27.148 MHZ attenna TX/RX system
I have a 27.148MHZ TX system I am transmitting an AM signal from to an attenna. Currently if I measure the power out of the TX system with a spectrum analyzer than I am getting approxamtely 30dB at my carrirer signal. So have hooked up a whip attenna speced out at SWR around 1.8-2 at 27.14MHZ. I measured the attenna with network analyzer and have confirmed a VSWR close to the specs. I go to hook up the attn. to the TX system. THen I measure the receieving power at the RX attenna via attenna -> spectrum analyzer. I get only about 15dB in at the RX attenna.
I want to ask if you guys think this loss is because of mismatch at the TX attenna? Am I probably losing power from reflections at the TX attenna? What accounts for the 15dB loss from TX to RX. Note: the TX and RX system and Attennas are right next to each other when I measure 15dB at the RX end.
Does anyone have a suggestion? Matching network? New Attenna?
Your measurement of received power is relatively meaningless. If the antennas are close, there is direct coupling effects between antennas that can change the performance of each antenna.
Far field measurement can be predicted and measured. Antenna directivity gain, distance, and frequency effect level of received power.
If I understand what you are saying...you are surprised that the power displayed when the receive antenna is connected to the spectrum analyzer is 15 dB less?
You do realize that the transmit power is radiated in all directions, while the receive power only subtends a small portion of those directions?
BTW, the measurement of "30 dB" is somewhat meaningless unless you relate it to a real power, like "30 dB above 1 milliwatt", which would be written as +30 dBm
Rich