Sinclair Spectrum Computer SSTV

[Klaas Robers]

I think it was in 1980 that I made a send and receive program for Hell (Feld Hell) on my Apple ][ computer. Ik had a fine High Resolution graphics mode, only black and white, but that was optimal for Hell. It was the first software solution for that mode. I made quite some QSO's with it. The program ran completely in machine language, including the timing. Everyone was surprised when it came on air.

I was absolutely confident in the timing, but we experienced that the old WW2 machines had drifted quite far away from the original designed speed. They could read my text, but it was drifting up or down by more than 45 degrees. When I told them that this was due to their setting of the gouvernor, they shifted to my speed. I hope that this is still their speed.

In 1981 / 1982 I abandoned working with the Aplle ][ (incompatible to everything).

[Steve Anderson]

...they shifted to my speed. I hope that this is still their speed.

I'm sure somewhere within the links I posted yesterday that infomation can be found...it may just take a while to track down...maybe reverse engineer circuit diagrams or mechanical drawings if possible.

In 1981 / 1982 I abandoned working with the Aplle ][ (incompatible to everything).

A few months ago I did consider home-brewing an Apple II or maybe an Apple I, just for the fun of it. I eventually came to my senses! There was, and still is nothing wrong with them considering the era they're from. But what to use it/them for once built?

I prefer to make stuff that is stand-alone, that is it requires no external equipment beyond, say, a monitor, a keyboard, mic/loudspeaker or even a power supply. A 'black box', stuff in, different stuff out.

Steve A.

What I haven't seen is a 'Hellschreiber Display' though they may have existed in some form or another. Basically its output is text on a (probably small) C.R.T. instead of a paper tape, not permanent, ideal for keeping secrets. Might be worth considering? Just another 'fun' project. Or lamps similar to an Enigma machine. Though in both cases the human 'in the loop' would probably slow things down.

Just found that there are PC programs that do just that!

[M3DVQ]

Yes, most people use PC software of course, as with SSTV and teletype etc. It's obviously more convenient, but less fun!

Since there's obviously some interest, I'll start a hellschreiber thread in off-topic to avoid disrupting Chris's thread any further

[acl]

Composite mod done and works a treat no Jail bars on video, new regulator on order. Keyboard faulty so new one of those on order. Recap kit to be ordered. Treated myself to a new white case.

Worth a look at https://www.retroleum.co.uk/ for spares

Regards Chris Lewis G6ACL

[M3DVQ]

If there's no jailbar striping on the display there's probably not a lot to be gained by changing all the electrolytics, although I suppose every little helps if you're going to attempt to use it in the vicinity of an HF radio
Be aware that depending on PCB revision, these boards are somewhat notorious for traces delaminating very easily and the plated through holes breaking.

[Steve Anderson]

Yes, most people use PC software of course, as with SSTV and teletype etc. It's obviously more convenient, but less fun!

Exactly my sentiment, and well put. I appreciate that many don't feel confident in building hardware from just a circuit diagram, a parts list and perhaps a software listing. So easy-to-use software is a valid alternative to get those interested involved.

Since there's obviously some interest, I'll start a hellschreiber thread in off-topic to avoid disrupting Chris's thread any further

Good idea, and thanks. I may get involved in some manner or another, though it's a whole new concept to me...I see you've made a start already!

viewtopic.php?f=8&t=3373

It is another means of Narrow-Bandwidth visual communication, though not television/pictures, moving or otherwise...

Steve A.

[acl]

Well here we go 20GBP off eBay. A digital device to replace the old cassette player. This device plays Spectrum TZX or TAP files. The plug in version does not appear to support TZX files although there are conversion programs. Anyway, power it up and it appears to work there is a 'noddy' display which shown the status and menu system. Someone has militarised a version to fit inside an old cassette tape.

TZXDuino works with the Acorn Electron, ZX Spectrum, ZX81 and Amstrad 6128.
Maxduino can play TZX or TAP for Spectrum, CDT for Amstrad CPC, CAS or TSX for MSX, ZX80/81 files, Acorn Atom and Electron, Dragon 32/64 and Oric Atmos.

[acl]

New case and keyboard fitted Not glued down yet

Test program run to check hardware

Well cut my legs off and call me shorty. G1FTU program loads

[acl]

It may need some settings "tweaking" but all in all not a bad for a Sinclair 48K Spectrum. I may try some of the other SSTV offerings.

Not bad for an eight bit machine

Regards Chris Lewis

[acl]

Hi there,

I managed to run the G1FTU SSTV 'fixed' software on my machines but now have bought a board that plugs into the expansion port and loads directly from a micro SD card. The problems I have encountered are formatting the card to FAT16 and it will only accept Tap or SNP files. I have tried running the fixed file in PC-based Spectrum emulators but have been unsuccessful saving as TAP or SNAP files.

Also available in orange

[M3DVQ]

.tap is a very basic format which represents the bytes saved and loaded by the spectrum's tape load and save routines. As such it works for anything which uses the standard routines but not anything that does "tricky" stuff for copy protection, which I assume is the case here.
I'm away from home at the moment, but I can create you a .sna you should be able to load ok next week.

[acl]

That would be wonderful, thanks .I have ordered some 2Gb SD micro disks as windows does not format to FAT 16 on these above 4Gb. I understand I can format them from the DOS prompt in windows 11. May be easier on my big Mac PC.

Warmest regards Chris Lewis

[acl]

Large_SDCards_and_FAT16.pdf

Formatting SD card

(55.58 KiB) Downloaded 1 time

Full_manual_V3.1.pdf

Manual of the plug in unit

(128.97 KiB) Downloaded 2 times

[Steve Anderson]

A few years ago I made a start on interfacing SD-cards for the purpose of storing NBTV/SSTV and related signals. First thing is the native 4-bit SD interface standard is proprietary and requires the payment of an obscene amount of cash to get a licence. The alternative is a free-to-use single-bit standard SPI mode. Obviously slower.

But for NBTV/SSTV and the like it might be fast enough. I never really established if it were/is or not. I eventually was able to read and write to SD cards, but only for those of FAT16, a maximum of 4GB, which isn't that bad for NBTV/SSTV and so on.

Then something (real work probably) came along and I paused the project. It's been in that 'limbo-state' ever since. Maybe now is the time to resume work on it?

The biggest hurdle I found is getting through the Initialization stage of the card. There is a flow-chart for this and at first glance it seems reasonably sane. It's not! Even if you limit the card to SPI mode only. Many have succeeded in this endevour, but I didn't quite there, almost, but almost isn't useful. Others found the single-bit SPI mode painfully slow, I never got to the point of speed tests.

I'll dig out my notes and maybe resume this, however, others may/probably have already got this going as I had hoped...there is/was a thread regarding this on this forum, somewhere...

I did my experiments on an 8-bit PIC microcontroller, there's no reason I can see that a Z80 couldn't handle it either.

Steve A.

Continuing...The 8-pic PIC I used had an instruction rate of 16MHz, 62.5ns per instruction. Whereas Z80s I suspect are somewhat slower. Whether this would have any impact on read/write speed I'm not sure. i.e. would the bottleneck be the Micro or the card?

[acl]

Hi Steve,

I think the Sinclair spectrum has some powerful surface devices helping the Z80 out controlling the micro SD card

Any progress on SSTV lately?

Regards Chris Lewis