DarkHelmet
-
Posts
9 -
Joined
-
Last visited
Reputation Activity
-
DarkHelmet got a reaction from Sshannon in Odd repeater splits or inputs?
Not only do you necrobump the thread, but you do it by spewing this horseshit.
A BpBr filter is nothing but a notch cavity with a anti-resonance reactance across it to improve close in pass. This will give a "band pass" with notches high and low from it in most designs. As you get further away from the pass frequency, past the notches, you'll see the pass band loss decrease. At 10-20 MHz away the band pass the match will be poor and the notch will be almost non-existent; 6 dB at best.
This repeater doesn't have a duplexer on it, it's fed from a window filter on receive and transmit goes into a combiner which is a number of true bandpass filters all feeding the same antenna.
Here's what the transmitter sees https://gallery.keekles.org/d/31221-1/chan+04+to+antenna.gif
You can see the RX filters here http://gallery.keekles.org/d/31182-1/dual+filters.gif
And with the RF pre-amp, this is an old (circa 1990) bipolar pre-amp with poor input match (-10 dB). This shows how important input match is. http://gallery.keekles.org/d/31185-1/Filters+with+pre-amp.gif
The TX and RX antenna have over 45 dB of isolation between them. This was measured as part of the system commissioning.
This issue is one of _ON_FREQUENCY_ interference. There is nothing that can be filtered. https://flscg.org/2021/05/tampa-gmrs-interference/
-
DarkHelmet got a reaction from gortex2 in Odd repeater splits or inputs?
Not only do you necrobump the thread, but you do it by spewing this horseshit.
A BpBr filter is nothing but a notch cavity with a anti-resonance reactance across it to improve close in pass. This will give a "band pass" with notches high and low from it in most designs. As you get further away from the pass frequency, past the notches, you'll see the pass band loss decrease. At 10-20 MHz away the band pass the match will be poor and the notch will be almost non-existent; 6 dB at best.
This repeater doesn't have a duplexer on it, it's fed from a window filter on receive and transmit goes into a combiner which is a number of true bandpass filters all feeding the same antenna.
Here's what the transmitter sees https://gallery.keekles.org/d/31221-1/chan+04+to+antenna.gif
You can see the RX filters here http://gallery.keekles.org/d/31182-1/dual+filters.gif
And with the RF pre-amp, this is an old (circa 1990) bipolar pre-amp with poor input match (-10 dB). This shows how important input match is. http://gallery.keekles.org/d/31185-1/Filters+with+pre-amp.gif
The TX and RX antenna have over 45 dB of isolation between them. This was measured as part of the system commissioning.
This issue is one of _ON_FREQUENCY_ interference. There is nothing that can be filtered. https://flscg.org/2021/05/tampa-gmrs-interference/
