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Author Topic: Can you recommend simple toggle switches for HF homebrew stuff?  (Read 430 times)

N3KXZ

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Can you recommend simple toggle switches for HF homebrew stuff?
« on: February 28, 2023, 05:36:28 PM »

I sometimes want to build an HF gizmo that could benefit from using several toggle switches rather than more sophisticated circuitry. There is a huge range in prices which I suppose indicates quality... does it? On the one hand I want something that is durable, but wow $4-$15! for a switch seems pricey to me when I want several for one project.

I don't see toggle switches ratings for frequency, only (generally) for voltage and current. I wonder... do inexpensive switches suffice for HF work?

Could you recommend specific brands or suppliers of  panel mounted toggle switches suitable for HF work? Low current and low voltage for things like attenuators and or selecting sections of receiver front end filters or tank circuits, etc.

Thanks,
Keith
N3KXZ
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K6AER

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Re: Can you recommend simple toggle switches for HF homebrew stuff?
« Reply #1 on: February 28, 2023, 08:17:00 PM »

Look at DigiKey or Allied Electronics.
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AC7CW

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Re: Can you recommend simple toggle switches for HF homebrew stuff?
« Reply #2 on: February 28, 2023, 08:52:59 PM »

switches are often spec'd in upwards of hundreds of thousand toggles before failure. I've seen those limits reached on manufacturing test equipment but it's unlikely that switch failure will be a factor in a radio project. If you are switching low currents and low voltages as in a lot of solid state designs about any switch should be ok. Arcing when the switch opens can occur at higher voltages and that will burn contacts. If you are switching rf then you need a switch specified for that perhaps.. learn about make-before-break and break-before-make.
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LA9XNA

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Re: Can you recommend simple toggle switches for HF homebrew stuff?
« Reply #3 on: February 28, 2023, 09:09:44 PM »

On HF on QRP levels normal toggle switches can usualy be used without problems.
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WB6BYU

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Re: Can you recommend simple toggle switches for HF homebrew stuff?
« Reply #4 on: February 28, 2023, 10:02:15 PM »

At 50 watts into 50 ohms, you have 50V at 1 amp.
(That makes the math easy.)

So any practical switch rated for 120 VAC at 2 amps
or higher should carry 100 watts.

Ratings for receive use are insignificant - signals
are way too small to matter.

HOWEVER, the issue often is impedance discontinuities
in the switch.  As you go higher in frequency, these will
cause a higher SWR.  Most switches will work on the
lower HF bands, and often on 10m, depending on
how much SWR you can tolerate due to inserting
the switch.

If you are using a tuner between the switch and the
radio, that should account for any SWR (but you may
need higher voltage and current ratings for the switch).


I’ve used standard DPDT toggle switches for switching
antennas at 100 watts, and others have used standard
household light switches (not the mercury type) mounted
in a, electrical box.  Attenuators often use slide switches
due to the short internal lead lengths, even at VHF.
(They give the best results with shields across each
switch, and sometimes between them.)

One of my receivers uses a doorbell pushbutton
because it happened to be ergonomic in that application.

For building projects, it isn’t always convenient to
run connecting wires all the way to a front panel switch
(unleaded it can be done with coax).  In that case
it is often easier to switch a DC voltage that controls
switching diodes (or relays), for example when
changing bands and you need to switch several circuits
at the same time.


Basically, if you are running over 100 watts, or using
very small switches, you need to pay attention
to the voltage and current ratings.  In the upper HF
range, pat attention to lead length.

At QRP or receive signal levels, just about anything
will work.

I have had some cheap switches fall apart when
subjected to heavy-handed use (or slammed in
the car door) but most are suitable for a receiver
sitting on a desk in the shack.

G4AON

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Re: Can you recommend simple toggle switches for HF homebrew stuff?
« Reply #5 on: March 01, 2023, 02:26:32 AM »

Keith, I have used ordinary miniature toggle switches in my home brew gear for some time, eBay item 284407188685 shows the type.

Using my home brew RX as an example, the AF filter switch has screened audio cable to the front panel, the centre off switch for pre-amp/attenuator switches relays, the on/off switch is in series with the main DC supply.

https://www.qsl.net/g4aon/

Prices are sometimes cheaper from the large suppliers, such as Mouser, but there is postage/packing that adds quite a lot unless you are ordering parts in excess of their minimum for free delivery.

73 Dave
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W1VT

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Re: Can you recommend simple toggle switches for HF homebrew stuff?
« Reply #6 on: March 01, 2023, 03:48:10 AM »

I've used slide switches for attenuators.  I used a file to make the square mounting holes in aluminum.  Toggle switches just require a round hole.  Two holes are better.  Many come with a mounting plate that will prevent the switch from rotating.  The 2nd hole fits into the mounting plate.

Zak W1VT
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K5LXP

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Re: Can you recommend simple toggle switches for HF homebrew stuff?
« Reply #7 on: March 01, 2023, 05:42:08 AM »

The issue isn't so much about conduction, or impedance so much at HF, but isolation from the common terminal to the "off" terminal.  Depending on what the switch is switching between, some degree of coupling may or may not be an issue.  When I was a kid running boatanchor HF rigs I used a large-ish (15A?) SPDT or DPDT bat handle toggle for a T/R switch.  Worked fine, and compared to some of the antennas I used there was no SWR issue introduced.  Back in those days building a step attenuator was a way to get a useful piece of test equipment or T-hunt accessory and I recall from the handbook or wherever the build article came from (similar to this one), it was discussed to use slide switches as they offered the best isolation and lowest capacity of common switches.  When I built an antenna switch matrix using relays I used a technique to strap the contacts of a DPDT relay to reduce the length of the signal path inside the relay which improved match and isolation.  Measured on a network analyzer these relays were now quite acceptable for my purposes up through 6M.  So the upshot of all this is to know what is an acceptable degree of mismatch, insertion loss and isolation you want or need, from there it's fairly academic to test different switches using basic equipment to see which ones work best for you.

Mark K5LXP
Albuquerque, NM
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N3KXZ

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Re: Can you recommend simple toggle switches for HF homebrew stuff?
« Reply #8 on: March 01, 2023, 09:23:59 AM »

Thanks to everyone for this interesting thread of replies, I learned and was reminded of several considerations. I do think isolation and impedance discontinuities are important in some uses. I had never really considered using slide switches because in the past I had so much difficulty cutting square holes in metal... maybe I should revisit that in the near future, but my fabrication skills and tools are minimal. You guys have so much more experience than I, and I appreciate you taking the time to reply.

Keith
N3KXZ
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K8AXW

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Re: Can you recommend simple toggle switches for HF homebrew stuff?
« Reply #9 on: March 01, 2023, 09:31:32 AM »

Keith, Google AllElectronics.  The have a wide selection of switches.  If you ever get a chance to attend a hamfest, do it.  You can find all kinds of fun stuff!
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WB6BYU

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Re: Can you recommend simple toggle switches for HF homebrew stuff?
« Reply #10 on: March 01, 2023, 02:19:42 PM »

Quote from: N3KXZ

...I had never really considered using slide switches because in the past I had so much difficulty cutting square holes in metal...



Much easier using a nibbler tool.

KL7CW

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Re: Can you recommend simple toggle switches for HF homebrew stuff?
« Reply #11 on: March 02, 2023, 11:28:07 AM »

If I had to evacuate quickly and could only take one tool from my shop it might be my nibbler tool, or for those of us over 80 perhaps  a magnifying glass !!
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