NBTV transmissions

Forum for discussion of narrow-bandwidth mechanical television

Moderators: Steve Anderson, Dave Moll, Andrew Davie

NBTV transmissions

Postby corne » Tue Jan 10, 2012 9:24 pm

Hello,

My name is Corné and I’m living near Eindhoven the Netherlands.
My interest in NBTV was raised when several people started building the Kerkhof NBTV.
Reading the NBTVA site I found that there are NBTV transmissions on shortwave. Up to now I’ve not been able to receive any NBTV signals.

Are there any regular NBTV transmissions? Are there any close to Eindhoven?



Some more info on my NBTV project.
Although I failed to receive any NBTV signals I started thinking about building a NBTV monitor using the KerkHof TV as a starting point. My design evolved over a couple of months. Now it has become a kind of universal monitor. I finished building it last November.
As it is now the monitor is capable of displaying anything between the NBTVA 32line standard and 625lines with 50Hz raster, using missing sync pulse synchronisation. I’ve also added a sync separator for PAL system and external sync inputs for future developments. It uses three 884 thyratrons for line and raster saw tooth generators, two ECC81s as deflection amplifiers, one ECC83 as sync separator, one ECL84 video amp and the well known DG7-32 CRT.
Here are two pictures of my TV monitor and screenshots of a 32line image and a 625line image.

Image
Image
Image
32line NBTV using PC as signal source (Not me in the picture)

Image
625line 50Hz PAL from portable DVD player
corne
"Fester, enough of the light-bulbs!"
 
Posts: 5
Joined: Tue Jan 10, 2012 6:18 pm
Location: Netherlands

Postby Viewmaster » Wed Jan 11, 2012 7:31 pm

Hello Corne,
That's a very well built and elegant monitor you have there. Included too a HV warning label I see.
Nice to see valves used instead of those uninspiring transistors that most of us use.

I looked at the March 2011, NBTVA newsletter and the transmissions are on 3700kHz in Single Sideband mode.
From my long past experience of short wave listening I think that this should reach you.

Welcome to the forum, BTW.
“One small step for a man,"......because he has Arthritis.
Albert.
User avatar
Viewmaster
Frankenstein was my uncle.
 
Posts: 1290
Joined: Fri Apr 06, 2007 4:50 am
Location: UK Midlands

Postby Steve Anderson » Wed Jan 11, 2012 9:09 pm

Hello Corné,

I echo Albert's welcome. I had not heard of the Kerkhof NBTV monitor, but doing a bit of 'Googling' turned up this...

http://www.youtube.com/watch?v=mTYpPpfRZS8

Although not stated it looks awfully like a DG7-32 being used too.

I've used the same CRT in several incarnations, a few rough photos are attached...

The associated thread is...

http://www.taswegian.com/NBTV/forum/vie ... 2&start=90

As you'll note I tend to use a mixture of tubes and sand-state devices. Part of the current version looks like this in 'Deflection 1.jpg' below, this is the deflection stages using a pair of ECC91s, progress has been stalled by other things...

I hope you enjoy your time here and well done on such a good looking build...

Steve A.
Attachments
crt_1_654.jpg
crt_1_654.jpg (368.22 KiB) Viewed 11841 times
crt_2_185.jpg
crt_2_185.jpg (297.97 KiB) Viewed 11841 times
Deflection 1.jpg
Deflection 1.jpg (85.84 KiB) Viewed 11841 times
User avatar
Steve Anderson
"Fester! Don't do that to 'Thing'"
 
Posts: 4219
Joined: Fri Mar 30, 2007 10:54 pm
Location: Bangkok, Thailand

Postby corne » Wed Jan 11, 2012 11:55 pm

Albert,
Thanks for the nice comment. The mechanical part of the build took more time than the electronic part.
I did my listening on 3700kHz but haven’t heard anything yet. I stay listening on that frequency and hope I’ll catch something soon.
Thanks.


Steve,
The Kerkhof TV in the Youtube link was displayed during an antique radio fair last year. The CRT used is a DG7-2 but it should have been a DG7-1 but these are very hard to find.

The wiring in your monitor looks a lot better than in my monitor. I’ve been able to hide the wiring in the chassis which is only 20mm high so you can imagine the mess in there.

A mix of solid-state and tubes is a good compromise when driving electrostatic deflected CRTs. Tubes can handle over voltages much better than transistors can.
I wanted to use as much tubes as possible in my monitor only the rectifier and clamp diodes are solid-state.
The biggest difficulty in designing the monitor with tubes was a good missing sync pulse detector. In all tube circuits I’ve seen a low pass filter is used. This makes detecting a missing sync pulse difficult and it gets worse if the number of lines in a frame increases. A one point I realised I could use a thyratron to detect the missing sync pulse and trigger the raster thyratron at the same time. So the third 884 thyratron in my monitor is the missing sync pulse detector. This circuit works very well over a wide frequency range.
corne
"Fester, enough of the light-bulbs!"
 
Posts: 5
Joined: Tue Jan 10, 2012 6:18 pm
Location: Netherlands

Postby Steve Anderson » Thu Jan 12, 2012 1:42 am

corne wrote:...I wanted to use as much tubes as possible in my monitor only the rectifier and clamp diodes are solid-state.


Using tubes is a link back to my teen years and being totally honest there's very few applications these days where they still outclass semiconductors..High-power HF transmitters...I mean high power...250kW+, magnetrons (your microwave oven and RADAR), TWT's for UHF TV transmission, and X-ray tubes.

So when I use tubes it is just as a whim, just 'cos I wanna and can. Never mind that an ECC8x uses nearly 2W alone in heater power, I just want to use them!

I do have some close relatives to the CRTs you mention, the DP7-5 which is the long-persistence version of the usual DG7-5 used in 'scopes. My intention is (one day) to use them in an old-style SSTV monitor...when will that happen? Who knows...

Steve A.
User avatar
Steve Anderson
"Fester! Don't do that to 'Thing'"
 
Posts: 4219
Joined: Fri Mar 30, 2007 10:54 pm
Location: Bangkok, Thailand

Postby Lowtone » Thu Jan 12, 2012 2:09 am

http://www.websdr.org/ Can i get the frequencie with this ?
r a d i o P T T v i s i o n
User avatar
Lowtone
Just nod and pretend you understand me
 
Posts: 285
Joined: Sat Jan 16, 2010 9:45 am
Location: France

Postby DrZarkov » Thu Jan 12, 2012 3:10 am

Welcome in the forum first.

Transmissions are, of there any transmissions, at Saturday, at 9 AM (Dutch time). Try not only exactly 3500 kHz, but +-something, too. Depending to the location of the transmitter, it can happen, that you are in the dead zone (too far for direct reception from the UK, not far enough for a reflection). But as with good areals in Eindhoven even direct FM receptions are possible, it should be possible to receive NBTV transmissions from the UK. (Generally spoken, if there are any transmissions...) At my old home shortwave reception was very difficult, now I have much better chances, but not yet a good antenna on the roof. I hope this will change soon.
User avatar
DrZarkov
I think I've had a cranial implosion.
 
Posts: 1037
Joined: Mon Feb 19, 2007 11:28 pm
Location: Kamp-Lintfort, Germany

Postby corne » Thu Jan 12, 2012 6:14 pm

Guten Tag,

If you are able to receive the transmissions from the UK in Moers, which is about 100km from my location, I should be able to receive it as well.
I’ll have a try this Saturday and coming weeks.

Thanks for the info.
corne
"Fester, enough of the light-bulbs!"
 
Posts: 5
Joined: Tue Jan 10, 2012 6:18 pm
Location: Netherlands

Postby AncientBrit » Thu Jan 12, 2012 6:44 pm

Welcome to the forum Corne.

I too have a nostalgia for valves (tubes) and CRTs.

Regarding the missing pulse detector, Steve A is too modest to mention it but he came up with a single PIC circuit that provides reliable detection and also outputs a continuous stream of 32 line sync pulses.

The circuit was published in the NBTVA newsletter a few issues ago.

Regards,

Graham
AncientBrit
Green padded cells are quite homely.
 
Posts: 858
Joined: Mon Mar 26, 2007 10:15 pm
Location: Billericay, UK

Postby corne » Thu Jan 12, 2012 8:57 pm

Hello Graham,

My involvement with valves(tubes) began when I had my Philips EE2003 electronics experimenter box . I kept destroying transistors until someone, I don’t know who, mentioned the valves could endure much more punishment than transistors. I then got hold of some valves, and it evolved from there.

Using the PIC controller is a good way of detecting the missing pulse.

Regards,
Corné
corne
"Fester, enough of the light-bulbs!"
 
Posts: 5
Joined: Tue Jan 10, 2012 6:18 pm
Location: Netherlands

Postby DrZarkov » Fri Jan 13, 2012 12:04 am

I don't know if I can receive it in Moers, I live here just a cpouple of month, and until now without shortwave antenna on the roof. Before that I lived near Venlo, with a lot of QRM from the solar paneels on our roof, so shortwave reception in the house was never perfect, only stronger signals went through.
User avatar
DrZarkov
I think I've had a cranial implosion.
 
Posts: 1037
Joined: Mon Feb 19, 2007 11:28 pm
Location: Kamp-Lintfort, Germany

Postby Viewmaster » Sun Oct 14, 2012 6:39 pm

AncientBrit wrote:
Regarding the missing pulse detector, Steve A is too modest to mention it but he came up with a single PIC circuit that provides reliable detection and also outputs a continuous stream of 32 line sync pulses.

The circuit was published in the NBTVA newsletter a few issues ago.

Regards,
Graham


Could someone please tell me what issue that was?
Or better still, maybe if Steve is reading this he could post the circuit here for me, please.
Thanks either way.
“One small step for a man,"......because he has Arthritis.
Albert.
User avatar
Viewmaster
Frankenstein was my uncle.
 
Posts: 1290
Joined: Fri Apr 06, 2007 4:50 am
Location: UK Midlands

Postby Steve Anderson » Sun Oct 14, 2012 7:23 pm

Viewmaster wrote:Could someone please tell me what issue that was? .


Albert, V35 #4, July 2010...

...any queries, you just have to ask...

Steve A.

Below is the actual 'chunks' I sent to Jeremy, he then lays them out to suit the newsletter...I have made some improvements and minor changes since...
Attachments
Fig 1.bmp
(96.94 KiB) Downloaded 608 times
Fig 2.bmp
(94.12 KiB) Downloaded 608 times
Fig 3A Colour.gif
Fig 3A Colour.gif (6.46 KiB) Viewed 10647 times
Fig 4A Colour.gif
Fig 4A Colour.gif (6.69 KiB) Viewed 10647 times
Fig 5A Colour.gif
Fig 5A Colour.gif (6.91 KiB) Viewed 10647 times
Fig 6.jpg
Fig 6.jpg (116.22 KiB) Viewed 10647 times
Missing Pulse 4A.doc
(29.5 KiB) Downloaded 382 times
User avatar
Steve Anderson
"Fester! Don't do that to 'Thing'"
 
Posts: 4219
Joined: Fri Mar 30, 2007 10:54 pm
Location: Bangkok, Thailand

Postby Viewmaster » Mon Oct 15, 2012 12:14 am

Steve Anderson wrote:
Viewmaster wrote:Could someone please tell me what issue that was? .


Albert, V35 #4, July 2010...

...any queries, you just have to ask...
Steve A.


Thanks very much Steve, for all that.
“One small step for a man,"......because he has Arthritis.
Albert.
User avatar
Viewmaster
Frankenstein was my uncle.
 
Posts: 1290
Joined: Fri Apr 06, 2007 4:50 am
Location: UK Midlands

Postby Steve Anderson » Mon Oct 15, 2012 5:25 pm

Viewmaster wrote:Thanks very much Steve, for all that.


No problemo...what's your source of signals? Club CDs or something else? I just wanna check that this would be OK with whatever source of NBTV video you might be using...

Steve A.
User avatar
Steve Anderson
"Fester! Don't do that to 'Thing'"
 
Posts: 4219
Joined: Fri Mar 30, 2007 10:54 pm
Location: Bangkok, Thailand

Next

Return to Mechanical NBTV

Who is online

Users browsing this forum: FlyMario and 10 guests