The AM Forum

I bought an Ameritron AL811H amplifier recently.....and it seems rather nifty, no doubt! The kind of construction that I like! I think that the cost of buying the parts separately and engineering my own design would probably cost double.

But I have a question and nothing is mentioned in the manual about it.

When my transceiver is in receive mode, is there some relay or some mechanism in this amplifier which disables the high power amplifier and connects the microvolt received signal to the transceiver?

I noticed the audio grade cables that come with the amplifier, their purpose is to interface the amp to a given transceiver's ALC and Relay terminals. My Kenwood has no such connections.

Will this be a problem for me?

Thanks and 73s
geo VE3GZB

George,

The relay in the Ameritron will connect the antenna straight through (bypass mode) during receive so you do not need any additional type of antenna relay. 

I am sure your Kenwood has the proper connections for ALC and relay control, generally through an accessory socket on the back.   Which transceiver model do you own?  I have a TS-520S, TS-820S, and TS-940 all of which have the proper connections for ALC and amplifier relay control.

The connections on the back of the Ameritron are RCA type audio connectors. The transceiver I have is a Kewood TS-830S. It has these DIN connectors on the back.

That amp is notorious for short tube life and the factory has had several revisions.

The first thing to check is the four 50 Ohm resistors that are connected to a pair if terminal strips on the far left of the tube sub chassis, they open when a tube arcs or is overloaded. You may not even be aware of an open and the other tubes are now sharing the full load. Also note that the genius who designed it didnt bother with a plate choke bypass cap. A 4700pf @ 3Kv is a good addition.

The Chinese 811's used are pure garbage. Id replace them with either NOS US made 811A's or Chinese 572B's which will last forever at that voltage.

Carl

QSL. I'll look out for these things.

George,

You will have to either build the cables or buy one already made.  Most of the JA gear uses DIN connectors for access to accessory equipment.

Thanks! Since I'm not going to find DIN connectors anywhere here to save my life, I'll look for a finished cable set on evilBay.

73s geo VE3GZB

Try RadioWorld, http://radioworld.ca/index.php? in Toronto.

My TS-820S has a "Remote" connector on the back, an Octal plug. Pins 4 and 5 are used to activate the power amp T/R relay.

Phil - AC0OB

If the Kenwood is like the Yaesu's, you only need one pin on the DIN connector to key the amp. You don't need a DIN plug for this. Just shove the appropriately sized wire into the correct slot on the transceiver's DIN connector and you're done.

The Kenwoods I've paid attention to float the ground connection so 2 shoved wires will be necessary.

For the faint of heart ebay has lots of these cables.