Well, things just keep falling in my lap! Anyone know anything about the Ramsey AM1?

There are at least two people on this forum who have talked about the Ramsey AM1, and as soon as they see your question they will be here to tell you their experience.

I think the AM1 is a variable oscillator, not crystal controlled. But I think one or more of the users have been able to add a crystal, which makes it a very real transmitter.

Stand by, they'll be here any minute.

Many have modified that unit to have a crystal or PLL. Go with a PLL if you need agility in frequency. Direct frequency crystals are not cheap. To get around that, you can use a divider and a higher frequency crystal and let the divider chip count that higher frequency crystal down to the frequency you need and use that for the AM 1's oscillator circuit.

Also it's good to go for external audio.

RFB

I have a 1000 KHz oscillator (can) (4 pole) in my junk box...will that work? I am interested in just staying in one place...when you say that direct frequency crystals are high, how much is high? Thanks again for the quick reply!

Dave VQX

The AM-1 is a decent way to get into AM broadcasting but it appears to me to be more of a "science fair project" than a serious transmitter. The L/C oscillator will drift in frequency which may make reception on digitally tuned receivers problematic. I have read articles by hobbyists who have gone to great lengths to stabilize the oscillator using special capacitors, temperature control, regulated power supplies, and so on and this is a great way to learn about transmitter electronics but it can be a major discouragement for those who seriously want to community-cast.

By all means build it and play with it but don't assume that this unit's performance is typical of Part 15 AM transmitters. You can probably get your 1 MHz osc. to work with it but this might not be simple. My recommendation is to get either the Ramsey AM-25 or the SSTRAN AMT-3000 or AMT-5000 kits. These are crystal controlled frequency agile PLL units which stay on frequency once set and are designed to effectively load into 3 meter antennas.

Neil

So here's a shorter version.

My AM-1 drifted horribly after
assembly and FMed a lot.

I had a friend replace some of
the caps, and then the transmitter
only drifted a little at start up
and then slowed down and stopped.

But I didn't like the FMing so the
AM-1 went into the attic in the
fall of 1993.

In the summer of 2002 I took it out
of the attic. I had thought about it a
lot.

The wooden logs in my brain started to
smoke. I was getting an idea!

I took the oscillator LC out. I built a
crystal controlled oscillator from the
the old Medium Wave Alliance website. I
got a crystal for 1700 kHz. (Yup, that
was really expensive.) But the oscillator
put out RF. And when I connected the osc. to
the two wires where the LC had been, the AM-1
worked! At that point I
had a fairly good Part 15 AM transmitter.
It didn't drift, it didn't FM, and it
worked reasonably well. I don't know if
it achieved 100 percent modulation, But it
got out about 3000 feet on the car radio.
That wasn't too bad, considering what it
was. The transmitter audio was very boosted
on the low end of the audio spectrum, between
about 100 to 500 Hz. I took an audio equalizer,
put it in the audio line, and brought those
frequencies down. Then I got better overall
modulation. Again - I don't know if it was
100 percent, but the AM-1 was sure better than
nothing.

I used the transmitter for many years. I
considered it expendable, so it sat out
in my backyard under a bucket through gigantic
rain storms and snow storms, and in the blazing
heat of summer. It sat on a cinder block under
the inside of the bucket. So it was elevated,
and it didn't get wet. A little yellow LED
was rigged up there so I could see it was
getting voltage.

AM-1 folklore says that people have put
an AM BCB crystal in the place of the LC
and they have had success just with that.

Also, some people have modified the output
network. I did not try either of those
things.

I think Neil had said above that the AM-1
is like a Science Fair Project. He is
correct. I did a lot of messing around with
the unit. After a while, it became a reliable
Part 15 workhorse.

Later, it was replaced by an SS-Tran AMT-3000,
which worked better.

But I sure had a lot of fun with it!

I had made a 3 meter antenna, a ground system,
and a loading coil, and this is how I achieved
the range I was getting.

It was a lot of fun!

Bruce, SLUG 88.3

"I have a 1000 KHz oscillator (can) (4 pole) in my junk box...will that work?"

Yes. Simply use it to replace the on-board variable oscillator. Take the "can" output and feed that to the trace where the output of the variable oscillator connects. Totally disconnect that internal variable oscillator..won't be needed.

"when you say that direct frequency crystals are high, how much is high?"

Well compared to say a 4Mhz crystal at about 6 bucks and a divider chip at about 2 bucks (or free by going through a junk box/salvage/scrap heap), versus a crystal for MW frequencies at 60 to 90 bucks. You could find one possibly from someone who has one on hand they are not using and may sell it reasonably. But considering how easy it is to make a simple divide by circuit off a 4 or 6 or other higher frequency crystal, why pay the extra costs?

I also will say the AM-1 unit is a very very basic kind of transmitter. Calling it a "science fair" type unit is about right. But there are some really good modifications you can do to that AM-1 unit and makes a great learning tool.

It has decent modulation and sound quality. And will sound far better than the TH unit that has to be modified for external audio.

For a starting unit, its decent enough to get you on the air.

RFB

I got it from Jan Crystals in
Florida.

The approach of using a higher
frequency crystal and dividing
it down is the better way to go,
if you are able to build that
kind of circuit.

For me, a guy with reduced vision,
it was easier to buy the expensive
crystal and take my chances. Still,
the above method is better.

I would hook that 1000 kHz osc. up to
the section that RFB mentioned.

I think you will enjoy the results.

Bruce, SLUG 88.3

Buy a 1700 crystal from Keith H. at Rangemaster. 10 bucks.

problem with that am1 is tpo is in the 30mw range hardly worth the time or expense. it is what it is a vfo house caster.

not at all suited for neighborhood casting.

good for learning basics and around house casting but not much else

I looked up the stuff on Ramsey's website, and it says that the AM1 (and AM25) are both 100 mW...is this a misprint, or misinformation?

in case of am1 100mw input iirc. also iirc it is not too efficient and does not get out very far. i had one and with a loaded 3m whip and grounded barely covered my house at the time

Is there any way to crank it up to legal output? Or maybe up the transistor before i put it together? Any suggestions?

rfb or radio8Z would be the ones to ask. i got fed up with mine rather qhickly

"Is there any way to crank it up to legal output? Or maybe up the transistor before i put it together? Any suggestions?"

Yes, but you might as well just re-design the thing completely. One thing that should be considered in the front of all this comparing is that right now, with what you got, that AM-1 is FAR BETTER to work with than the TH with the ISD chip. Better in more ways than one.

For example..the AM 1 is ready for external audio. The AM 1 has a connector for an external antenna. The AM 1 is easily modified for stable frequency operation. The AM 1 is more open to modifications than the TH ISD chip unit will ever be.

And most important of all, you will spend far less time working with that AM 1 than the TH ISD unit trying to add external modulation, an external antenna connector..which by the way would void it's FCC certification, so why bother messing with that thing when you got another unit with everything you need there already that you don't have with the TH unit?

The AM 1 is NOT a SSTran, or a Rangemaster or anything else. It is what it is and considering alternatives available to you at this moment, that AM 1 unit will put you on the air much faster and in less time than you will spend on trying to get the TH ISD chip unit to do what you need it to do.

RFB