Here's what I know at this time.
Today I am unable to display any PDF files. Attempts to see them result in a window asking if I want to browse them or download them. Repeating.
Two days ago was the last time I viewed a PDF file.
Between then and now I have not knowingly made changes to anything.
Frustration dictates that I leave the problem alone and do something else.
This winter I will return to the problem and try to fix it.
After three hours of wrestling I gave up trying to repair the PDF function of Firefox and downloaded Sumatra PDF Reader from Sourceforge which does the job.
With a printed schematic in hand there is the RF semiconductor, Q2, MRF581 NPN power transistor.
That doesn't look beefy enough to drive a CC coupler.
The circuit itself receives no ink, just a short paragraph about the feedback circuit.
Doesn't even talk about how to load into an antenna, for those on foreign soil.
It is a product that doesn't take itself very seriously.
Glad you made it, Carl.
Under the wrong or right(?)
conditions, the LPA-1 might be a
"cpmb generator." I would be
afraid to use it.
Thank you Robert for the info
on the mismatch problem. That
definately is a problem.
Bruce
What is a cpmb generator?
I meant to write - "comb generator."
I'll be alright.
Bruce
Nothing in the instructions define the 1 W rating. Is it 1 W peak? 1 W RMS? 1W PEP? It is mentioned casually that it is a linear amplifier. If so, then the output transistor (MRF581) would handle the the power level, but with a high case temperature (don't touch it). It doesn't have a heat sink.
Worse yet, and I speak from experience, is that the MAV3 input transistor can easilly be blown out by applying more than 20 mW of RF power to the input jack. This device is actually a small integrated circuit called a "MIMIC" intended for microwave up to 2 GHz. It must have some very small geometry ciruitry on the input side. The Ramsey instructions don't mention the blowout danger, but the datasheet for the device does. The maximum input signal without damge is 13 dbm. It says it presents a 50 ohm load.
I had a couple of LPA1s. I blew the first one by attaching it directly to an AMT3000. After I realized the input power limit, I connected through a trimpot to act as a level control and started at the zero level and adjusted it up. I figured I would adjust it slowly upward until the LPA1 output looked good on a scope across a 50 ohm load. Well, I did that and began to see a sope deflection with a waveform that was so bad, it looked almost random. As I approached a defelection that at least had some excursions to the 1 W peak level, the totally crappy waveform didn't change (except for amplitude), and then poof, I blew the MAV3 out. In retrospect, I should have been measuring the input power to prevent MAV3 damage.
Another thing I found is that both the MAV3 and the output transistor are fed collector voltage through small 5.6uH inductors. That seems awfully small for the BC band. It amounts to XL=60 ohms at 1700 kHz and XL=19 ohms. Those are both very small reactacnes to be used to decouple the RF from the power supply. At 100 MHz (FM band) their reactances are XL=3519 ohms. Much more reasonable.
My instant conclusion is that the LPA1 might work OK for the FM band but not so good for MW. This is also supported by the fact that FM does not require a linear amplifier (I suspect the LPA1 is not really a linear amplifier).
I have never, over all the years, seen a report that anyone has successfully used and LPA1 as a linear amplifier for MW operation. I would like to hear if anyonw knows of any successes.
One last comment. The LPA1 is billed as a "great laboratory amplifier" which implies that it may be of use to knowlegeable RF engineears who can interpret the underlying component specifiecations and "reverse engineer" the circuit to see what it really does and do what is necessary to make it work.
I'm not suprised. Compared to a guy
like you, I have no experience with this
stuff at all. But I can tell you this: I know
when something is too good to be true.
Just the term "linear amp" makes me
uneasy. When I was 14 years old, I
had CB friends who were blowing away
the whole radio spectrum - with "linears" -
or so it seemed.
Anyway, I know "Carrier Current" is on it's
way out. But I know how to put the AMT-3000
onto CC safely. I think it's fun.
The idea of higher power for CC without having
to find old CC stuff on the internet - well - who
knows what will happen.
Great info about the LPA-1 Phil. Usng it would
give me nightmares. I would be dreaming about
running away from FCC guys who would be
pounding down my door.
Bruce
Good info from all. That's why we have dialog as opposed to analog.