i have a vx2000 mic processor i will trade for a factory made (not home-brew) medium wave (1600-1700khz) isotron or will sell for $100.00 plus shipping.
i have always wanted an isotron to experiment with and have become aware there may be a couple floating around in members hands here.
contact kc8gpd at hotmail dot com
Build one. They are easy to make. I've described one before here, and its buried in the thread abyss somewhere, but I will describe it again here.
2x large aluminum pie plates (top and bottom pieces)
2x 2 inch diameter Christmas wrap spool each 4 ft long, combined to make an 8 foot long tube.
1x #22AWG solid copper insulated wire.
1x 320pf air variable or old AM radio tuning capacitor.
Mount the two aluminum pie plates to the tube, one at the top with the plate upside down, and one at the bottom with the plate right side up. Wrap 180 turns of the #22 AWG solid copper insulated wire close wound, starting at the bottom about 1 inch from the bottom pie plate. Then for the rest of the length of the tube, wrap the wire around the tube with about a 4 inch gap between the windings until you reach the top. Connect the top of the wire to the top plate.
The bottom of the coil's wire connects to your TX output. The bottom pie plate connects to the ground of the TX. Tap the coil in the close wound section about 1/3 way up the coil. You may tap it a few times for peaking. Connect the variable cap from TX ground to one of these taps. Tune for maximum field strength.
Wala, a poor man's Isotron and works very very well.
RFB
I must have missed the original post in which RFB gave Isotron instructions, so I am delighted it has come back for a re-run.
The nutty antennas are the ones that get my interest, and Isotron has been accused of being "nutty", or at least it has been treated skeptically by some.
But when seasoned and experienced broadcasters like RFB tell us that it works well, that it a fabulous endorsement.
If you (RFB) have the time and willingness, can you take us on a word guide tour of what the Isotron actually does, from one part to the next, to generate an RF radiant signal?
Thank you.
"The nutty antennas are the ones that get my interest, and Isotron has been accused of being "nutty", or at least it has been treated skeptically by some."
Usually the accusation, or treatment of skepticism towards the Isotron is from those who have not even tried one, or built one. Just a lot of baseless...well accusation and skepticism.
An Isotron is a large LC resonant tank circuit, not all that different from a conventional monopole with a loading coil and ground radial system. In fact, place a cap hat on top of a 3 meter monopole which sits over a ground radial system and you pretty much got the same thing as an Isotron. The cap hat is your top plate, the monopole radiator and loading coil is the center part, and the ground radial system is the lower plate.
The name itself describes the Isotron's intent. It is an antenna designed for self contained resonance capability without the need of a ground system, which is perfect for situations where access to the dirt is hindered, such as in a hi rise building/apartment or nothing but concrete below.
It requires no coax and is not designed or intended to use a coax..so please all you coax will radiate blah blah's put that worn out broken record away because the Part 15 MW Isotron is NOT DESIGNED or INTENDED to have a coax!!
The Part 15 MW Isotron is designed to have the transmitter at the base of the antenna, just like a conventional 3 meter monopole system has the transmitter at the base of the antenna system. And again, the Isotron is designed to function with no ground radial system whatsoever.
It works incredibly well versus a plain old loaded up piece of wire, and somewhat more rigid too, meaning it wont swing and ding-a-ling with the air from the circulating fan in the room.
In an outdoor setup, the Isotron works best elevated and side mounted to it's support structure as well as isolated electrically from that support structure. NO ELECTRICAL CONNECTION!!!
I used a home built Isotron very similar to the one I described above with an SSTran AMT3K purchased off ebay and did the modifications on the SSTran website to configure it for 50 ohm load matching. The signal penetrated through the apartment building and over into the surrounding apartment buildings far better than the simple wire setup using that same transmitter when it was configured for loading up to a wire and using it's internal matching network, and even when using an external loading/matching network after bypassing the internal network.
The home brew Isotron is only different from the manufactured one in that the top plate in the home brew unit does not have a tunable top plate section, thus the reason for the tuning cap and tap along the lower portion of the coil. My next home brew unit will have a tunable top plate using a piece of fiberglass rod and a lock down clamp so that the top plate and connection can raise and lower, as well as the taps and tuning cap on the lower portion of the coil for further peaking.
I suggest to those who find their skepticism and accusation taking over their minds to build one or buy the manufactured Isotron and try it. Connect it as described and don't try to cook the books by connecting it improperly or improperly tuning it. It deserves far better treatment from those who have not even taken that baby step of actually using one.
I've used it in those impossible to access dirt ground situations and found it to be very effective compared to the simple dangling wire. You will too.
RFB
might consider a like new condition talking house external ATU in trade as well but it would have to be clean and in like new condition.