Re: jFET oscillator on Specan
Hi Jim ,
Thanks for replying.
I'm running off a Biono battery (about 13.3 volts) but the transistors are specked for 25v and sample circuits show 15v.? I agree about cheap parts, so I 'll test when the J310s come in.
Yes I checked the resistors., but I'll recheck
-----Original Message-----
From: Jim Allyn - N7JA <jim@...>
To: [email protected]
Sent: Mon, Mar 7, 2022 2:54 pm
Subject: Re: [HBTE] jFET oscillator on Specan
I haven't built that particular oscillator but I have designed MPF102 and J310 oscillators operating from 100 MHz to above 500 MHz.? (Mine didn't use quartz crystals, mostly they used LC, microstrip, or ceramic resonators.)? A quick glance at the schematic doesn't reveal anything that would lead me to believe that it won't oscillate, nor do I see anything that might burn out the FET.? The source bias resistor is 470 ohms, which is right in the normal range, and 12 volts is fine for drain voltage.? My best guess is that the devices are something other than MPF102s.? Other possibilities would be that the supply voltage is considerably higher than 12 volts, or the source bias resistor is something much lower than 470 ohms, but I assume you have verified those.? Bad parts.
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Re: jFET oscillator on Specan
No, I did get them from e-bay and no I didnt test them.? I ordered J310s from ebay also, but I will test them
Thanks for replying
Andy? Km4TRT
-----Original Message-----
From: Jim Strohm <jim.strohm@...>
To: [email protected]
Sent: Mon, Mar 7, 2022 1:29 pm
Subject: Re: [HBTE] jFET oscillator on Specan
On your first tries, did you get semiconductors from Tier 1 vendors, or off of eBay? ? On any case, did you test them first?
73
Jim N6OTQ?
Sent from my quenched-gap spark transmitter.?
On Mar 7, 2022, at 11:50 AM, KM4TRT via groups.io <garello@...> wrote:
?
[Edited Message Follows]
Hi,? Trying to get a JFet oscillator to work.? I'm using Ashar Farhans schematic for his spectrum analyzer.? (100 mhz 2nd Oscillator) So far I've built two boards and burned out Q1 in each board even though I've checked all the traces/components with ohm meter/cap checker.? Any one had experience with this design? I used the MPF 102 j fets, but have since sent for j310's (which is what Ashar originally used. https://drive.google.com/file/d/0BzRNYeu10K6DdE1CSDVfZUdTdzg/view?resourcekey=0-m4_gR-o3xRUQfTF4m44fag
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Re: jFET oscillator on Specan
It doesn't say to remove the 1/4-20 bolt for ALL of the inductors, but you should.? The bolt is only a form to wind the inductors on.
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Re: jFET oscillator on Specan
I haven't built that particular oscillator but I have designed MPF102 and J310 oscillators operating from 100 MHz to above 500 MHz.? (Mine didn't use quartz crystals, mostly they used LC, microstrip, or ceramic resonators.)? A quick glance at the schematic doesn't reveal anything that would lead me to believe that it won't oscillate, nor do I see anything that might burn out the FET.? The source bias resistor is 470 ohms, which is right in the normal range, and 12 volts is fine for drain voltage.? My best guess is that the devices are something other than MPF102s.? Other possibilities would be that the supply voltage is considerably higher than 12 volts, or the source bias resistor is something much lower than 470 ohms, but I assume you have verified those.? Bad parts.
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Re: jFET oscillator on Specan
On your first tries, did you get semiconductors from Tier 1 vendors, or off of eBay? ? On any case, did you test them first?
73 Jim N6OTQ? Sent from my quenched-gap spark transmitter.?
toggle quoted message
Show quoted text
On Mar 7, 2022, at 11:50 AM, KM4TRT via groups.io <garello@...> wrote:
? [Edited Message Follows]
Hi,? Trying to get a JFet oscillator to work.? I'm using Ashar Farhans schematic for his spectrum analyzer.? (100 mhz 2nd Oscillator) So far I've built two boards and burned out Q1 in each board even though I've checked all the traces/components with ohm meter/cap checker.? Any one had experience with this design? I used the MPF 102 j fets, but have since sent for j310's (which is what Ashar originally used. https://drive.google.com/file/d/0BzRNYeu10K6DdE1CSDVfZUdTdzg/view?resourcekey=0-m4_gR-o3xRUQfTF4m44fag
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jFET oscillator on Specan
Hi,?
Trying to get a JFet oscillator to work.? I'm using Ashar Farhans schematic for his spectrum analyzer.? (100 mhz 2nd Oscillator)
So far I've built two boards and burned out Q1 in each board even though I've checked all the traces/components with ohm meter/cap checker.? Any one had experience with this design?
I used the MPF 102 j fets, but have since sent for j310's (which is what Ashar originally used.
https://drive.google.com/file/d/0BzRNYeu10K6DdE1CSDVfZUdTdzg/view?resourcekey=0-m4_gR-o3xRUQfTF4m44fag
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Re: Specan log detector and power regulators
Hi Ellis,
I too am making a "specan". I have the log detector working on a separate board(using it as a sweeperino), but not far along enough in testing to put the shields on.? I left open tracks on the top layer to solder the shields.
I'm curious if you have made the 100MHz 2nd oscillator yet.? I've built 2 and have burned Q1 both times.? I've checked and double checked the circuit board and pin outs. to now avail. Need some help here.
Andy KM4TRT
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As much as I dislike mentioning the name ... Amazon. Many more to choose from. I ordered one batch from BoJack to experiment and test a crystal test fixture to go with my NanoVNA. All were active and perfomed as expected. I compared the 10 MHz ones with a couple of older 10 MHz crystals from International Crystal, couldn't tell the difference.
? ?
? ?
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Re: Quick and dirty GPSDO
Hi Bill Got it - thanks for the explanation. The print statements?are, as you say, not used without the phase detector, so they have no effect. -- Sverre
LA3ZA
http://la3za.blogspot.com
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Re: Quick and dirty GPSDO
BTW, the frequency comparison is actually taking place at 2.5 MHz, not the (in this case) 10 MHz, thus the factor of four to convert the frequency error count to Hz, or fractions thereof.
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Re: Quick and dirty GPSDO
The print statements are not executed if the phase detector is bypassed - note the?if USE_PHASE_DETECTOR.?If this is set FALSE, those statements are skipped.
The multiplication and division convert the raw error counts to frequency in HZ for the display. The original code as well as Erik's displayed this information in scientific notation. Not being fond of on-the-fly conversions, especially if not in engineering units, I made the NANO do the work :-)
The stable count (C) is the number of times that the algorithm reaches the distance (D) count and remains within tolerance. the 'L' indicates that the algorithm was in lock during the previous C passes. At least that is my understanding of how this works. If anyone can offer an improved interpretation, I am all ears!
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Re: Quick and dirty GPSDO
I also had to comment out all the Serial.print statements in the?PPSinterrupt() procedure. Probably some critical timing issue. I have a question about the meaning of the C in the display, showing the stable_ count variable, coming from the code below. And why is md_FL multiplied by 4, I cannot find anything similar in the original F2DC code? 73 Sverre LA3ZA
else
? ? md_FL = float(measdif * 4);? ?// why *4?
? md_FL = md_FL / 100;
? lcd.print(md_FL);
? lcd.print("Hz ");
? if (USE_PHASE_DETECTOR)
? {
? ? lcd.print(" A");
? ? lcd.print(int(p_delta_average));
? ? p_delta_average = 0;
? }
? else
? { lcd.print(" D");
? ? lcd.print(duration);
? }
? lcd.print(" C");
? lcd.print(stable_count);
? lcd.setCursor(15, 1); // added lock state indicator oct '21 web
? if (good)
? ? lcd.print("L");
? else
? ? lcd.print("#");
}
-- Sverre
LA3ZA
http://la3za.blogspot.com
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Re: Quick and dirty GPSDO
That was it! Thanks, now it locks
Sverre LA3ZA
On Sat, Feb 26, 2022 at 6:25 PM Bill Buoy < bill@...> wrote: SVERRE,
Take a look at whether your gps outputs GPRMC or GNRMC to begin a valid fix. I am using a uBlox gps off Amazon. The default output from those is GNRMC, most others start with GPRMC. Search for GNRMC in my source code and change it.?
Sorry I didn¡¯t catch this earlier - I had the same issue when I first started playing with this last fall. Very frustrating until I started questioning whether my GPS was defective and decided to monitor the serial output.?
73,
Bill
-- Sverre
LA3ZA
http://la3za.blogspot.com
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Re: Quick and dirty GPSDO
SVERRE,
Take a look at whether your gps outputs GPRMC or GNRMC to begin a valid fix. I am using a uBlox gps off Amazon. The default output from those is GNRMC, most others start with GPRMC. Search for GNRMC in my source code and change it.?
Sorry I didn¡¯t catch this earlier - I had the same issue when I first started playing with this last fall. Very frustrating until I started questioning whether my GPS was defective and decided to monitor the serial output.?
73,
Bill
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Re: Quick and dirty GPSDO
Thanks Bill,
I downloaded the?code and it identifies itself as "V.5.4 F2DC PD0EK", but still hangs on "Waiting for GPS". I'll have to look into this more tomorrow, maybe there are some subtle differences between the GPS signals
73
Sverre LA3ZA -- Sverre
LA3ZA
http://la3za.blogspot.com
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Re: Quick and dirty GPSDO
Good day, Sverre,
I uploaded my latest revisions, along with a jpg of the front of the unit showing the display. I am sure that this is the latest. After a restart/fresh upload,, the top line should show 10.0M, the second reads "V5.4 F2DC PD0EK" until the GPS starts. Once the GPS starts, the top line should display the UTC time...
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The following files and folders have been updated in
the Files area of the [email protected] group.
By: Bill Buoy <bill@...>
Description:
updated sketch for the GPSDO
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Re: Quick and dirty GPSDO
Thanks? Bill, But I cannot see that the date has changed from 16 February in the file area. Are you sure the upload went without problems? -- Sverre
LA3ZA
http://la3za.blogspot.com
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Re: Quick and dirty GPSDO
Sverre: I got the clock to work using examples from previous versions of Erik's program and from examples from FD2C. Probably not the cleanest or prettiest way, as I am just learning C using this as a learning exercise. Take a look in the folder I posted today:? /g/HBTE/files/Q&D%20GPSDO73, Bill N5BIA
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Re: Quick and dirty GPSDO
take a look at the code I uploaded this afternoon. probably not the cleanest way, but I managed to cobble together Erik's code and some if the examples I got from FD2C and got it to work. I'm not really familiar with C, so this has been slow going for me, but at least I'm learning....
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Jim Allyn - N7JA
Bill Buoy - N5BIA