Part 15 AM outdoor installations tend to utilize bottom loading of the 3-meter vertical antenna for a number of practical reasons, such as listed here:
1.) the Part 15.219 3-meter rule can best be met by mounting the transmitter near the ground and close to the antenna;
2.) being close to the ground the power and audio connections can be conveniently brought to the transmitter.
But we hear stories of security, resulting in stolen or damaged transmitters due to their easy access by intruders. To increase security for an outdoor installation a transmitter mounted 10-feet in the air at the top of the antenna would be more difficult for vandals.
Difficulties of top-mounting/loading a part 15 system are listed here:
1.) getting power and audio up to the transmitter;
2.) grounding.
?
to make adjustments to the system.
Damage to ground mounted system is a concern which I had to face just yesterday. The base coil on my system is weather protected by an inverted 1 gallon ice cream bucket (empty) which has served well for a couple of years. The monitored DC current feed to the transmitter had dropped so I investigated and found that the cover was smashed and the coil form was wet from rain. I assume that one of my deer "inspectors" misstepped and did the damage.
Letting the coil dry in the sun and replacing the bucket fixed the trouble but there is no way to prevent this from happening again so I keep a couple of spare buckets handy.
Neil
This subject brings up something I have said in other posts is one of the problems of AM broadcasting with outdoor equipment. Even if you have your own property you still have to worry about vandalism and theft. If the transmitter and coil etc. is on top instead of at ground level what stops someone from just knocking it over? And what stops someone from yanking the power and audio wires? or the ground wire to the inplanted radials?
Maybe you have to build a fence or something around it. Maybe a wooden shed with a lockable entrance would help, along with being in a good neighbourhood.
Mark
The notion of "good neighborhoods" is mythical.
People act all smiley on the front of their face, but have you heard their back-stabbing gossip; their secret schemes to get your station shut down?
The best bet for security is to have your transmitter indoors, or on a roof.
AM is problematic on a roof due to grounding issues, but FM is certainly viable (I did that on Bowen Island).
And, as I've reported here previously, in a house I had in Pitt Meadows I managed to come up with a creative scheme for AM. I lived in a rancher, and used a Talking Sign with a wire antenna. I mounted the transmitter on the ceiling of the rancher (in my studio) right beside the outer wall, and drilled a hole in that wall. I threaded the wire antenna outside and mounted it inside a PVC pipe that I attached to my eve - the top of the wire just managed to clear the roofline.
I was amazed at the range I was able to achieve. In one direction, I heard my signal (weak, with noise, but listenable) at a range of about 1 1/2 miles (it was clear, open field). In other directions, with buildings as obstructions, it was less but still reasonable (over 1/2 mile).
I wish I could do that now. I'm in a 3 level townhouse with an attic, no outside antennas allowed, and I'm still trying to come up with a scheme to get some range. My studio is on the bottom floor, and currently I have the antennas inside the window sill there - range is poor on both AM and FM, due to the number of buildings in the complex. I'd be happy with 1/4 mile on AM (probably less on FM), but right now it's a lot less than that.
I'm thinking that I might try a Whole House transmitter in a window sill on the top level (that particular transmitter because of its size, the Decade and others I have won't fit). Or try to somehow hide a ProCaster outside at ground level or on a balcony (if it's hidden, you don't have to worry so much about security).
The Wholehouse 3 works at FCC part 15 out of the box....you may have to do the "hidden" way of power increase to get to BETS-1. The decade already works at Canadian levels and is much better......From the second floor at a window you should get to the area nicely. Try tilting the decade on its side or holding it on the window sill someway(duct tape) or if you have a balcony just sit it out there. You can enclise it in plastic or other weathrproof container and no one will even know what it is, or care, and if they like oldies you'll be the hit of the place!
Mark
Fortunatly Neil lives in a nice neighborhood with nice neighbors.
The Decade CM-10 works at Canadian levels and is the same as the CZH transmitters and may fit on the window sill perfectly.
Mark