I wrote this a few years ago in response to the same question on another forum...
"In the early days of C band, the two most critical components of a satellite system were the downconverter and the LNA, or Low Noise Amplifier. The next generation of systems went from the single conversion downconverters to block downconversion. The LNA and block converter were joined either by a piece of low loss coax or an "N connector" coupler. A way to counter the loss between the LNA and the downconverter led to the joining of those two devices, called a Low Noise Block converter (LNB). A waveguide is a metal channel that "guides" the signal from the opening at the mouth of the feedhorn to the pickup probes in the throat of the LNB. Just like coax, waveguides can be lossy, so a way was developed to counter this loss by joining the LNB together with the feedhorn into a single Unit . This is what we know today as an LNBF , or Low Noise Block converter Feed."
Im not sure i understand.. one of my dishes, has what looks to be a all in one feed horn and scaler ring, the other one has a adjustable scaler ring, does that have anything to do with the differance between a LNB OR LNBF??...I just purchased a new LNB?? PANORAMA -#ER863 this says..."15k C-LNB on the box, this is what the "F" type cable or what ever attaches to. im having a hard time finding sattalites with a tv out at the dish, what im using is just a regular antenna feed type cable from the LNB from the dish to the reciever, could this be a problem?
You should use RG-6 coax for your cabling. Lnbf's don't have a servo motor mounted on the feedhorn. Servo motors are usually little blue square boxes that have a red, black, and white wire going to your analog receiver to move a little probe inside the feedhorn to change from Horizontal to vertical and vice versa.
An lnbf does this electronically with varying voltage on the coax. Like the little lnbf's work on Dish and Direct tv satellite dishes.
Both types of feedhorns are still adjustable within the scalar ring so you can match the Focal distance on your dish and get the best signal. That adjustment is critical to your reception.
Lnbf would be the most simple and straight forward to use for a beginner.