The AM Forum

One of my favorite transmitters is a CE 100V.  But the darn thing with its big humming transformer and 45 year old, hard as rocks rubber feet uses my desk as a sounding board.  My finiky friends complain about hum which is plain old acoustic noise, transmitter to desk, to microphone. It's driving me crazy too.   Isolating the microphone helped but still it makes a racket. 

So I've been thinking of putting something under the old gray box to isolate it from the desk.  Our audio afficianados use Sorbothane hemispheres to isolate audio components (insert sarcastic comment here).  Maybe these would help.

Do any of you know anything about these?  Is there somewhere to get them for less than $10 each?

Jon

...YOU KNOW THIS ANSWER HAS TO COME FROM A CANUCK....
...SPONGE RUBBER PUCKS ARE THE ANSWER..SAME SIZE AS A REGULAR PUCK,BUT HARD ENOUGH TO HURT,WHEN BLOCKING A SHOT...I GUESS MY AMERICAN FRIENDS WOULD CALL IT A "HOCKEY PUCK",BUT WE KNOW IT AS A "PUCK"..BENDABLE,AND SOFT,THESE BABIES ARE AN EXCELLANT ANSWER..TIM..SK..

This sounds like an excellent idea.  I'm off to the sporting goods store.  It will be interesting to see if I find any in California.

Thanks,

Jon

there are lots of sporting goods stores in Calif......  klc

Hi Jon,

What a blast from the past. I used to be in "that" business. It's been 15 years since I have heard the word SORBOTHANE. Ya, we have the sponge rubber pucks here that would work but you may also try some high density foam, about 2" thick.

Good luck.

Paul
VE7KHz

Spongy foam packing from a computer box might do it. You might find one blowing around the neighborhood on garbage day.
This stuff is the "squeezie" foam used recently in shipping, not the hard cast foam from a few years ago.

I had a CE100V and it didn't hum at all.  Perhaps you need to tighten up the xformer bolts, mounting points, and align the cabinet so it doesn't vibrate.  Something's resonating and/or loose or it wouldn't transfer the vibration to the cabinet enough for it to be heard in a microphone.

73 John

I used a stack of work area static pads that fit under my Johnson 500's Power Supply Modulator. I bought them at the local surplus place. Those and a pad under the mic. stand finally killed the noise.
Keith

I once picked up some rubber shock mounts from a surplus outfit in Florida (Marlin Electronics or something like that - never get their catalogue any more, so don't know if they are still in business).  They are like miniature versions of the motor mounts that go under a car engine.  These are little rubber cylinders with a threaded stud sticking out of each end.  I have some small ones, about 5/8" in diameter with 8-32 threaded studs, and some larger ones, about 1 1/4" in diameter, with standard 1/4" threaded studs.

I had a problem with the plate transformer in the Gates BC1-T doing the same thing.  Remounted it using a set of the larger shockmounts, and it completely cured the problem.  Better still, the threaded studs were the same as the original mounting screws, so I was able to use the original screw holes and mounting hardware.  That completely cured the problem.

Does the CE100V have a 600 ohm inpoot? Perhaps a 600 ohm to 600 ohm isolation transformer would attenuate the 60hz hum? Just a thought.......

Regards,
          Joe Cro N3IBX

There are shock mounts called Lord mounts... The small ones (#8 to #10 studs) are used to isolate instruments etc in aircraft panels... They are available in many sizes up to 5/8" studs (maybe larger)and are basically a rubber cylinder with a threaded stud sticking out each end...... available from aircraft outfits like Wag-Aero,  Univair, Chief aircraft, Aircraft Spruce and specialty etc.... You can google for these guys.....I do however agree with JN that tightening up the transformer mounts and cabinet mounts is the first thing to check..Good Luck,,,,,Steve

I'm pursuing the Hockey Puck Solution as Plan A.  But this is California and the hockey puck selection is pretty dismal. The first sporting goods store only had ordinary, normal hockey pucks although for a small premium I could get them with various logos. There were no sponge rubber hockey pucks.  I'm sure I'll find them if I keep looking.

I'll tighten the bolts too and may go for the fancy mounts of some kind as the third idea. 

BTW, Don, nice article in ER on relay sequencing.  Once you look at it, it's so straightforward, but why didn't it occur to me?  (Don't answer that).

Jon

Hey,  Jon,

Your  hum is not really that bad,  but UR 100 V sounds so good that am sure trhat U wanna make the station perfect.

You might also try Neoprene foam,  as is or once was used in  Wet Suits ... mabe a dive shop / Surfer shop is easier to find here in CA.


OH,  Yea,  and this foam also used in Mouse Pads ... perhaps stack a few thicknesses under the feet of the 100 V ...

73  GL  C U on AM,    DE   Vic  KF6RIP   .  .

Hi Vic,

I've been away from the Silicon Valley QTH for a week so I haven't done a darn thing about the hum.  I went right through Santa Cruz today.  I should have stopped at O'Neils Surf shop looking for the Neoprene.  I could install some .001 caps in the audio path.  That would take care of it too.   Good to hear from you.

Jon

Marlin P. Jones & Associates,  www.mpja.com - still in business, they have some good stuff at good prices.