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AL-811 amp and magnum 257hp

O

Onthecoast

W9WDX Amateur Radio Club Member
Sep 13, 2012
256
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I'm using my magnum 257hp as my primary rig for 10 meter work. I recently acquired a like new AL-811 for cheap and was trying to figure out how to get the radio to key the amp but was at a loss
 
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Onthecoast said:
Yeah I was thinking about that but was hoping I would be able to get the radio to do it
Click to expand...

well you need to make a circuit that takes the RF in one connector, passes it back out (to the amp) and ALSO senses the RF coming in and completes the circuit, this would take the place of the foot switch
 
binrat said:
Simple approach would be a foot switch to key the amp.
Click to expand...

thats the best option available for that rig. a foot/hand switch that first keys the amp, and then keys the rig, and verse visa on unkeying.

or get a radio with a real amp keying circuit
 
There's another way this would work, you'd just need to drill a small hole in the back of the radio to accommodate a 1/8" mono jack.


Take a small surface mount relay with a 12VDC coil (Radio Scrap has these in stock) run a wire from the PTT pin on the radio to the anode (non banded end) of a 1N4148 switching diode. Take the cathode of that diode (banded end), and run it to one of the coil leads on the relay. Then run a wire off the other coil lead on the relay and put it to a +12V source in the radio. This will activate the relay when keying the mic.

Run 2 wires off the normally open set of contacts on the relay to a 1/8" mono jack. You can then make a patch cable that has the 1/8" plug on one end, and an RCA plug on the other that will plug into the amp. With this setup, this will allow you to key the amp up when you key the mic. The only thing you'll have to do is find a location for the 1/8" jack.

I do this on all my bases, since I have an AEA LA-30 linear that requires the same type of PTT switching as your AL-811.


Hope this helps, and good luck!

~Cheers~
 
Last edited:
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As Hookedon6 mentioned, make SURE the amplifier is keyed BEFORE the radio. Doesn't have to be by much; 10ms should be plenty. AL-811s don't generally take too kindly to being hot-keyed.
 
ExitThirteen said:
There's another way this would work, you'd just need to drill a small hole in the back of the radio to accommodate a 1/8" mono jack.


Take a small surface mount relay with a 12VDC coil (Radio Scrap has these in stock) run a wire from the PTT pin on the radio to the anode (non banded end) of a 1N4148 switching diode. Take the cathode of that diode (banded end), and run it to one of the coil leads on the relay. Then run a wire off the other coil lead on the relay and put it to a +12V source in the radio. This will activate the relay when keying the mic.

Run 2 wires off the normally open set of contacts on the relay to a 1/8" mono jack. You can then make a patch cable that has the 1/8" plug on one end, and an RCA plug on the other that will plug into the amp. With this setup, this will allow you to key the amp up when you key the mic. The only thing you'll have to do is find a location for the 1/8" jack.

I do this on all my bases, since I have an AEA LA-30 linear that requires the same type of PTT switching as your AL-811.


Hope this helps, and good luck!

~Cheers~
Click to expand...

Definitely helps a lot. Is there a way to incorporate a delay?

BJ radionut said:
60 watts drive MAX....on SSB
20 watts drive........... CW/AM
Run the Amp at 500 watts out and she will serve you well
All the Best
BJ
Click to expand...

Sounds like solid advice and a solid plan

n0zna said:
get a relay from mfj,i use the one from them on my ft450d and worked great,ran a fl2100b for yrs...73 Foot switch is good too...
Click to expand...

Does the relay buffer do rf sensing though?
 
gee,.....you must have gotten a REAL deal on the 811,

FWIW, I would either sell the radio and get a radio with an installed rca jack, designed to carry the 12 VDC (directly to ground) amperage....

or sell the amp and get an RF sensed keyed amp.;)


just a question,..... does the 811 even have the 10 meter board installed?
 
In some cases you may want to drive the amp with another radio that would not be modified. Sometimes it makes more sense to install a simple RF sniffer circuit inside the amp to make it key with any radio. You can do this with a TIP-120 Radio Shack transistor and a 1N60 germanium diode across the base and emitter connection (black band on the base).

Ground the emitter. Connect the collector to the center of the existing RCA key line (side of relay coil that needs to be grounded to key). Loosely couple the base to the RF input connector. Do this by wrapping an insulated wire around the wire already connected to the RF input jack. Use just enough wraps to make the amp key at the lowest drive level you will use (3 or 4 wraps should be close).

If you use it on SSB or with reduced carrier on AM you may need to add a small delay. Do this by adding a small electrolytic cap between the collector and ground. The larger the cap, the longer the delay to unkey. I'd start with 100 mfd because this amp does not require a lot of current to key the relay. You do not have to mount the TIP-120 on a heatsink.

PS: If the amp does not have 10 meters, just cut the green wire on the input wafer of the bandswitch.
 
hookedon6 said:
gee,.....you must have gotten a REAL deal on the 811,

FWIW, I would either sell the radio and get a radio with an installed rca jack, designed to carry the 12 VDC (directly to ground) amperage....

or sell the amp and get an RF sensed keyed amp.;)


just a question,..... does the 811 even have the 10 meter board installed?
Click to expand...

I'd say it was a pretty good deal. Not a steal but half price for an unused 811. I thought that was a fair deal.

It is 10m capable but it is not the export version. You have to cut the green wire.


Shockwave said:
In some cases you may want to drive the amp with another radio that would not be modified. Sometimes it makes more sense to install a simple RF sniffer circuit inside the amp to make it key with any radio. You can do this with a TIP-120 Radio Shack transistor and a 1N60 germanium diode across the base and emitter connection (black band on the base).

Ground the emitter. Connect the collector to the center of the existing RCA key line (side of relay coil that needs to be grounded to key). Loosely couple the base to the RF input connector. Do this by wrapping an insulated wire around the wire already connected to the RF input jack. Use just enough wraps to make the amp key at the lowest drive level you will use (3 or 4 wraps should be close).

If you use it on SSB or with reduced carrier on AM you may need to add a small delay. Do this by adding a small electrolytic cap between the collector and ground. The larger the cap, the longer the delay to unkey. I'd start with 100 mfd because this amp does not require a lot of current to key the relay. You do not have to mount the TIP-120 on a heatsink.

PS: If the amp does not have 10 meters, just cut the green wire on the input wafer of the bandswitch.
Click to expand...

10/12 is now available with the cutting of the switch. I'm a tech right now so that's all I have since I don't know CW yet.

I'm currently using the ARB70412 to key the amp with my IC-7000 but I would like to move it to the car and the amp will have to stay behind. Not really mobile size.
 

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