P7 Cop McDonald monitor(s).

Forum for discussion of SSTV topics. Slow Scan television (SSTV) is a picture transmission method used mainly by amateur radio operators, to transmit and receive static pictures via radio in monochrome or colour.

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P7 Cop McDonald monitor(s).

Postby Steve Anderson » Tue Aug 24, 2021 6:52 pm

Ever seen a 'real' original SSTV display on a P7-type CRT, i.e. the old Cop MacDonald format from the 50s or 60s? No? I haven't either. Armed with a small selection of P7-type CRTs I'm hoping to experience it before this year is out...or at least before I peg it!

The biggest factor is the selection of the CRT, but whatever it is it needs to end in xxxP7 (US) or start with DPxxx (Europe). My choice is the 5ADP7 (aka DP13-34 in Europe). I have others, e.g. DP7-5 but I feel they're too small to resolve 120/128 lines and do the mode justice.

Now, the first hurdle to get over is the voltages required, for the 5ADP7 around +3kV plus +1.5kV. This is not a 'small' tube so allocating space is also an issue. Then there's the issue of generating those high voltages. I'll be doing it via high-voltage transformers, but if there are suitable 'inverters' out there, why not?

The mechanical drawing below is identical for the 5ADP7...sorry, it's imperial units...convert to decimal imperial units, then multiply by 25.4 to get mm...

Steve A.

5ADP1_4.JPG
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Re: P7 Cop McDonald monitor(s).

Postby Harry Dalek » Wed Aug 25, 2021 6:29 pm

Nice Tube and so project Steve !
My Deep image Monitor is in off topics for some reason i don't think we had SSTV topic at the time
viewforum.php?f=19
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Re: P7 Cop McDonald monitor(s).

Postby Steve Anderson » Thu Aug 26, 2021 1:10 pm

One item I've been contemplating is how to make the CRT quickly and easily swappable. A rapid and easy change between a P7 version for SSTV and a P1 (standard green 'scope phosphor) for NBTV. Plugging the CRT bases repeatedly in and out isn't ideal, so perhaps a flexible 'tail' that ends in some form of connector would take the stress off the CRT base.

Perhaps two 'cases', one for the P1 CRT, the other for the P7. A separate 'active' unit would be common for both containing all the active electronics, controls, power supply etc.. The 'cases' being totally passive only containing the appropriate CRT. Food for thought...

As the two CRTs are identical (5ADP1 & 5ADP7) with the exception of the phosphor a great deal of the requirements would be identical or at least quite similar. Plus with a 1-2m 'umbilical' the CRTs can be placed some distance away from transformers and other magnetic fields.

Steve A.
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Re: P7 Cop McDonald monitor(s).

Postby Steve Anderson » Fri Aug 27, 2021 2:17 pm

The first issue I've run into with my idea/concept above is the additional capacitance of the 1-2m umbilical added to what the deflection amplifiers and the grid/cathode drive arrangement have to cope with.

This shouldn't be a problem for the 5ADP7 which will generally be used at SSTV rates. But for the 5ADP1 I had planned for a 128x128 50Hz usage which requires around 4-500kHz of video bandwidth and much faster sweep rates from the timebases/deflection amps. That's incompatible with the extra few hundred (probably) pF added by the umbilical. So it appears that the 'remote CRT cases' will have to have some active electronics inside, but an absolute bare minimum.

More thought required...

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Re: P7 Cop McDonald monitor(s).

Postby Harry Dalek » Fri Aug 27, 2021 9:09 pm

Steve Anderson wrote:The first issue I've run into with my idea/concept above is the additional capacitance of the 1-2m umbilical added to what the deflection amplifiers and the grid/cathode drive arrangement have to cope with.

This shouldn't be a problem for the 5ADP7 which will generally be used at SSTV rates. But for the 5ADP1 I had planned for a 128x128 50Hz usage which requires around 4-500kHz of video bandwidth and much faster sweep rates from the timebases/deflection amps. That's incompatible with the extra few hundred (probably) pF added by the umbilical. So it appears that the 'remote CRT cases' will have to have some active electronics inside, but an absolute bare minimum.

More thought required...

Steve A.


Deflection amplifiers at least i think your thinking ? could have both CRTS in the same case if they are both using the same power supply or supplying that via a external case .
Might be easier just to have side by side in a experimental case with the electronics .
Its a lot of work to do both but in the long run getting one at a time to working stage you will get there .
Having the 180 line one i am thinking your thinking of as the other CRT project...... would be be good to be wired up if you ever want to change to 240 line or something like that later on instead of teh pain of having to remake it all .
Well thats me saying that 3 or 4 monitors in a row.
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Re: P7 Cop McDonald monitor(s).

Postby Steve Anderson » Fri Aug 27, 2021 10:10 pm

Well, I learnt my lesson with 'The Brute'. It ended up too big, cumbersome and heavy to comfortably move. If it won't fit into a standard 19" equipment rack (it didn't, at least width-wise) it's too big. If more than 4RU (7"/178mm) it's too tall. In either case it's going to be too awkward and heavy. Using what is an oscilloscope tube of 5" the best resolution with a line-width of 0.03"/0.76mm, even 128-lines is asking a lot. So I'm stopping there. More lines, sure it'll 'work', but a tube of that calibre cannot resolve such fine detail. A good and big TV, maybe, better still a VGA or better PC monitor. That I've put on hold due to chip shortages, but I will come back to it come the revolution...

So I want to make it easy to move, each chunk being not too big, not too heavy, and moreover potentially expandable... Also, looking at standard modern car, I doubt 'The Brute' would fit into the boot/trunk, I used to have a small van/estate type thing, no problem, but not any more...
Gina 1.jpg
Gina 1.jpg (41.99 KiB) Viewed 2360 times

I named her after my mother...

The photo makes it look more like a hearse, which it was never used for...30 years old, 600,000km, (1990 model) still looked, drove and passed safety/emission tests each year OK, and a diesel (now bio-diesel)...still in use daily by the people who bought it...anyway, the rear roof wasn't high enough for a coffin and the flowers on top...and a dark green/brown colour, not black...
Steve A.

The basics of a standard 19" equipment rack...again, like the BNC connector, designed by the British Navy...I'm led to believe...actually, reading the article I have linked to, it's AT&T's fault in the US...I'm sorry, Your Majesty...guess I can kiss my Knighthood goodbye!

https://en.wikipedia.org/wiki/19-inch_rack
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Re: P7 Cop McDonald monitor(s).

Postby kd2bd » Sat Aug 28, 2021 6:34 am

P7 is a dual-color, dual-persistence compound phosphor. Its flourescence has a short persistence with a blue-white color, while its phosphorescence (afterglow) has a long persistence and appears yellow-green.

So, a "cheap and dirty" option might be to use a single P7 tube behind a blue filter to block the yellow phosphorescence for NBTV operation, or a yellow filter to block the bright blue-white flourescence for SSTV. 8)


73 de John, KD2BD
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Re: P7 Cop McDonald monitor(s).

Postby Steve Anderson » Sat Aug 28, 2021 12:41 pm

Yes John, that's a thought. My wife works for a local TV station, she may be able to get offcuts of suitable filters from the lighting department.

Lee Filters in the UK are probably the best known in Europe and I know my wife's TV station uses them...so there is a chance...

https://www.leefilters.com/lighting/colour-list.html

The good news is that blue and yellow are widely spaced within the visible spectrum, so the filters don't need to be optically narrow-bandwidth, makes matching the filters to the CRT easier...the P7 peaks are at 558nm (green/yellow) and 440nm (blue).

So the plan of attack (Plan B) would be to get the P7 CRT going first and see if those filters do the job. If not retreat to Plan A, two CRTs...

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Re: P7 Cop McDonald monitor(s).

Postby Harry Dalek » Sat Aug 28, 2021 11:08 pm

Came across this while studying phantastron circuits
Australian handbuilt SSTV monitor c1972 which uses phantastron timebase circuits:
Click to enlarge.
p1 sounds like used with a 35mm camera?
https://frank.pocnet.net/sheets/201/5/5LP1.pdf
https://frank.pocnet.net/sheets/041/5/5LP1A.pdf
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The electromagnetic spectrum has no theoretical limit at either end. If all the mass/energy in the Universe is considered a 'limit', then that would be the only real theoretical limit to the maximum frequency attainable.
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Re: P7 Cop McDonald monitor(s).

Postby Steve Anderson » Mon Aug 30, 2021 12:35 pm

I suspect that was used as a 625 monitor, the time-constants in the deflection amps are way too short for SSTV. There also is no form of sub-carrier demodulation. And the use of a P1 CRT is a clue too.

No idea why two stages of differential amps are used for both X and Y deflection.

The CRT is run at quite low voltages, it must have been quite dim.

I also came across this some years back and I don't recall the item mentioning SSTV, I've lost the link since then...

Steve A.

I've changed my avatar to a screen-shot of the real first SSTV image that I was happy to post (Those prior were boring test patterns and the like). This was done via the MkI SSTV-625 Up-converter. It shows what can be done with just 128 lines...and that's after conversion...

Also, consider that this forum has a maximum avatar dimensions of 128x128 pixels, so anything you see here as an avatar can be displayed on the 128-line SSTV system, though only in monochrome...

The avatar isn't quite 128x128 as the old TV I used as a display device needed a 'going-over' to get it back to how it should be. But without any data (a manual) I was happy it just worked as is...and it still does the last time I used it, maybe two years ago...perhaps I should fire it up and make sure it hasn't expired in the interim...the problem is I don't have any 625 sources, except if I carry the thing downstairs and try the 'Y' or maybe (if it has one) PAL output of the set-top box.

However, that's not the theme of this thread. We should be able to achieve the same or better via 'direct drive' and long photographic (perhaps digital) exposures...or alternatively ...damn, whilst spell-checking I've forgotten what I wanted to say...senility, I'm now starting to forget who I am...as Phil Collins said on stage, "Getting old sucks." I cannot agree with him more...but the grey matter (occasionally) still does work...

Who here is older than I? Born February 1956...not many I suspect...though Albert, well done...
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Re: P7 Cop McDonald monitor(s).

Postby grahamhunt » Mon Aug 30, 2021 8:31 pm

August 1948 I remember the king and I don't mean Elvis
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Re: P7 Cop McDonald monitor(s).

Postby Klaas Robers » Tue Aug 31, 2021 5:46 pm

September 1944..... and I am still not feeling old.
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Re: P7 Cop McDonald monitor(s).

Postby Harry Dalek » Tue Aug 31, 2021 8:49 pm

Steve Anderson wrote:I suspect that was used as a 625 monitor, the time-constants in the deflection amps are way too short for SSTV. There also is no form of sub-carrier demodulation. And the use of a P1 CRT is a clue too.

No idea why two stages of differential amps are used for both X and Y deflection.

The CRT is run at quite low voltages, it must have been quite dim.

I also came across this some years back and I don't recall the item mentioning SSTV, I've lost the link since then...

Steve A.


Yes it doesn't look like a SSTV monitor from the circuits is this for Am ? see the deflection plates are AC coupled ,i was thinking he kept the screen results via photography as a P1 would be pretty useless here ,not mentioned but perhaps flying spot scanning any case i love home made gear like this so i am glad its been documented !
The link is here below Steve it is a good read helps me .
http://www.vk6fh.com/vk6fh/phantastron.htm
Oh and i am a young...un 1960
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Re: P7 Cop McDonald monitor(s).

Postby Steve Anderson » Wed Sep 01, 2021 12:13 pm

Thanks for the link Harry, the page has been added to since I last saw it. A useful resource to tuck away in your "Reference - Timebases" folder...

It appears we have a lot of knowledge and experience within those gathered here...

Steve A.
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Re: P7 Cop McDonald monitor(s).

Postby kd2bd » Wed Sep 01, 2021 12:19 pm

The P1 monitor pictured above is an NBTV monitor. It appears that Chris, VK3AML, uses the phrase "Slow Scan Television" to describe the many different varieties of slower-than-broadcast-standard television methods.

The monitor can be seen in VK3AML's youtube video at 22:11.

BTW, 1964. :)

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