[Amps] Why not use the ORANGE button?

[Roger (K8RI)]

On 5/23/2015 9:37 PM, Charles Henry wrote:

I wanted a full size rig and the FT5000MP is all of that.  It takes 
about the  same 60 watts in class A to get the legal limit out of my 
DX-2sp.  75 watts is max for class A at which the amp draws the least 
power.  In class A it dissipates the most power with zero signal.

There is a specific sequence for setting up the audio and drive for the 
5000MP just as there is for Icom and Kenwood rigs.  I don't know about 
the 990 Kenwood, or the new, $15,000 Icom, but even on class AB1 the 
Yaesu is much cleaner than older rigs with little overhead.  I would 
assume the Kenwood and new Icom benefit from backing off on the drive 
and a proper set up with little customization

As to the K3, I didn't see any complimentary comments relating to the 
quality of the transmitted signal. To the contrary, I did see complaints.

Unless you can listen to an A/B comparison between the two rigs "on a 
quiet band", most comparisons would mean little. I can state the Yaesu 
is rated with a cleaner signal.  Of course, driving the amp with only 
60-70 watts AB1 gives a pretty clean signal as well as it's well away 
from the compression knee and there are no leading waveform spikes to 
drive the amp into saturation.

Jim had it correct with those rigs running 100 watts when capable of 
200. They take advantage of that headroom.

It seems as if we are passing on the old habits from generations back of 
squeezing every db possible out of of a circuit/final. Tune the final 
properly whether a Triode, or Tetrode and don't drive SS amps anywhere 
near that compression knee. Yes the Orange/Red button (the one on mine 
is decidedly orange) makes a difference on an analyzer.  Does it make a 
difference to adjacent stations on the bands?  I don' know as I've never 
received an on-the-air  complaint.  I have received surprised sounding, 
"Did you say you are running a Tetrode final?" No doubt from tetrodes 
being driven by rigs with a decided leading edge spike, particularly at 
reduced power.

The DX-2sp is capable of running 2500 PEP, so it's loafing along at 1500 
with substantial compression, or even on digital although I've been told 
that will kick the final into high blower.  We've reached that time of 
year where it's time to send the big amp back to the shop.  That amp can 
make this tiny room all warm and toasty.  High blower is downright 
noisy, yet in that 30 X 40 foot shop, it's hardly noticeable.

To get that 2X headroom in SS is about the cost of another Chinese 
8877/3CX1500A7
Doesn't it make more sense to gain the headroom instead of having to 
resort to predistortion (either adaptive, or fixed)
Headroom is simple as is negative feedback. Predistortion is at least 
one more thing to go wrong.
To paraphrase a rather infamous author, "never let a good headroom go to 
waste!"  Which is why we'll probably never see it used except in 
computer controlled amps.


73

Roger (K8RI)


> I see extoling comments re K3 clean xmitter.  What about the Yaesu transceivers with the ORANGE button (some call it red)?  Any Yaesu owner has stepped up to the plate and said he just uses his orange button on (ALWAYS at full power, max RF power knob fully clockwise).... and explains and extolls that strategy to put out cleaner signals???
>   
> Someone, please just state how much the orange button Yaesu-s help, preferably compared to the K3.
> Thanks mucho,
> 73, Charly
>   		 	   		
> _______________________________________________
> Amps mailing list
> Amps at contesting.com
> http://lists.contesting.com/mailman/listinfo/amps
>


---
This email has been checked for viruses by Avast antivirus software.
http://www.avast.com