KnightKit AM Broadcaster, A Close Look Inside

I had one of those as a kid. It really put out a signal. We overdrove the audio input but it still sounded better than I expected. It gave my loser friends and me the perfect opportunity to make fools of ourselves all over town. I must say we took full advantage of the situation.

I suppose at this point I don't know if our antenna was legal or not in its day. I don't think the rules said anything about a ground wire in those days and I had it mounted in my attic just a couple of feet from the antenna connection outside the window. My antenna was this CB ground plane with drooping radials. The auto parts stores in those days sold loading coils for car antennas to improve reception. I put one on the antenna and it seemed to make a difference.

I hope everyone who had one of these transmitters had a much fun as we did...

I still have mine! Still works fine.  i think I wrote about if here a few years ago.

I love this guy's videos!

And there's an outfit selling reproductions of this transmitter kit on eBay.  They're $119 + shipping.

Might be fun to put another one together 50 years after I built my first one!

TIB

Thanks, TIB, for the information. I might get one of those. My original seemed to work better than any Part 15 transmitter I've had since although I hope the anticipated Rangemaster changes my mind about that...

John

W9LWA

I guess it all depends on what you mean by "works better".

If you're looking for the best range, then you have to look at field strength, and there's evidence that in identical conditions, of all the current crop of transmitters, the Rangemaster is tops.  There was some question about the AMT5000, but since it's no longer in production, the issue is moot.

If you're looking for sound quality, that's different again, and somewhat subjective.

But even if you take range as the be all and end all, I have to say that there are other factors determining range that can dwarf field strength.  Ground conductivity is huge, as well as what kind of ground you can install in your location.  Topography, obstructions, background noise levels, interference, even weather, all can play a significant role in range.  It's why people using identical transmitters in different locations with different installation parameters can get vastly different ranges - everything from well under 1/4 mile to over a mile.

I wonder what the field strength of those Knight Kits would be in a transmitter test?  I also wonder whether the ranges remembered from using those transmitters come more from the reduced background noise levels in those times (and maybe a not so strict compliance with Part 15).

I also built one of these circa 1959 and still have it and it still works.  Out of curiosity, a few years ago I measured the DC power input to the "final" stage (the oscillator) and if memory serves it was about 180 mW.

My original installation had the transmitter mounted on a shelf about a foot below the basement ceiling with the antenna wire running up one foot and horizontal for nine feet.  There was no intentional ground but I suspect the power line and the audio feed from my bedroom "studio" upstairs served this function.  I knew nothing about coil loading antennas and wonder what effect such loading would have had, though I am not interested enough to experiment now to find out.

None of our family cars had radios so the only range checks I made were bicycle mobile with my Motorola transistorized portable and checks with neighbors.  The AM noise floor was greatly lower then compared to now and neighbors could hear the station up to a quarter of a mile away.  My portable could hear it at about the same distance with a good signal.

Countless hours were spent by me with my high school buddies playing with this thing.  To this day I find it hard to believe that I never received an electrical shock from it.  I used it for a short time in college but academic demands forced QRT for many years until I found time to occasionally fire it up again just for the fun of doing so.

Neil

I'm not surprised to hear it was a bit overpowered. My dad would take me out now and then in the blue '67 Mercury station wagon and we still had a pretty good signal for a couple of miles. I also had a similar transmitter from Lafayette that never worked nearly as well, but it probably wasn't giving me 180 millawatts instead of 100, either. Ignorance was bliss about a lot of things back then.

One day I thought it would be a good idea to write the FCC and ask how legal it would be to somehow put a transmitter up on a tower and feed it from a studio in the house kind of like Rangemasters do now. As I recall, they said it might violate the rules and they were keeping my inquiry on file. I thought that was quite an honor. My parents suspected differently...

<p style="text-align: left;"><b>Really fun thread!</b></p>
I missed the experience of the

Knightkit transmitter.

Our bunch have a parallel story.

We had the Lafayette KT-195 transmitter kit.  (Two of them,

actually.)   We also had 2 Lafayette

990177 phono oscillators that used 12BE6 and 35W4 tubes.

They were all bad performers

and were very dangerous if not

operated in a very very careful way.

The rest of our story is very much the same.

Transistor portable radios were

attached to bicycles.

There were all sorts of antennas and experiments with ground connections.  There were long audio cables going back to our

first "studios" with almost broken record players, and silly looking microphones that were

part of unused intercom systems.  And there was one

tape recorder with a motor that

made scraping sounds when it was running.

It was one of the best times of my life.

1969.  Oh my.

Brooce, Hartford CT

I just watched the video Neil mentioned about the KnightKit transmitter.

It was GREAT.

Best Wishes

Brooce

I've probably mentioned this before, but here's a cool story about the Knight transmitter from 1957: