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Re: L604, L612, L904 setpoints

 

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Ok, so¡­¡­turns out, user error. ?I learned a lot and had some realizations while I was typing this email to tell you what my readings were. ?It left out what frequency to set the signal generator to, so I set it to the frequency it populated on the screen, which generated a signal but no audible tone. ?I had to off set it by 15hz like all the other sections instruct to do. ?That made the adjustments reasonable.

Now I was able to successfully get it aligned. ?Much better now. ?I will do final checks tomorrow. ?Only thing left is the SWR-2 section of the alignment, but I need to set up a 100ohm dummy load for that part.

Thank you for your willingness to help! ?And to correct myself from earlier, the Motorola R2600 is able to do just about everything. ?I do like the precision of the CMU200 as an SSG for the transmitter alignments.

I know you shouldn¡¯t have to do alignments on them unless there is a problem, but this radio was originally deemed irreparable and I did extensive work on it. ?So I felt better about it after going through the whole alignment procedure before gifting it back to my dad to ensure it was at its best. ?


On May 1, 2025, at 2:05?PM, Andrew Lenton via groups.io <a@...> wrote:

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What is your fault, what is the rsfio not dooing?

KR

Andrew

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On 1 May 2025, at 12:39, "Craig- KB4RU via " <gmail.com@groups.io target=_blank>[email protected]> wrote:
Thank you so much Andrew for jumping in. My CMU200 can set the output down low enough. ?How do you minimize leakage for the WFM adjustments? ?

I am going to double check with the oscilloscope when I get back to it tomorrow at the end of the feed line to make sure I¡¯m generating the correct level at the radio end. ?

Another question for you is the RX Total Gain,
Says to set 25db of AF level between 500uV and no signal. ?(Or 30db for HF). ?The 500uV signal is consistently at 8.6db and the adjustment only makes changes on the noise floor when the signal is off. ?So I tried adjusting it so the noise level is 25/30db difference but I can¡¯t get it that far apart. ?I max out the setting at the highest gain and I¡¯m still off a little bit. ?So either something isn¡¯t right with the radio, or I¡¯m not understanding the procedure/setting. ?I am assuming I¡¯m looking for 25 db difference on the AC millivoltmeter and not the S meter on the radio, but not getting the changes I was expecting.

Any input on what I am doing wrong or what the problem could be? ?I will verify with the oscilloscope the SSG signals at the end of feed line disconnected per the footnote, but wondering if you could give any additional clarity.

Thanks,
Craig, KB4RU

On May 1, 2025, at 4:09?AM, Andrew Lenton via groups.io <a@...> wrote:

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Hi I have replied a fair few of these radios, all with 100% success.

With regards alignment I have never had to pefrom this on received. I have set up the bias on PA transistors after replacement, which is also rare.

Unless you have a professional RF signal generator it is hard to aligned the RX, one reason is when you set levels down at -120dBm you get leakage unless the the signal generator is professional. ?10,000 plus!

The new siglent RF signal generators only go down to -105 dBm fir this reason of leakage.

You also need a decent audio signal generator never use a PC or laptop.

99% of the time, if you need to realign it is because some has twiddled it.

KR

Andrew

Get
On 1 May 2025, at 03:21, "Craig- KB4RU via " <gmail.com@groups.io target=_blank>ki4coa=@groups.io> wrote:
I was planning on making a video of the process once I get the kinks worked out. ?I am learning and this is not an easy radio to work on, and I¡¯m suspecting the service manual has some typos, or I am not understanding something correct. ?

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