Batboard

Hi everyone!

My beloved Motorola R2014D is generating spurious RF signals. Here's an example: With the R2014D turned on and in monitor mode - not generate - a nearby receiver (2-3 feet away) which is tuned to most any frequency from 500kc to about 20mhz will pick up spurs from the motorola. It seems to be particularly noticeable in the AM broadcast band.

If I turn off the R2014D, the offending signals disappear too. I've tried changing the image switch setting, no luck.

Is this normal for these comm analyzers? Not good if one needs it to align an HF or BCB receiver.

Thoughts much appreciated.....

- Darrell/KA7BTV

If you put a spectrum analyzer on some of the best service monitors available, you will be surprised at some of the spurious signals that they generate. I had one, which I will not mention the brand, was putting out the correct signal that I had programmed in but it was also putting out two spurs either side of the main carrier that were 10db higher in signal than the center frequency.

My two bits worth:
NO it is NOT supposed to radiate.
Why it is radiating is another matter.
Broken coax shields, loose shields on the RF synthesizer are possibilities.
I have heard of power supplies generating RF, so try switching the reference to EXT (switch on bottom of unit)
If the problem remains the power supply is at fault.
There have been certain electrolytic caps used in these units that do not last very long. They have red epoxy on the terminal end. Usually have a clear shrink wrap.
same as the 5V regulator in the CLB MSF. Replace these if you find them.
Do not disturb anything in the power supply for at least 5 minutes after the AC power is removed.

bernie wrote:My two bits worth:
NO it is NOT supposed to radiate.
Why it is radiating is another matter.
Broken coax shields, loose shields on the RF synthesizer are possibilities.

Not to mention loose hardware (screws) just about anywhere from the motherboard to the top and bottom covers.

Sorry so long to get back to this. Thanks everyone, I haven't looked into this problem yet but if I do find the cause then I'll post it here for future reference for others.....

- Darrell

Most of the major oscillators, as well as the receiver module, is located on the bottom of the machine.
Major modules are cards under the 'hood'.
I just made up a sheet of the boards and module assemblies and taped it to the cover of my 2001D/HS, so I have a handy reference to know which board/modules is located where.

But if there are loose or missing screws, bad board contacts, as well as corroded ground connecctions, you can create your own IMD products and generate spurious emissions from the 'diode effect'. This same problem has been well documented in towers that have been standing for years in often wet weather.

Broken shields on interconnecting cables, especially to and from master oscillators and timebases can cause energy to be radiated out of the cables and front panel controls through inductive coupling.

I despise spurious anything, so I ground-ground-ground everything to a ground bus with solid earth ground.

I have been lucky with having no problems with signal leakage from either analyzer, so I feel lucky.......so far.

Good luck with tracking down your culprit.

Usually, this problem is caused by loose hardware on the Synthesizer (A9) module or the cover screws (top & Bottom). If it IS the covers, be sure to clean out any dust accumulated in the gaskets.