"All the interest in connecting the external loading coil antenna to the AMT5000 came as a big surprise to me. One prime objective in the design was to eliminate the need for the external loading coil."
I certainly see the point in the design and it makes sense...but...
When someone takes the time to build a home made 3 meter antenna system, which could employ an elaborate ground system or unique loading coil..fine tune it and get it to perform at its peak, it should be expected that they will be interested in using that same antenna system with the new TX.
Let's see what others report comparing the use of the internal vs the external. That is what I am really watching out for with all this.
RFB
I agree wholeheartedly with careful examination of solder connections. I have seen occasions where they look good, but are still open. Mostly bad solder connections are caused by not applying heat long enough. I have always recommended flowing solder and then holding the iron on the pad for and additional few seconds (2 or 3 seconds). Sometimes, with insufficient heat, the solder will mound up around the wire lead, but not flow to the lead. The result is it looks good, but no contact. Holding the iron on the pad for an additional few seconds pretty much ensures the solder will flow to the pad and the lead. When in doubt, re-flow ALL solder connections for a few seconds with a clean tip and a touch of fresh solder . Doing this may take 15 or 20 minutes, but save hours of frustration and troubleshooting. Additionally, the methodical process of re-flowing every connection will force you to look at each one along the way, which may indicate some surprises you missed before.
I wouldn't worry at all about continuity between the top and bottom in the plated-through holes. Stringent requirements of high hole count and high density, multi-layer boards have driven the PC manufacturing industry to a very high reliability level. Any manufacturer that didn't do well in PC fabrication quality has long since gone away. SSTRAN transmitters use only a 2-layer board with hole and trace dimensions quite large by industry standards in order to ease manual assembly. We have been using the same high-quality vendor since 2003. I have yet to encounter a discontinuity in the plated-through holes, other than after a component removal that was done improperly. Checking for plated-through hold discontinuities would be tedious and error prone. I wouldn't bother.
Let's see what others report comparing the use of the internal vs the external. That is what I am really watching out for with all this.
Me too, but I am confident the AMT5000, using just a vertical whip or copper pipe, without an external loading coil, will perform better than the AMT3000 with the external loading coil in the same location with the same grounding as the AMT3000 base-loaded antenna. It should perform at least as well, or better than the high priced competitor under the same location and grounding conditions.
Of course, using a big external air core loading coil should perform even better. That is an option I included for those who want to experiment with the ultimate Part 15 setup (this option isn't available in the high-priced competitor's transmitter). I think that is of lesser importance right now than validating the performance of the AMT5000 with just a vertical antenna and a decent ground system. Valid apples-to-apples comparisons against the high priced competitor transmitter are welcome.
"Of course, using a big external air core loading coil should perform even better. That is an option I included for those who want to experiment with the ultimate Part 15 setup (this option isn't available in the high-priced competitor's transmitter)."
One thing is for sure the 5K unit has plenty of advantages over the other $$$ units, particularly the choice of the matching method.
Carl mentioned about one very useful feature, the test point holes on the board for meter probes. Nothing better than hands free meter probing preventing "slips and shorts".
I mentioned the feed through points merely as another option to consider if all other checks don't find the problem. But I think going over those solder connections will resolve kc8's problem.
RFB
closeups of my sstran board
Rev. Chrysafis:
Tomorrow when my brain is renewed I will set mine alonside the screen and compare everything visible to your pics.
You did a super neat job, so obviously you were very careful to get it right.
If nothing shows up in my inspection I'll see if I can photograph mine for you.
This gathering of RF radio engineers provides the most wonderful scholarship on figuring out how to make things happen.
RFB, your idea of feeding my window with a small capacitance worked! Now I have reached my first peak tuning with the AMT5k!
At first I used a 62 pF cap, and that opened the door on C1 actually causing my current readings to change. With the direct 4,000 pF from the window antenna those readings wouldn't budge from one number. But the 62 pF would not peak.
So I got a 20 pF cap and on S5, tuning for 1550kHz, I knew something was happening because the current numbers started going through more changes in the shortest turns of C1 than they had with any other jumper. It hit a highest number and started to descend and I knew this was the payoff of the week. There was even enough room to turn one full time clockwise to get that special notch.
I'm going to put this on my job resume'.
That's good to hear Carl! Now those who have window pane antennas have hope! 😀
RFB
While SSTRAN claims that using the external loading coil and antenna on its website is an option for the AMT 5000, it is leaving the related engineering work up to its customers.
Hello kc8gpd, Rev. Chrysafis:
I do spot something in your pics that would cause a problem.
S16 and S17 should BOTH be the same, jumpered or unjumpered, depending on your power.
If you are using AC power they are BOTH unjumpered.
If you have a DC power source they should BOTH be jumpered
i found that this am. removing them did not change anything. i have uploaded pics of solder side. same link as above.
To kc8pgd, Robert, in picture 8, in the upper left quarter of the picture, I see two leads that you might want to clip because they look like you might have overlooked clipping them, but they are not the problem you are looking for (I don't think).
Have you tried, while it is turned on and being detected (you said there was some small sign of life) used a non-metalic (wooden stick, tooth pick) device to poke at each part and each connection? That is a method that has helped me find jiggly connections.
I will study the pictures some more once I get some other stuff taken care of. Keep thinking and looking, you will find it.
phil says i might have the resister network backwards which would keep the pll from locking on to a frequency. that is a big job removing and reorienting so i will wait a while till i feel up to that task
Encouraged by solving the "how to get a peak" situation, I will now conduct a comparison test between the AMT3000 and AMT5000. It will only be semi-scientific, but I will describe significant steps so that maybe we will be able to end up with a rough sketch.
To begin with, my antenna is "unapproved" in the real technical world, but it does the job I want it to do. The point here is that it is NOT an ideal antenna, and therefore the field of measurement will be in a smaller area than would be expected with a great antenna. There is no point describing the antenna in detail. The main thing about it is that it is less than perfectly efficient.
This morning I attached the AMT3000 and tuned it by setting my Zenith Transoceanic Radio for Manual RF Gain, turned the RF Gain down until I could just barely hear my signal at 1550kHz. At first the transmitter output tuning range was set for 82uH, an ordinary setting for this frequency. I tuned C5 until I heard the signal on the Zenith jump up to a louder level. But I noticed that C5 was fully inter-meshed, and changed the RF jumper range to 56uH, and was able to get an even louder RF level from the Zenith with C5 more in the middle of its range.
In a short time I will drive away, noting the distance not in feet, which would only be a wild guess, but in terms of "lots," or "households." I will be driving west, and in the past I have heard the signal at 1550 for a distance of 3-lots plus one cross-street.
But we are starting fresh with a newly modified antenna and a better-tuned AMT3000. The result could be different from before.
At 1:30 PM CDT I turned on the car and tuned the radio to 1550 kHz. The signal from AMT3000 was received full strength right alongside the house. The transmitter/antenna was about 60' away, facing south. I backed down to the street, north, then slowly drove west.
Despite the fact that the antenna is back behind the row of houses, it came in at grade A strength for 270' on the street.
The compound angle that points back to the transmitter gives a straight line distance of 388', figuring in the 152' from the back of the house to the street.
The weakened signal at the boundaries lasted two more lots, approximately 180 additional feet.
The next step will be to install the AMT5000 and see how well it does by comparison. The weather is changing. It went from sunny to windy and cooler in two hours. If tomorrow at around 1 PM is somewhat like the weather today, I'll do the second half of this signal contest.