Failing to hook up my amp…Sigh

[Nashua Area Radio Society]

Hi clubbers,

I have an Icom 7300 at home.I’m currently testing out an Ameritron AL-80B amp. I was all set to go but now I’m confused. When I looked in the 7300 full manual, it states that I need to establish an ALC connection from the radio to the amp (using an RCA cable) and a “SEND” connection from the radio to the amp (again using an RCA cable) which presumably sends a small DC voltage to the amp to let it know to do it’s thing when I key down the PTT button. Here’s a pic of the back of my 7300: (the 2 ports I’m talking about are in the top-middle of the unit, with the cable hanging out. The left port is the ALC port…with the cable in it…and the right port is the “SEND” port…with the cable hanging.)

[attachment file=5828]

Now, on the back of the amp, I have a similar ALC port, but nothing akin to the”SEND” port on the 7300 (My antenna is currently unplugged). Here is a pic of that:

[attachment file=5829]

So my question is, where on the amp do I put the other RCA cable that comes from the “SEND” port of the 7300?

 

Attachments:

You must be logged in to view attached files.

[Fred Kemmerer]

Hi Brian,

Generally, most amplifier manufacturer’s do not recommend the use of ALC because its easy to create lots of distortion products and splatter this way. The best thing to do is to just use and RCA pin cable to connect the Key out on the IC-7300 to the key in on your amplifier. Before you test, turn the power output on your radio down to 5W or less to start with and put a dummy load on your amplifier. Key the radio up and confirm that you amp is keying up and putting out more than the 5W in from the radio. Next, adjust the power out on the IC-7300 until you amp produces slightly less than its rate power output. This is the correct drive level for you amp and you should have a nice, clean signal on the air this way. Note that the best drive level may be a little different as you switch bands.

ALC just causes you amp to dial back its output if the Tx is overdriving it. The problem is that the combination of the amp and the transceiver doesn’t dial back in a completely linear way. This can cause significant distortion and resulting splatter on the air. When you see someone who is very “loud” but seems to have an overly wide signal on the air, more than likely they have ALC connected and are overdriving their AMP in hopes that ALC will somehow correct this. It cannot.

Have fun with your new amp!

73,

[KU1V]

Thanks for the ALC info.  I have never used it because I did not understand and reading some of the amp manuals for set up really was confusing.

Hope my assessment is correct,  but where  I frequently use head set and boom mic and made my connection on my 7300 by removing the mic and installing a special Heil plug for my headset and mic, along with a foot pedal.  This arrangement gives me a buffer for my amp if amp ever has a voltage problem on the keying circuit to add protection to the radio.  Apparently this foot pedal has a delay circuit which keys amp ahead of radio to prevent hot switching that maybe of concern with my old type amp.

What a great radio.  73

 

[Nashua Area Radio Society]

Thanks Fred and Mike for the input. Since I have the long weekend, I’ll try playing around with it to see how well it works. So much to learn!! And I mean that in a good way.

[Fred Kemmerer]

FB Brian. If you get it working, put it on the air as part of our 37th Anniversary Event this weekend. The combination of the amp and the special event should help you stir up more interest that you’re used to.

73,

[Author]

Posts