TUBE AMP CABLE

[Robalo]

When you use tube amps, what kind of cable would you prefer? just the amp relay cable, or with the ALC?

ex:
IC706MK2-TL922A

I don't have any of these, but I was listening to a conversation and sparked my curiosity. what would be better?

 

[Captain Kilowatt]

that would really depend on what the amp could handle for drive levels. If the amp could accept the full output from the exciter without being over driven then ALC is not really necessary. The ALC connection is used when the amp can be fully driven by less than the maximum power available from the exciter. Example: the amp will produce full output with 70 watts of drive but you forget to reduce power from the exciter and hit it with a full 100 watts. The first you know about is when some guy 15 KHz away comes onto your freq. and tells you that you are splattering all over the band because you were too busy to watch the grid current. :headbang

 

[hookedon6]

i use both. a piece of cable and a couple RCA jacks are cheap.

even if, your amp needs (say) 50 watts to drive it to full output, and you have adjusted your exciter to 50 watts.

there is still a good chance that you will EXCEED the 50 watts into the amp.

almost all exciters will "OVERSHOOT" when they first key up.

no, you won't see it on an AVG or a PEP meter, you may or may not see it on a scope, but it still does happen.

 

[SIX-SHOOTER]

Keying Cables?

I NEVER use the ALC with my AMERITRON 811H just the keying line from my HEIL FS-2 footswitch & an AMERITRON ARB-704 keying buffer.About 45 watts of drive is all I need so that's why NO ALC connection!

SIX-SHOOTER

 

[wavrider]

Depends on the amplifier and the tube.

Tetrode, Triode, tube etc etc, if there is no risk of over driving the amplifier and "splattering" the band then no alc needed as long as the Plate current and Grid current are within manufactures ratings.

 

[hookedon6]

I NEVER use the ALC with my AMERITRON 811H just the keying line from my HEIL FS-2 footswitch & an AMERITRON ARB-704 keying buffer.About 45 watts of drive is all I need so that's why NO ALC connection!

SIX-SHOOTER

gee, i dunno, this is a quote from the guy that DESIGNED your amp in reference to their operation with ICOM radios.

Using power controls in most radios to reduce drive more than 50-70% for amplifiers is generally a bad idea. This is because many exciters (radios) have ALC-overshoot issues. The ALC or power overshoot problem worsens as output power is reduced below maximum.
There are exceptions. The Yaesu FT1000/ FT1000D has a drive control and a power control that functions in all modes. Backing the drive control off so ALC is barely registering assures there is no overshoot.

On the other hand some ICOM rigs, no matter how they are adjusted, will overshoot beyond the factory rated power levels. I have an IC-706 that will overshoot to 130 watts or more when set at any power level, even 20 watts! I had an IC-775DSP that would go over 200 watts of very short RF peak output power when set at 75 watts. These radios, or other radios like them, can trigger arcs in amplifiers and are generally rough on components.


Tuning loading RF amplifiers tune PA tank adjustments

like i said, a cable is cheap

 

[Toll_Free]

You need to do the 9 volt battery with a pot trick.

There is ALC overshoot. ALC is a joke, it's not even worth hooking up.

Create yourself a power control that plugs into your ALC jack on the RADIO. Run POWER and AM CARRIER wide OPEN on the radio, then use the pot on the 9 volt battery to set PEP or carrier levels.

No more ALC overshoot because the ALC is ALWAYS at a fixed voltage, no more waiting for the cap in the linear's ALC lead to charge up, losing 4 or 5 half-cycles in the process (overshoot).

w8ji has the schematic on his AM website.


--Toll_Free

 

[Robalo]

thanks guys. 73s