[vcf-midatlantic] ZX81/TS1000 with a modern TV

[Jeff S]

My belief is that the new ATSC compatible TVs have a disadvantage in that
they try to auto fine-tune RF signals fed to them. I'm sure they are all
capable of displaying the signals from old sources, but the tuning logic,
most likely digitizer based direct sampling, will lock onto the strongest
signal, even if it potentially overdrives the RF decoder's input.

Older TVs generally had analog fine-tuning, even automatic (AFT) style.
This probably allowed the ability of the TV to attenuate stronger than
normal signals to some degree to get them to display.

Just a theory... until it is disproved. :)

Jeff Salzman

On Mon, May 23, 2022 at 8:04 PM Dean Notarnicola via vcf-midatlantic <
vcf-midatlantic at lists.vcfed.org> wrote:

> Yes. I have a very recent 4K 70” set and it does ATSC and old school NTSC
> just fine with a top loader NES with RF only.
>
>
> On Mon, May 23, 2022 at 7:24 PM Dave McGuire via vcf-midatlantic <
> vcf-midatlantic at lists.vcfed.org> wrote:
>
> >
> >    Yes, but this is NTSC-modulated VHF RF.  Can current TVs receive
> > that?  I was under the impression that they don't.  (I don't have one,
> > no free time to waste)
> >
> >             -Dave
> >
> > On 5/23/22 19:06, Dean Notarnicola via vcf-midatlantic wrote:
> > > I’ve yet to find a TV that can’t do ATSC and NTSC.
> > >
> > > On Mon, May 23, 2022 at 6:26 PM Glenn Roberts via vcf-midatlantic <
> > > vcf-midatlantic at lists.vcfed.org> wrote:
> > >
> > >> I have no experience with Sinclair but didn’t they have a built-in RF
> > >> modulator? That would put out an old style UHF or VHF signal that a
> > modern
> > >> digital TV can’t decode. I believe you’d need an older TV to test
> these…
> > >>
> > >> Sent from my iPad
> > >>
> > >>> On May 23, 2022, at 5:54 PM, Dean Notarnicola via vcf-midatlantic <
> > >> vcf-midatlantic at lists.vcfed.org> wrote:
> > >>>
> > >>> I’ve read that the ULA on some older TS and ZX units do not put out
> a
> > >> 100%
> > >>> proper NTSC signal, something do with the contrast. It may be that
> > modern
> > >>> TVs have issues, but CRT tuners can deal with it. Considering they
> are
> > >> all
> > >>> demonstrating the same behavior, these units may be fine.
> > >>>
> > >>>
> > >>>> On Mon, May 23, 2022 at 4:32 PM Jeff S via vcf-midatlantic <
> > >>>> vcf-midatlantic at lists.vcfed.org> wrote:
> > >>>>
> > >>>> The K cursor is normal, and standard. The ZX81 does not have any
> kind
> > of
> > >>>> intro or status boot screen. If you're seeing the K, then unless
> > there's
> > >>>> something wrong with the keyboard, you should be able to see any
> > numbers
> > >>>> you type.
> > >>>>
> > >>>> On Mon, May 23, 2022, 4:21 PM Bob Shuster via vcf-midatlantic <
> > >>>> vcf-midatlantic at lists.vcfed.org> wrote:
> > >>>>
> > >>>>> So I have two (2) Sinclair ZX81s (US version - one is still an
> > unbuilt
> > >>>>> kit), and three (3) Timex-Sinclair 1000s.  I’ve connected them to a
> > TV
> > >>>>> using an RCA-coax adapter and tuned to the correct channel, but I
> > get a
> > >>>>> grey screen with the “K” cursor visible.  I’m unable to get past
> > this.
> > >>>>> This is for all four units.  They seem to tune in white momentarily
> > >> then
> > >>>>> switch to fuzzy grey - with the “K” still visible.  This was both
> on
> > a
> > >>>>> large 4K OLED set and a small HD LED TV, and I suspect they are
> just
> > >> too
> > >>>>> new to deal with the monochrome signal.  I don’t have a CRT TV to
> > test
> > >>>>> with, just old monitors (which of course don’t have antenna
> > >> connections.)
> > >>>>>
> > >>>>> Any advice?  I’m selling these, so I’m not getting into modding
> them,
> > >>>> just
> > >>>>> want to confirm they’re working properly.
> > >>>>>
> > >>>>> Bob Shuster
> > >>>>
> > >>
> >
> >
> > --
> > Dave McGuire, AK4HZ
> > New Kensington, PA
> >
>