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Author Topic: IC-706mkiig strong birdies  (Read 406 times)
VE3IVM
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Posts: 54




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« on: March 09, 2003, 02:48:14 AM »

I noticed very strong stable carrier around 469 KHz, 742 KHz and 1485 KHz (seems to be a harmonic of the second one) with antenna disconnected, "RF/SQL" control fully engaged. Attenuator changes nothing, so the signal is leaking internally. Also rotating "Shift" control changes these signals' tone, which is not the case with from the air signals.

I am wondering if anybody has this problem . If you have a 706mkiig, could you disconnect the antenna and run a quick test for me?

Thanks
Ivan
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G4REK
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Posts: 79




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« Reply #1 on: March 12, 2003, 06:51:04 AM »

  I have a 706 but it dosent exhibited this problem when connected to a ordinary p.s.u BUT when used on the switched mode supply there are many birdies present especially on 7 megs. could this be your problem??

                  Jim g4rek..........  
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VE3IVM
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Posts: 54




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« Reply #2 on: March 12, 2003, 01:01:40 PM »

Thanks for your help, Jim.

No, this is not a power supply issue- the problem is still there either at home or mobile (the radio gets power from car's battery, engine is running or not does not make any difference). In fact it does not bother me because ham bands are OK, but I just feel it is not supposed to be there and potentially may lead to distortion or reception of mirror signals.

It looks like a leak from the PLL unit somewhere between 1st and 2nd IF. Will also try to hook up a scope to find out where it comes from.

If nothing helps, I will try to reset the CPU, just need to back up programmed frequencies and labels first.


Ivan

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N8FVJ
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Posts: 692




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« Reply #3 on: March 19, 2003, 09:02:19 PM »

Actually the IC-706 series is full of birdies everywhere. They are also emitting from the radio to the point of interferring with others radios in a ham shack. I consider it a poor design from Icom. I simply sold my radio a few weeks after purchasing it. Too bad the FT-100D had a few issues maring its reliability as the receiver, noise blanker & DSP is superior to the the '706' series radios. More reference to this Icom issue is in the eHam 'Reviews' section.
For the record, I own an excellent IC-746PRO that does not have this problem.
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VE3IVM
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Posts: 54




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« Reply #4 on: March 22, 2003, 02:21:55 AM »

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VE3IVM
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Posts: 54




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« Reply #5 on: March 22, 2003, 02:25:19 AM »

Ops, previous posting did not come through. Let me try again:

********
OK, I feel much better Wink after reading a review here:

http://www.qsl.net/kk5dr/706G.htm

At least it indicates nothing is wrong with my unit.. Smiley .Long list of birdies found by the author matches mine by 80%.

If you want to check yours, no need to go through 88(!) birdies listed in the review. Just listen around 30,60,69 and 150MHZ in SSB or CW mode. And buy a pack of earplugs before running this test...

Ivan
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VE3IVM
Member

Posts: 54




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« Reply #6 on: March 27, 2003, 10:18:04 PM »

After spending a day with a scope I can tell VFO wave shape is bad and when it enters 1st mixer it is modulated by digital noise. Multiple internal signal leaks seem to appear mostly because of unfortunate PCB layout, component placement, and lack of shielding.
There is also serious cooling problem with 5V voltage regulator. All together contributes to the Subject of this discussion.

I'll probably post my findings in a separate thread  soon.

Ivan.
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