[ARC5] Command Sets and Interference

[Roy Morgan]

At 06:06 PM 9/12/03 -0500, David Stinson wrote:
>Roy, I've known you on here many years and I hate to take public
>exception with you, but

Dave,

It sounds like you have experience and understand these transmitters 
well..  I am always glad to hear from folks with something to add to the 
discussion.. particularly when it is based on practical experience.

>the "ARC-5 TVI" thing is a myth,
>born of improper operation/tuning of the radios and
>poor 1950s-1960s television front-ends

I agree with you. The improper operation you mention would likely include 
the use of too high plate voltages on the transmitters that I mentioned.

>  All that hacking, sawing, shielding and bypassing
>is utterly unnecessary if the radios are run as-designed

Hooray for that.. this gives me more enthusiasm to get one or two of them 
running..   The hacking and shielding I told about was done on a 
transmitter that I got from a ham about 1959.  We lived in an extreme TV 
fringe area, and for sure the TV's in use both had 21 mc IF's and wide open 
front end sections.  I never ran that transmitter, but he must have had a 
lot of TVI troubles.

>*and* any bad componants are replaced *and* the output
>roller coil contacts are cleaned in the way I outlined here
>some years ago (small arcs in the oxides will play heck with a TV).

It sounds like some careful cleaning is in order,  and maybe a tiny (TINY!) 
bit of De-Oxit or Pro-Gold applied to the roller and its shaft.

>I've run them in the same room with a TV with rabbit ears-
>no problems.  However, if you have a TV that is suseptable to
>fundimental overload, nothing will help except working on the TV.

I live now in a neighborhood with lots of houses and cable TV service via 
buried cables.  One day I asked a cable service person how many folks in a 
typical neighborhood like this actually used the cable. He said about 
half.  That means that many folks use off the air signals with some sort of 
antenna.  I am hoping that most TV front ends are much better than the ones 
I clobbered in the late 50's (running 6 meters) because I am planning to 
operate HF RTTY with some non-trivial power in the future.

>I've done the work with service monitors and spectrum analyzers
>... The short version is that the ARC-5 command transmitters are cleaner
>than modern synth rigs.

This is good news.  I would like to run my ARC-5 transmitters as much 
original as possible.

>The person with the problem needs to provide details on how
>he is running and tuning his rigs, plus the situation of
>the television (cable, antenna?).

Good point.. It always helps to know more about the situation.  I'm glad to 
see Sean and Dave trading more information about the actual conditions 
where the TVI is happening.. we'll all learn a lot.

Roy

- Roy Morgan, K1LKY since 1959 - Keep 'em Glowing!
7130 Panorama Drive, Derwood MD 20855
Home: 301-330-8828 Work: Voice: 301-975-3254,  Fax: 301-948-6213
roy.morgan@nist.gov --