Cutting jumpers for AL-80B for 17 meters

[kb1ngb]

I recently acquired an Ameritron AL-80B. I've not been able to get more than a 150 watts out of it on 17 meters. Seems fine on everything else.
I was told there are some jumpers that need to be adjusted or cut in order to get the most out of 15/17. This isn't covered in the manual. Anyone know anything about this mod or have a link to a page that might describe it?

Thanks in advance
73
Mark

[K7KBN]

You might want to check the SWR your exciter is seeing when you use 17 meters into the amplifier. #The tuned input circuitry uses common components for both 15 and 17, and you have to adjust the input to whatever point works best for you on both bands. #If the input SWR is too high, your exciter may be folding back on its output, reducing drive.

I find that the internal tuner of my IC-738 is a good cure for the exact same problem with my AL-1200.

[kb1ngb]

1:1 is easily obtained on the manual tuner with the amp on standby. Also while on standby, the internal tuner on the FT 2000 will bring the swr on the radio to 1:1 regardless of how much drive is applied. However, once the amp is turned to the operate position the swr on the radio jumps to 3:1 so you are right, the amp is affecting the swr although it stays 1:1 on the external tuner regardless of how much drive is applied. The manager at HRO said there is a jumper that needs to be cut but he can't find the data sheet on it in order to remedy this. If you can clarify how you use the internal turner I'm all ears. Sorry for the questions of a relative newbie.

[ad5x]

No - There is no wire to cut to make 17 meters work better. The high SWR is turning down your transmitter drive. There is a 15/17 meter input coil you can adjust for best SWR. You need to find a compromise adjustment for best SWR on both 15 and 17 meters. Or use an in-line antenna tuner between your radio and the amplifier to "fix" the SWR.

Phil - AD5X

[kb1ngb]

Here's another stupid question...how is this coil identified and adjusted? Obviously I'm assuming you adjust it and then re-apply power, attempt to tune and adjust further without power until you achieve the compromise point? Being new in general and even newer to amps I don't want to touch something and either damage myself or the equipment. There is no discussion of this in the manual.

Thanks for your advice and patience with a newbie!

[K7KBN]

If you look on the back of the amplifier you should see a number of small holes labeled "80", "40" ... one for each band. The 15 meter hole might say "15/17" or something like that. You will need to find a NON-metallic alignment tool, probably around 0.1". You insert the tool in the hole and carefully line it up with the slug in the coil, into which it should fit securely.

Then, with the amplifier connected to a dummy load, you simply adjust the coil for the best compromise for 15 and 17 meters - and yes, this has to be done with the amplifier operating. Not necessarily at full power, but it has to be operating. Watch the SWR meter on the exciter and find the happy medium.

[K7KBN]

My first Ameritron amplifier was an AL-811H, and I still have the manual. I checked, and it shows the rear view of the unit with input coil adjustments for 160, 80, 40, 30/20 (uses same circuit), 15/17 (again) and "AUX" (which is 10/12). My present amplifier is an AL-1200, about 12 years old. The manual doesn't show these adjustments at all, and neither manual describes how to adjust them.

The "jumpers" that the sales guy was talking about were probably internal wires that inhibit operation on 10/12 meters. At the time these amplifiers were designed and marketed, FCC regs prohibited them from working that close to 11 meters. As most hams who've been licensed for more than a few years have found out, this "modification" involved removing a particular green wire, which Ameritron will point out if you send them a copy of your license. If yours works on 10/12 meters, this wire would seem to have been removed already.

Anyway, I suggest you check out the input coil adjustments and/or using the FT-2000 internal tuner to see if it will enhance the drive to the amplifier on 17. As I said, that works for my purposes. Good luck!

Incidentally, in the back of the manual you should find a schematic labeled "Input Board" or something like that. That will show you just how the circuit is configured for each switch position/band(s).