1957 Hotpoint interference when used on cable

[Don Lindsly]

Portable TVs of the 50s were intended to work on a built in antenna so they had decent sensitivity. Channels assignments were alternated so adjacent channel and intermod rejection were not the primary design objectives. IF traps were fewer or often omitted altogether. The design served the intended markets quite well. What you see on cable would be expected in current conditions.

The VCR is operating with no other channels so it will not suffer interference. You could try padding the cable signal by about 20 db, or whatever it takes to keep just above the threshold of snow. That will reduce intermod and likely adjacent channel interference as well.

[JCFitz]

Originally Posted by Don Lindsly

Portable TVs of the 50s were intended to work on a built in antenna so they had decent sensitivity. Channels assignments were alternated so adjacent channel and intermod rejection were not the primary design objectives. IF traps were fewer or often omitted altogether. The design served the intended markets quite well. What you see on cable would be expected in current conditions.

The VCR is operating with no other channels so it will not suffer interference. You could try padding the cable signal by about 20 db, or whatever it takes to keep just above the threshold of snow. That will reduce intermod and likely adjacent channel interference as well.

Checking the tuner alignment revealed that the tuner is very poor at rejecting adjacent channels even though the alignment is good.

[peverett]

Andy is correct about the poor selectivity of the tuners on older sets. In my earlier days(late 1960s, early 1970s), I lived in a part of Oklahoma where a relatively weak channel 9(CBS-OKC) was next to a very strong channel 10(ABC-Ada, Oklahoma). It was very common for the ABC channel to bleed into the CBS channel on the TVs of the time. This was over the air-not cable.

[ChrisW6ATV]

Originally Posted by JCFitz

Checking the tuner alignment revealed that the tuner is very poor at rejecting adjacent channels even though the alignment is good.

When I first used to read Consumer Reports magazine in the early 1970's, this was a frequent problem with sets they tested. They would specifically warn of likely problems with "cable TV systems that use all available channels". I guess that means some cable systems left adjacent channels blank at that time (and, of course, the system would have not gone above channel 13); when I first had cable TV in the mid-1980's, every channel was used.

[peverett]

To mostly get around this, I use a modern VCR as the cable tuner for the older TVs that have the biggest selectivity problem.

I have found that the RCA's with the Nuvistor RF amplifier seem to have pretty good selectivity, while cheaper sets like the GE Portacolor are very poor.