View Full Version : FMBA1
09-30-2001, 07:54 AM
What does the FMBA1 actually do? It just takes power (AC, right?) and amplifies before the signal is 'out' on the antenna, right? What would this do in a set up like, say, FM100, FMBA1, and TM100? And it (the FMBA1) works when receiving signal as well, correct? (In this manner is all it does is clean up the signal, because on a receiver-type setup isn't the FMBA1 between the antenna and the receiver? ie it cleans what is 'brought in' from the antenna, right?)
In essence, can I think of the FMBA1 as 'part' of the antenna when it's hooked up?
09-30-2001, 07:59 AM
Follow up question...
Can the FMBA1s be 'stacked'? ie Use 2 or three in series to boost further?
Just a thought...
11-21-2001, 01:57 AM
:eek: Nobody has responded...humm....
The primary purpose of the FMBA1 is to boost or pre amplify broadcast signals at the antenna, before they lose more strength traveling down the coax to the receiver.
Yet, Ramsey's description does note that it can be used in reverse to amplify an out going signal up to 1 watt. In that case, you would want the FMBA1 as close to the output of the transmitter as possible.Not having built one of these units, or seen a manual for one I can only speculate that the FMBA1 does not employ any low pass filtering, as it was intended to only amplify incoming signals, so any harmonics produced by your transmitter would be amplified along with your fundamental.
As for stacking them, I don't think you will gain any increase in power. Of course, if you live in the U.S.A. all of this is just for informational and educational purposes only.
The FMBA1 does use low pass filtering, both on its input and output. As I understand it, the intended use for regulated countries [that is countries like the US, Canada and many more that have strict regulations] would be as a high quality FM antenna preamp. The closer to the antenna - the better! This is because you amplify less noise, as even the best coax is not perfect.
Where regulations permit, the FMBA1 makes a rather nice RF power amp for the FM band - and it will take micropower FM transmitters - let's say 5 to 25 mw and amplify them to about one what. The input low pass filtering is designed to clean up harmonics from the boosted transmitter - and the output filtering from the amp itself. I encourage anyone interested to check out the PDF instruction manual on the website.
For transmitter purposes, the idea is to mount the main active part of this rig as close as possible to the transmitting antenna. This is to avoid coax losses which might say drop your watt down to half a watt or less, depending on the length and quality of the coax.
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