[ARC5] On Hacking

[Geoff]

In REALITY, the finals are more efficient at a higher B+ and are even rated 
at 750V for CW. A pair of 1625's are factory rated at 150W ICAS CW input and 
without air cooling. Im sure you can do the math for a typical output using 
an efficient tank circuit.

Any so called harmonic distortion is an effect of excessive drive and 
forcing the finals into a deep Class C hard switch configuration. A spectrum 
analyzer shows this clearly.

In ICAS ham CW service the convection cooling with the louvers provided is 
sufficient. There is a difference between normal hot and too hot.

The military prefered to run the equipment conservatively, particularly in 
AM service.

In the future many on here should be sure of their  facts instead of 
sounding like a political candidate or TV talking head and making up 
erroneous pronouncements on the fly that conform to their biases.


----- Original Message ----- 
From: "Mike Hanz" <aaf-radio-1 at aafradio.org>
To: <jfor at quikus.com>
Cc: <arc5 at mailman.qth.net>
Sent: Tuesday, October 16, 2012 2:15 PM
Subject: Re: [ARC5] On Hacking


> Those are valid points, John, _*/if/*_ the set was operated within its
> standard voltage and current design envelope.  Unfortunately, some hams
> wanted a lot more power out of them, using plate voltages that exceeded
> the published 600v maximum by significant margins.  That kind of
> mistreatment drives a healthy increase in harmonic distortion.  I have a
> couple of examples here given to me by a very smart NRL RF engineer that
> has the usual screen wire, bypassed power and control leads, and an
> added capacitor to complete the pi matching network into a 50 ohm
> resistive antenna load.  He claimed he was getting close to 100 watts
> out of those little boxes.  I'm not sure how he was cooling them...he
> must have used a blower hung on the side of the tube compartment.  I
> don't see how he could have obtained any appreciable life out of the
> tubes at that level without forced cooling.  But then again, 1625s were,
> what...a quarter apiece?
>
>  - Mike  KC4TOS
>
> On 10/16/2012 1:40 PM, J. Forster wrote:
>> I was waiting for that canard.
>>
>> The TVI rep was fror two reasons:
>>
>> 1. Ham gear manufacturers condemned the ARC-5 and similar sets to sell
>> their hardware.
>>
>> and
>>
>> 2. The ARC-5, and many other similar vehicular transmitters, had
>> electrically short antennas and these were resonated by the output
>> (variable) inductors in the sets. This was a high-Q circuit, so would 
>> kill
>> harmonics well.
>>
>> Any time I see an ARC-5 with a SO-239, I know it belonged to a ham with
>> little to no understanding of its proper operation.
>>
>> -John
>>
>> ================
>>
>>> One might forget the TVI "improvements" that were necessary, especially 
>>> in
>>> urban and suburban locations, to keep one's neighbors from storming the
>>> castle like was done to Doctor Frakenstein!
>
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