Malcom Technical Support

Working on getting it here.  bear with me.

ICOM 271(A/H) / 471(A/H)

These radio's are generally trouble free, except they do use plastic trimmer caps, which can cause problems. Ceramic replacements eliminate problems that may arise from these caps.

• Symptoms:

  • 271: hash or ruff sounding receive. no Tx or Rx. Frequency jumps around. dirty sounding Tx (mainly SSB)

  • 471: Most commonly is 430/440 works, but 440/450 won't or vise versa. Low power and/or Rx sens. on one end of the band, Ok on the other.

• Solution:

  • The 271 is not that bad. It uses 2 in the PLL, one for the PLL reference (10.24Mhz) and one in the metal box for the VCO.

  • The 471 is however a different story, it uses 36 trimmer caps of various sizes and values, most are on the RF/YGR, with the balance in the PLL. The RF/YGR is fairly straight forward alignment, the PLL however needs a bit more precision. It is divided into two parts, a LO and a bandpass filter. The LO needs to be peaked at it's 2 band references (we use 435 & 445 on the display) and align for 0Dbm (or more) output from this section is for best results, but as low as -6Dbm will still work. The BPF is the sensitive one, 0Dbm is minimum and no more than a 2Dbm ripple from 430 to 450 is required for best operation. So you will need a spectrum analyzer that has a 2db range.471 Alignment PDF (400K file)