| Author |
Message |
    
Crappie
New member
Username: Crappie
Post Number: 8
Registered: 12-2001
| | Posted on Friday, June 03, 2005 - 12:39 pm: | 
|
vco frequency changes from receive to xmit.
mfgr deleted vr-21 which should have avoided this. can an adjustment for vco xmit freq only be accomplished on the s-9 radio? |
Tech808
Moderator
Username: Tech808
Post Number: 5956
Registered: 8-2002
| | Posted on Friday, June 03, 2005 - 6:23 pm: |
|
Crappie,
Sorry, I cannot help you on this one as I have not worked on any of the S-9 Radios.
Sam sent me an S-9 to do the Review and after the Review on the S-9 Radio I returned it to Magnum International.
Try Calling Sam Lewis (Owner of RF Limited / Magnum International) at: 1-877-624-6869
I am sure he will be able to answer your question for you.
Lon
Tech808
CEF808
N9OSN |
Bc910
Advanced Member
Username: Bc910
Post Number: 521
Registered: 7-2004
| | Posted on Friday, June 03, 2005 - 9:47 pm: |
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Funny, I have the same problem, but mine is sooooo slight it doesn't seem to effect any thing, SSB or AM. I just aligned it all so that I wouldn't see it on the counter. I know it's still doing it but I also know it doesn't effect any thing and if I can't see it then I don't care any more  You know what they say "out of sight, out of mind"
BC |
Crappie
New member
Username: Crappie
Post Number: 9
Registered: 12-2001
| | Posted on Saturday, June 04, 2005 - 1:07 am: |
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Bc910 In my s-9 it makes 50 hz difference in LSB mode. You can not only see it, you can hear it. So I aligned it to be 25 hz low on xmit and 25 hz hi on receive. With covers back on and the ensuing additional warm-up, the radio drifted 250 hz and the above 50 hz difference in receive and xmit was reduced to 12 hz which is slight as you said. I just hate to use my radio for three hours waiting for it to become what it should be after 20 minutes of use! Thanks very very for your input. |
Bc910
Advanced Member
Username: Bc910
Post Number: 525
Registered: 7-2004
| | Posted on Saturday, June 04, 2005 - 7:51 pm: |
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Isnt there a TX offset vr? I didn't ply with it but I would think that that is what it would do...right?
BC |
Crappie
Junior Member
Username: Crappie
Post Number: 10
Registered: 12-2001
| | Posted on Sunday, June 05, 2005 - 3:19 pm: |
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Bc910 The tx offset vcr was deleted in a redesign of the clarifier. Now we have tr901, th01, and some small components. None of these are variable.
Crappie. |
Bc910
Advanced Member
Username: Bc910
Post Number: 530
Registered: 7-2004
| | Posted on Sunday, June 05, 2005 - 8:43 pm: |
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coulda sworn mine had one, did they re-design the clarifier since the S9 has been produced?
BC |
Crappie
Junior Member
Username: Crappie
Post Number: 11
Registered: 12-2001
| | Posted on Sunday, June 05, 2005 - 9:42 pm: |
|
They must have redesigned it at some point in its development, because the radio and the schematic does not have one. The master board top overlay and the physical pcb in the radio show a location for it marked vr15. the same is true for the associated d38. The Galaxy 99v and 88hl equivalents have it as vr21 (as inferred in my first post above).
Crappie |
Magnetron
New member
Username: Magnetron
Post Number: 1
Registered: 6-2005
| | Posted on Saturday, June 25, 2005 - 8:52 pm: |
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I've seen this type of behavior before. Small changes in the +8 supply voltage will cause frequency shift in the oscillators that rely on a stable supply voltage. Try monitoring the +8 voltage and vco when switching from receive to transmit. What i've done to fix this in some radios, was to replace the 8volt regulator circuit with a 7808 1-amp regulator. The regulator will require a heatsink. This small shift in frequency is generally not noticable in AM or FM but definately noticable in SSB.
Just got my S9 last week and havn't used it on ssb so don't know if I have same problem(which I probably do). hope this helps |
Magnetron
New member
Username: Magnetron
Post Number: 2
Registered: 6-2005
| | Posted on Sunday, June 26, 2005 - 12:38 am: |
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Upon further investigation, there is another issue with how voltage is being fed to the 10.965mhz oscillator used for AM/FM transmit and SSB transmit+receive. When in the AM/FM mode, this oscillator gets voltage for transmit thru diode d94. The S9 schematic I have has many errors. There should also be another diode used to feed power to the oscillator in the SSB mode. The problem is that when in the SSB mode and we switch to transmit, the diode used for AM transmit may cause a shift in the voltage being applied the the oscilator causing a shift in transmit frequency. Basically what happens is that there are 2 sources of voltage to the oscillator and which ever is the highest wins control. I first ran across this problem with an rci2950 years ago. To solve this will require adding 1 or 2 diodes in series with the diode used for AM transmit, thereby allowing the SSB voltage supply to control the oscillator(AM diode d94 assuming the schematic is correct). |
