Buzzy Antenna Relay

[WA1QHQ]

I have a Dow Key type antenna relay with a solenoid actuator, that is a solenoid with a movable rod in the center with a stop at one end of the rod, the other end pushes against the relay contacts. The coil voltage rating is 120 VAC and it buzzes loudly when energized but otherwise works fine. The buzzing is like that of one of those electric engraving pens only not quite as loud. If anybody has knowledge of what might be wrong please let me know so I can press this thing into service if it can be repaired.

[KB3DKS]

  Clean the selonoid, Make sure all components are tight, if the coil assm can be moved try aligning it. Lubrication, Also if the stop is adjustable try a thin piece of rubber from a bicycle tire innertube to cushion the stop point or something similiar so it is not metal to metal. If the selonoid slug is laminated see if the rivits have loosened up.
 The old washing machine laminated ones were good for buzzing when they got old.

Bill, KB3DKS in 1 Land

[Jim, W5JO]

If Bill's suggestion doesn't work run it on 24 VDC.

[WA1GFZ]

Mark,
Check how the mating magnetic surfaces land may need a few file strokes. There needs to be a good magnetic path to the shunt winding or it will buzz.
They do work well on 28 VDC.

[AB2EZ]

In addition to what others have suggested:

The following cured the buzzing on one of my DowKey relays....

I took a 2 inch long piece of ordinary plastic electrical tape, and ran it from one side of the solenoid over the top, to the other side of the solenoid. I pressed down on the top to make sure the tape was making a good contact to the top of the solenoid. That fixed the problem.

It appears that the top of the solenoid (essentially a disk about 1 inch in diameter) was vibrating. The plastic tape damps out the vibration.

Stu

[Steve - WB3HUZ]

Yes. I've done that too. That disk makes a nice buzzer.

[WA1GFZ]

cool idea. My shack is almost clean enough to put the Viking 2 on the operating desk. I'll have to give it the tape job before  I slide in to the final position. 

[K8WBL]

Mine 120 VAC Dow key does the same thing on my Globe Scout...annoying..I will try some of these suggestions as well.

73,Tim K8WBL

[N2DTS]

I have been working on a relay sequence problem when using the 3X4d32 rig, the TR relay seems to open before the RF stops for some reason, and in playing with the TR relay contacts, I could make the relay buzz real loud!
If the relay can not close hard enough, it will buzz.
I bent the contacts back away from each other and it was silent again...

Brett

[K9AAL]

I had this problem too.  I made a minimal adjustment to the transmit antenna relay contact.  I loosened the retaining nut on the relay's female coaxial connector that connects to the transmitter.  I then turned  the connector to minimally decrease the gap between the moving contact and the coaxial connector relay contact.  That eliminated the buzz and I tightened the retaining nut.  I then had to readjust the contacts for muting the reciever.  Seems to be a satisfactory fix. 

George, K9AAL

[WU2D]

Get some Vaseline.

Actually is the coil form loose on the core? Give it a bath with some polyeurathane.

Mike WU2D

[k4kyv]

I have a very large HV RF contactor type relay designed to switch open wire line.  The open contacts are very widely spaced and the contacts themselves are nearly the size of a dime.  Unfortunately, the thing buzzes like a chain saw, so I spring mounted it, kind of like the old double button carbon microphones used to be spring mounted inside a ring, except that the relay is spring mounted inside a wooden box with a latchable door on it.  With the door closed, I hear a slight klunking sound on "make", but the buzz is completely inaudible.

A T/R relay sequencing error converted my dow-key into a solid block of charcoal.  That's what prompted me to design the sequencing delay circuit that I wrote up in the ER article.

[WA1QHQ]

Well, I finally decided to figure out what was going on with the buzzy Dowkey relay, mainly to get it off my bench to clear space for other things.

K9AAL was on the right track with this. I popped the little end plug that exposes the TX and RX contacts and sure enough there was essentially no gap, the wiper was pinched between the TX and RX contacts. What had caused this was the contacts are actually screwed into the SO239 connector. The TX contact had become loose and whenever a connector was mated with the SO239 recepticle and rotated as it was threaded on the TX contact would rotate toward the RX contact. Eventually the two contacts were threaded against each other. It was simple to fix once I recognized what was going on, just tighten up the TX contact and reset the contact gap for minimum back pressre against the solenoid while still making good electrical contact. That is the key to making the solenoid buzz as low as possible, the harder it has to push the louder it will buzz.

[W9GT]

A T/R relay sequencing error converted my dow-key into a solid block of charcoal.  That's what prompted me to design the sequencing delay circuit that I wrote up in the ER article.

I seem to go through Dow Key relays with regularity on my old Federal 167B Marine transmitter.  (813s modulated by 811As) Seems like it likes to burn up contacts after awhile on the transmit side, of course.  I'm not sure if the damage and arcing occurs on make or break, but after a few years of use, the contacts start sparking and arcing and eventually stick and fail.  Perhaps, some attention to the sequencing of make and break times would help in this regard.  I have also considered just "rolling my own" and building up a heavy duty antenna relay using a big surplus ceramic-insulated relay with big contacts that I salvaged from some old piece of gear and mounting it in a minibox with some connectors.  The Dow Keys are just handy to use, but maybe not rugged enough when used to switch the antenna on a big AM rig.

I have also had some measure of success running AC-type relays on DC, the only negative factor is that sometimes after a little use, they retain some residual magnetism and become sticky or hang-in too long.

73,  Jack, W9GT

[k4kyv]

I have also had some measure of success running AC-type relays on DC, the only negative factor is that sometimes after a little use, they retain some residual magnetism and become sticky or hang-in too long.

I run all my relays on DC, include a few that were designed for 110 vac.  I have had only one or two to ever get sticky like that, and those were actually designed to run on DC (command  set relays).  One of  those was due to some kind of sticky gooey stuff running out of the coil and gumming up the mechanics, but the other appeared to be magnetic.  I put a piece of tape between the pole pieces and that maintained a small air gap when the relay was closed, and it never stuck again.

If you only occasionally have that problem due to magnetism, you can prevent it by periodically reversing the polarity of the DC to the coil.  You could even wire in a small DPDT toggle switch for the purpose.