Warning: Creating default object from empty value in /homepages/11/d132647312/htdocs/Amfone/mkportal/include/SMF/smf_out.php on line 47
Relays for receiver antenna switching?




 
The AM Forum
December 11, 2019, 04:12:18 PM *
Welcome, Guest. Please login or register.

Login with username, password and session length
 
   Home   Help Calendar Links Staff List Gallery Login Register  
Pages: [1]   Go Down
  Print  
Author Topic: Relays for receiver antenna switching?  (Read 1616 times)
0 Members and 1 Guest are viewing this topic.
Opcom
Patrick J. / KD5OEI
Contributing
Member
*
Offline Offline

Posts: 7355



WWW
« on: August 07, 2019, 10:04:55 AM »

Regular unsealed relays can get a coating of oxide or dirt on the contacts, enough to stop very tiny signals from getting through it.

For switching 1uV signals, Reed relays may be an option being small and sealed, but there is contact bounce.

I have used mercury wetted contact relays for audio stuff and never had any issues whatsoever even with older used relays as long as they were good.

The mercury wetting would seem to make the contact more reliable and it eliminates noises caused by bouncing.

What about receiver RF input switching on the HF bands? These miniature pcb-mount 1KV ones are available. Usually they are rated lower voltages but this is interesting.

GI Clare Mercury Wetted Relay
type CUP P001A505 1-form-A one
NO 2A 1000V
coil-5V

Don't care about the mercury. It's not getting out of these things.  If it were used as the receiver-to-antenna part fo the TR switch, wonder if it would do for HF?

Has anyone tried this kind of relay?


* 1.jpg (41.96 KB, 528x450 - viewed 104 times.)
Logged

Radio Candelstein - Flagship Station of the NRK Radio Network.
KD6VXI
Contributing
Member
*
Offline Offline

Posts: 2057


Making AM GREAT Again!


« Reply #1 on: August 07, 2019, 12:05:08 PM »

Plating relays and contractors with Cool Amp really helps with any residual resistance build up.

It also helps with lowering contact resistance to very low levels.

Plate liberally.

--Shane
KD6VXI
Logged
KK4YY
Member

Offline Offline

Posts: 425


Your best isn't as good as you can be.


« Reply #2 on: August 07, 2019, 04:34:16 PM »

My trick has been to use a DPDT relay and wire the two poles in parallel. Not a perfect solution, but it works well enough. If your going to buy a relay, there those with bifurcated contacts that essentially do the same thing.


Don
Logged

All your worries won't add a day to your life, or make the ones you have any happier.
W1RKW
Contributing
Member
*
Offline Offline

Posts: 4163



« Reply #3 on: August 07, 2019, 05:30:20 PM »

I've done what Don has done as well without issue. 

hermetically sealed relay?  Yaesu had an issue with the FT-102 and had a fix with a new relay that was essentially  hermetically sealed and possibly bifurcated as well. Not a 100% sure though on this.

Logged

Bob
W1RKW
Home of GORT. A buddy of mine named the 813 rig GORT.
His fear was when I turned it on for the first time life on earth would come to a stand still.
Opcom
Patrick J. / KD5OEI
Contributing
Member
*
Offline Offline

Posts: 7355



WWW
« Reply #4 on: August 07, 2019, 09:44:12 PM »

Bifurcated are the cat's meow!

Did try some non-hermetic large bifurcated leaf ones before and had the problem but they were very old. Maybe I put bad parts in my TR switch to start with.
Got boxes of old relays including some surplus telephone company ones, all way tarnished. If some have the soft contacts like Gold I should try one. Some have double contacts on one arm, like bifurcated but with bump-type contacts fitted on them. Have not tried any of those, so dirty I guess it put me off.

The question about the mercury-wetted and regular-type reed relays is more about having excessive capacitance in the receive antenna circuit since the conductor in both kinds goes right through the middle of a coil.

Just Learned that mercury-wetted relays including the 'octal' plug-in types have the glass ampoule sealed containing hydrogen under high pressure. A reason not to bust them! Also, Hydrogen will leak out through the glass wall of a pressurized containment over time.

May be time to put frugality aside for this one thing, go hermetic and bifurcated..
Logged

Radio Candelstein - Flagship Station of the NRK Radio Network.
WBear2GCR
Member

Offline Offline

Posts: 3732


Brrrr- it's cold in the shack! Fire up the BIG RIG


WWW
« Reply #5 on: August 08, 2019, 05:52:05 PM »

Pretty simple to test for the "excess" capacitance, I would think.
The other thing would be to test for isolation between contacts...

There seems to be in the back of my mind some reason or other that mercury wetted
relays are contraindicated for low level signals. Of course it may be the other way around.

Another option is just reed relays. No oxygen to make the contacts get nasty.

Telco contacts often were designed to be "self cleaning" via a wiping motion.
Especially those that had the contacts that were at 90 deg to each other...

I know this stuff has been covered somewhere... in books or online.

                          _-_-
Logged

_-_- bear WB2GCR                   http://www.bearlabs.com
MikeKE0ZUinkcmo
Member

Offline Offline

Posts: 369



« Reply #6 on: August 09, 2019, 06:12:22 AM »

I remember, somewhere in the foggy past, something about applying a fraction of a volt of DC with a mil or two of current load would help keep the contacts in good condition.   

Those that wipe would be the best bet I'd think.

 
Logged

Mike KE0ZU

Bold Text and PICS are usually links

https://mikeharrison.smugmug.com/
Opcom
Patrick J. / KD5OEI
Contributing
Member
*
Offline Offline

Posts: 7355



WWW
« Reply #7 on: August 09, 2019, 10:27:58 AM »

I've thought about wiping. When I worked for Alcatel, we had a line length simulator instrument. Inside were many boards filled with dozens of relays and hundreds of resistors.
It had a self cleaning function which would run every time a new line length was selected. The thing would rattle and buzz operating the relays many times to make sure they were exercized. We use to say 'exorcized' because of the racket going on for 20 seconds or so.

There is an article including intermittent receiving issues:
https://www.w8ji.com/relay_cleaning_and_life.htm

Some technical advantages of mercury wetted contacts that seem to apply to contact problems are on page 2of this PDF file:
http://bunkerofdoom.com/relay/pb/JM_MERCURY.pdf

Just seems to me that a sealed unit is best for the tiny signals, and the above PDF seems to say that mercury wetting eliminates the wear and contact resistance issues.

If no one has tried this kind of relay then it's for me to measure the thing and see how it works.
Logged

Radio Candelstein - Flagship Station of the NRK Radio Network.
WBear2GCR
Member

Offline Offline

Posts: 3732


Brrrr- it's cold in the shack! Fire up the BIG RIG


WWW
« Reply #8 on: August 09, 2019, 10:50:05 AM »

Perhaps more data/info in this (yet to read it):
http://www.ni.com/product-documentation/4199/en/
and:
https://www.eevblog.com/forum/beginners/signal-relays-(1khz-1mhz)/

Teledyne used to offer relays like these, but in what looked like metal transistor/early IC packages"
https://www.te.com/usa-en/products/relays-contactors-switches/relays/mil-aero-relays/high-frequency-relays.html?tab=pgp-story

see attached too.

* Coto_Reed_Relay_Technical_-_Applications_Info.pdf (2495.41 KB - downloaded 57 times.)
Logged

_-_- bear WB2GCR                   http://www.bearlabs.com
KK4YY
Member

Offline Offline

Posts: 425


Your best isn't as good as you can be.


« Reply #9 on: August 09, 2019, 03:00:11 PM »

There was a problem with the relays in the Kenwood TS-430S going intermittent on receive (ask me how I know). Kenwood issued a repair and modification.

The mod put a small maintenance current through the relays to keep them working.

https://www.qsl.net/wb4kdi/Kenwood/TS-430S/Service%20Bulletins/asb0902.html

Edit: The idea of this is to provide a DC current for the relay to switch that creates a small arc which refreshes the contacts every time it switches. The input and output must be DC blocked by capacitors, which is easy enough to do for a receiver, if it isn't already. By using this method, probably just about any general purpose relay would suffice for a T/R application.


Don
Logged

All your worries won't add a day to your life, or make the ones you have any happier.
MikeKE0ZUinkcmo
Member

Offline Offline

Posts: 369



« Reply #10 on: August 12, 2019, 06:41:56 AM »

Quote
...The mod put a small maintenance current through the relays to keep them working...
In my earlier post, I couldn't remember the particulars but it seems KW found the same ancient fix keeps the relay contacts bright.

-------

Those relays were used quite a lot during the 60s and 70s in military equipment.   They drew a lot of current but could withstand fairly high "G" shock load and vibration.



Logged

Mike KE0ZU

Bold Text and PICS are usually links

https://mikeharrison.smugmug.com/
WBear2GCR
Member

Offline Offline

Posts: 3732


Brrrr- it's cold in the shack! Fire up the BIG RIG


WWW
« Reply #11 on: August 13, 2019, 12:19:01 AM »

Yeah Mike!
That's one of those Teledyne relays! Cheesy
Logged

_-_- bear WB2GCR                   http://www.bearlabs.com
Opcom
Patrick J. / KD5OEI
Contributing
Member
*
Offline Offline

Posts: 7355



WWW
« Reply #12 on: August 13, 2019, 01:16:28 AM »

Those are some snazzy relays! so tiny. Is that a TO-5 can?
In almost every way, at some time, we get to see a particular pinnacle or zenith of technical evolution. That's what those look like.
Logged

Radio Candelstein - Flagship Station of the NRK Radio Network.
MikeKE0ZUinkcmo
Member

Offline Offline

Posts: 369



« Reply #13 on: August 13, 2019, 10:34:40 PM »

Yep, TO-5.   I've had maybe 20 of those things for at least a decade or so, and maybe used ...1!
Logged

Mike KE0ZU

Bold Text and PICS are usually links

https://mikeharrison.smugmug.com/
Opcom
Patrick J. / KD5OEI
Contributing
Member
*
Offline Offline

Posts: 7355



WWW
« Reply #14 on: August 14, 2019, 07:13:41 PM »

Surprisingly they are still made and also offered on the auction site.
Logged

Radio Candelstein - Flagship Station of the NRK Radio Network.
K6JEK
Contributing
Member
*
Offline Offline

Posts: 1135


RF in the shack


« Reply #15 on: August 25, 2019, 02:42:03 PM »

Plating relays and contractors with Cool Amp really helps with any residual resistance build up.

It also helps with lowering contact resistance to very low levels.

Plate liberally.

--Shane
KD6VXI
Cool-Amp? How is it I've lived as long as I have and never heard of this stuff. Is this the right product: https://www.cool-amp.com/conducto-lube
Logged
Pages: [1]   Go Up
  Print  
 
Jump to:  

AMfone - Dedicated to Amplitude Modulation on the Amateur Radio Bands
 AMfone 2001-2015
Powered by SMF 1.1.21 | SMF © 2015, Simple Machines
Page created in 0.044 seconds with 19 queries.