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Author Topic: Mirage A1015  (Read 2593 times)
KF6A
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Posts: 214




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« on: March 01, 2010, 08:20:29 AM »

I've searched and didn't find this covered.

I'm considering buying a used Mirage A1015 6m amp, brown face, pre-mfj, it has not been modded for RF sensed switching and I would like to do so. Mirage said they will send me the info to do the mod but they said they have the A1015G info and they are not sure if it the same as the A1015 non-G model.

Is the modification the same? From searching I read I would need a resistor and other posts say I need a cap as well. I'll be using this with a 706 so please don't tell me to just use the RCA jack because I'm not going to buy or make an interface to hard key it.

If you feel the info is too sensitive, so the cbers don't get their hands on the info, please feel free to email me at kf6a at arrl dot net.

TIA
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WB2WIK
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« Reply #1 on: March 01, 2010, 09:51:27 AM »

It's not too sensitive, it's just a bad idea generally.

RF sensed T-R switching works okay for continuous carrier modes like FM, but on SSB it creates huge failure rates in amplifiers because there's no possibility for using a timing loop.

I did this "mod" for one guy years ago...turns out all the RF sense circuitry was actually on the board, and a small coupling capacitor was missing to activate it.  It was obvious just looking at the board -- I didn't even have the schematic.

You may find the same thing!
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K0BG
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« Reply #2 on: March 01, 2010, 11:05:46 AM »

Building an interface requires a spare plug for the 13 pin jack. It's the same as for a Kenwood, and they cost $8. Two 2n3904 transistors, two resistors, and you can build it dead bug style inside the plug! Here's the info: http://www.k6xx.com/radio/ic706amp.html

It's also on my web site here: http://www.k0bg.com/feeding.html#keying
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KF6A
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Posts: 214




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« Reply #3 on: March 01, 2010, 11:42:01 AM »

Building an interface requires a spare plug for the 13 pin jack. It's the same as for a Kenwood, and they cost $8. Two 2n3904 transistors, two resistors, and you can build it dead bug style inside the plug! Here's the info: http://www.k6xx.com/radio/ic706amp.html

It's also on my web site here: http://www.k0bg.com/feeding.html#keying
This is why I dislike online forums. Advice not asked for and specifically requested it was NOT wanted, is given. Thanks.
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KF6A
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Posts: 214




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« Reply #4 on: March 01, 2010, 11:45:28 AM »

It's not too sensitive, it's just a bad idea generally.

RF sensed T-R switching works okay for continuous carrier modes like FM, but on SSB it creates huge failure rates in amplifiers because there's no possibility for using a timing loop.

I did this "mod" for one guy years ago...turns out all the RF sense circuitry was actually on the board, and a small coupling capacitor was missing to activate it.  It was obvious just looking at the board -- I didn't even have the schematic.

You may find the same thing!
Thanks for your concern about possible failure rates your opinion is noted. The amp will be used for FSK441 and JT6M.

So, does anyone know if the mod is the same?


TIA
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WB2WIK
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« Reply #5 on: March 01, 2010, 06:36:49 PM »

Should be, I'd say.

Have you opened up the amp to study the circuit?  The RF sense circuit of course includes a diode rectifier followed by a transistor current amplifier, there's not a lot to it.  There is normally "adjustable" dropout delay, with a pot that changes the R-C timing.

If you see all of that with two PCB holes that have nothing installed in them, just install a 220 pF (or so, not critical) capacitor and you hopefully will be good to go.
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WB2WIK
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« Reply #6 on: March 01, 2010, 06:41:32 PM »

And BTW the "failure rate" issue really can be a problem, sometimes.

Using RF sensed keying exercises the relays a lot and causes them to "hot switch," because they must have a carrier present before anything happens.

I've lost more relays in SS amplifiers due to this issue than any other.  If I'm "lucky," it's only the relays that fail and not the output transistors.  (Those have also failed due to being driven before the output relay switches.)
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KE3WD
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« Reply #7 on: March 01, 2010, 08:34:15 PM »

Alan was just trying to help you out. 

I was going to try also, but after reading your snooty reply to Alan's attempt to help you, I will leave you to your own snoot. 

enjoy

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KF6A
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Posts: 214




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« Reply #8 on: March 01, 2010, 08:43:40 PM »

Alan was just trying to help you out. 

I was going to try also, but after reading your snooty reply to Alan's attempt to help you, I will leave you to your own snoot. 

enjoy


Why would my reply offend you or anyone else when I specifically stated I was not interested in hearing about hard keying? How is his (or yours for that matter) reply helping in any way, shape or form when I specifically stated I wasn't interested in hard keying. My reply is hardly snooty and is right in line with a proper response for someone responding to something explicitly requested to not reply about. If anything YOUR reply is snooty AND off topic.

I'm the OP. I determine the topic, not you or anyone else. If you don't like the terms I've set or the topic of the thread do not click on it.
« Last Edit: March 01, 2010, 09:08:20 PM by Dan » Logged
KF6A
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Posts: 214




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« Reply #9 on: March 01, 2010, 08:46:08 PM »

Should be, I'd say.

Have you opened up the amp to study the circuit?  The RF sense circuit of course includes a diode rectifier followed by a transistor current amplifier, there's not a lot to it.  There is normally "adjustable" dropout delay, with a pot that changes the R-C timing.

If you see all of that with two PCB holes that have nothing installed in them, just install a 220 pF (or so, not critical) capacitor and you hopefully will be good to go.
Thank you for the very helpful information Steve. I have not purchased the amp yet so I have not seen the internals. I am trying to find out if this is feasible before spending the money. It sounds like it should be so I thank you again for the information.
« Last Edit: March 01, 2010, 08:54:44 PM by Dan » Logged
KF6A
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Posts: 214




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« Reply #10 on: March 01, 2010, 08:50:33 PM »

And BTW the "failure rate" issue really can be a problem, sometimes.

Using RF sensed keying exercises the relays a lot and causes them to "hot switch," because they must have a carrier present before anything happens.

I've lost more relays in SS amplifiers due to this issue than any other.  If I'm "lucky," it's only the relays that fail and not the output transistors.  (Those have also failed due to being driven before the output relay switches.)
As you've previously stated, in threads I've seen you reply to when I searched, I've also owned many "bricks", all of them used RF sensed switching and I have never had an issue with any of them. This could be attributed to the fact that I do not try nor expect QSK switching speeds and I set the delay so that there is no more wear on it than if it was hard keyed. I have never lost a relay in any of my amps, I've never blown a set of finals and I've never lost a pre-amp. I'm either doing something right or I am defying the statistical odds. I prefer to think the former.
« Last Edit: March 01, 2010, 09:10:07 PM by Dan » Logged
WB2WIK
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« Reply #11 on: March 02, 2010, 11:07:01 AM »

>RE: Mirage A1015       Reply
by KF6A on March 1, 2010    Mail this to a friend!

As you've previously stated, in threads I've seen you reply to when I searched, I've also owned many "bricks", all of them used RF sensed switching and I have never had an issue with any of them. This could be attributed to the fact that I do not try nor expect QSK switching speeds and I set the delay so that there is no more wear on it than if it was hard keyed. I have never lost a relay in any of my amps, I've never blown a set of finals and I've never lost a pre-amp. I'm either doing something right or I am defying the statistical odds. I prefer to think the former.<

::I'm not sure, but you've been fortunate for sure.  There is a difference between RF sensed keying and using an external key line, in that rigs providing the contact closure for keying an external amplifier provide that signal FIRST (so the amp's relay switches) prior to actually generating the RF signal.  The difference is only milliseconds, but it's a difference, and gives the amp relay time to switch and settle, so it's not "hot keyed."

In most high-end rigs and all Ten Tec products, that keying loop delay is programmable and can be set to properly accommodate the amplifier being used.

73

Steve WB2WIK/6
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KE3WD
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« Reply #12 on: March 02, 2010, 03:54:44 PM »

OP or not, you don't own the damn thread. 

Even given that, it is not a license to be so anal. 

Lighten up, "specifically".  OK? 
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KF6A
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Posts: 214




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« Reply #13 on: March 02, 2010, 04:09:24 PM »

I'm not sure, but you've been fortunate for sure.  There is a difference between RF sensed keying and using an external key line, in that rigs providing the contact closure for keying an external amplifier provide that signal FIRST (so the amp's relay switches) prior to actually generating the RF signal.  The difference is only milliseconds, but it's a difference, and gives the amp relay time to switch and settle, so it's not "hot keyed."

In most high-end rigs and all Ten Tec products, that keying loop delay is programmable and can be set to properly accommodate the amplifier being used.

73

Steve WB2WIK/6
I'm aware of the differences between hard keying and RF sensed (I've owned many amps of both types, VHF, UHF and HF, for many years and haven't had a problem with any of them). I respect your viewpoint and it has been duly noted.
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KF6A
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« Reply #14 on: March 17, 2010, 03:21:11 PM »

I purchased the amp and have been using it with great results for a while now. Turns out the amp has already been modified for RF sensed keying. Works FB.   Grin
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