[Boatanchors] AM linear question

[Dennis DuVall]

The process of setting up a linear amplifier for AM is complicated by the requirement that the amp be first adjusted for operation at the PEAK power level expected to be encountered which, in turn requires an RF drive source capable of providing this.   This creates a problem if a small rig like a Ranger or an Elmac AF-68 is used, neither of which is capable of providing sufficient CW power to properly tune up the amplifier (presuming GG 3-1000Z, pair of 3-500Zs or equivalent here).  When I run  my HB 3-1000Z setup with an AF-68 I tune up the amp using my Cubic Astro 103 which can provide any value of CW 0 - 100W.     As someone else pointed out modern SSB rigs that offer an AM option conveniently cut the carrier level back automatically when switching to AM after tuning up in the CW mode.  

I've considered building up a screen or suppressor modulated AM exciter specifically for use with the linear.  Grid modulated rigs, of course, have to be tuned up just like a linear, i.e., loaded and tuned to the CW level and then cut back to 1/4 of this for talking, thus providing the tune-up and operate drive values required by the linear. 

Alternately, however, there is a way to tune up a big linear with a small rig like a Ranger or Elmac. The technique involves use of a loud, verbal utterance containing a long string of repetitive voice peaks and tuning the linear to maximize the output amplitude of these.  Many northeastern hams will remember the YYYEEEEEEEEERRRRRRRRIIIIIIIIII tune-up wail used by one well know AMer. 

Dennis D.  W7QHO
Glendale, CA

*************
> On Dec 9, 2015, at 6:56 PM, Bry Carling <bcarling at cfl.rr.com> wrote:
> 
> Yes, and in fact the majority of commercial broadcast transmitters nowadays use low level modulation fed to a linear amplifier.
> 
> Best regards - Brian Carling
> AF4K Crystal Co.
> http://af4k.com <http://af4k.com/>
> 
> Tel: 321-262-5471
> 
> 
> 
> 
>> On Dec 9, 2015, at 7:23 PM, WA5VGO <hbrnut at suddenlink.net <mailto:hbrnut at suddenlink.net>> wrote:
>> 
>> I'm not saying it can't work. It can work well. The problem is, most commercial amplifiers don't have the cooling and power supply necessary to do the job, and there is a large group of guys out there that have no idea of what it takes to tune a linear amplifier for AM. The guy running the 811A's was driving it with a B&W 5100B running full tilt. These guys get a 50-100 watt AM rig, hang an SB-200 on the tail end of it, tune for maximum output and let it rip. 
>> 
>> Darrell
>> 
>>> On Dec 9, 2015, at 6:13 PM, Paul Baldock <paul at paulbaldock.com> wrote:
>>> 
>>> Correctly adjusted linear amplifiers and AM are an excellent combination and should be encouraged. Most of the modern 100W SSB rigs when set to AM will automatically limit the carrier to 25 watts, drive your typical well adjusted 10dB linear amplifier such as a pair of 3-500Zs and you have 250 watts of carrier with a potential for 1000+ watts PEP, and a nice clean signal.
>>> 
>>> With this combination we have 1000s of amateurs that can contribute and extend the life of Amplitude Modulation on the bands. If you are trying to limit AM to Vacuum Tube Rigs and High Level Modulation then AM operation will dwindle to even less than it is now.
>>> 
>>> - Paul  KW7Y
>>> 
>>> at 03:48 PM 12/9/2015, WA5VGO wrote:
>>>> Generally speaking, linear amplifiers and AM are a bad combination.
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