[ARC5] On Hacking and TVI

[Kenneth G. Gordon]

On 16 Oct 2012 at 10:40, J. Forster wrote:

> I was waiting for that canard.

Not a canard, as such: a true situation. I view it as a group of 
misunderstandings of the true situation. TVI DID occur: the cause was NOT 
what was first thought it was.

> 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.

There were at least two OTHER reasons, good reasons, for TVI at the 
time-period: 1) many, if not most, TV owners were viewing very weak, 
marginal signals on crummy antennas, or with cheap, very poorly designed 
preamps, and as a result, it didn't take a very strong off-frequency signal to 
cause fundamental-overload, and 2) many TV sets of the period had 21 MHz 
IF strips. Another reason was that there was NO filtering in any TV set at the 
time. The manufacturers were at fault, big time.

I remember many, many times going to neighbors' home and seeing them 
patiently watching pictures that were ALMOST recognizable due to the noise, 
static, lack of a decent antenna, weak, fringe-area signals, etc. I hated TV at 
the time. Still do.

However, you rightly state that the attempts at minimizing TVI by hams were 
not really conducive, in most cases, to a proper solution either. I really doubt 
if any of us COULD have done anything effective against TVI over a 
considerable period of time, due to poorly designed, manufactured, and 
imporperly-used TV sets.

> 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.

Agreed. Which were most of us at the time.

Ken W7EKB