Print

[W7TMD]

I just got a new to me AL-80b and I noticed the SWR between the radio and amp was over 2.5 on 15/17m when I engaged the amp.
obviously it has low output as well.(The antenna has a low 1.5 SWR)
  IS something wrong with the amp or is this normal?  The amp is tuned for highest wattage out. The ALC is not connected.
The rest of the bands are fine and have a low SWR 160m through 20m between the transceiver and the amplifier.

Thanks for any helpful advice!
Tom

[AA7IS]

It does have tuned input.
It could be that the previous owner had no need for that particular band and never noticed it from the very beginning.
It wouldn't be the first time a Amp came out of Ameritron not quite 100%.
I would do a visual inspection of the tuned coil and the caps to look for any obvious issues like overheating arcing etc..
You may just need to tune the slug for a low SWR on the input side.

[W7CXC]

The input should be "tuned" for either 15 or 17 for lowest swr or you may split the difference and use the tuner from the exciter rig ( if it has one) to make a match. It will not have a low input swr on 15 and 17 with the same setting.  Just the way it is built. Fine amp and if you take care of it will last a LONG time. Happy with mine for sure.

[W1NK]

You *might* (can?) get an acceptable (not flat) input SWR on both bands.  It will take some tweaking of the input coil and going back and forth between 15 & 17.

Speaking of the input coil, please be sure to use a plastic tuning tool (available from DXE) and not a metal one.  You'll run the risk of breaking the slug with the metal tool.

Frank, W1NK

[N4OI]

As stated, you may want to retune that 15/17m selection...  Personally, I would focus on 15m since it does not make much sense to me to use an amp on 17m...  Just sayin'   

73, Ken

[W7TMD]

Thanks for all the helpful advise! Its very appreciated!!

[W1QJ]

The AL80b did at some point have two removable links and the input board. It’s little known because I don’t believe it’s discussed in the manual.  The links can be opened up by snipping  the two jumpers.  This is supposed to allow the 15 meter input circuit to tune 17 meters a lot better with a low swr than obtainable without snipping the jumpers.  Of course once jumpers are snipped the 15 m input is now the subordinate band for best swr.