Recently a member mentioned improvements
that were made to his Ramsey AM-1. I
believe it had to do with the modulation scheme.
I have had an AM-1 for 20 years. Although it
is not the greatest thing in the world,
I think it is a fantastic unit for learning
about radio transmitters and Amplitude Modulation.
After my recent move, I found my AM-1.
After modifying it for crystal control, I wound a
gigantic loading coil on a bucket and got it to
go 1/2 mile. (This was years ago.)
I did a bunch of other things. I had crystals for
1590, 1670, and 1700 kHz.
It was a ton of fun.
It sat frozen under a bucket under a snow bank
for a whole winter. It was fed by audio and power
cables that went through the yard from the indoor
set-up.
I don't believe it did 100 percent modulation, which
of course was a problem, but I learned a great deal.
This was way before other transmitters, such as
the "Talking House," or AMT-3000 were available -
even before the Ramsey AM-25.
I am trying to put mine back on air just for fun.
(I have other AM transmitters, too.)
As mentioned, we moved a while back, and I don't
have a "workbench" yet.
Brooce, DOGRADIO and all sorts of other Part 15 experiments.
Let's see, Bruce MICRO 1700 moded his Ramsey AM-1, just like the other member he mentioned, Radio8Z has modified a Knight Kit tube transmitter by also adding a crystal.
I wouldn't know how to do such a mod to a VTO (Variable Tuned Oscillator) so I hope someday one of you who has the knowledge will provide a lesson with pictures.
I don't have anything to modify at this time, but who knows what tomorrow will bring?
If I'm not mistaken the mod might be as simple as replacing the VC with the crystal. Either way it surely has to be an easy mod, I look forward to seeing how its done!
I can tell somebody's a radio jock with that double spaced typing there, ha ha. 🙂 For those who don't know, common practice was to double space live read announcements to avoid messups while reading the copy...
If it's the usual VFO, and especially if series tuned, it might be as simple as replacing the coil with the crystal, and the cap with a variable for trimming the frequency.
Crystals act as weries/parallel resonant devices but one needs to be careful not to overdrive them with too much power. The easiest way to use them is to place them in the base circuit of the oscillator, usually connected from the base to circuit ground.
If a crystal is forced to resonate in a mode (series or parallel) for which it was not designed then the frequency can be off several hundred Hz in the BCB but this is almost always better than letting the oscillator free run.
The tuned circuit (coil and capacitor) needs to be retained and is tuned for maximum output with the device under crystal control.
Brooce's tale reminds us of the value of even simple circuits as learning tools.
Neil
was where I found the schematic for the
oscillator circuit I built.
The MWA was a bunch of Part 15 AM BCB experimenters
that were on the net before Part 15.Us.
And I think the MWA disolved (sp?) a few years before
this site came on...
Anyway, I think the schematic is still on the net somewhere.
As I recall, it was a Colpitts. I chose it from many in the
MWA site because it did not need an RF choke. (I had most
of the other parts.) I used the very same osc. circuit in the
13.560 MHz Part 15 transmitter that I built a few years later.
So we know that the circuit works from the AM BCB up to
at least 13 MHz.
Some experimenters have put crystals in place of the LC -
and I bet that works, although I have never tried it.
I know that Ramsey Electronics no longer sells kits, but
when they did, the first thing I did was get and build their
FM-10 FM transmitter.
Then every once in a while I would get a Ramsey catalog.
And when I did, life would literally STOP as I took the
thing all over the house and read it from front to back.
When the AM-1 came out in 1994 (??) I had to have
one right away.
I can remember later on how I got it running, with
the help of a good friend. More on that later.
I have another transmitter that runs on a crystal,
which I may just convert over to an LC VFO.
(The opposite aproach.)
And that it my "trusty" LPB carrier current transmitter.
I've had that since 1980. For now I'll just say that
it's on 1020 kHz and there are problems with that.
I want it on 620. I missed a fundamental 620 kHz
crystal just barely a few years ago on E-bay. This
is an older tube transmitter which needs a fundamental
rock. I might just put an LC in it's place and tune it
to 620. It's been done before. This transmitter is
strictly for experimenting, and would never be on
the air (excuse me, cough cough, running through the
AC line) for any length of time. (I did have some success
with a homemade CC coupler, again - more on that later.)
This is all I can remember right now, but I think the
satisfaction of working with these simple rigs is, well,
great.
I mentioned that I had crystals for 3 frequencies in the
AM band, up near the top. I bought one at a time over
a long long time period. 1700 kHz was first. That's why
my official user name on this site is MICRO1700. That name
has sort of been lost in a clutter of many other fun names
for other fun Part 15 experiments, as many of you have
probably observed. The crystal were not inexpensive.
That first 1700 rock was 35 bucks. I had a rock from
a Heathkit communications receiver that ran on 1681.
I went with that for quite a while before the 1700 rock
came in the mail.
I don't really know the name of my "station" right now.
It's on FM with an MPX-96 (from North Country Radio)
which runs too much power so it runs into a bunch of
attenuators. It covers the house and yard and a little
bit beyond. Even tho it doesn't go very far, I get
tremendous satisfaction from this FM set-up.
Things happen very slowly here.
Because my eye are messed up, it took me
several months to build my AMT-3000.
(A few soldering connections a week.)
I did have a few problems and I sent it
back to SS-Tran. But that's another thread.
My dogs are calling me.
Brooce, station ??
Please excuse any typos or whatever.