If C1 is not in the circut if an external loading coil and antenna are used, as RFB guesses, how would the tuning for high efficiency be accomplished? SSTRAN would know if C1 is in the circuit or not when an external loading coil and antenna are used and how the tuning is supposed to be done for high effieciency in that case.
looking at schematic it appears C1 never gets bypassed on c2 and the toroid can be.
should have missing parts today. think xyl picked up mail from mom this morning on her way home from job.
i will probably hook up the Aphex 320 D and SPF 300 for processing. drive it with my laptops using raduga automation, and the SSTRAN wire antenna. i will tune up the sstran to optimum and then do some testing then i will setup the hamilton in the same configuration and see who has the best range and sound.
keep in mind my hamilton belonged to bill blew of wsjl so it is a pretty old revision board and have no idea how it differs from later revision hamiltons.
consequently i believe he was the start of the issues with the ground lead and fcc. he got into a whizzing contest with langhorn field agents and dared them to shut him down. i'm sure fry's rantings didn't help since the FCC does read these forums. but if everyone remembers this is when the clustering and ground lead issues first came into play, quite a few years before the fry rantings. i lived in NJ at the time and had many conversations with him. i wonder whatever happened to him and his studio. me, bill, and mick got 3 of his 5 transmitters, but what happened to the rest of his equipment is a mystery. i recall radioboy was suppose to buy the remaining equipment from him but i think that fell through. that was the last it seems anyone has ever heard from bill b.
Update: i now have the missing parts
So at that point...the external loading coil and antenna will have to be within a certain parameter in order to mesh up right with the circuit design to achieve that efficiency point.
Given all the variables from site to site, and one antenna/coil design versus another, that "window" to capture the efficiency point will be like a shot in the dark blindfolded with welder goggles on.
Well maybe not that bad!
But I suspect those using the external option will have to do some experimenting with their
antenna systems.
It will be interesting to hear all of the results.
RFB
Verifying, the air trimmer C1 is on the AMT5000 antenna line at all times with a range of .6 - 6 pF. The filmtrim cap, C2, can be switched in with jumper S1, range 3 - 36 pF.
Looking at the instructions for CONSTRUCTING A BASE-LOADED ANTENNA, made available as an extension to the AMT3000, which is probably a standard form of loading coil/antenna, I don't see that it would work any differently if added to the AMT5000. You find the tap on the coil with the best peak, then trim with the capacitor(s).
Finding the peak point to optimize the efficiency of Q1 (final RF output of AMT5000) is based on matching the capacitance presented by the loading coil/antenna. The instructions for constructing a base-loaded antenna do not mention that design's capacitance, but it would seem to me that if it is out of range of C1 and C2 you would simply add a trimmer to your coil to reach the desired capacitance.
For comparison, the trimmer in the AMT3000, C5, is 12 - 100 pF.
If any of my view needs correcting please comment.
There may be an instance where two or more locations will easily match up their existing antenna system to the 5K and be within the tolerance window to obtain the efficiency point.
But that is what it is all about...experimenting and finding what works.
RFB
"Looking at the instructions for CONSTRUCTING A BASE-LOADED ANTENNA, made available as an extension to the AMT3000, which is probably a standard form of loading coil/antenna, I don't see that it would work any differently if added to the AMT5000. You find the tap on the coil with the best peak, then trim with the capacitor(s)."
One can certainly have both the internal toroid coil active while feeding a second external coil down the line, but I think that would defeat the efficiency factor by a lot since two loading coils are in the path. One or the other, or perhaps both are going to rob signal or simply throw off the entire mess from even working at all.
Either way..it would seem that a bit of reconfiguring of the external antenna system is in order, be it adding a trimmer cap or more ground radials or reconstructing a new loading coil to mesh up the right way to the internal toroid of the 5K unit.
Who knows...that mail box antenna may come to fruition sooner than we think!
Hope to see more results and reports from owners of this unit and their existing systems.
RFB
Maybe I wrote something that gave an unintended notion, but I have not suggested using both the internal and an external coil at the same time with the AMT5k.
Please re-read my message with the knowledge that I am only addressing the addition of an external loading coil.
The jumper S2 bypasses the internal inductance coil.
i need those who have successfully got their amt5000 working to email me hi res detailed pictures of their board so i can compare to mine and see where i might have went wrong in assembly. i cant seem to get a solid static free signal even sitting right next to radio and i cant get even distorted audio on mine. i **THINK** i might barely have a carrier because i was tweaking with the tuning and heard something on my tuner but not full quieting nor any audio.
Can you make a high res picture of your board so that several of us could all inspect it? That, plus any high res pics you get of other boards might expand the chances of finding any mistakes.
i will in a little bit. probably after the xyl goes to work or if she goes to take a nap before work. if not definitely tomorrow.
I am still back here examining the performance of the AMT5k, but I am up against my insane window antenna, which has so much capacitance that it will not peak up. If I don't get that "peaking" effect there is no point comparing to the AMT3000.
It appears that my window antenna has a capacitance around 4,310 pF. That's way above the 26 - 30 pF typical range of a properly located 3-meter antenna.
I have noticed that stringing a 3-meter wire in the outer corner of this room gives a capacitance of 60 pF, which I assume is a "corner effect." I'll dabble some more with that. After all, PhilB did advise to keep the antenna away from surfaces and objects. I'm sure the reason is precisely because surfaces and objects drive the capacitance figure way up.
Someday I will build an outdoor stick with radials, but not this week.
Using an indoor 3-meter wire doesn't get me a signal out in the yard, so I am mistaking windmills for giants (reference to novel "Don Quixote" - which may not make much sense, but that's where my brain is).
But I am having fun and this is not a complaint nor disappointment.
The AMT5000 is a great gift to the Part 15 community.
This is real learning, here in the RF arena, and it is good for mental health.
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. The option is there, but it isn't covered in detail in the manual. The web page: http://www.sstran.com/pages/sstran_buildant.html is so far unchanged and it only describes tuning for peak as is done for the AMT3000.
To use the external base loaded antenna with the AMT5000, the jumpers related to tuning should be set as follows:
S1 OFF
S2 ON
S12 ON
S13 ON
Jumper S2 bypasses the toroid. Jumpers S12 and S13 bypass the small inductors used for tuning below 1350 kHz. Jumper S1 should be open so the big trimmer capacitor C2 is not connected. C1 (6 pf) trimmer remains connected, but has no effect on tuning with the base loaded antenna.
The base loaded antenna capacitance is fine tuned by means of the length adjustment portion of the base loaded antenna.
To tune the base loaded antenna, adjust the tap point and the antenna length to get the highest peak as indicated by the voltage across the "RF INPUT CURRENT" test terminals. The equivalent to "adjusting C1 one full turn clockwise" is to lengthen the antenna slightly to add about .7 pf. Calculations show the required length increase adjustment is about 3 inches when using 1/2" copper pipe.
"i might have went wrong in assembly. i cant seem to get a solid static free signal even sitting right next to radio"
Well looking at the images provided on your facebook link a few posts back, I don't see any real problems with the exception of a few solder points that appear to be "cold" and "ringed" around the leads at a couple IC locations.
I would go back and touch up all the solder points and then confirm that the feed through connections points are making contact to their opposite sides.
Anyone remember those old RCA televisions that had those stupid rivets inserted through the PC board to make contact with foil patterns on the other side of the board, and the plague of bad connections from those feed through inserts?!!
Those sets sure made us mom and pop repair shops a good run of income for the day...that was about the only thing I admired about those particular sets..their steady income in soldering and inserting a small wire strand through those inserts to ensure a solid contact.
Check continuity on those feed through points. It is rare, but perhaps you have a board that has a flaky feed through somewhere...perhaps one or more. If there is one, I would check for more.
RFB
"It appears that my window antenna has a capacitance around 4,310 pF. That's way above the 26 - 30 pF typical range of a properly located 3-meter antenna."
You can attempt to tune out that excess capacitance on that window antenna by applying in parallel other capacitor values, bringing that 4k pf window antenna more into the ball park where you need it.
Just remember, capacitors in parallel result in opposite of parallel resistors. The capacitance increases, where as parallel resistors decreases in resistance.
And do not be afraid to experiment. Try some in both parallel and series. After all, its all about learning and discovering what works and what wont.
RFB