Back in March, Neil Radio8Z posted an in-depth paper on increasing the efficiency of the AM25 Ramsey transmitter.
http://www.part15.us/index.php?q=node/2714
Back in March, Neil Radio8Z posted an in-depth paper on increasing the efficiency of the AM25 Ramsey transmitter.
http://www.part15.us/index.php?q=node/2714
Even while working on many other projects, I have decided it is surgery time for the AM25.
It is hoped the AM25 can serve as a foot in the door to carrier current broadcasting. Admittedly this is not exactly what Neil had in mind, as his enhancements are geared toward a 3-meter antenna system, so we are taking a preliminary look see.
There is another off-site paper on enhancing the AM25 which seems primarily geared toward going well above 100mW so as to drive a carrier current system, with an interesting little coupler design.
http://teslapress.com/am25.html
Wow!
I wonder what RFB thinks of this?
Best Wishes
Bruce, DOGRADIO STUDIO2
Know This Much
Good question, Dog Radio 2.
In fact, RFB was involved on the original Ramsey Enhancement thread and was rebuilding his Ramsey AM25 but I don’t think we ever heard the outcome.
About What?
“I wonder what RFB thinks of this?”
The over done modifications by Mr. Trinkaus or Neil’s enhancements?
No worry I will restate here.
Neil’s enhancements: Work very well. I do not use my Ramsey AM 25 unit because my station operates in AM stereo and the stand-by 3 meter stick system is equipped with a Chris Cuff Alfredo C-QUAM exciter/transmitter. But I was interested in how well the enhancements would perform. There are a few enhancements made by AM 25 owners out there.
Mr. Trinkaus’s seriously over-done modifications:
As the sub-title says…seriously over done. Way over done. In my opinion, instead of butchering up the unit like that, I would have built a whole new transmitter instead of having a “half n half” of circuits where one is designed around low power operation while the other is ridiculously over built using components intended for high current and high power.
Not to mention the “neatness” of those modifications are less than optimum. And no doubt the thing draws far more current than it should be, and why the author stated “Get two or three 2396’s, because you, too, will be experimenting” and large heat sinks to boot, like try it till you find one that does not blow.
The coupler…that is a coupler?! LOL. Although it can work, and is a very basic form of coupler, I do not recommend it simply because it is not safe! Also that method of coupling does not isolate your TX output from 60 cycle return hum nor does it compensate for the ever changing inductance on the line while maintaining proper impedance matching for the TX and maintain the tuning on the line side.
It is..simply put..a quick and dirty coupler that will get you on the air in CC mode, but not in the best, or safest manner.
Your better off leaving your AM 25 alone, strap it for the 1 watt power option and use a simple coil of wire wrapped around an extension cord plugged into a power socket. Or apply Neil’s enhancements for improved RF transfer efficiency and the coil of wire wrapped around a power cord for a safer and less interaction back to the TX and better coupling for CC.
RFB
Hi RFB.
Yup. I wasn’t talking about Neil’s
work. I was wondering about the article
by Mr. Trinkaus.
I probably mentioned this in another
thread, but my LPB RC-6A will be coming
back to me. My good friend in NJ just
doesn’t have the time to work on it.
And considering how much stuff he has in
his life – I don’t mind.
My plan is to retube it and get it onto 1020,
which is quiet during the day here. And as
mentioned before, a crystal for 1020 is very
inexpensive from AF4K’s website. There IS
a company that makes crystals that operate below
1 MHz, but they cost at least 75 or 80 bucks. I
don’t want to risk that kind of money on something
that might not work right.
I’d like to make a coupler – like a big LC
with a whole lot of line cord wrapped around it
because that’s really easy for me. But I will
probably have to attenuate that 6 watt RF down
to some lower energy level.
Right now my eyesight is really getting in the way,
but if something is large like that, I can probably
do it.
Oh well, we’ll see where it goes.
Thanks for the info.
Bruce, DOGRADIO STUDIO 2
Modified Modification
I found that using a different toroid material will boost the efficiency of the AM-25 modification by about 10% though the original values I posted work well.
The new numbers are:
L4 = 40 turns on T50-2
L1, L2 = 50 turns on T50-2
C3, C5 = 1nF
C4 = 1.6 nF
If you are considering running up to 1 Watt it may be a good idea to use larger toroid cores of the type 2 material. The original T44-15 cores used in the Ramsey were not the best choice of size or material. One of the cores in my original AM-25 discolored due to overheating when bench testing at the published adjustment specs in the manual (around 350 mW).
Neil