RBTVMOD

The place to discuss reduced bandwidth fast scan amateur television on 70cms and below
G4KLB
Posts: 197
Joined: Wed May 28, 2008 10:46 am

Re: RBTVMOD

Post by G4KLB » Sat Apr 23, 2016 8:14 pm

Hi, Rakesh.

More PCBs should be in the BATC Shop in about a week.

G4KLB
Posts: 197
Joined: Wed May 28, 2008 10:46 am

Re: RBTVMOD

Post by G4KLB » Sat Apr 23, 2016 8:18 pm

Those that have reserved RBTVMOD PCBs, will all get there boards direct from me, the rest of the stock is on the way to the BATC shop.

G4KLB
Posts: 197
Joined: Wed May 28, 2008 10:46 am

Re: RBTVMOD

Post by G4KLB » Tue Apr 26, 2016 11:06 am

I have posted boards to everyone who requested them, the remaining few will appear in the BATC shop shortly.

g0mjw
Posts: 362
Joined: Sat Sep 20, 2014 9:15 am

Re: RBTVMOD

Post by g0mjw » Tue Apr 26, 2016 5:15 pm

Mine arrived thanks - are there updated instructions?

G4KLB
Posts: 197
Joined: Wed May 28, 2008 10:46 am

Re: RBTVMOD

Post by G4KLB » Wed Apr 27, 2016 12:19 am

The software and RPi setup is the same as DigiThin except you chose I Q output instead of DigiThin (in gbmenu)
It will work set as DigiThin but only at SR333.

The local oscillator requirements are the same as DigiThin and Digilite, The LO level for the AD8345 is -2dBm (DigiThin is a little higher)

Layout, circuit and parts list are here https://wiki.batc.tv/Talk:RBTVMOD.

I normally print out the parts list and an A4 size copy of the PCB (don't usually have the luxury of a silk screen!) and work from that.

If you have a RPi b+ and above you will need an extended header if you want the PCB to sit on top of the RPi (it doesn't have to)

g0mjw
Posts: 362
Joined: Sat Sep 20, 2014 9:15 am

Re: RBTVMOD

Post by g0mjw » Wed Apr 27, 2016 5:05 pm

Thanks - I just tried a DigiKey order as BOM. I hadn't realised they now also prepay VAT and duties like Mouser. It makes it much cheaper. Digikey stock many RF parts that its hard to get elsewhere (excepting Mouser). I had to order a few extra bits to get above the free shipping threshold. There are some moderately difficult to fit ICs.

Mike

g0mjw
Posts: 362
Joined: Sat Sep 20, 2014 9:15 am

Re: RBTVMOD

Post by g0mjw » Sun May 01, 2016 11:56 am

Digikey did well so I have the parts and decided to have a go this morning. I have all the parts in except the modulator. That one looks a little daunting. How do you fit it without an oven?

Mike

G4KLB
Posts: 197
Joined: Wed May 28, 2008 10:46 am

Re: RBTVMOD

Post by G4KLB » Sun May 01, 2016 11:48 pm

It is the same modulator as the 70cm Digilite, so you should get some advice on here.

I lightly tin the pad on the underside of the AD8345, removing most of the solder, too much solder and the pins will be too far of the PCB
I use a flux pen and 26swg solder. Flux the pads, position the device, solder one of the outer pins and check its aligned correctly, (plenty of light and a good magnifier needed here) solder the rest of the pins. You may short out some pins with too much solder, remove any excess with solder wick.
When you have the correct amount of solder, add plenty of flux again and even with a fairly large clean iron tip you wont have any shorts.(even if you bridge two pins at once) I do this fairly quickly sliding the iron away from the device.

Turn the board over and heat up the ground pads, feed a small amount of solder in the via if you want, do this quickly, as its possible to unsolder the other pins at the same time.

Inspect closely and clean off the flux residue. (I use IPA for that)
Its not as difficult as it looks. :D

Having said all that, the prototype DigiLite's used an AD8345 without the pad under the device connected at all, and was never a problem.
AD8345.jpg
AD8345.jpg (374.17 KiB) Viewed 1923 times

From the AD8345 Data Sheet:

SOLDERING INFORMATION
The AD8345 is packaged in a 16-lead TSSOP_EP package. For optimum thermal conductivity, the exposed pad can be soldered to the exposed metal of a ground plane. This results in a junction-to-air thermal impedance (θJA) of 30°C/W. However, soldering is not necessary for safe operation. If the exposed pad is not soldered down, then the θJA is equal to 95°C/W.

g6pep
Posts: 5
Joined: Sun Nov 22, 2015 10:05 am

Re: RBTVMOD

Post by g6pep » Wed May 25, 2016 7:16 pm

G4KLB wrote:... Layout, circuit and parts list are here https://wiki.batc.tv/Talk:RBTVMOD.

I normally print out the parts list and an A4 size copy of the PCB (don't usually have the luxury of a silk screen!) and work from that.
Hi Colin,

I went onto the Wiki, in search of the layout for the RBTVMOD board. I was only able to find an excerpt of the layout, showing the I and Q test points. Did I miss something?

Also, is the artwork for these boards available somewhere? Who should I contact?

73, John.

G4KLB
Posts: 197
Joined: Wed May 28, 2008 10:46 am

Re: RBTVMOD

Post by G4KLB » Thu May 26, 2016 5:28 am

Silk screen now on the Wiki, more PCBs in the BATC Shop ............ off to work now.

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