Quote:
Originally Posted by esquared
Nope. Without knowing more about their link budget, it's not immediately clear which should be which.
Judging from the photos and clever use of MS-paint, the internal antenna is roughly 1/4 wave, and the external roughly 1/2wave for the 902-928MHz band. Assuming no poorly placed metallic structures, and that you aren't purposefully pointing the antennas end-wise at each other, you should get a nice fat pattern off both. Once again, for the interested reader, RFCafe has lots of fun info about antennas, power, patterns, etc. IN particular, check out http://www.rfcafe.com/references/ele...a_patterns.htm
I've got to hand it to the IFI RF guys though, they tuned their transmit strength to be JUST under the FCC limits. Particularly on the RC side  If there is a signal strength problem, it's not on the transmit side.
I'd say those are my 2 cents, but at this point I'm up to about a buck's worth.
--Eric |
The parts adjacent to the shield appear as though they might be the first and 2nd IF filters, probably 455kHz and perhaps 10.7MHz or higher, and are only stuffed on one of the boards. So my guess would be that the internal antenna is Tx, and the external is Rx. It seems odd they wouldn't just diplex the external antenna.
As to the Tx power, I was a bit surprised to see that was considered passing and do note a "unc." in the pass/fail column but saw no discussion on it in the report... but certainly that is not a problem for us to consider here as the error is potentially on the side of a tiny bit too much power.
I have my doubts that this is a link budget, antenna tuning, external interference (cell phone or otherwise) issue, but speculation and facts are two different things and IFI is in the best position right now to analyze the facts.
Thanks,