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   Home   Help Search  
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Author Topic: Relay timing  (Read 1275 times)
WE6C
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Posts: 20




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« on: November 05, 2017, 09:54:16 AM »

Hi all, I have an old AL-80 (no "A" or "B"). I also have an Icom IC-746. The keying voltage of the AL-80 was measured at 14 volts at 125mA. This I believe is too much for the 746 so I built a buffer (two transistors and a few other parts) which ties into the 13.8 volts on the 746's accessories din. Another pin is grounded on transmit.

The buffer works but what I've run into is the radio transmits RF before the relays on the amp are completely engaged. I can see an SWR spike at the beginning of transmit on the 746 using CW. I have not tried this but I'm sure using SSB, no VOX, would be fine since when the mic is keyed, there will be a few milliseconds before any voice/RF but I would still not be comfortable with that.

I realize that a QSK circuit will most likely solve this but I neither need QSK or the QSK expense on this amp.

Any suggestions?

Thanks and 73, Bob  WE6C
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W1QJ
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Posts: 2602




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« Reply #1 on: November 05, 2017, 10:05:46 AM »

Typical problem.  You could use MOX switching or add some vox  delay depending on your sending speed so the relay isn’t in/ out so often.  Other than that not too much can be done easily.  Some radios have RF delay and that can be set high.  In rag chew CW MOX is the simple fix.  Not too many older amps can switch faster than a radio.  Newer expensive amps have QSK, older ones not.  Fact of life of using old amps with new radios.
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NI0C
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« Reply #2 on: November 05, 2017, 10:50:36 AM »

For a number of years, I've used one of several K1EL keyer circuits (currently the WKUSB) for CW.  These keyers have a PTT output that can key your amplifier with programmable lead-in and tail times (referenced to the separate CW output) suitable for your gear.  Using the AL-80 amps, 20 msec for lead-in, and 70-100 msec tail time should work.   
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AC6CV
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Posts: 299




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« Reply #3 on: November 05, 2017, 10:54:36 AM »

Set the Icom delay at 20 ms. I believe it is adjustable. If the older Icom delay insn't adjustable just make sure the delay is turned on. Many of the tranceivers are just on or off, about 20 ms.
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WE6C
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Posts: 20




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« Reply #4 on: November 05, 2017, 03:15:35 PM »

Thanks guys for the info. I do not find anywhere in the 746 menu where a transmit delay is adjustable. Lou, your idea will work. I also looked up the K1EL keyers. Very nice, I may have to consider one of these.
Thank you.
Bob  WE6C
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W1QJ
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Posts: 2602




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« Reply #5 on: November 05, 2017, 04:06:43 PM »

Bob, I think I have a K1EL keyer and will consider selling it. Lou
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WE6C
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Posts: 20




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« Reply #6 on: November 05, 2017, 04:22:47 PM »

Lou, My e-mail is good on QRZ
73
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W1QJ
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Posts: 2602




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« Reply #7 on: November 05, 2017, 04:49:01 PM »

Bob, it appears to be a P-1 keyer not K1EL
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AC2RY
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Posts: 280




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« Reply #8 on: November 05, 2017, 09:11:01 PM »

Thanks guys for the info. I do not find anywhere in the 746 menu where a transmit delay is adjustable. Lou, your idea will work. I also looked up the K1EL keyers. Very nice, I may have to consider one of these.
Thank you.
Bob  WE6C

Page 44 of User Manual. https://www.scribd.com/document/37338092/Icom-IC-746-Instruction-Manual
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WE6C
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Posts: 20




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« Reply #9 on: November 06, 2017, 12:45:31 AM »

AC2RY, I checked both the PDF page 44 and the actual page 44 and the only thing I see is the "delay from transmit to receive" which is the semi-break in delay. There is also a "VOX delay" which is the time from transmit to receive. I see where it says, "suitable interval for returning to receive after transmitting"

Am I still missing it?

Thanks for the link. Bob  WE6C
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AD5X
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Posts: 1547




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« Reply #10 on: November 06, 2017, 04:46:11 PM »

Many older Icom radios, including the 746, do not have a menu adjustment for amp-key-to-RF-out delay. I know the amp-key-to-RF-out delay on my IC-706MKIIG is about 12ms, and I measured a IC-7000 at 8ms.  Since non-QSK amps use relays that take approximately 15ms or so to switch, this means that these radios will hot-switch with non-QSK amps.

Phil - AD5X
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WE6C
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Posts: 20




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« Reply #11 on: November 07, 2017, 03:49:18 PM »

Phil, That's the way I read it but was hoping I did miss something since that would have been an easy fix.
Bob  WE6C
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AD5X
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Posts: 1547




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« Reply #12 on: November 08, 2017, 02:55:19 PM »

You might want to check out http://qsk2500.myfreesites.net/.  The QSK2500 resolves these problems (both key and unkey) and will work with any amp.  It is a bit pricey though (almost $400 I think).  Anyway, I did a review of this in QST awhile back.

Phil - AD5X
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AA2UK
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Posts: 303




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« Reply #13 on: November 09, 2017, 08:57:16 AM »

Aren't these radio prone to an instant full power spike when initially keyed?
I think it can be controlled using the ALC circuit.
Bill, AA2UK
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WE6C
Member

Posts: 20




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« Reply #14 on: November 09, 2017, 09:09:42 AM »

You might want to check out http://qsk2500.myfreesites.net/.  The QSK2500 resolves these problems (both key and unkey) and will work with any amp.  It is a bit pricey though (almost $400 I think).  Anyway, I did a review of this in QST awhile back.

Phil - AD5X
Thanks Phil. I'll dig out the magazine.
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