 04, 2017 6:42 PM To: 'BITX20@...<mailto:BITX20@...>' Subject: RE: [BITX20] the arrival December 16th. Waiting to here back…the potentiometer for the balanced modulator is missing…not sure if this is just a redesign. Mine came without the Raduino. Billy Shepherd Bartholomew Co 911 Center 131 S Cherry St. Columbus, IN 47201 From: BITX20@...<mailto:BITX20@...> [mailto:BITX20@...] Sent: Wednesday, January 04, 2017 5:52 PM To: BITX20@...<mailto:BITX20@...> Subject: Re: [BITX20] the arrival Great! What date did you order it? Rich KC8MWG On Wednesday, January 4, 2017 2:13 PM, "Billy Shepherd billy.shepherd@...<mailto:billy.shepherd@...> [BITX20]" <BITX20@...<mailto:BITX20@...>> wro te: 2 weeks to ship for free from India to Indiana, awesome! [cid:image001.jpg@...][cid:image002.jpg@...] [cid:image003.jpg@...] |
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Re: the arrival
10 business days (Mon-Fri)? Or 10 days total? Rich KC8MWG On Friday, January 6, 2017 3:07 PM, "Billy Shepherd billy.shepherd@... [BITX20]" <BITX20@...> wrote:
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Re: the arrival
Billy Shepherd
Took 10 days from the point that it was “put in a bag”…also was not able to track it after that…just showed up 10 days later.
From: BITX20@... [mailto:BITX20@...] Sent: Friday, January 06, 2017 3:03 PM To: BITX20@... Subject: Re: [BITX20] the arrival Checked the India Post tracking on mine today. Looks like it was shipped on Monday, and arrived (and subsequently put into a bag in Mumbai) yesterday morning (Mumbai time). Next destination is ISC New York. We'll see how long customs holds onto it once the plane arrives. I am simply hoping it arrives before the Straits Area Amateur Radio Club, which I belong to, meets on the 17th, as I want to try to drum up some interest in this as an affordable club project. Rich KC8MWG On Friday, January 6, 2017 2:26 PM, "Billy Shepherd billy.shepherd@... [BITX20]" <BITX20@...> wrote: After a week I emailed HF Signals to see if they received my order. They emailed back immediately and advised it would ship in next 24 hrs and it did. From: BITX20@... [mailto:BITX20@...] Sent: Thursday, January 05, 2017 6:21 AM To: BITX20@... Subject: Re: [BITX20] the arrival Mark, Me too, same day, haven't heard a thing. Joel Caulkins KB6QVI On Jan 4, 2017, at 9:27 PM, 'Mark W' k3mrk1@...<mailto:k3mrk1@...> [BITX20] <BITX20@...<mailto:BITX20@...>> wrote: I ordered the upgrade on 12/23 and haven’t heard a thing yet. Mark K3MRK From: BITX20@...<mailto:BITX20@...> [mailto:BITX20@...] Sent: Wednesday, January 04, 2017 6:42 PM To: 'BITX20@...<mailto:BITX20@...>' Subject: RE: [BITX20] the arrival December 16th. Waiting to here back…the potentiometer for the balanced modulator is missing…not sure if this is just a redesign. Mine came without the Raduino. Billy Shepherd Bartholomew Co 911 Center 131 S Cherry St. Columbus, IN 47201 From: BITX20@...<mailto:BITX20@...> [mailto:BITX20@...] Sent: Wednesday, January 04, 2017 5:52 PM To: BITX20@...<mailto:BITX20@...> Subject: Re: [BITX20] the arrival Great! What date did you order it? Rich KC8MWG On Wednesday, January 4, 2017 2:13 PM, "Billy Shepherd billy.shepherd@...<mailto:billy.shepherd@...> [BITX20]" <BITX20@...<mailto:BITX20@...>> wro te: 2 weeks to ship for free from India to Indiana, awesome! [cid:image001.jpg@...][cid:image002.jpg@...] [cid:image003.jpg@...] |
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Re: the arrival
Jack Purdum
Me too, 12/26...nada... Jack, W8TEE From: "Billy Shepherd billy.shepherd@... [BITX20]" To: "'BITX20@...'" Sent: Friday, January 6, 2017 2:26 PM Subject: RE: [BITX20] the arrival
?
After a week I emailed HF Signals to see if they received my order. They emailed back immediately and advised it would ship in next 24 hrs and it did.
From: BITX20@... [mailto:BITX20@...] Sent: Thursday, January 05, 2017 6:21 AM To: BITX20@... Subject: Re: [BITX20] the arrival Mark, Me too, same day, haven't heard a thing. Joel Caulkins KB6QVI On Jan 4, 2017, at 9:27 PM, 'Mark W' k3mrk1@... [BITX20] > wrote: I ordered the upgrade on 12/23 and haven’t heard a thing yet. Mark K3MRK From: BITX20@... [mailto:BITX20@...] Sent: Wednesday, January 04, 2017 6:42 PM To: 'BITX20@...<mailto:BITX20@...>' Subject: RE: [BITX20] the arrival December 16th. Waiting to here back…the potentiometer for the balanced modulator is missing…not sure if this is just a redesign. Mine came without the Raduino. Billy Shepherd Bartholomew Co 911 Center 131 S Cherry St. Columbus, IN 47201 From: BITX20@...<mailto:BITX20@...> [mailto:BITX20@...] Sent: Wednesday, January 04, 2017 5:52 PM To: BITX20@... Subject: Re: [BITX20] the arrival Great! What date did you order it? Rich KC8MWG On Wednesday, January 4, 2017 2:13 PM, "Billy Shepherd billy.shepherd@... [BITX20]" > wro te: 2 weeks to ship for free from India to Indiana, awesome! [cid:image001.jpg@...][cid:image002.jpg@...] [cid:image003.jpg@...] [Non-text portions of this message have been removed] [Non-text portions of this message have been removed] [Non-text portions of this message have been removed] |
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Re: the arrival
Checked the India Post tracking on mine today. Looks like it was shipped on Monday, and arrived (and subsequently put into a bag in Mumbai) yesterday morning (Mumbai time). Next destination is ISC New York. We'll see how long customs holds onto it once the plane arrives. I am simply hoping it arrives before the Straits Area Amateur Radio Club, which I belong to, meets on the 17th, as I want to try to drum up some interest in this as an affordable club project. Rich KC8MWG On Friday, January 6, 2017 2:26 PM, "Billy Shepherd billy.shepherd@... [BITX20]" wrote:
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BITX 40 Questions
steve.shorey@ntlworld.com
开云体育Hi folks I have got my BiTX40 board?all going in a nice box using an AD9850 DDS/PIC controller. Although it works pretty well? I do have a few issues that have annoyed me a little - and perhaps others here?may have resolved. Audio hiss - not the LM386 ( I know the mod to drop its gain down). The hiss is already present on?its input, as a quick fix I put?small R/ C network across the VOL control? to roll?the treble off?- makes a huge difference. are they all?like this?? Carrier balance - on TX the carrier balance is poor?- listening on another RX it wont null out with the preset pot -? even my ancient tube rigs are better. I imagine its either mismatched diodes or a poorly wound toroid. I expected a couple of pf caps (one?variable) ?to ensure a good carrier null, but they are not present in the design. Lastly - I found any condenser mic capsule I tried?sounded dreadful so went with a low imp dynamic comms mic and blocking cap..but I had to add a single transistor preamp to get enough gain. Still a fun radio though!!! Regards - Steve G3ZPS Sent from Windows Mail |
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Re: the arrival
Billy Shepherd
After a week I emailed HF Signals to see if they received my order. They emailed back immediately and advised it would ship in next 24 hrs and it did.
From: BITX20@... [mailto:BITX20@...] Sent: Thursday, January 05, 2017 6:21 AM To: BITX20@... Subject: Re: [BITX20] the arrival Mark, Me too, same day, haven't heard a thing. Joel Caulkins KB6QVI On Jan 4, 2017, at 9:27 PM, 'Mark W' k3mrk1@...<mailto:k3mrk1@...> [BITX20] <BITX20@...<mailto:BITX20@...>> wrote: I ordered the upgrade on 12/23 and haven’t heard a thing yet. Mark K3MRK From: BITX20@...<mailto:BITX20@...> [mailto:BITX20@...] Sent: Wednesday, January 04, 2017 6:42 PM To: 'BITX20@...<mailto:BITX20@...>' Subject: RE: [BITX20] the arrival December 16th. Waiting to here back…the potentiometer for the balanced modulator is missing…not sure if this is just a redesign. Mine came without the Raduino. Billy Shepherd Bartholomew Co 911 Center 131 S Cherry St. Columbus, IN 47201 From: BITX20@...<mailto:BITX20@...> [mailto:BITX20@...] Sent: Wednesday, January 04, 2017 5:52 PM To: BITX20@...<mailto:BITX20@...> Subject: Re: [BITX20] the arrival Great! What date did you order it? Rich KC8MWG On Wednesday, January 4, 2017 2:13 PM, "Billy Shepherd billy.shepherd@...<mailto:billy.shepherd@...> [BITX20]" <BITX20@...<mailto:BITX20@...>> wro te: 2 weeks to ship for free from India to Indiana, awesome! [cid:image001.jpg@...][cid:image002.jpg@...] [cid:image003.jpg@...] |
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Re: Si5351 VFO - Low Pass?
I know I have RFI problems in the house, between the WiFi and the CFL lamps. So much so, that I can only reliably receive two or three of the local AM broadcast stations in the house whereas if I take a radio outside I can pick up a LOT more (and no, I don't live in a "Faraday cage - we have a wood framed house with vinyl siding; only the roof is metal, but the problem existed before the metal roof was installed). Rich KC8MWG On Friday, January 6, 2017 12:29 PM, "jgaffke@... [BITX20]" wrote:
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Re: Si5351 VFO - Low Pass?
It's quite common for noise sources in the house to go up the coax and come back in from the antenna.
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Could be you need a good "common mode choke". ?? ?? My totally uninformed opinion: ?I think the Si5351 noise everybody's talking about is likely hash from the processor driving it. ?And that if this less-than-optimal LPF is reducing the noise to where it's as good as the analog VFO, that's good enough. ?The ideal would be to clean up the noise somehow without band specific filters, then we're back to switching only two filters if we want a multiband rig. ? The diode ring mixer wants to be driven hard. ?The ideal is for two of the diodes to turn on for 1/2 the LO cycle, the other two diodes to turn on for the other half of the cycle. ?Anything less, and changes in the other input signal (from the antenna when receiving) can disrupt the desired action of this commutating mixer. ?A square wave is actually preferred, and a perfectly clean sine wave from the LO will have a totally non-linear response from the diodes anyway since the current through a diode is exponential with voltage, not linear like a resistor. Of course I may well have totally different opinions once I get a Bitx to play with. Jerry ---In BITX20@..., <caulktel@...> wrote : If your using the QRPlabs VFO for the BitX40, then the LPF you bought for 40 meters is optimized for 7-7.5MHz. You need a LPF for the actual VFO output which is 4.5-5MHz. The 7MHz one is probably helping to clean the output somewhat, but is not optimal.? On Jan 5, 2017, at 9:53 PM,?dvoorhees@...?[BITX20] <BITX20@...> wrote:...I'm experiencing a high level local noise, but without the antenna it's very quiet.? ? |
Joel Caulkins/N6ALT
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