I was hoping you'd pop on here. This is a new install, and no additional tower space available. Frequency separation is 5.2 MHz. One TPO is 9 kw, the other 3 kw, into a dual-three-pole branch combiner, utilizing existing 1-5/8" air Heliax. Five-bay half-wave spacing, slant V. One vendor is offering a traditional configuration with rigid interbays, end fed, cable and tuner at feed point. The other is offering a five-way power divider with cabling to the bays. It's been so long since I've dealt with this end of the business, and never with a diplexed FM before.R. Fry said:If this is a new installation for two non-D FMs, then the answer will depend on the frequency separation, and choice of antenna OEM. Closer frequency spacing may make such projects more feasible, but also may require a fairly long length of rigid line at the antenna input used to optimize the antenna system for the best Z match at those frequencies. The downside here is that close frequency spacing also can drive up the cost of the hardware needed in the transmitter room(s) to combine the two channels with acceptable isolation/r-f IM products.
If this is an existing installation to which a 2nd FM is to be added, then there may be additional costs -- which best are addressed by getting a specific quote from that antenna OEM.
Bill Wolfenbarger said:I was hoping you'd pop on here. This is a new install, and no additional tower space available. Frequency separation is 5.2 MHz. One TPO is 9 kw, the other 3 kw, into a dual-three-pole branch combiner, utilizing existing 1-5/8" air Heliax. Five-bay half-wave spacing, slant V. One vendor is offering a traditional configuration with rigid interbays, end fed, cable and tuner at feed point. The other is offering a five-way power divider with cabling to the bays. It's been so long since I've dealt with this end of the business, and never with a diplexed FM before.