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Author Topic: How To Properly Setup A PTT/TR Relay  (Read 10884 times)
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flintstone mop
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« on: May 12, 2015, 08:44:41 PM »

I have made a bad discovery. I thought I had a good idea going here for a Master PTT and TR relay. I found out by looking closely to the SWR meter on my Kenmore TS850 and the new addition to the shack, an ALS 600 amplifier, that there is a brief moment of high SWR. Just a blip of high SWR. Enough to kick the ALS600 offline. It thinks there is a bad load. Apparently there is a lag for the actual T/R relay to switch over the antenna over to transmit.

How could I work around this problem? I hope I do not need to get complicated with a sequencer......


The ALS600 is great for fast QSY on the upperbands SSB chatter on 12 and 17M. ...and YES AM operation on 10M. 125 carrier watts and the amp makes plenty of PEP!! Sounds really nice. Lottsa pos peaks!!
Fred
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Fred KC4MOP
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« Reply #1 on: May 12, 2015, 09:11:05 PM »

Try a DPDT relay. One set of contacts is the antenna switch-over, the other keys the transmitter/amp. The transmitter/amp won't come on until the antenna is switched over. If that is still too quick, the second set of contacts can throw another relay to key the fire in the wire. When you drop the relay power (un-key) the relays will both open at the same time. That seems to work here. (The two relay setup.)
Bill
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Bill KA8WTK
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« Reply #2 on: May 12, 2015, 09:42:41 PM »

Build a sequencer.  That amplifier may not like even a momentary spike encountered from the use of a single relay.  If you are not using a sequencer you do NOT want to use two separate relays.  So, while Bill's suggestion is better than what you are currently using, a sequencer is even better.  There are many different circuit designs.  I like Don, K4KYV's design best

Good reading.  Important reading.  http://amfone.net/Amforum/index.php?topic=28629.0

Al

PS:  Don's circuit can be found in Electric Radio #198, Nov, 2005
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N1BCG
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« Reply #3 on: May 13, 2015, 11:07:46 AM »

I used three 4PDT relays to create a sequencer. Each relay triggers the next, so there's a degree of "fail safe" to the design. The transmit (key) and receive (unkey) sequence is determined by whether parallel or series wiring is used for each controlled device. The R/C timing circuits consist of a 1k resistor and 47mF cap. Here's the order of switching:

XMT: RCVR MUTE/ANT RELAY -> VFO ON -> XMTR/AMP ON

RCV: XMTR/AMP OFF -> VFO OFF -> RCVR UNMUTE/ANT RELAY

The antenna relay is on a parallel N/O loop through the first and third relays. It requires either to be activated, so it's the first circuit to close and the last to open.

Receiver muting is on a series N/C loop through the first and third relays. It requires both to be deactivated, so it's the first circuit to open and the last to close.

The VFO is on N/O contacts on the second relay to put it mid sequence. It would have been fine operated like the antenna relay or receiver mute, but I had the extra relay.

The transmitter/amp is on a series N/O loop through the first and third relays. It requires both to be activated, so it's the last circuit to close and the first to open.


* sequencer.jpg (3209.36 KB, 3264x2200 - viewed 743 times.)
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flintstone mop
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« Reply #4 on: May 13, 2015, 06:45:58 PM »

Thanks for the useful info and scheezo. I'll look at Don's sequencer and see what's involved. There is a ham selling sequencer kits for $20.00, W6PQL.
This has been going on for a while and the ALS600 did not like open RF circuit even for a milli second. My big AL1500 would kick itself offline, at times, when I use it in the AM mode. The Grid protection ckt would kick in after the amp did not see a good load on the outpoot.
So, now is the time to correct it.
I always wondered what the high SWR blip was on my TS850 meter.
Fred

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Fred KC4MOP
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« Reply #5 on: May 14, 2015, 02:02:43 AM »

I used three 4PDT relays to create a sequencer.

I am a big fan of simple and relatively indestructible RC timing for uses like this. Where extreme reliability is wanted, plastic type capacitors are not so costly.
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flintstone mop
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« Reply #6 on: May 18, 2015, 07:17:04 PM »

I received a W6PQL sequencer, $30.00 built and tested. And ordered some dpdt relays that can be mounted on a panel to rebuild my PTT system. I will resurrect this thread to show a picture

Fred
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« Reply #7 on: August 03, 2016, 11:07:25 AM »

I just ordered the W6PQL sequencer.  It looks pretty nifty!  My shack currently just has one T/R switch which switches everything at the same time.  It also has a second set of contacts that I can use to key this device.  

Off of his device, I just need to rig the antenna relay, drain voltage and microphone input to the amp (if I go with Heising modulation) for events (in that order).  The 3 upper events can't sink much current, so I'll add external relays for those.

Jon
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MikeKE0ZUinkcmo
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« Reply #8 on: August 04, 2016, 07:17:46 AM »

Here is another sequencer schematic.   I found this long ago somewhere, and it's not mine, but looks awfully similar to Clark's drawing.  



Mike
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Mike KE0ZU

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« Reply #9 on: August 04, 2016, 08:58:15 AM »

I used three 4PDT relays to create a sequencer. Each relay triggers the next ...

In my 1st job out of school I worked with a guy who designed time delay circuits with dozens of relays. It was one big "relay chase". More delay, just add another relay. He'd also bend the contacts for "fine tuning".
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w1vtp
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« Reply #10 on: August 04, 2016, 10:49:43 AM »

I used three 4PDT relays to create a sequencer. Each relay triggers the next ...

In my 1st job out of school I worked with a guy who designed time delay circuits with dozens of relays. It was one big "relay chase". More delay, just add another relay. He'd also bend the contacts for "fine tuning".

There are more elegant ways to accomplish sequencing but who can argue against the sound of several relays in coming in during a RX / TX transition

Al

PS: You can get Don's original article on his sequencer from November 2005 ER. The original text might be helpful
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« Reply #11 on: August 05, 2016, 11:25:49 AM »

Fred,

I use a series of DPDT cascade relays for keying my ALS-600 and AL-82 amplifiers with all the rigs that I drive them with. It's cheap and pretty much bullet-proof as far as making sure things engage in the right sequence. I sure would not try using it for CW - QSK though!

73,

Rob W1AEX


* aex cascade relay system for t-r.jpg (51.65 KB, 1176x841 - viewed 361 times.)
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W3RSW
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« Reply #12 on: August 06, 2016, 12:22:27 PM »

If your running AM where fast T/R or break-in CW switching is not paramount, but you want to simply and properly sequence relay switching of signal in, signal out and amplifier cathode current, you can use a 3 pole, double throw open frame relay.

The relay physical dimensions are large enough that simple blade bending of each throw will accomplish the proper timing.

This is what I've done in my twin 813 amplifier.

Here is the common armature bending sequence for each blade.

When carefully and equally (across the carrier) pushing on the armature center:

The output (to antenna, etc.) contact should obviously close first.
The input (from 10 watt driver, etc.) contact should close second.
The amplifier cathode or bias contact should contact last, but nearly at
same time as the input contact.

I'll try to find the link to site where more info was available along with additional  circuits for E-timing of T/R relays, etc. ; have only found the PDF copy so far from when I built the 813 amp.


* link input and corner angle.JPG (2114.6 KB, 2592x1944 - viewed 335 times.)
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« Reply #13 on: August 29, 2016, 10:44:26 PM »

I built this circuit, and I'm thinking that I bought the wrong comparator chip.  None of the outputs go high when the voltage on the (+) pin exceeds the voltage set up by the voltage divider on the (-) pins.  

I've modified the schematic with the pin numbers to suit the NTE834 chip that I used.  I've verified my wiring with voltage reading at the pins.  The voltage divider is working properly at all (-) pins, and the rising/falling voltage is seen at all the (+) pins.  

I put the voltmeter lead directly onto the output pins of 1, 2, 13 and 14 but there's never a change.  

Any advice on this one?

Jon


* IMG_0730.JPG (2303.35 KB, 4032x3024 - viewed 424 times.)

* IMG_0731.JPG (2305.62 KB, 4032x3024 - viewed 405 times.)
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MikeKE0ZUinkcmo
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« Reply #14 on: August 29, 2016, 11:06:21 PM »

I suspect what you have is an LM339 or similar device.   Wire one of your stages as shown in the schematic below using your current IC, and I'd think it would work.



If successful, just rewire the others as well.

The data sheet for the LM339 is here, just input LM339 in the box where it says transistor.

Mike




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Mike KE0ZU

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« Reply #15 on: August 29, 2016, 11:20:11 PM »

I suspect what you have is an LM339 or similar device.   Hook the base of your output transistors directly to the output pin of the IC, and tie one end of the 10K resistors to +12.

  The NTE834 output is open collector...It can sink current but cannot source it. What Mike proposes should work.

Jim
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ka1tdq
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« Reply #16 on: August 29, 2016, 11:30:51 PM »

Oh, ok!  So you're saying to do this... ?

Jon


* FullSizeRender-16.jpg (1367.9 KB, 4032x3024 - viewed 418 times.)
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MikeKE0ZUinkcmo
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« Reply #17 on: August 29, 2016, 11:34:48 PM »

Yep, just like my schematic.

Mike
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Mike KE0ZU

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ka1tdq
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« Reply #18 on: August 30, 2016, 12:16:28 AM »

Bingo!  Thanks! 

All 4 events work and the timing is as it should be.  Tomorrow I'll finish connecting the LED's and the relays. 

Jon
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ka1tdq
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« Reply #19 on: August 30, 2016, 07:26:33 AM »

Here's a 20 second video showing the pretty green LED's...

https://www.youtube.com/watch?v=JIed17iWy-o

Jon
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