I have Micom-XF and the scanning is not very useful. When scanning is moves from channel to channel with out regard to the squelch opening, the operator has to "get to the radio" to make it stop scanning by pressing the scan key (or the PTT sw)?
Has anyone used a Micom-2? Are the scanning options improved? Programable delay Etc?
Pete
Micom-2 Scanning?
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richyradio
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This is a complicated issue.
HF radios use, for voice, single side band modulation. This is a form of AM, except that there is no carrier wave that can be used to generate a conventional squelch signal, i.e., one that detects the presence of a valid carrier on freq, regardless of voice.
For that reason, monitoring HF channels (such as is done by the USCG and is required of ships at sea) is arduous duty; you have to sit for extended periods listening to "no signal" noise.
About 1980 or so, a number of folks (ICOM being the first, if I'm not mistaken) adapted VOX-type technology to this problem. Squelch is an on-off switch, not a pot. When engaged, it ungates audio to the speaker, and the output of the audio detector is processed by a circuit that samples a narrow slice of the AF spectrum thought to be dominated by human voice; the result of that filtering is put through an overdriven AF amplifier, and the output of that is used to gate audio (except that a high value is considered valid, rather than a low value of a non-voice slice, as is done for FM squelch control).
The ICOM system was first employed in the original IC-M700, a big box HF set that was nominally intended for maritime use but in fact has seen widespread service for military, paramilitary and commercial purposes. (Note: this is not the same as the M-700 currently sold by ICOM; for some reason, they re-used the model designation.) Properly adjusted, the ICOM M-700 squelch system works pretty well: minimal first syllable clipping and reasonably quick end-of-speech closing. However, it is subject to some falsing by white noise or data.
For those of us sometimes obliged to maintain an extended watch on an SSB channel, the M700 with this feature is a real blessing. And this is why original M700s are in great demand, even though they went out of production about 10 years ago.
ICOM did not, to my knowledge, ever try to mate this system to a scan function.
Every other HF radio that I'm aware of uses a "squelch" function that is actually tied to the Signal Strength meter, which in an SSB radio is really an indication of modulation amplitude, not on-freq signal strength, and has two vices: (a) to be useful, the setting must be quite high (well above the sensitivity of the receiver with legitimate incoming voice signals -- i.e., you're going to miss valid traffic) and (b) it will be tripped by any noise, not just voice on valid freq. For that reason, scanning radios (such as the WJ or the ICOM R-71 series), use a timer to end the scan pause. If they did otherwise, the radio would continuously hang up on non-valid signals.
Its all in the nature of the SSB emission.
HF radios use, for voice, single side band modulation. This is a form of AM, except that there is no carrier wave that can be used to generate a conventional squelch signal, i.e., one that detects the presence of a valid carrier on freq, regardless of voice.
For that reason, monitoring HF channels (such as is done by the USCG and is required of ships at sea) is arduous duty; you have to sit for extended periods listening to "no signal" noise.
About 1980 or so, a number of folks (ICOM being the first, if I'm not mistaken) adapted VOX-type technology to this problem. Squelch is an on-off switch, not a pot. When engaged, it ungates audio to the speaker, and the output of the audio detector is processed by a circuit that samples a narrow slice of the AF spectrum thought to be dominated by human voice; the result of that filtering is put through an overdriven AF amplifier, and the output of that is used to gate audio (except that a high value is considered valid, rather than a low value of a non-voice slice, as is done for FM squelch control).
The ICOM system was first employed in the original IC-M700, a big box HF set that was nominally intended for maritime use but in fact has seen widespread service for military, paramilitary and commercial purposes. (Note: this is not the same as the M-700 currently sold by ICOM; for some reason, they re-used the model designation.) Properly adjusted, the ICOM M-700 squelch system works pretty well: minimal first syllable clipping and reasonably quick end-of-speech closing. However, it is subject to some falsing by white noise or data.
For those of us sometimes obliged to maintain an extended watch on an SSB channel, the M700 with this feature is a real blessing. And this is why original M700s are in great demand, even though they went out of production about 10 years ago.
ICOM did not, to my knowledge, ever try to mate this system to a scan function.
Every other HF radio that I'm aware of uses a "squelch" function that is actually tied to the Signal Strength meter, which in an SSB radio is really an indication of modulation amplitude, not on-freq signal strength, and has two vices: (a) to be useful, the setting must be quite high (well above the sensitivity of the receiver with legitimate incoming voice signals -- i.e., you're going to miss valid traffic) and (b) it will be tripped by any noise, not just voice on valid freq. For that reason, scanning radios (such as the WJ or the ICOM R-71 series), use a timer to end the scan pause. If they did otherwise, the radio would continuously hang up on non-valid signals.
Its all in the nature of the SSB emission.
Thanks,
The voice squelch works well on the Micom-X when scanning, that is to say that the squelch only opens when voice traffic is heard. The radio scans slowly and would work great if the radio would just stop scanning if the squelch opened. The changing of channels does not seem false the detector.
I have programmed all of the USCG and National Guard SAR frequencies and it's very annoying when it "jumps past".
The Motbat tech said their (-2 or -3) radio will stop when the voice sq opens. I am assuming that the Micom-2 voice detector works at least as well as the 1989 Micom-Xn.
Pete
Any comments on the ICOM-m802
The voice squelch works well on the Micom-X when scanning, that is to say that the squelch only opens when voice traffic is heard. The radio scans slowly and would work great if the radio would just stop scanning if the squelch opened. The changing of channels does not seem false the detector.
I have programmed all of the USCG and National Guard SAR frequencies and it's very annoying when it "jumps past".
The Motbat tech said their (-2 or -3) radio will stop when the voice sq opens. I am assuming that the Micom-2 voice detector works at least as well as the 1989 Micom-Xn.
Pete
Any comments on the ICOM-m802
You only need to program 4 USCG freqs: 2182 (the HF equivalent of 16FM), 2670 (the HF equivalent of 22FM), 4125 (simplex channel sometimes used in lieu of 2182 for greater range, and monitored by most USCG HF capable stations (of which there are only a few)), and 6501 (the shore side of ITU CH. 601 (6200 for ship); this is the primary SCN for vessels in distress and is monitored by all USCG HF capable stations). Any other channel would be by designation on one of the above.
My experience with the later model ICOM HF sets is limited. Frankly I found them not very user friendly and of poor sensitivity, but the latter may well have been due to the installation, which I wasn't on board long enough to assess.
6215 simplex is informally used as a calling channel amongst cruising yachts, with switching to a traffic channel usually on 6 or 8 megs simplex.
My experience with the later model ICOM HF sets is limited. Frankly I found them not very user friendly and of poor sensitivity, but the latter may well have been due to the installation, which I wasn't on board long enough to assess.
6215 simplex is informally used as a calling channel amongst cruising yachts, with switching to a traffic channel usually on 6 or 8 megs simplex.
Micom-2 Squelch
Hello,
The MICOM-2's squelch is DSP-based, and works VERY well - but it isn't adjustable. It seems to distinguish things like RTTY and carriers and ignores them, but variable noises will open it - and you can't tighten the threshold to get rid of weak interference (which might not be too bad, 'cuz I've seen folks keep tightening the other kind until they might as well turn it off!)
73 DE Hartley
The MICOM-2's squelch is DSP-based, and works VERY well - but it isn't adjustable. It seems to distinguish things like RTTY and carriers and ignores them, but variable noises will open it - and you can't tighten the threshold to get rid of weak interference (which might not be too bad, 'cuz I've seen folks keep tightening the other kind until they might as well turn it off!)
73 DE Hartley
Hartley,
Thanks for the Micom-2 info, it good to hear from someone who has used one!
As for the frequencies, we normally monitor the USCG air frequencies 5696, 8983 and the air national guard 5711, 6712, 6713.5 7813 11440.
The ICOM M802 manual reads very much like the Micom's it would be nice if a can find an owner. The ICOM radio is a lot less expensive.
Pete
Thanks for the Micom-2 info, it good to hear from someone who has used one!
As for the frequencies, we normally monitor the USCG air frequencies 5696, 8983 and the air national guard 5711, 6712, 6713.5 7813 11440.
The ICOM M802 manual reads very much like the Micom's it would be nice if a can find an owner. The ICOM radio is a lot less expensive.
Pete