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Author Topic: Drake TX to Ameritron Amp  (Read 1372 times)
N3WAK
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Posts: 279




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« on: February 15, 2010, 08:14:07 AM »

Hello Drake and Ameritron Elmers.  I am a neophyte, so would appreciate your expertise.  

I want to buy my first--and hopefully last--amp.  I have weighed all the pros and cons of getting an amp of modest power, and I understand the philosophy behind spending money on improving my antenna vs. buying an amp.  So, I have already made the decision to buy an amp.  

Now for my questions.  The amp is an Ameritron ALS-600 solid state 600 watt amp.  I will be using the amp with two rigs, but the one I can't figure out is how to hook it up to a Drake T-4XB transmitter through the Drake AC-4 power supply.  

I have spoken to a technician at both Ameritron and at DX Engineering but neither was familiar with the Drake B line.  

(1)  Should I use a buffer between the amp and the transmitter?  If so, do you have a recommendation for one I could buy--the ARB 704 from Ameritron, the one from Harbach Engineering, or one from The Heathkit Shop?  Or a different one?  

(2) If I don't use a buffer, do I simply hook a shielded audio cable between the AGC jack on the AC-4 and the ALC jack on the amp?  

(3) If I don't use a buffer, do I hook a shielded audio cable between the VOX relay on the AC-4 and the relay phono connector on the amp?  (I have tracked down both the two pin Drake plug and John Kriner's kit to change the two pin Drake female to an RCA female, so I have two ways to skin that cat.)  

(4) If I DO use the buffer, do I run the above AGC/ALC cable directly between the AC-4 and the amp, but run the relay cable between the VOX jack and the buffer and then from the buffer to the amp?    

My guesses are:  a) I in fact can directly run the AGC/ALC cable from AC-4 to amp, but b) cannot or should not run the relay cable directly from AC-4 to amp.  So, I'm kinda stuck right now, and don't want to order the amp without knowing in advance how to hook it up, and whether I need a buffer, too.  

The other amp I've considered is the Ameritron 811, but the no-tune feature of the SS amp really appeals to me.    

Thanks in advance for any help you can offer me.  73, Tony  N3WAK
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KA5N
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« Reply #1 on: February 15, 2010, 08:40:29 AM »

The reason keying interfaces are needed are usually because one is trying to key an old amplifier with a high voltage relay using the relay (or solid state circuit) of a modern transceiver.  In your case you are going the other way where the amplifier requires that a low voltage needs to be pulled to ground.
The Drake requires an external antenna relay with an addition contact closure to key the amplifier.  This is explained in the manual. If you follow the manual no keying interface is needed.

I would be much more concerned about driving the Ameritron amp with the Drake.  The Drake has no way to reduce the power output (just lowering the mike gain is a non-started that has been discussed many times on this forum)and you have no ALC circuitry.  With the power available from the Drake you run the risk of severely overdriving the Ameritron and probably damaging it.  So if you persist in going this route you are going to have to build a high power attenuator pad to get the drive down to a reasonable level.  You will still have the possibility of high power spikes causing problems.

In short this pair is not a good match.

Allen
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KA5N
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« Reply #2 on: February 15, 2010, 08:41:57 AM »

I reread your post and I mispoke about the ALC.
Sorry
Allen
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WB2WIK
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« Reply #3 on: February 15, 2010, 06:03:07 PM »

>Drake TX to Ameritron Amp       Reply
by KB3TLC on February 15, 2010    Mail this to a friend!
Hello Drake and Ameritron Elmers. I am a neophyte, so would appreciate your expertise.<

::I've actually done this (B line with ALS-600) so let me try to answer you as accurately as possible.

>I have spoken to a technician at both Ameritron and at DX Engineering but neither was familiar with the Drake B line.

(1) Should I use a buffer between the amp and the transmitter? If so, do you have a recommendation for one I could buy--the ARB 704 from Ameritron, the one from Harbach Engineering, or one from The Heathkit Shop? Or a different one?<

::Absolutely NOT required, just a waste of money.  The ALS-600 uses 12V low current keying, and the T-4XB uses a keying relay that can actually support high voltage, higher current keying.  You certainly CAN use a keying interface, but there's absolutely no reason to.

>(2) If I don't use a buffer, do I simply hook a shielded audio cable between the AGC jack on the AC-4 and the ALC jack on the amp?<

::Again, you don't need any sort of buffer for this application.

>(3) If I don't use a buffer, do I hook a shielded audio cable between the VOX relay on the AC-4 and the relay phono connector on the amp? (I have tracked down both the two pin Drake plug and John Kriner's kit to change the two pin Drake female to an RCA female, so I have two ways to skin that cat.)<

::The answer is "yes."  VOX 2-pin connector to the amplifier's keying line (RCA phono) and a separate (preferably shielded) cable from the "AGC" connector on the Drake to the ALC output connector (also RCA phono).  Works fine and IS compatible.

>My guesses are: a) I in fact can directly run the AGC/ALC cable from AC-4 to amp, but b) cannot or should not run the relay cable directly from AC-4 to amp.<

::Not true, why would you guess that?  The Drake is set up to key any kind of amplifier made by anybody.  It uses a power relay for this and could probably key the AC line to many amplifiers if it had to (hi hi).  Don't worry about a keying interface, not required.

>The other amp I've considered is the Ameritron 811, but the no-tune feature of the SS amp really appeals to me.<

::The only drawbacks to the ALS-600 are:

1.  To use it on 10/12 meters, there's a lot more to that modification than just "clipping a wire" like in the AL-811.  Ameritron can supply you with the conversion kit, but I've done this and it's not a 2-minute job.  More like 30 minutes, and you have to take the amp apart to do it.

2.  The amp is very easy to overdrive, especially with a tube rig like the T-4XB which can output about 120-130W.  The ALS-600 can accept about 100W PEP drive (maybe) but you NEED to connect the ALC and properly adjust it to prevent overdriving the amp; otherwise you can damage the amp.

3.  The ALS-600 has no "tunable output" of any kind, so it really needs to look into a very well matched antenna load.  As such, with MOST antennas on 80m or 160m, and with SOME antennas on other bands, you WILL need an antenna tuner to use it.  If you have beams and such on the higher bands that have a great SWR, no sweat.  But on bands like 80m and 160m where almost no  kind of antenna provides a decent match across the band, the ALS-600 will "fold back" in output power as soon as it doesn't like the load, which starts happening at maybe 2:1 VSWR.  If you have an 80m dipole tuned for the middle of the band with a great SWR at 3750, the ALS-600 will like that; however that same dipole will be 3:1 or more at band edges, and it will NOT like that, and throttle power back to a couple of hundred Watts or less under such mismatch conditions.

A tube amp with a pi-net or pi-L output circuit will accommodate such mismatches all by itself and not need a tuner: You tune the amp for maximum power transfer and up to 3:1 or possibly even 4:1 it will be reasonably happy, saving the cost of an external tuner.

The tube amp is also harder to overdrive; however a T-4XB WILL overdrive an AL-811 also, so you'll still need the ALC connection, and proper setting of the ALC level on the amp.
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N3WAK
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« Reply #4 on: February 18, 2010, 05:54:25 AM »

Allen and Steve--Thank you for your time answering my questions!  Based on your responses, and the recommendation of WB4HFN, I've decided to get the plain-vanilla Ameritron 811 600 watt tube amp.  For a lot of reasons the no-tune SS amp appealed to me--primarily laziness, and, secondarily, it would be easy to ship to be repaired--but I'll give the tube amp a try.  I have tracked down a cable with the Drake two pin plug on one end and a phono connector on the other, so I should easily be able to hook the amp to the T-4XB through the AC-4.  I won't use a buffer with that rig, but I did order one so that I have the option of unhooking everything and reconnecting the amp to my (currently dead) Icom 746pro.  With my coax-fed resonant inverted vees, my SWR is pretty low, and I have a Drake tuner if I need to use it (although with unbalanced output).  I will also take care not to overdrive the amp.  All is good, and thanks for the Elmering!  73, Tony N3WAK
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K9FON
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« Reply #5 on: February 18, 2010, 11:54:29 AM »

The Drakes are known for being a little "wild" in the power output category. That solid state amp might be a bad choice. You would have been better off getting a high drive amp like the L4B or a Heathkit SB 220.
If you want to key the amp with the rig simply use a footkey.
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WB2WIK
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« Reply #6 on: February 18, 2010, 06:43:17 PM »

Tony, the AL-811 will do the job; however if you didn't order it yet, consider the AL-811H.  It's a better amp -- not just for the extra power, but it's a better and more stable design.

This is "hearsay" to some extent, as I don't even own one.  However, the designer of both these amps is a frequent poster here on eHam.net and he says "buy the AL-811H" because it's neutralized and just a better performer.
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K6LO
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« Reply #7 on: February 18, 2010, 06:54:15 PM »

My Drake isn't wild.  Mostly it just sits there and puts out about 100 watts.
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