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Re: Willem xProm programmer ...
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Re: Buffer amplifier for 10MHz ?
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Re: msi 2500 sdr as a panadaptor
wn4isx
I used a amplifier based on the PA0RDT "Mini-Whip" because of it's low input impedance and low noise floor.
You might be able to get away with just using the J-FET input stage and feeding the output to your SDR or, if that doesn't work, go with a plain jane PNP output transistor because you are not dealing with the wide range of signal strengths an antenna is exposed to.
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You could probably even get away with using a lower quality J-FET like the 2N3819 or MPF102 (or is it MPF101....been too long since I used one, I have oodles of 2N3819 so I use them for general purpose N-Channel J-FETs).
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I had a spare "PAR0DRT" "Mini-Whip" I prototyped for an oscilloscope low capacity wide bandwidth (to me 0 to 30MHz qualifies as wide bandwidth on my bench) scope probe. I built a compact version for the scope then reassembled the prototype as a general low input impedance buffer. |
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Re: Buffer amplifier for 10MHz ?
wn4isx
The SN74LVC1G17 is rated to ~100MHz, most will work up to at least 150MHz. ? Operation is simple, feed you sloppy signal in and get a clean signal out with extremely sharp transitions, it won't be a perfect 50/50 square wave unless your input is a clean sine wave or triangle wave. ? They also work great at 10MHz. ? There are other similar ICs with similar specs. I've used the SN74LVC1G17 and know it works extremely well. ? It does require 3.3V max Vcc. ? ? Good luck. ? |
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Another and last file I intend to add to "Diode Commutation EMI"
wn4isx
"Investigation_and_Reduction_of_EMI_Noise_Due_to_the_Reverse_Recovery_Currents_of_50_60_Hz_Diode_Rectifiers.pdf"
Abstract¡ªAlternating current (ac)/ Direct current (dc) power
converters with dc-bus filters can achieve high power density, however, it was found in this article that the reverse recovery currents of the 50/60 Hz diode bridge can lead to significant electromagnetic interference (EMI) noise violating EMI standards above 150 kHz. This article analyzed and quantified the mechanism of the EMI generation due to the reverse recovery currents of the 50/60 Hz diodes. It was found that although the reverse recovery of the 50/60 Hz diode bridge repeats at a frequency of 50/60 Hz, the EMI can be very high above 150 kHz due to the operating principle of electromagnetic compatibility spectrum analyzers. Two techniques were proposed to reduce the EMI due to the reverse recovery of the diode bridge. The analyses were validated by either simulations or experiments. ?
Note: The 150kHz upper limit is extremely optimistic. I've had 1968 1N4004 diodes produce commutation EMI up to above 10MHz. Pretty intense too.
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Re: Some observations on linear power supplies
wn4isx
To emulate a regulator failure, I use a LM317/338 with a suitable diode between it and the load, I adjust the LM317 for 0.7V higher then the design goal, use a suitable resistor (or 2N3055 rigged to draw the right current as an active load), a SPST push button switch connected to a 24V 10A power supply.
The crowbar is after the diode.
Push the button and you place 24V on a 5V/6V/9V/12V (13.67V) 'rail'.
Oh I have a variety of DC magnetic circuit breakers that open faster then a fast blow fuse will blow.
If the OV crowbar works properly, the SCR turns on and the circuit breaker opens.
I've blown the epoxy top off some SCRs.
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This is after testing the OV crowbar with a series light bulb and an adjustable DC power supply.
Slowly increase the voltage and note where the OV crowbar fires. The power supply dips for a moment then returns to the set value.
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I rebuilt the power supply for the R390A/URR (24V nominal, 26.5 optimal) and included a OV crowbar.
Because the receiver is connected to a ~100 foot random wire antenna, even on calm afternoons, a stray breeze or insect landing on the wire can induce an extremely short transient that will trip the OV crowbar if you don't have a delay capacitor.
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The R390A/R392 are fine receivers but you need to be Arnold Schwarzenegger to tune them. There is one knob for kc another for mc, the receivers have gear/cams inside that can give you quite the workout. They are great for dedicated monitoring of a single frequency, not so friendly to a 73 year old who likes to tune the band, jumping from one frequency to another.
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I loaned it [gave it really as I have zero intention of taking it back] to a younger member of our shortwave club who loves it.
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For TTL/CMOS/ Perseus, etc, I try not to have transients on the Vout rail. Try really hard and generally succeed. My failures were with pre 3 terminal regulators. Trying to roll you own precision 24V power supply with limited knowledge was a learning experience. Fortunately my V+ in was 30V so the R392 tolerated short mistakes with no magic smoke escaping,.
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Re: Some observations on linear power supplies
On Friday 07 February 2025 04:05:02 pm wn4isx via groups.io wrote:
On Fri, Feb 7, 2025 at 02:02 PM, Roy J. Tellason, Sr. wrote:Okay... If I where going to use a TRIAC, I'd use it in SCR mode with the PNP transistor.In addition to having some triacs on hand, the thought also occurs to me to use a complementary cross-coupled pair of transistors in place of that SCR. Collector of each one is tied to the base of the other one. You can vary the value of the capacitor C1 to achieve different firing delays. There are systems that can tolerate a few milliseconds of overvoltage.I'm not sure how you'd tell what something would tolerate. "Absolute maximum" ratings for say CMOS parts is absolute maximum... Reduce the value to speed up the delay, remove it for super fast but be aware the circuit might be prone to tripping on exterior events like nearby lightning.They mention using a small inductor in that web page. I'm thinking this might be a good place to use some of those ferrite beads I've accumulated. I use 50nF and I'm not bothered by falses but it still trips if I emulate a regulator failure.How do you do that? Call me paranoid but when I built a linear power supply for a Perseus SDR (~1K in 2000) I used two OVP crowbars in series with two SCRs at the output of the filter capacitor and two SCRs, one each, at the output of the OVP.I'm reminded of a service call I did once. The company made paper filters for all sorts of commercial applications. The output of the paper making process was rolls of paper, which were stacking up and they were running out of room to put them in. The machine I was there to work on would take a roll of paper and punch big circles out of it. The electronics was a couple of boards full of 4000-series CMOS parts, and the power supply was driven by a variac! One sensor was cabled in the same conduit as a 240V motor drive cable, I wanted to remove the wire from inside of that conduit but was overruled. There were two sets of boards but they were somewhat different revisions so you had to swap them both, if you were sure that you had a good set, which they weren't. It was me, another contractor from a different company, and the "fixer" who was the guy working there who was supposed to keep stuff running. Then they flew out a guy from the factory that mde this thing, which is when we found out that the boards were different revisions. I did sketch out a crowbar circuit to the fixer, told him that they needed something like that in there, I don't know if they ended up building one or not. They wanted to know if I stocked piles of 4000-series CMOS parts, I didn't at that time, I think bad power supply design, no overvoltage protection, no indication of the boards being different contributed to their situation. I was out there for a couple of days, dunno how long it took them to get it finally fixed... -- Member of the toughest, meanest, deadliest, most unrelenting -- and ablest -- form of life in this section of space, ?a critter that can be killed but can't be tamed. ?--Robert A. Heinlein, "The Puppet Masters" - Information is more dangerous than cannon to a society ruled by lies. --James M Dakin |
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Willem xProm programmer ...
Perhaps someone here can help - looking for some advice on programming a DQ48F010 and PQ28C65 (flash/EEPROM roms) via a Willem 5.0
programmer - they are not listed (as far as I can see) in the supported device list. Please feel free to point me to an active forum for the subject. I suspect that it may be possible to configure the beast for them via the jumpers/switches - perhaps some kind person can provide advice as to how to go about doing this?? Changing the device to something that is supported in not an option as is buying a new programmer unless it is very cheap/free (I am a pensioner). Regards, Dave |
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Buffer amplifier for 10MHz ?
I am using an SI5351 to generate 10Mhz and 100Mhz digital reference signals via 50ohm 5m long BNC cables but the SI5351
seems to struggle producing a reasonable square waveform at 10Mhz. What would be the best buffer circuit for this application? and could the same work for 100Mhz ?? Regards, Dave |
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Re: Some observations on linear power supplies
wn4isx
On Fri, Feb 7, 2025 at 02:02 PM, Roy J. Tellason, Sr. wrote:
The overvoltage circuit at are all effective but the one with the PNP transistor and SCR are the most stable as far as trigger point. If I where going to use a TRIAC, I'd use it in SCR mode with the PNP transistor. ? You can vary the value of the capacitor C1 to achieve different firing delays. There are systems that can tolerate a few milliseconds of overvoltage. ? Reduce the value to speed up the delay, remove it for super fast but be aware the circuit might be prone to tripping on exterior events like nearby lightning. ? I use 50nF and I'm not bothered by falses but it still trips if I emulate a regulator failure. ? Call me paranoid but when I built a linear power supply for a Perseus SDR (~1K in 2000) I used two OVP crowbars in series with two SCRs at the output of the filter capacitor and two SCRs, one each, at the output of the OVP. ? |
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Re: Some observations on linear power supplies
On Thursday 06 February 2025 04:18:01 pm wn4isx via groups.io wrote:
For overvoltage protection?I'd use something like the one shown inInteresting stuff there. I like the one using a triac, since I have a fair amount of those on hand here. The mention of using small inductance got me to thinking about the ferrite beads and cores I have on hand here, too... -- Member of the toughest, meanest, deadliest, most unrelenting -- and ablest -- form of life in this section of space, ?a critter that can be killed but can't be tamed. ?--Robert A. Heinlein, "The Puppet Masters" - Information is more dangerous than cannon to a society ruled by lies. --James M Dakin |
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A new file copied to the "Diode Commutation EMI"
wn4isx
I've added another file to "Diode Commutation EMI" folder. ? "Shortwave Hum" is a real world explanation of how bypassing diodes can reduce SW Hum and intermodulation, ? I copied the web page at http://www.ll-leasing.com/pritch/shortwav.htm to a PDF "Shortwave Hum." ? I could quibble at some of the non technical, not quite accurate, information, but the webpage is a practical 'how to' based on the author's personal experience with linear wall warts. ? If you have a switchmode power supply wall wart, you are doomed. ? |
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Locked
Files added
wn4isx
I've added a folder "Diode Commutation EMI" that explain the causes of diode commutation EMI and steps to mitigate it.
There are other solutions today, special diodes with controlled turn off characteristics exist,?
There are soft turn off diodes, and, oddly enough, fast recovery diodes. I suspect there are others but those are the only two I have any experience with.
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The "MicroSemi 302 Rectifier Reverse Switching Performance EMI" is extremely detailed. I wish I'd had this paper in 1974.
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understanding noise output in a mixer purely by datasheet
Hello , I am assembling the bits and peaces of what I learned and trying to implement them into my mixer shown in the link below. there is the -174+10log10(BW) of the component my mixer is 10GHZ so its -174+100=-74 also the is conversion loss which affects the noise level. The harder thing for me to understand is the modulation affects because we can put unwanted spurs into our working band which could also ruin the SNR. Is there some mathmatical example I could use to assmeble all these factors together? Thanks. |
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