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My Icom IC-706mkIIg transceiver has two output ports:

  • one for its VHF/UHF bands (i.e. 2m/70cm)
  • one for the HF bands, and also 6m!

I have a couple of broadband VHF/UHF antennas whose transmit specs include the 6m (50MHz) band, so I'd rather have the 6m band output on the VHF/UHF port. I understand for example that the Yaesu FT-817ND allows some configuration of which bands use which of its two ports, but do not see anything similar in my Icom's menu settings.

Is there any modification available to move 6m handling to the IC-706mk2g's VHF port, whether a setting I've missed, a jumper inside, or even some minor circuitry rework?

Otherwise could I accomplish this without undue loss — or expense! — via some combination of diplexers and/or other filters?

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If you don't find a solution based on modifying the radio, this is a reasonable use for two diplexers. You can, in principle, hook them up two different ways:

schematic

simulate this circuit – Schematic created using CircuitLab

These two configurations have in theory the same requirements for the two diplexers — one which separates 30− and 50+ MHz and one which separates 54− and 144+ MHz. However, the second configuration has two advantages:

  • It should have less insertion loss at other than 50 MHz, since the other bands pass through only one diplexer and not two.
  • The bottom left diplexer deals only with frequencies 54 MHz and below, — it does not need to have good performance at UHF.

A brief search (I didn't check all the specifications in detail) shows that suitable duplexers are available from several brands (Comet, Diamond and MFJ) for prices around US $60-80 each.

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  • $\begingroup$ Thanks! Your first example is embarrassingly obvious now that I've seen it, and the second is a nice optimization. I'll have to take a look at which duplexers are more commonly available, although my initial research is turning up commercial duplexers up in the same price range as a second discone! $\endgroup$ – natevw - AF7TB Feb 21 '17 at 22:51
  • $\begingroup$ @natevw-AF7TB Not sure what you mean by "more commonly available" — both solutions require the same two diplexers. I'm seeing prices around US \$70 each, so \$140 for the pair. The lowest cost solution might be to use just one HF/6 duplexer and put up a separate, simple 6 meter antenna, certainly. (Don't forget to count the price of the feed line…) $\endgroup$ – Kevin Reid AG6YO Feb 21 '17 at 23:01

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