Saturday 1 September 2012

Will the Icom M700 marine radio TX on all bands

The question comes up from time to time but untill yesterday I had never seen the full answer, in the past we have read that a secret internal switch had to be moved, some said a thin blue wire needed cutting, read on to find out the truth.

This radio has been around a very long time, twenty five years and more I guess? When it came out it was seen as a strong set and easy to program its 48 memories. Icom had also made the set workable on frequencies other than the genuine marine bands, or did they?

I have read and been told that all Icom M700 will tune and transmit on the ham frequencies, I have Just found the at least some of the truth of  this information on the web.

This board that may need attention is underneath the main part of the set, the old but refurbished Philips soldering iron was really handy here.

Right click on the photos for a larger view and clearer picture.

Check near Q3 and to the right of which is a small white unit. to me that looks like it  has had its wire burnt through to restrict the Icom M700 transmitting on all bands.

Not so neat but check that the solder now connects the wires and the circuit works now as it was intended to when it left the factory.

The set now works as it should do, the LSB can be accessed on the mode switch, fully to the left there is a blank space, thats LSB, the next to the right will be USB, both as required on the ham frequencies.


Note, we owe this valuable information to Joachim.

Joachim's Ham-Radio and Radio-Frequency Blog (A Solderful of Secrets) - from Longwave to Microwaves.

Saturday, November 21, 2009 Icom IC-M700D mod .

Despite what is told on the internet, there are version of the Icom IC-M700 which actually block out transmission on frequencies outside the marine bands.

Recently, I obtained one of those, the IC-M700D. This radio has got a "Posthörnchen" on it, meaning that the FTZ (Fernmeldetechnisches Zentralamt) gave its blessings. This however means, the radio does not do what it is not supposed to, i.e. transmit outside the marine bands.

Luckily, there is a service manual for the IC-M700 (no D!) available on the internet.

Browsing through the circuit description reveals that LOGIC CIRCUITS holds on control of the receive and transmit frequencies. The manual further recites that IC1006 outputs signals "mute signals for outside the marine bands to P40 and P41. Ah! In the schematics diagram, P40 and P41 (pins 7 and 8 of IC11006) enable a voltage called "TMU" via transistor Q1003. The schematics diagram further shows a wire bridge W1037 shorting the base of Q1003 to ground. Hmmmmm, with W1037 installed, the transistor is never engaged to release the TMU voltage. Could TMU be an acronym for Transmitter Mute?

Let's have a look

Joachim, many thanks, your blog and information in it has been long searched for by many!


The Web

Saturday, November 21, 2009 Icom IC-M700D mod