I have a European version of the TK880 UHF mobile which officially covers 440 - 470MHz (the USA version covers 450 - 470MHz, I think).
I have successfully programmed the radio down to 430MHz but its very deaf at 430MHz. Sensitivity at 435MHz is just about OK but declines significantly at 434MHz and below.
I wonder if anybody has modded a TK880 to get better RX sensitivity below 440 MHz (or 450MHz)?
Front end RX alignment is done at 440.05 (25), 455.05 (93) and 469.95 (250). Tuning is very broad with no RX improvement achieved for in-band frequencies.
In-band RX performance of the UHF TK880 also appears to be relatively poor. Official narrow band sensitivity is quoted as 0.35uV (-116dBm). My "optimized" UHF TK8180 (after realignment) has much better weak signal performance than the TK880...around 7dB better!!
Is it possible to manually adjust the TK880 front end BPF's to get better RX performance?
Is it possible to hex edit the "low" 440.05 tuning frequency to 430.05 to get better out of band sensitivity?
The RX VCO is in lock at 430MHz (the TK880 does RX at 430 MHz) but does the RX VCO voltage level effect RX sensitivity? The service manual states that the RX VCO should be at 1.5v or above.
Overall I'm disappointed with the "in-band" 440 - 470 MHz TK880 RX sensitivity compared with the TK8180....but maybe its just my radio??
Thanks
I have successfully programmed the radio down to 430MHz but its very deaf at 430MHz. Sensitivity at 435MHz is just about OK but declines significantly at 434MHz and below.
I wonder if anybody has modded a TK880 to get better RX sensitivity below 440 MHz (or 450MHz)?
Front end RX alignment is done at 440.05 (25), 455.05 (93) and 469.95 (250). Tuning is very broad with no RX improvement achieved for in-band frequencies.
In-band RX performance of the UHF TK880 also appears to be relatively poor. Official narrow band sensitivity is quoted as 0.35uV (-116dBm). My "optimized" UHF TK8180 (after realignment) has much better weak signal performance than the TK880...around 7dB better!!
Is it possible to manually adjust the TK880 front end BPF's to get better RX performance?
Is it possible to hex edit the "low" 440.05 tuning frequency to 430.05 to get better out of band sensitivity?
The RX VCO is in lock at 430MHz (the TK880 does RX at 430 MHz) but does the RX VCO voltage level effect RX sensitivity? The service manual states that the RX VCO should be at 1.5v or above.
Overall I'm disappointed with the "in-band" 440 - 470 MHz TK880 RX sensitivity compared with the TK8180....but maybe its just my radio??
Thanks