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Author Topic: IC-730  (Read 4868 times)
KD8TFG
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Posts: 76




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« on: April 04, 2013, 06:27:08 PM »

I just recently purchased an Icom IC-730 online, that was listed as being fully functional upon getting the radio the only thing that I can find wrong is the output on ssb is no more than 15w into a dummy load, while out put on the radio in AM mode is around 45w into a dummy load. Receive appears to be functioning as it should.

I am looking for any input to figure out the low out put on ssb

Thanks
Gary
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AC2EU
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« Reply #1 on: April 04, 2013, 08:03:04 PM »

Are you using a tone or voice to test the ssb?
Voice transmission spikes are too fast to be tracked by a mechanical meter in SSB mode.
Chances are that there is no problem unless the mike gain is too low or it's not the original mike.
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WB2EOD
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Posts: 219




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« Reply #2 on: April 04, 2013, 10:42:54 PM »

It is not unusual in SSB for a meter to indicate only a fraction of the power you expect. 
The meter may not be able to respond to the voice peaks. 
Based on your observation of the AM power output, I think it is fair to say the rig is OK.
Measure the output in a straight carrier mode (CW FSK FM).
This should result in a reading in line with specs. 

Hope this helps
73
WB2EOD
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KD8TFG
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Posts: 76




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« Reply #3 on: April 05, 2013, 02:12:10 PM »

Thanks for the help, the thing that baffles me the most total current draw on ssb is only 3 amps on full out put and 16 amps on a dead carrier.
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WB2WIK
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« Reply #4 on: April 05, 2013, 03:45:03 PM »

Thanks for the help, the thing that baffles me the most total current draw on ssb is only 3 amps on full out put and 16 amps on a dead carrier.

What happens to the current if you whistle into the microphone and hold the whistle for a few seconds?

Regular "speech" on SSB, without heavy processing, normally indicates very low "everything" on meters, even when PEP is actually okay.
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KD8TFG
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« Reply #5 on: April 05, 2013, 05:33:24 PM »

It will peak at 4.5 amps max
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AC2EU
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« Reply #6 on: April 05, 2013, 08:19:07 PM »

It will peak at 4.5 amps max

Again, the meters are too slow!
If you have a peak capture feature on an Digital ammeter, that will show the spikes.
As you see, there is a world of difference between a dead carrier and wide spectrum SSB spikes.
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N3DT
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« Reply #7 on: April 06, 2013, 06:07:23 AM »

I would say he needs a peak reading meter.  Or test it in CW or FM if it goes there. If it's good there, it's probably good.
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K5RT
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« Reply #8 on: April 06, 2013, 09:09:51 AM »

What microphone are you using? Try another mic. Preferably one that is known to work with an ICOM.
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KD8TFG
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« Reply #9 on: April 06, 2013, 10:59:15 AM »

It is the stock ic-730 mic.  In trying different bands ie. 15m the current draw on usb is around 13 amps vs 4.5 amps on 10m usb
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K5RT
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« Reply #10 on: April 06, 2013, 06:18:43 PM »

We're starting to collect some good info. Do you have a dummy load? We need to understand if you have an antenna problem (high SWR), or a radio problem, and if its a radio problem, is it limited to 10 meters?
Have you tested on LSB?

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KE9PP
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Posts: 11




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« Reply #11 on: April 10, 2013, 09:01:49 AM »

If the problem is confined to 10 Meters there is the possibility that some CB'er with a "golden screwdriver" has been inside trying to get the rig on 11 Meters (I hope not).
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K1CJS
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« Reply #12 on: April 10, 2013, 11:03:53 AM »

Just a thought to throw into the discussion--there are also golden screwdriver bearers that aren't or were never CBers.  I know an extra licensee who never picked up a CB whose 'golden screwdriver' is so shiny from use that absolutely NOBODY that knows him lets him get anywhere near their rigs unless they're right there with him!
« Last Edit: April 10, 2013, 11:06:32 AM by K1CJS » Logged
K1FPV
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Posts: 33




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« Reply #13 on: April 16, 2013, 04:51:04 PM »

I have an old IC-740, a close brother of the IC-730. I had a similar problem with it. It turned out that caps in the mic amplifier circuit being so old, opened up. I found the problem while whistling into the mic and looking at both sides of the audio coupling caps to see attenuation using my oscilloscope.

I'm assuming, you never tried to modulate the radio on AM? You just had 40 watts of carrier which is about right for that radio.

Bill/K1FPV
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KD8TFG
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Posts: 76




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« Reply #14 on: May 20, 2013, 06:13:46 PM »

The problem turned out to be the person I bought the radio off included the wrong microphone with it. I just picked a SM-5 microphone and am getting full out put on all bands
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