Ameritron AL-811 Soft key

[RichardHartman]

I recently acquired an 811. The gentleman I got it from said the soft key was bad and was just using a foot pedal. I'm trying to figure out what exactly does soft key mean? Is it a buffer for overloading at key up? If so I already have an ARB 704 for my Icom. Would this work until I can get the 811 repaired?

73

KC8DVE

 

[BJ radionut]

Richard: That amp does not need an external keying unit. (interface)
I have one of those amps also, never used interface for any radio.
Then if the amp is keying via a foot switch, should be fine via TX ground from radio.
What Radio? How was the foot switch hooked up?
All the Best
Gary

 

[BJ radionut]

Soft Key is a term used to represent Low Voltage (12vdc or less) Low current circuit (milliamp range) switching to engage the internal T/R relay in the amp and is triggered by circuit in radio via cable going to the relay. (RCA jack on the amp)
This is opposite of the old Heathkit SB series relay circuit that was 120 VDC which can fry modern transceivers!

 

[NightThumper]

As Gary has stated: That amp doesn’t need an external or internal (aka Softkey). The softkey merely makes older amplifiers such as the Heathkit SB220, Drake and such amplifiers work with more modern transceiver's that can’t handle the higher current or voltage keying relay found in older amplifiers.

I use a foot switch on my AL-82 when using a radio that doesn’t have a keying circuit such as my 10 meter Lincoln II+.

A foot pedal closes/activates the keying relay by shorting it to ground. Typically the foot switch is connected to the relay jack on the back of the amplifier and is engaged via foot switch prior to keying your transceiver.

73
Brad
KE0XS
South of Pittsburgh

 

[RichardHartman]

Soft Key is a term used to represent Low Voltage (12vdc or less) Low current circuit (milliamp range) switching to engage the internal T/R relay in the amp and is triggered by circuit in radio via cable going to the relay. (RCA jack on the amp)
This is opposite of the old Heathkit SB series relay circuit that was 120 VDC which can fry modern transceivers!

OK sounds good. I will be using my Icom 7300, AL 811, MFJ 994b tuner and homebrew EFHW 80-10. The way I understand for running less power out of the amp I should still tune it for max at max drive and then then just cut back my drive level to the desired out put, is that correct? Thanks again for all your guys help with these crazy questions.


73

 

[BJ radionut]

Richard: I am, having run that amp for years off/on, this amp requires no more drive than 50w PEP.
I tune mine with about 25 watts carrier in CW mode. Then a very quick touch-up tune with 50 watts carrier.

I suggest getting the amp control cable which has the ALC cable. This assembly has two cables running from radio control point.
#1 RCA Jack marked relay
#2 ALC (also RCA jack)
The ALC helps control any over drive.
(The IC-7300 is notorious for ALC overshoot) (as many radios are)
This is a way to help control that issue
This amp should be operated (IMHO) to where PEP Output reaches about 500 watts. 160 thru 20 meters
(10/15 meters should not exceed 400 watts PEP)
It is important to watch the GRID current level when operating. Grid current should not reach higher than mid-scale on voice peaks. (again IMHO)
This will extend the life of the tubes greatly.

Icom IC-7300 Amp Relay Cable With ALC & Relay Buffer

Icom IC-7300 Amp Relay Cable With ALC & Relay Buffer | eBay

ALC is likely to cause you more frustration than good. There is an actual miniature relay inside that will switch up to 200V @ 1.5A. FYI - Color coding I use is RED for relay and WHITE for ALC. A word about ALC.

www.ebay.com

Security Measure

www.ebay.com

Good Guy! He's a Ham~!
The ALC provides a feedback voltage that comes from the amp and adjustable via rear panel knob. This small signal once adjusted correctly helps hold the drive level in check, it helps slow any big swing in drive level that can reduce tube life. This signal can also help maintain drive to keep the rig/amp operation from splattering on voice peaks.
Just a couple suggestions Richard.

I also have used 572B tubes in mine. These tubes are direct drop-in replacements for 811A's. They however are constructed much stronger than the presently available 811A's.
Thus, they are much less susceptible to the overdrive condition.
These tubes however have risen in price over the last few years dramatically.
I have had the same set of Svetlana 572B's installed for like 10 years...have used this amp on couple Field Days and gave them a workout.
These tubes are still I would say about 80%...about 450 watts...
Nobody will EVER notice the difference signal wise between running this amp at 600 watts vs. 450-500w.
All the Best
Gary

PS: I have other amps that I use normally (Drake L4B for EX

I keep this one around, because small desktop size and it is the only amp, I have that covers the 160m band, other than a Solid-State amp which I presently run mobile.

 

[RichardHartman]

Richard: I am, having run that amp for years off/on, this amp requires no more drive than 50w PEP.
I tune mine with about 25 watts carrier in CW mode. Then a very quick touch-up tune with 50 watts carrier.

I suggest getting the amp control cable which has the ALC cable. This assembly has two cables running from radio control point.
#1 RCA Jack marked relay
#2 ALC (also RCA jack)
The ALC helps control any over drive.
(The IC-7300 is notorious for ALC overshoot) (as many radios are)
This is a way to help control that issue
This amp should be operated (IMHO) to where PEP Output reaches about 500 watts. 160 thru 20 meters
(10/15 meters should not exceed 400 watts PEP)
It is important to watch the GRID current level when operating. Grid current should not reach higher than mid-scale on voice peaks. (again IMHO)
This will extend the life of the tubes greatly.

Icom IC-7300 Amp Relay Cable With ALC & Relay Buffer

Icom IC-7300 Amp Relay Cable With ALC & Relay Buffer | eBay

ALC is likely to cause you more frustration than good. There is an actual miniature relay inside that will switch up to 200V @ 1.5A. FYI - Color coding I use is RED for relay and WHITE for ALC. A word about ALC.

www.ebay.com

Security Measure

www.ebay.com

Good Guy! He's a Ham~!
The ALC provides a feedback voltage that comes from the amp and adjustable via rear panel knob. This small signal once adjusted correctly helps hold the drive level in check, it helps slow any big swing in drive level that can reduce tube life. This signal can also help maintain drive to keep the rig/amp operation from splattering on voice peaks.
Just a couple suggestions Richard.

I also have used 572B tubes in mine. These tubes are direct drop-in replacements for 811A's. They however are constructed much stronger than the presently available 811A's.
Thus, they are much less susceptible to the overdrive condition.
These tubes however have risen in price over the last few years dramatically.
I have had the same set of Svetlana 572B's installed for like 10 years...have used this amp on couple Field Days and gave them a workout.
These tubes are still I would say about 80%...about 450 watts...
Nobody will EVER notice the difference signal wise between running this amp at 600 watts vs. 450-500w.
All the Best
Gary

PS: I have other amps that I use normally (Drake L4B for EX

I keep this one around, because small desktop size and it is the only amp, I have that covers the 160m band, other than a Solid-State amp which I presently run mobile.

In the string up above I mentioned that I had Ameritron ARB704(12) for Icom. I think you stated that it didn't need a buffer but from what I understand in this reply is I should have the buffer and ALC control because of the 7300. If I am correct the ARB704 will do exactly what your suggesting I buy from Ebay. It has an Icom control cable to run from accessory on the 7300 and cable to run from the alc on the 7300 direct to the 704. Then the 704 has an amp out and alc out to run direct to the 811. Is this ARB 704 going to achieve what your suggesting? I just want to make sure I'm not missing something. Thank you.


73

 

[BJ radionut]

Richard: Sorry did not return answer sooner. I had to look at specs for that unit. (Never used one that I remember)
Only had my IC-7300 for like 3 weeks sold it.
MFJ, says as long as the correct cables are used it should work.
Thus, that DIN Plug connection to the IC-7300 ...then to DIN connection on control interface...then 2/RCA to RCA cables (simple audio style) for the relay and ALC should be done deal.
The ALC feedback voltage must just be a feed-thru coming out of the control interface (no isolation).
Thus, the control knob on back of amp should work to control drive.
GL
All the Best
Gary

 

[DavidSmit]

Hello, friends! Please tell me on which ferrite ring the neutralization transformer in AL 811 is made (ring material) Thank you!