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Group Project: Building the Hedghog 405 standards converter  

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FRANK.C
(@frank-c)
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Hi Frank
The BBC research and development site is a great resource. We are so lucky to have it.
It has many papers on standards conversion.
A couple more example are:

Choice of interpolation apertures for line-store standards converters
Digital line store standards conversion: Determination of the optimum interpolation aperture function

Frank

www.electronics.frankcuffe.ovh

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Posted : 09/12/2018 11:17 pm
Nuvistor
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Yes I saw those papers, I must admit a lot of it is over my head but I take in what I can.

The list on the Data part of this forum gives an easy to find link to the papers. Yesterday I spent reading about the site survey for what would become the Holme Moss Ch 2 BBC transmitter site and how they decided on that location. Then to Les Platons in the Channel Islands and how a 1Kw TX on Ch 4 would cover both islands.

A document on 3 cheap FM converters to be used with a MW radio to evaluate how well they worked, not very well was the outcome.

The BBC did a lot of R&D, presume it’s now very little if any.

 

 

Frank

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Posted : 10/12/2018 9:29 am
FRANK.C
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 I have added legends to the Hedghog website suitable for the smaller Multicomp case case suggested by Golborne Vintage Radio Forum member Neutron.

Frank

hedghog small back a
hedghog small front a

www.electronics.frankcuffe.ovh

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Posted : 26/12/2018 1:37 pm
FRANK.C
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If anyone wants one I have a number of Hedghog  PCB's for sale. The cost is 7 euro which includes UK postage.

Frank

www.electronics.frankcuffe.ovh

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Posted : 28/12/2018 2:10 pm
FRANK.C
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I have been ask a few times if I would supply complete Hedghogs but as I have said right through this project I am not in a position to do that. Forum member Freya(Stephen) has stepped into the breach as he has told me that he is willing to supply complete Hedghogs. So anyone looking for a complete one, can get in contact with him.

Frank

www.electronics.frankcuffe.ovh

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Posted : 16/01/2019 6:47 pm
FRANK.C
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I have updated the program so the converter can convert from 16:9 to both 4:3 and 5:4 as well as converting from 4:3 to 4:3 and 5:4. To facilitate this the top two positions of the tone switch are now used to switch between 4:3 and 16:9 input. The selection of 400 Hz or 1KHz tone is now done on the DIP switch SW8-D. The new program file and legends to suit can be downloaded from the Hedghog web page.

aspect ratios

.

www.electronics.frankcuffe.ovh

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Posted : 03/02/2019 5:58 pm
Doz
 Doz
(@doz)
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I'm about to order some PCBs from PCBway (for other projects) Does anyone want any hedghog PCBs while I'm at it?

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Posted : 06/02/2019 3:39 pm
Doz
 Doz
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Posted by: FRANK.C

I have updated the program so the converter can convert from 16:9 to both 4:3 and 5:4 as well as converting from 4:3 to 4:3 and 5:4. To facilitate this the top two positions of the tone switch are now used to switch between 4:3 and 16:9 input. The selection of 400 Hz or 1KHz tone is now done on the DIP switch SW8-D. The new program file and legends to suit can be downloaded from the Hedghog web page.

aspect ratios

.

Crikey! Missed that! Thanks Frank!!

 

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Posted : 06/02/2019 3:40 pm
mfd70
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After many months of collecting the components mostly from China, I finally had enough  parts fitted to enable me to power up the board to see if anything would work. Much to my surprise it did ! As I'd mounted everything using standard workshop solder and iron, I was expecting some issues, but other than the R2R resistors which needed a few touches with the iron, everything else seemed in order. As I've not fitted the hex switch yet, I used an external modulator to test, however there was a spike at about 150Mhz so something is happening at RF. Now that I'm happy its serviceable, I'll get some switches and a box.

DSC006470005

As you might notice, I mounted the crystal and 1N4001 on the wrong side of the board.

The power LED also flashes, is this normal ?

DSC006420001
DSC006410002

These are on the old 1400, with various linearity issues.

DSC006440004
DSC006430003

On on my Sony, which looks a lot better.

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Posted : 27/07/2019 1:41 pm
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FRANK.C
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Hi mfd70
Well done! great result. 👍 

With regard to the cases there is another case that I believe does suit it is a
Hammond RM2015S
Available from Mouser and Rapid and probably more suppliers as well.
I haven't tried it but the from the data sheet it looks identical and even the part number is similar.

With regard to the flashing LED it will depend on what version of firmware you have. looking at the test card you haven't got he latest version. You are probably better to up grade to it.
But regardless of which version you have having all the DIP switches in the off position should stop the LED from flashing.

Frank

www.electronics.frankcuffe.ovh

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Posted : 27/07/2019 3:47 pm
mfd70
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The hedghog is taking a bit more shape now, I had trouble with the phono sockets so gave up on the original case and used another of the type I used for the PICGEN 405 generator. This gave me more space so I used front and rear BNC's for video in and out and DIN for audio, I also used a 4 pin XLR to suit my workshop DC distribution. 

There is a strange patterning fault on the video however, it looks like PSU noise but I tried it with a linear supply and it was still the same, it looks like an analog fault, the patterning can be minimized by fine tuning, but both patterns are fine.

IMG 0122
IMG 0119
IMG 0118
IMG 0117

 

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Posted : 22/08/2019 10:40 pm
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Nuvistor
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Have you tried a different TV, its possible that if one of the traps in the IF is not correct it may be letting through a spurious signal from the generator.

The pattern looks about the same frequency as the 0.8Mhz grating on the Philips test card, you can judge what is the frequency by comprising with the frequency gratings on the test card. Then look for beats between the various frequencies being generated, vision carrier, sound and Chroma.

If the modulator is double sideband it may be a beat from the other sideband.

Sound/Chroma beats can be a problem but with 6Mhz sound it may be a high 1.6Mhz, if you are using 5.5Mhz, that would be just over 1 Mhz.

Just some thoughts.

Frank

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Posted : 22/08/2019 11:25 pm
FRANK.C
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Hi mfd70
It has come along well. The larger case will keep it nice and cool.

If the test patterns are clean one possibility for the patterning could be pick up from the audio/video leads to the sockets. The FPGA operates at high speed and so has the ability to generate unwanted digital noise.
I used PCB mounted sockets to help prevent pick up.

Is the pattering still there when not connected to a audio/ video source? If so disconnect the audio/video leads from the Hedghog PCB to check for pick up.

Frank

 

www.electronics.frankcuffe.ovh

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Posted : 22/08/2019 11:55 pm
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