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Author Topic: Help with Icom IC-7800 Off frequnecy  (Read 2195 times)
W4AJF
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Posts: 263




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« on: February 28, 2013, 03:41:50 PM »

Hi all, I just bought a used IC-7800 (2004 build) and find it's off frequency by like 20-30hz. Yes, I have re booted, CPU reset, RIT etc is not on, I used the built in reference adjustment system the radio has (turn Calibrator marker on and use the REF ADJUST) but it makes no difference.

Any help GREATLY appreciated if you are familiar with the IC-7800 and this issue.

Thanks,

Adam Farber W4AJF
Woodland Hills, CA
adamf@eeco.com
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W2AEW
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« Reply #1 on: February 28, 2013, 04:02:58 PM »

I'm not specifically familiar with your rig, but it sounds like the internal calibrator is off a little.  Do you find the error is greater as you go to higher bands? If so, your reference oscillator may be off (if the rig uses one like this).  You can check, and maybe even adjust it to typically less than 1Hz accuracy by zero-beating against WWV as described here:
http://www.qsl.net/w2aew/adjustrig.htm
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W4AJF
Member

Posts: 263




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« Reply #2 on: February 28, 2013, 04:08:48 PM »

Hi, thanks for the reponse, it's about the same across the bands, but I don't think you understand, as mentioned the reference adjustment does nothing, you can NOT zero beat because the adjustment does not vary the frequency- THAT is the problem.

Anyone out there familiar with the IC-7800 and can offer any help?

Thanks,

Adam farber W4AJF
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N4RSS
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Posts: 263




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« Reply #3 on: February 28, 2013, 07:24:22 PM »

If you haven't already I suggest you join the IC-7800 group on Yahoo
http://groups.yahoo.com/group/ic7800/?yguid=342641336

and pose your question there
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W4AJF
Member

Posts: 263




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« Reply #4 on: February 28, 2013, 07:29:43 PM »

Good idea, shall do, thanks, Adam W4AJF
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W4AJF
Member

Posts: 263




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« Reply #5 on: February 28, 2013, 09:18:42 PM »

Whoops, I meant to say the radio is off by 200-300hz, any one have any suggestions that is familiar with the IC-7800?

Thanks,

Adam Farber
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TANAKASAN
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Posts: 933




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« Reply #6 on: March 01, 2013, 01:38:26 AM »

I wonder why everyone is having calibration issues this week?

This one is way too complicated to describe in a single Elmers post so you're going to have to download some stuff.

1) Make 100% certain that your 10.0000000 MHz oscillator is working properly and that it's set accurately. The oven in these devices has been known to fail.

2) If you don't have the manual then download a copy from http://www.icom-france.com/files/not-IC-7800-v2-angl.pdf and go to page 13-5 where you will find instructions for internal calibration. It's page 176 on my PDF viewer.

It's possible that the internal calibration in your rig has been wiped and maybe the CMOS battery needs replacement given that the rig is nine years old. This would explain why resetting the CPU does not cure the problem. Does it retain the correct time setting when unplugged from the mains?

Tanakasan
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W4AJF
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Posts: 263




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« Reply #7 on: March 01, 2013, 01:54:57 AM »

Hi Tanakasan, thanks for the post. If you read my Original post it says that I have already  tried the calibration and it did nothing.  The radio retains the correct time and settings when unplugged.

Anyone out there know what to try or possibly know someone who makes an external TCXO unit for this radio that plugs in to the BNC jack on the back, I have seen homemade ones before. If anyone can help or has the skill to make one at a decent price I would appreciate any info.

Thanks,

Adam Farber W4AJF
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M6GOM
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Posts: 993




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« Reply #8 on: March 01, 2013, 08:18:05 AM »

Personally on HF I don't think I'd bother too much unless doing a mode such as JT65 which is super critical. If it is 20-30Hz out then that is only 1ppm on 28MHz and only twice what it'd be out with a TXCO.

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W4AJF
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Posts: 263




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« Reply #9 on: March 01, 2013, 08:23:17 AM »

Hi, it's 200-300hz off.  Adam W4AJF
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K6AER
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Posts: 3530




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« Reply #10 on: March 01, 2013, 01:14:43 PM »

Just a cpouple of things to know. How did you determine the radio is off 200-300 hz?

Is the RIT set to Zero?

Is the offest on the first receiver or the second receiver?

Is the transmitter frequency also off?
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W4AJF
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Posts: 263




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« Reply #11 on: March 01, 2013, 01:32:25 PM »

Hi, thanks for the post. RIT is off (mentioned that in first post), RX and TX are off by that, when someone is on 28.400.00 I have to be on like 28.400.25 to be on frequency. It's on both receivers, for sure it is off frequency and displays symptoms of a bad TCXO.

Thanks,

Adam Farber W4AJF
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K6AER
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Posts: 3530




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« Reply #12 on: March 01, 2013, 04:09:06 PM »

250 Hz is a long way fo the TCXO to be off. What did ICOM service recommend you do.
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W4AJF
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Posts: 263




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« Reply #13 on: March 01, 2013, 04:19:25 PM »

Hi, what else- SEND IT IN...Adam W4AJF
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NR4C
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Posts: 310




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« Reply #14 on: March 05, 2013, 10:07:32 AM »

"Send it in!"

...bc  nr4c
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