CraigF wrote: "I had asked if the same situation could be posturized as possible if a coil were installed IN a metal box under the antenna."
My immediate reaction was to wonder the same thing and evenb leap to a decision... deciding that coils should be mounted in metal boxes.
Also, I agree that the coil in a metal box will be changed in value caused by reactance with the metal around it.
Outdoor coils have been protected from weather by sealing them with varnish or placing them in plastic buckets, but metal seems right.
Of course we can go "All Coil" on Blare OnAir.
craigf Your last post really has me at interest, specially since I am working on bringing my Chris Cuff C-Quam AM STEREO transmitter out of the dorment period.
Chris Cuff who is a member of several facebook groups, is the one who desinged the AM C-Quam Stereo transmitters and sold the kits on ebay. He had a bunch of PC boards etched at a place that does that and has just told me he has some boards left and all the plans to build the kits. Even Bill DeFelice loves Chris Cuff's AM stereo transmitters. So what does that tell you? That Chris is a highly respected hobbiest just like us.
If new interest is gained in AM stereo, he might mass produce those kits again.
Any who, I am about to replace the generic transistor my already assembled kit had with a 2N3035 type, this will put that danged thing up to part 15 100mW, then I will be looking at building an outdoor antenna for this AM transmitter which is currently crystaled for 1250KHz, that is unless I buy another crystal to go to a higher frequency.
I am trying to get Chris Cuff to join this forum board and participate in discussions about AM stereo, he told me on Facebook, he is going to attempt putting together tube operated kits as well.
I know many say there are no AM stereo radios out there, but I got one off ebay, it's a Realistic TM-152 and it works quite well for a used item many years old.
I would like to have a forum board section set aside for primary discussion of AM stereo basics and see if Chris will participate with us on one of his interests.
Any who, I'm getting tired, time for bed, but I'm really interested in ANY discussions about AM antennas at this point and time, I think my town needs an AM stereo radio station and I'm gonna be it!!
Night all!
Bruce.
I might add that comercial AM Antenna Tuning Units have a large inductor housed in a metal box.
I think it would be great if Chris joined the group. I would also like to see a quality stereo transmitter available. I would be interested in one myself to tinker with.
I am not sure how much of a market there will be for any AM transmitters. Granted there is interest, but unlike cell phones, not everyone has or needs one!
Another good piece of information! Of course, it is probably best with the power available to most commercial stations!
Coils in boxes are apparently good things if adapted to the transmitting environment/matching etc.
That looks like the arrangement I have for my 1710 operation here in Druid Hills.
Just an update, my order from Mouser for those 2N3035 transistors just came in, time to work on my AM C-Quam stereo transmitter and finally work with an AM transmitter.
Bruce.
I recall reading in the 1958 ARRL handbook that antenna tuner coils and transmitter final tank coils should be shielded in a metal box, could be solid or perf, to reduce harmonic radiation.
I need to find my old ARRL books. That makes sense, and on a side, yet related note, I find it amazing what those guys did in the 50's to go mobile HF!
And on another side note, yet related. A properly designed coil with a narrow bandwidth, can help reduce harmonics. A screwdriver antenna is fairly efficient at that because of its narrow bandwidth when tuned to a specific frequency. They work wonders to help kill harmonics of less than properly designed mobile amplifiers.