04.05.2024 145.430 UPLINK BLOCKING SOLUTION

On Sunday March 3, 2024 the persistent 145.430 uplink (RX) channel blocking issue was fixed (or so far so good).

RTSA Measurements made in February, at Yaesu DR-2X RX input from the duplexer, found some anomalous spectra at the 144.830 MHz RX input.  Some transient and some persistent over periods of 10's of seconds.

Note that the 145.430 Repeater input frequency (144.830 MHz center screen RTSA), is only 44 KHz above the 144.390 MHz AX.25 Packet/APRS frequency.  Notably there was splatter coming from some APRS squawk (or other AX.25 packet burst) on 144.390 MHz.  This "splatter" is bursty (short duration), and may cause a noise fart on the repeater input (if in NBFM/NBFM repeat mode) , but unless there are long bursts of packets on 144.390, the brevity of these bursts doesn't coorelate with the blocking issue, which at times could last for 10's of seconds.

See the videos below:

The RTSA spectrum above is measured after the duplexer, and FM Broadcast Band Bandstop Rejection filter.

The 98.1 FM Broadcast signal (10 KW transmitter, 14 feet away) is very attenuated, and not visible above the average noise floor of the RTSA.

The DR-2X front panel LCD touch screen, showing the RX indicator blinking on and off, without keying the repeater TX (enabling the repeater).  That blinking has stopped after installing the FM Broadcast Band Bandstop Rejection filter.

The FM Broadcast Band Bandstop Rejection filter details are below, about $17 on Amazon.