All this talk about tube transmitters sent me into the attic last night to see if I could dig up this little bugger. Not only did I find it, but it still works! Built this from a kit when I was in Jr. High so that would be about about 45 years ago. Darn I feel old now.
Had a bit of hum in the signal but could only hear the hum it on the stereo receiver in the living room, sounded fine into the portable radios. Don't know what I'll do with it now that I've dug it out. Probably display it in the studio, I suppose.
TIB
That is a nice Rig man. I almost forgot the ceramic phono and mic inputs of those older AM Transmiters. What sort of range did you get? Did this transmitter seem to be effected by proper antenna matching or was it like some of the older transmitters where as the longer the wire was the further it would go? I'm trying to remember rather it was a Knight kit some of those students were using on AM when I was a kid or what? I just remember one student at the 3rd floor used some sort of bed spring in combo with some metal pipe for an antenna and it went miles. We were known off campus by a few who did listen. It was fun to entertain the campus and play Radio jockey with them. I'd like to know the range you got with yours?
I was like 12 or 13 years old. I don't remember much about range, in fact I don't remember even caring LOL! I had a mic plugged in and would talk and play records by putting the mic in front of the speaker on my record player. I was strictly interested in broadcasting to my sister upstairs in her bedroom and the kids in the house next door. And for that it was fine.
My test here, now, as a grownup only included walking around the outside of the house, and I could hear it fine.
I should really clean it up and give it a bit more of a test. I imagine come new capacitors would take care of the hum.
TIB
That looks to be in great condition. They characteristically had hum and I found that this depended on how it was connected to the outlet. Reversing the plug in the receptical changes the hum.
I ran mine with a 10 foot antenna and no ground other than that of the power lines and got a range of several hundred feet using a pocket receiver. I was never happy with the audio of this unit and found that if I fed the audio into the speaker output using an external amplifier that it sounded much better than the stock connection.
It is nice to see one of these which still lights up.
Neil
The first Knight Kit AM Transmitter I had used larger tubes, 50L6GT and 35Z5GT, and was a magic experience being able to BE on the radio alongside all the disc jockeys, personalities, announcers and music.
Then came the Knight "Wireless" Broadcaster Model 38 K 051 which is the same one Tim has.
My horizontal antenna was facing the wrong way, although I kept trying to reach Patricia's house so she could listen, but at least I had an excuse for showing up at her house for "tests."
Correction: Tim's is the Wireless Broadcaster-Amplifier Model 83 Y 706.
The schematics for all three versions have been scanned and given to the ALPB Librarian, Jeff Station8, who will be posting them at thealpb.com.
You could probably attenuate the Mic unput and connect it to a mixer of some sort or into your computer and broadcast that way. I'd really like to know what type of range you could get with one of these. I swear that some of the students at the School for the Blind had this when I was around 7-8 and I'm 52 now. I just remember an AM Transmitter and we done it till I was 12-14. So if it was the same one I can tell you it will at least go 1/4 to 1/2 mile to 3 miles. Yes its a big jump but it did depend on what these guys did. Some had a huge length of wire and I don't know what type of matching (If any) they did. We had off campus listeners and even the teachers heard us on air. One felt he had to monitor our little station and sometimes gave us lessons on how to talk on the Radio and reading the school lunch menu at times. Morning shows just before class was fun too as we done those at times. It was really recommended to us however that we did it after school, but once in a while it got fired up before class and at lunch time.
It seems to be in very good shape.
Is that a power transformer on the
top? If so, there wouldn't be any
electric shock problem on the cabinet.
(Unlike the Lafayette KT-195 or LA-320,
although I remember MRAM fixed one of
those up and made it a very good transmitter.)
Am I right about that?
Brooce, WLP
That is a transformer on top but it is for audio and not power. The unit uses Heising modulation which requires a choke and this transformer performs that function. The early models had a choke and the later ones had a transformer which had the secondary connection available on a terminal strip on the top of the case to which you could attach a speaker to hear the audio.
In the later models, the modulator and RF final circuitry was connected directly to the power line input but the preamplifiers were somewhat isolated by use of resistors on the ground and power connections with capacitors coupling the preamp ground and audio signals. This preamp ground was connected to the case and one could get a "tingle" if one touched the case and a nearby ground. Somehow many of us survived despite this, but I suppose those who didn't aren't here to tell about it.
Neil