LO off QRG


Lucijan
 

Hello !

I am new hire so warm hello for all IC7000 owners.
My rig serve me perfect for 6 years in many UHF SHF test and I am still fascinated with it.
To be quick: my LO is off. On 2m 1,2 kHz and on 70 cm 4 kHz. I am low with LO so I can not reach exact LO of 124.032 . In DDS calibrating routine I tried from OOh to FFh but nothing happens after returning to main menu as additional problem. Of course I press SET button ; )
When I adjusting DDS LO i can see change. This change is not sufficient to be exactly on 124.032. I am always off and little bit down.I can change cca 100 Hz from 00 to FF. When I step out from service routine no change is noticeable on real QRG like DDS service routine doesn't catch. Do I make something wrong?. I tried to find answer from previous messages but I am not sure I get right one. I have USA version of radio and frequency counter. In normal OTH REF Adjustment I can change almost 7kHZ range but always down of proper frequency. Could some other setups interfere? Could I improve situation with master reset?

If someone went true this issue on his radio please advice!
Thanks in advance.
Best regards, Luci , 9A1Z


igor-m <mikki@...>
 

Hi, the same issue here. EU version, 13y old 7k.
With the OTH menu #51 I get about 4.5kHz diff from 0-100%.
"Luckily" at the 100% setting it is only 5Hz low (at around 20MHz).
While messing with the REF OSC adjust menu (stock hex 9B here) I see none influence on the TX frequency (and yes, I press SET).
I've been measuring the frequency at a dummy load while TXing in AM or RTTY mode.
I would be happy to know for what is the "hex adjust" menu actually good for.
My current understanding is that while changing the hex value I must see a change in the TX frequency..
Any hint plz?


igor-m <mikki@...>
 

Corrected: "With the OTH menu #51 I get about 150Hz diff from 0-100% (at 20MHz).


Steve W3AHL
 

Using my calibrated Agilent 8924C analyzer I see OTH #51 vary by 1330 Hz from 0-100% when measuring the 124.032 MHz 2LO signal at P4.  When transmitting on CW or AM at 20 MHz it varies 215 HZ from 0-100%.

In Maintenance mode, adjusting the REF setting from 0-FF changes the 124.032 MHz 2LO by 1300 Hz, but does not affect the TX frequency when returned to normal mode -- just as you saw.

I don't have an explanation for why it behaves that way.  But if you have accurate frequency measurement equipment and follow the adjustment procedures, you should have adequate adjustment range in menu #51 to calibrate your TX/RX signal at UHF and below.  You should verify that your DDS REF 2LO is at exactly 124.032 MHz.  Then perhaps verify your RX frequency in normal mode by zero beating to a commercial transmitter at the highest frequency possible.

It is possible for the X1 VCTCXO reference oscillator to drift with age, but that would only be suspect if can't adjust the 2LO REF signal to 124.032 MHz in Maintenance mode.  

Steve, W3AHL


Helmut Wabnig
 

On Sat, 09 Jan 2021 12:52:18 -0800, you wrote:

Using my calibrated Agilent 8924C analyzer I see OTH #51 vary by 1330 Hz from 0-100% when measuring the 124.032 MHz 2LO signal at P4.  When transmitting on CW or AM at 20 MHz it varies 215 HZ from 0-100%.

In Maintenance mode, adjusting the REF setting from 0-FF changes the 124.032 MHz 2LO by 1300 Hz, but does not affect the TX frequency when returned to normal mode -- just as you saw.

I don't have an explanation for why it behaves that way.  But if you have accurate frequency measurement equipment and follow the adjustment procedures, you should have adequate adjustment range in menu #51 to calibrate your TX/RX signal at UHF and below.  You should verify that your DDS REF 2LO is at exactly 124.032 MHz.  Then perhaps verify your RX frequency in normal mode by zero beating to a commercial transmitter at the highest frequency possible.

It is possible for the X1 VCTCXO reference oscillator to drift with age, but that would only be suspect if can't adjust the 2LO REF signal to 124.032 MHz in Maintenance mode.

Steve, W3AHL
I once had a 700 with exactly this problem.
Cannot calibrate down, reaches 100 % in menu 51.

What I found is the analog control voltage to the oscillator chip VFO
was off and not in spec. Voltage coming from the CPU box.
The oscillator is at the lower side of the pcb, which made me angry.
:-)
Sold the radio as "defect".

If you have a chance to borrow another 7000,
swap the CPU box to find out what happens.

OE8UWW


igor-m <mikki@...>
 

@Steve and Helmut: thanks for the hints.
I started to doubt that I can see a change of the TX freq (while changing the hidden adjust hex value) after I had a look in the service manual - the "frequency scheme" picture there.
It could be the changing of the voltage (while changing the maintenance REF OSC hex value) changes the oscillator's frequency actually, but the TX frequency stays unaffected because the change "somehow cancels out" within the frequency scheme. It is not easy to formalize the change from that picture, though.
Hopefully, the setting the master frequency as described in the service manual will help with the aged crystal..
Igor


igor-m <mikki@...>
 

On Sat, Jan 9, 2021 at 09:52 PM, Steve W3AHL wrote:

..
In Maintenance mode, adjusting the REF setting from 0-FF changes the 124.032 MHz 2LO by 1300 Hz, but does not affect the TX frequency when returned to normal mode -- just as you saw.
I don't have an explanation for why it behaves that way.  ..

I've asked Icom Europe on this (a week back), none answer yet.
My gut feeling tells me the change of the maintenance mode REF setting from 0-FF must change the TX frequency in AM CW RTTY modes, provided you do not touch the OTH #51.
If the the maintenance mode REF setting from 0-FF "really changes the control voltage of the VCTCXO" then your TX frequency must change accordingly.
No way it stays the same after the return to the normal mode..
Igor


Steve W3AHL
 

Igor,

There is much that goes on in the firmware that makes it hard to predict how the hardware will work.  But the behavior you see is normal.  Setting the REF frequency accurately will either solve your problem or tell you there is a problem with the oscillator or the control voltage from the CPU.

Your unit's hex value for REF of 9B is higher than typical in the four radios I have recorded the values for ((typically 55-76), but accurate measurement is the only way to set the frequency so that the IF stages work corrrectly.

Steve, W3AHL


igor-m <mikki@...>
 

Steve, when you change the tuning voltage wired to the VCTCXO the TX frequency (measured with a counter at the dummy load) has to change too, imho. The 7000's firmware or hardware has not got any internal means how to determine "how much the frequency of the xtal has changed by applying certain voltage difference". There is none internal reference except the master VCTCXO oscillator.
Thus, when your external counter show 21.000.000 at the TX dummy load with "5F" hex, and you change it to "2C" you must see a change of the TX frequency after returning from the manufacturing menu. The important assumption is there is the "VC" TXCO module soldered on the board, the DAC works and the firmware has not got a bug as well.
Would be great if we will come to an understanding "how the stuff works", as this is a topic people here discussing for a decade already :)