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440 Band Off Frequency

Kenneth W. Campbell <n6pcd@...>
 

Hi all,

I've a interesting problem with my 7000: Seems that the 440 MHz band, FM mode, has gone off frequency 5 kc low. In order for, say, 446.300 to have clear audio, the VFO needs to be at 446.305.  The problem is consistent on the 440 band.

This is not a problem on the 144 MHz band.

I've already performed the master reset procedure.

Any ideas?

All the best,
Ken N6PCD

Dennis Klipa
 

Ken,

I had this problem on one of my IC7000. We noticed that it was ever so slightly off frequency on HF.  It was usable on VHF but not UHF, but I didn't use it there.  Turns out the primary oscillator (not the right name but I can't think of it right now) was off frequency.  The amount it was off on HF and even VHF was small.  However, to get to 440, the main frequency gets multiplied several times and so does the error and my radio was way off on 440 just like yours.

I sent it in to Icom repair in Michigan.  Matt repaired it.  If it is off a little, it can be adjusted.  In my case he needed to replace something that wasn't cheap.  So if you don't use it on 440 you might not want to bother. I suggest you talk to Matt at SAR Technical Services,  269-429-2334.

Best Regards,
Dennis, N8ERF


On Sun, Mar 18, 2018, 1:14 AM Kenneth W. Campbell <n6pcd@...> wrote:
Hi all,

I've a interesting problem with my 7000: Seems that the 440 MHz band, FM mode, has gone off frequency 5 kc low. In order for, say, 446.300 to have clear audio, the VFO needs to be at 446.305.  The problem is consistent on the 440 band.

This is not a problem on the 144 MHz band.

I've already performed the master reset procedure.

Any ideas?

All the best,
Ken N6PCD

Helmut Wabnig <hwabnig@...>
 

On Sat, 17 Mar 2018 22:00:09 -0700, you wrote:

Hi all,

I've a interesting problem with my 7000: Seems that the 440 MHz band, FM mode, has gone off frequency 5 kc low. In order for, say, 446.300 to have clear audio, the VFO needs to be at 446.305.  The problem is consistent on the 440 band.

This is not a problem on the 144 MHz band.

I've already performed the master reset procedure.

Any ideas?

All the best,
Ken N6PCD
The IC-7000 oscillator is very temperature dependent.
You have to re-adjust the reference frequency in the OTHER menu
when temperature changes a lot and causes frequency drift
in the higher frequency ranges, especially VHF and UHF.
Find a commercial station in the VHF or UHF,
tune in SSB with an offset of 500 Hz and adjust
the difference tone to 500 Hz using a smartphone app.
Im am using the app "Spectroid", but there are many others.
Alternatively you could use a guitar tuner at 440 Hz.
If the frequency iy stored in memory, the whole procedure
takes less than a minute.

OE8UWW.

Kenneth W. Campbell <n6pcd@...>
 

Hi Dennis,

Thanks for taking the time to reply, I really appreciate it! I've been exchanging emails with Scott Malcolm of MTS Technical Services about the problem. He fixed a 718 for me last year with excellent results.

The part in question is the TCXO. Scott says it's rare that they cause a problem but he's seen it before. Says if performing the master reset procedure doesn't clear the problem, that part is about the only thing that would cause the error. The higher the tuned frequency, the greater the error.

As I traded a 706 MKII-G straight across for the 7000, it's worth having the repair done!

All said the best,
Ken N6PCD

Kenneth W. Campbell <n6pcd@...>
 

Hello Helmut,

Thanks for the reply! I'll take a look at that.

All the best,
Ken N6PCD 

Steve W3AHL
 

The Reference Oscillator is subject to frequency drift due to several causes, which result in the need to recalibrate it using the OTHER menu #51 adjustment.  I would try that before sending it in for repair.  While the oscillator is specified to have +/- 0.5 ppm frequency stability, that is only the short term stability with reference to gradual termperature change.  The long term aging is specified at +/- 1 ppm/year.  The oscillator frequency is voltage controlled via a D/A converter on the CPU, which its datasheet does not fully specify long term drift characteristics but probably exceeds 1 ppm.  I have seen units needing adjustment that be in the range of about 2 KHz shift on 440 MHz, but seemed to remain within spec afterwards.

I tend to recalibrate my 7K's Ref Osc about once a year.  Allow the unit to warm up with power on in the typical ambient operating environment for at least 30 minutes.  Then zero beat to the highest WWV frequency you can receive or calibrate as others mentioned to another reference signal (but not in FM mode, since the frequency accuracy will not be adequate for other modes).   Recheck the calibration occasionally to verify it is reasonably accurate still.  If not, there may be a problem with X1 on the DDS board or some other part.  I've never personnally known any of the loca hams to have to repair a 7K due to frequency drift that couldn't be adjusted with the menu 51 calibration (there's a reason it's there!), but VCO's can certainly fail, as can the DDS IC's and their controlling register chips.

Steve, W3AHL

Kenneth W. Campbell <n6pcd@...>
 

Hi Steve,

Thanks for a the reply, I'm finding this group to be a treasure trove of great information! I'll give the procedure you outlined here a try and report back to the group my results.

73/DX de Ken N6PCD