RBTVMOD

The place to discuss reduced bandwidth fast scan amateur television on 70cms and below
g6pep
Posts: 5
Joined: Sun Nov 22, 2015 10:05 am

Re: RBTVMOD

Post by g6pep » Thu May 26, 2016 4:23 pm

G4KLB wrote:Silk screen now on the Wiki, more PCBs in the BATC Shop ............ off to work now.
Thanks for that.

I wonder whether, in your haste this morning, you missed my question about artwork. I seem to remember your writing that you didn't design the PCB layout yourself but rather that someone else did it - hence the reason for asking who to contact.

John.

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

Re: RBTVMOD

Post by G4KLB » Thu May 26, 2016 5:17 pm

Hi John,

The Artwork is on the Wiki now if you would like to make your own PCBs.

73
Colin

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

Re: RBTVMOD

Post by g6pep » Thu May 26, 2016 10:40 pm

Thanks.

John.

VK5YYY
Posts: 43
Joined: Sun Sep 27, 2015 1:47 am

Re: RBTVMOD

Post by VK5YYY » Wed Jul 13, 2016 1:59 pm

We connected the I/Q output from the GPIO bus of RPi to an old school I/Q modulator from the junk box
2 1K pots were applied from the I and Q outputs to ground and a 1uf capacitor to isolate the wiper from the modulator
Hey presto we got a MER of 15, much simpler than half a digilite, but a bit crude
One of the quadrants has a high level , now to figure out how to bias these things
A bit of filtering wouldn't go astray

Can anybody supply any info on how these older style modulators were biased, an application note or a circuit
It's done with constant current from what I can gather
Attachments
WP_000784.jpg
couldn't be simpler
WP_000784.jpg (139.89 KiB) Viewed 1627 times
WP_000781.jpg
I/Q modulator circa 2000
WP_000781.jpg (135.45 KiB) Viewed 1627 times

F6DZP
Posts: 151
Joined: Fri May 27, 2011 9:59 am
Location: Poitiers - France
Contact:

Re: RBTVMOD

Post by F6DZP » Fri Aug 12, 2016 7:30 am

With my first prototype using the LTC filters (before the RBTVmod version), I have done some test using a SMIQ-03 IQ modulator. I could get good result and MER, but we are obliged to reduce the value of I and Q to a max of 0.5v if I remember well and take care of the offset.
When all is well set, you get a good result.

Jean-Pierre F6DZP

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