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Author Topic: National NC-300 S-Meter at Max in CW Mode  (Read 3635 times)
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W1TTL
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« on: September 29, 2020, 09:25:25 PM »

Hi Everyone,

My S-meter has been working fine in AM mode, however, when in CW mode, it has a maximum deflection.  I followed the instructions to zero the S-meter with R44 and that worked fine.  As soon as I switch the mode to CW, the S-meter pegs to the max, even with the antenna terminal grounded.

Any advice where I should look first?  I am going to star aligning the radio and for some of the steps, it looks like I need to be in CW mode and watching the meter for max deflection.

73,
Tony
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MikeKE0ZUinkcmo
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« Reply #1 on: September 29, 2020, 11:01:09 PM »

In the manual, page 11, para 3-5

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K1JJ
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« Reply #2 on: October 02, 2020, 09:23:58 PM »

Only a cheap pimp would design a receiver with an S-meter circuit that doesn't work on CW....   Grin

T
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Use an "AM Courtesy Filter" to limit transmit audio bandwidth  +-4.5 KHz, +-6.0 KHz or +-8.0 KHz when needed.  Easily done in DSP.

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W1TTL
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« Reply #3 on: October 02, 2020, 10:12:07 PM »

Mike,

Thanks so much!  I was pulling my hair out.  I missed that section in my manual so I appreciate you copy and pasting it.  I would’ve NEVER guessed that you couldn’t measure CW signal strength.  I wonder why National did that in such a top shelf receiver?

73,
Tony W1TTL
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Pete, WA2CWA
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« Reply #4 on: October 03, 2020, 12:15:05 AM »

Mike,

...  I wonder why National did that in such a top shelf receiver?

73,
Tony W1TTL

Probably because it always seemed like the receiver was a "work in process". The number of service bulletins and addenda that they issued, is roughly around 14 or 15 sheets.
Fortunately, many years ago, I acquired the NC-300 factory test and alignment procedure manual that National used on the manufacturing assembly line. This info was only used in the factory. They never issued it to the public.
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Detroit47
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« Reply #5 on: October 05, 2020, 10:21:06 AM »


[/quote]

I acquired the NC-300 factory test and alignment procedure manual that National used on the manufacturing assembly line. This info was only used in the factory. They never issued it to the public.
[/quote]

Can you scan and post this?
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Pete, WA2CWA
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« Reply #6 on: October 05, 2020, 01:57:56 PM »


Quote
I acquired the NC-300 factory test and alignment procedure manual that National used on the manufacturing assembly line. This info was only used in the factory. They never issued it to the public.

Can you scan and post this?

It's been listed on my site, www.manualman.com for the last, at least, 20 years.  Cheesy
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Pete, WA2CWA - "A Cluttered Desk is a Sign of Genius"
W2JBL
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« Reply #7 on: October 24, 2020, 12:07:59 AM »

AGC is disabled in the CW mode, and the S meter goes to the pin. If you want it to work on CW put the mode switch in the SSB position. 
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WBear2GCR
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« Reply #8 on: October 24, 2020, 09:24:16 AM »


Quote
I acquired the NC-300 factory test and alignment procedure manual that National used on the manufacturing assembly line. This info was only used in the factory. They never issued it to the public.

Can you scan and post this?

It's been listed on my site, www.manualman.com for the last, at least, 20 years.  Cheesy

I think he was asking you to share this one with the community...
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Pete, WA2CWA
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« Reply #9 on: October 24, 2020, 01:59:09 PM »


Quote
I acquired the NC-300 factory test and alignment procedure manual that National used on the manufacturing assembly line. This info was only used in the factory. They never issued it to the public.

Can you scan and post this?

It's been listed on my site, www.manualman.com for the last, at least, 20 years.  Cheesy

I think he was asking you to share this one with the community...

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Pete, WA2CWA - "A Cluttered Desk is a Sign of Genius"
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