The AM Forum

I bored you recently with posts about some audio problems with my Valiant. Simultaneous with the audio issue was a perceived loss of the famous Valiant Kerchunk, Kerthunk or just plain 'ol Thunk heard when squeezing the PTT.

After spending some time chasing the audio, tightening the self-loosening transformer screws and replacing the rectifiers it was time to lovingly place the transmitter back in its shell. The cabinet went on, all the cabinet screws put in place and tightened. Lo and behold, the trademark Kerchunk once again resonates throughout the room when I activate the transmitter. Of course, it could also be my imagination, but I wonder if there is a magnetic field drawing in the metal cabinet or something. Or, perhaps the aliens have returned and I need to secure my tinfoil cap on my head.

I would go with the tinfoil cap just to play it safe.

Kerchunk is good.............sizzle, flash, bang is not good.

Craig,

Roger that - I love Kerchunk!

I think the noise is caused by the choke flexing the cabinet.

I suspect what your hearing is normal due to amplification with the cabinet installed through the hard rubber feet amplified with it sitting on your counter, shelf or desk.
Try putting something under the rubber feet to insulate and isolate the noise. You could use a smart phone and record video and post it here for an example. It could also be the metal cabinet vibrating on the chassis somewhere. On my valiant I had an issue with the upper long screws proper feeding through the metal tabs in the cabinet. I thought maybe the threaded end of the chassis was stripped. I learned a method for installing them. I use a flashlight and locate the metal tab thru the top of the cabinet and I use an old resister with heavy wire and curl a small hook on the end, rotate it thru a hole in the cabinet and hook the underside of the long screw and lift it to align with the hole in the tab. This issue may be due to the previous owners replacement of these long fasteners, but it works for me.
Other than that you could put on the tinfoil hat. Hi hi de k7iou

Thought-generating ideas, and thanks.

To be clear: I don't want to eliminate the Kerchunk. To me, it is the sound of the Valiant from fifty years ago; it just sounds 'right'. Similarly, the smell of some foods will remind one of good times in the past. My post was simply an observation as opposed to a request for ideas on how to eliminate the phenomenon.

The Kerchunk was either gone or much reduced when the transmitter was out of it's cabinet, returning as soon as it was back home. The four long screws were easily installed through the guides and into the threaded receptacle at the front. Maybe I just got lucky. I found placing the small screws around the apron in place first, but not tightening them at all seemed to align the chassis to the cabinet so the long screws went right in. I'm no tech guru, as evidenced many times here on the forums, but my uneducated suspicion is some sort of magnetic field builds and then collapses upon transmit, causing the cabinet to resonate, flex or something similar.

KERCHUNK!

Many FB AM QSO recordings contain that sound.

I have an old Valiant mounted far away from the mic and was trying to figure out a way to get the sound back.

Ah yes, I believe you may be referring to the British Royalty, Lord Alistair Kerchunk. Of the Kerchunks upon Ariel. The first Earl of Kerchunk was known for his wit and width. Need I amplify?

I was saving this for April 1, but it seems appropriate.