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Post by jimhenry2000 on Apr 19, 2017 22:14:13 GMT
I am now even more frustrated than I can possibly describe in a polite manner. I've tried everything I can think of plus what has been suggested. No matter what I do I get 0.144v when measuring RF input current, and 2.688v when measuring RF input voltage. Based on the formula this means the transmitter is putting out less than 4 mw (0.0387072). I get this value across the entire range of tuning C1. As Carl suggested I confirmed that S1 was not connected (it never was). I powered off the xmtr during every change just to be safe to the transmitter. I tried the RF peaking procedure using each of the three jumper positions suggested by the manual (S8,S9,S10). Same results. I also replaced this jumper with a brand new one in case the first one was bad and again went through the peaking procedure using all three jumper positions again. Same results. I inserted a capacitor in the antenna line. I went from feeding the coax to just a long wire again. I changed from using my cheapo Extech VOM to my Fluke 110 DMM. I also tried adjusting c25 to see if the readings changed. They did not. BTW I still don't get why the manual says to keep the slot of C25 lined up front to back but since you can rotate this cap several times the manual doesn't mention how many turns up or down this cap should be rotated when the slot is lined up front to back. Two days ago I was getting the best range ever even getting over the mountain  behind my house. Now I don't even get down to the end of my driveway (800ft).. If you can see it on the attachment, that longes red line was over 9000 feet. How it got over the mountain and I could hear it baffles me, but anyway that was 2 days ago, not now. Any ideas? Oh, That's Right, the CoaxOver the course of the back and forths I lost sight of the coax and wasn't sure it was still in place or not. Now that we know, I'm guessing that all that coax is swamping the signal with capacitance that is throwing it out of the designed range. By adding a 20 pF or other small value of capacitor in line with the antenna you might be able to get the tuning back into range. |
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Post by Admin on Apr 19, 2017 22:28:40 GMT
So what changed? What is the last thing done before the readings fell drastically?
Same meter? Made sure probes plugged in for voltage measurement? Set for DC voltage? Coax splice still OK?
CHECK and DOUBLE CHECK...
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Post by Deleted on Apr 19, 2017 23:22:06 GMT
More About Jumpers
Jim reports: "I tried the RF peaking procedure using each of the three jumper positions suggested by the manual (S8,S9,S10). Same results."
The range of jumpers changing the inductance of the loading coil is more than only S8, S9, and S10.
My AMT5000 peaks using S7.
And there's S3, S4, S5, S6 and two extra inductors S12 and S13.
I read your post at Part15_us and see that your change from excellent results to poor results coincided with adding a ground. Where is the ground wire attached to the transmitter?
Try it without that ground.
Added Note: I am very glad that you had a superior result along the way, because that demonstrates the transmitter is able to do its job. Our job is to recover that result.
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Post by jimhenry2000 on Apr 19, 2017 23:37:35 GMT
So what changed? What is the last thing done before the readings fell drastically? Same meter? Made sure probes plugged in for voltage measurement? Set for DC voltage? Coax splice still OK? CHECK and DOUBLE CHECK... I changed from my ExtI've walked theech VOM to my Fluke 110 DMM to rule out the meter. The day this changed which was either yesterday or the day before, two things happened. 1) My landscaper arrived to mow the lawn. I met him before he started and gave him a heads up. I told him not to worry about driving over the radials as they were all stapled down to the lawn. I showed him the traffic cone on top of the hill where the antenna is and the copper ground ring that all the radials home back to. I also warned him of the low hanging coax running from my second floor deck which is outside the room that is my shop and studio. I have the coax suspended from a strand I have running from the second floor roof to a tree but it (the coax) is hanging pretty low as I will be getting rid of it soon once I complete my outdoor enclosure. Perhaps he ran into it (I was not home most of the day). 2) Our contractor came to power wash the house. So no doubt everyone will believe it is one of these two events, but I'm not convinced that damaging the coax or the ground could effect behavior when the transmitter is inside the house, and also since I disconnected the coax and changed antennas (original long wire). However I can't think of anything else to try so tomorrow I will bring the antenna back in, disco the coax, and see if anything changes. If I resolve the issue I will just start the process for the outdoor install and mount it in the enclosure. |
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Post by jimhenry2000 on Apr 19, 2017 23:54:38 GMT
Carl, My manual only lists S8, S9, S10 as valid jumper settings for 1610 khz, although I actually did also try S7 but same results, no change in readings as I run C1 through its range. Yes, about that ground. The 100ft of RG6 I bought is suitable for burial and includes an extra ground lead at each end and I had neglected to ground the end closest to the house so then I grounded it. The ground lead at the antenna side runs down the mast and is bonded to the copper ground ring that the radials home to. That ground ring is grounded to an 8ft ground rod via AWG #10 which is about 100 ft away. That ground rod is right below my 2nd floor deck. The ground lead of the 5000 runs directly to that same ground rod, a distance of about 30 ft. So when I grounded the other end of that coax it also went to that same ground rod. Since it's directly over that ground rod it was just a straight drop of about 15' down to that same ground rod. I disconnected it today but still no change. More About JumpersJim reports: " I tried the RF peaking procedure using each of the three jumper positions suggested by the manual (S8,S9,S10). Same results." The range of jumpers changing the inductance of the loading coil is more than only S8, S9, and S10. My AMT5000 peaks using S7. And there's S3, S4, S5, S6 and two extra inductors S12 and S13. I read your post at Part15_us and see that your change from excellent results to poor results coincided with adding a ground. Where is the ground wire attached to the transmitter? Try it without that ground. Added Note: I am very glad that you had a superior result along the way, because that demonstrates the transmitter is able to do its job. Our job is to recover that result. |
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Post by Deleted on Apr 20, 2017 0:41:55 GMT
Off the Chart
Jim spoke, saying: "My manual only lists S8, S9, S10 as valid jumper settings for 1610 khz."
Yes, but the manual assumes you have a 3-meter antenna with direct connection to ground with no long wires in the path.
You are DRAPED in long wires: the coax, the coax shield, the ground wire, and probably another wire running out to the radials.
By now the chart in the manual means nothing because what you have is so far off of what was designed in the transmitter.
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Post by jimhenry2000 on Apr 20, 2017 2:01:25 GMT
Good point Carl. Weather permitting Thursday I will start from scratch and re-peak the xmtr the way I received it, with the 118" long wire antenna and I'll see what happens. My gut feeling is that nothing will change but I hope you are correct. Off the ChartJim spoke, saying: " My manual only lists S8, S9, S10 as valid jumper settings for 1610 khz." Yes, but the manual assumes you have a 3-meter antenna with direct connection to ground with no long wires in the path. You are DRAPED in long wires: the coax, the coax shield, the ground wire, and probably another wire running out to the radials. By now the chart in the manual means nothing because what you have is so far off of what was designed in the transmitter. |
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Post by Deleted on Apr 20, 2017 13:39:30 GMT
Browsing Through My AMT5000 File Folder
Looking at e-mail exchanges with PhilB, inventor of the AMT5000/3000 dated from 2011, I note that my measured impedance of my Wintenna was 4,000 pF, not uF as previously printed. This will not effect Jim's project but is a correction.
This next quote from a message of Oct. 10, 2011 is more on point to what we've recently being discussing.
"AMT5000 Initial Tuning for Familiarization"
Paragraph 5 - Antenna capacitance is very important. The tap points (of the toroid coil) suggested in the manual for various frequencies assume the antenna capacitance is in the 25 pF to 30 pF region. This will be true for 102" stainless steel whip, a half-inch or three-quarters inch copper pipe a few inches less than 118", and the 118" white antenna wire. Other shorter, longer or fatter antennas will have lower or highr capacitance respectively, and should not be used until you are thoroughly familiar with the effect of the toroid taps.
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Post by Druid Hills Radio on Apr 20, 2017 18:29:46 GMT
Browsing Through My AMT5000 File FolderLooking at e-mail exchanges with PhilB, inventor of the AMT5000/3000 dated from 2011, I note that my measured impedance of my Wintenna was 4,000 pF, not uF as previously printed. This will not effect Jim's project but is a correction. Mr. Know-It-All puzzled asks: "When did impedance start being expressed in capacitance units?" |
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Post by Deleted on Apr 20, 2017 19:15:29 GMT
Mr. Doesn't Know It All YET replies
At first I didn't understand Mr. It All's question: "When did impedance start being expressed in capacitance units?"
It took me about 25-seconds in a state of perplexity to reach the point where I could honestly say, "Oh, right! Good point. "Impedance" was a Spoonerism actually meaning "capacitance!"
We are lucky to have a Member who Knows All-of-It so that lagging members can be "course corrected".
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Post by Druid Hills Radio on Apr 20, 2017 19:38:07 GMT
Mr. Doesn't Know It All YET repliesAt first I didn't understand Mr. It All's question: " When did impedance start being expressed in capacitance units?" It took me about 25-seconds in a state of perplexity to reach the point where I could honestly say, "Oh, right! Good point. "Impedance" was a Spoonerism actually meaning "capacitance!" We are lucky to have a Member who Knows All-of-It so that lagging members can be "course corrected". Mr. Know-It-All does not know-it-all as first thought. He had to find out what the definition of Spoonerism was/is. |
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Post by Deleted on Apr 20, 2017 20:58:46 GMT
Re-Correcting a Previously Mistaken Correction
Upon closer check to literalcy it was not a Spoonerism as first said, but rather a malapropism.
With these adjustments we inch closer to a day of perfection and, we have little doubt, acceptance into full society.
Keep these notes close to the AMT5000.
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Post by jimhenry2000 on Apr 20, 2017 22:55:31 GMT
Everyone, thanks to all of you for your help! I built a dummy load with a 47 ohm resistor and a 30pf capacitor, disconnected the antenna and replaced it with the dummy load and voila! I could then peak the transmitter, which I did. Even more amazing, I then reconnected the antenna and was again able to peak the RF to about 110 mw. So I believe the problem is in the coax. In fact yesterday I took the 102" antenna off the 25' tower and set it directly on the ground below (inside a traffic cone to keep it vertical) and the xmtr power went from 4mw to 8mw. Thanks again! (The attached file is a vid of my 25' telescoping mast, but when I had it on my deck in Michigan where I used it for DX'ing SW and AM Broadcast stations) 11658327_10205521140962553_745800373_n.mp4 (418.51 KB) Browsing Through My AMT5000 File FolderLooking at e-mail exchanges with PhilB, inventor of the AMT5000/3000 dated from 2011, I note that my measured impedance of my Wintenna was 4,000 pF, not uF as previously printed. This will not effect Jim's project but is a correction. This next quote from a message of Oct. 10, 2011 is more on point to what we've recently being discussing. "AMT5000 Initial Tuning for Familiarization" Paragraph 5 - Antenna capacitance is very important. The tap points (of the toroid coil) suggested in the manual for various frequencies assume the antenna capacitance is in the 25 pF to 30 pF region. This will be true for 102" stainless steel whip, a half-inch or three-quarters inch copper pipe a few inches less than 118", and the 118" white antenna wire. Other shorter, longer or fatter antennas will have lower or highr capacitance respectively, and should not be used until you are thoroughly familiar with the effect of the toroid taps. |
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Post by Deleted on Apr 20, 2017 23:31:36 GMT
Chalk It Up As a Success for the ALPB and the Part 15 Community
Jim Henry, I am relieved that you returned to square-one and determined that your transmitter is not at fault.
It is great that in the process you ended up getting the experimental setup working after all.
The combined effort of all the part 15 people who submitted suggestions pointed the way.
We'll all be arriving in 15-minutes for beverages on the deck!
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Post by jimhenry2000 on Apr 22, 2017 6:55:55 GMT
Carl, Any suggestions on the audio cables I will need to feed the xmtr from 150 ft. away? Thanks. Jim Chalk It Up As a Success for the ALPB and the Part 15 CommunityJim Henry, I am relieved that you returned to square-one and determined that your transmitter is not at fault. It is great that in the process you ended up getting the experimental setup working after all. The combined effort of all the part 15 people who submitted suggestions pointed the way. We'll all be arriving in 15-minutes for beverages on the deck! |
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behind my house. Now I don't even get down to the end of my driveway (800ft).. If you can see it on the attachment, that longes red line was over 9000 feet. How it got over the mountain and I could hear it baffles me, but anyway that was 2 days ago, not now. Any ideas?
