The below posting was from 2017 and regarded re-aligning the front end of a TK8180 to improve RX sensitivity. The factory defaults do not provide optimum RX sensitivity. After re-aligning the front end. RX sensitivity performance is very good.
I have recently acquired another TK8180 which was from a later production run. I found that the "factory default" values had been changed which resulted in better RX sensitivity "out of the box" but I was able to still improve sensitivity by again re-aligning the front end.
The original default values from the service manual were 95, 123, 151, 173, 195.
The later default values in the newer TK8180 radio were 90, 117, 144, 165, 186
The new optimum values after re-alignment were 70, 105, 120, 165, 190
NOTE that the new optimum values were almost identical to the optimum values from the earlier TK8180..the only difference was 120 for the 3rd value rather than 130..but using 130 would probably make little difference!!
I also changed the narrow SQ threshold values (L,C,H) from 175, 169 and 166 to 130, 129 and 128. The TK8180 SQ now opens on really weak signals.
The front end filters on my UHF TK8180 were originally 94, 122, 150, 172, 194 and the values after alignment were 70, 105, 130, 165, 190.
The service manual default values were more or less identical to the original values in my radio (there was actually a difference of 1 unit for some reason (95, 123, 151, 173, 195)...but tuning is so broad that 1 unit has no difference...its actually difficult to notice a sensitivity change on a 5-10 unit difference!!).
However, the optimum values in my TK8180 will not necessarily be the optimum values in your radio...you really need to align your radio using a very weak signal source...ideally a signal generator...then you can tune the front end filters for maximum quieting ie. less hiss.
Its best to use a signal generator but a great source of a weak signal is the local oscillator of a HT or scanner. I use my Kenwood TH-F6 which has an IF of 57.6MHz. To get to a test frequency , say 400.05 MHz, you subtract 57.6 from 400.05 which equals 342.45MHz...so if I set the RX on my TH-F6 to 342.45, the RX local oscillator will put out a super weak signal on 400.05 MHz...which can be used to align the TK8180. Connect the TK8180 to, say, a mag mount antenna and then bring the TH-F6 close to the antenna so that you hear a super weak signal on the TK8180..and then align for maximum quieting. You need to repeat this for all 5 test frequencies.. 400.05 to 469.95 MHz.
Different HT's have different IF freqs so you will need to research the IF of your UHF HT. Also sometimes you need to add or subtract the IF freq to get a weak signal on a test freq. Experiment using two HT's - one on RX and the other as a weak signal source using the IF freq!!!
I have recently acquired another TK8180 which was from a later production run. I found that the "factory default" values had been changed which resulted in better RX sensitivity "out of the box" but I was able to still improve sensitivity by again re-aligning the front end.
The original default values from the service manual were 95, 123, 151, 173, 195.
The later default values in the newer TK8180 radio were 90, 117, 144, 165, 186
The new optimum values after re-alignment were 70, 105, 120, 165, 190
NOTE that the new optimum values were almost identical to the optimum values from the earlier TK8180..the only difference was 120 for the 3rd value rather than 130..but using 130 would probably make little difference!!
I also changed the narrow SQ threshold values (L,C,H) from 175, 169 and 166 to 130, 129 and 128. The TK8180 SQ now opens on really weak signals.
The front end filters on my UHF TK8180 were originally 94, 122, 150, 172, 194 and the values after alignment were 70, 105, 130, 165, 190.
The service manual default values were more or less identical to the original values in my radio (there was actually a difference of 1 unit for some reason (95, 123, 151, 173, 195)...but tuning is so broad that 1 unit has no difference...its actually difficult to notice a sensitivity change on a 5-10 unit difference!!).
However, the optimum values in my TK8180 will not necessarily be the optimum values in your radio...you really need to align your radio using a very weak signal source...ideally a signal generator...then you can tune the front end filters for maximum quieting ie. less hiss.
Its best to use a signal generator but a great source of a weak signal is the local oscillator of a HT or scanner. I use my Kenwood TH-F6 which has an IF of 57.6MHz. To get to a test frequency , say 400.05 MHz, you subtract 57.6 from 400.05 which equals 342.45MHz...so if I set the RX on my TH-F6 to 342.45, the RX local oscillator will put out a super weak signal on 400.05 MHz...which can be used to align the TK8180. Connect the TK8180 to, say, a mag mount antenna and then bring the TH-F6 close to the antenna so that you hear a super weak signal on the TK8180..and then align for maximum quieting. You need to repeat this for all 5 test frequencies.. 400.05 to 469.95 MHz.
Different HT's have different IF freqs so you will need to research the IF of your UHF HT. Also sometimes you need to add or subtract the IF freq to get a weak signal on a test freq. Experiment using two HT's - one on RX and the other as a weak signal source using the IF freq!!!
The TX is spot on and no re-alignment was required.
