ETF Modulator - UK Vintage Radio Repair and Restoration Discussion Forum

Sean Williams · 4th Oct 2005, 4:39 pm

Hi All,

I have just finished building the PCB for the ETF modulator - I thought I would share some observations with you all.

The board is very well made, but for later production runs some modifications may be a good idea.

1 The coil formers could do with having a bit more room so that a proper mounting job can be done - either by drilling a .25" hole in the board to allow a mechanical solution, or moving the layout so a standard aladdin type can be accomodated.

2 Some of the solder pads are rather small, and as a result of through hole plating passing leads of larger components can be tricky.

3 Some form of output filtering is essential - the onboard components are not effective with harmonics being generated at significant levels right into the UHF range

But otherwise a simple item to build, and once you have the board it should cost less than a fiver to populate.

With careful choice of coil dimensions you can tune it to channels 1-4 just by moving the slugs......

A picture below!

Cheers
Sean

high_vacuum_house · 4th Oct 2005, 6:02 pm

Hello there,
I look forward to building one. I bought one the week before if I remember correctly but it hasn't arrived yet (dam post!).

I have all of the components apart from the 2 coils and it looks a simple project to build. I think it must go into a screened box to prevent problems.

Christopher Capener

Steve_McVoy · 5th Oct 2005, 6:10 pm

We intentionally didn't put much filtering in the output, because the harmonics won't bother the sets it is designed to work with. The values of the two capacitors and the inductor in the output could be fiddled with to increase harmonic suppression. The board should be fitted in an aluminum box to reduce radiation.

The next time we have PC boards made we will create more space for the inductors. We will also increase the pad size on the components that have larger diameter leads.

If anyone else has comments on the kit, please send PM

Sean Williams · 5th Oct 2005, 6:22 pm

Hi Steve,

Point taken on the harmonic emmissions, but it is a problem when you have various HAM recievers in the same room, and of course we all ought to do our bit to supress harmonic emmissions.....

I certainly had no gripes regarding the modulator board, just a couple of suggestions - considering the low cost of the parts this is really very good - it may be worth looking at a double sided board with a ground plane on the upper face - this will allow a screen to be attached to keep the audio and video oscillators seperate, and reduce mixing products from the oscillators.

I am very pleased however with the unit thus far, when I have finished the build I will post some more observations.

I wonder has a review been done for anyone of this design - if not I would be happy to do so!

Cheers
Sean

ppppenguin · 5th Oct 2005, 7:50 pm

Sean

Well worth you writing a review. Either for this forum, the BVWS Bulletin or both. I know you are very well equipped for the RF side of things but if you need any extra input on the video side I'm always willing to help.

4th Oct 2005, 4:39 pm	#1
Sean Williams Dekatron Join Date: Feb 2005 Location: St.Ippolyts, Hitchin, Hertfordshire QRA IO91UW Posts: 3,529	ETF Modulator Hi All, I have just finished building the PCB for the ETF modulator - I thought I would share some observations with you all. The board is very well made, but for later production runs some modifications may be a good idea. 1 The coil formers could do with having a bit more room so that a proper mounting job can be done - either by drilling a .25" hole in the board to allow a mechanical solution, or moving the layout so a standard aladdin type can be accomodated. 2 Some of the solder pads are rather small, and as a result of through hole plating passing leads of larger components can be tricky. 3 Some form of output filtering is essential - the onboard components are not effective with harmonics being generated at significant levels right into the UHF range But otherwise a simple item to build, and once you have the board it should cost less than a fiver to populate. With careful choice of coil dimensions you can tune it to channels 1-4 just by moving the slugs...... A picture below! Cheers Sean Attached Thumbnails __________________ Engineers make things work and have spare bits when finished

4th Oct 2005, 6:02 pm	#2
high_vacuum_house Octode Join Date: May 2003 Location: Belper Derbyshire Posts: 1,989	Re: ETF Modulator Hello there, I look forward to building one. I bought one the week before if I remember correctly but it hasn't arrived yet (dam post!). I have all of the components apart from the 2 coils and it looks a simple project to build. I think it must go into a screened box to prevent problems. Christopher Capener __________________ Interests in the collection and restoration of Tefifon players and 405 line television

5th Oct 2005, 6:10 pm	#3
Steve_McVoy Pentode Join Date: Feb 2004 Location: Columbus, Ohio, USA Posts: 150	Re: ETF Modulator We intentionally didn't put much filtering in the output, because the harmonics won't bother the sets it is designed to work with. The values of the two capacitors and the inductor in the output could be fiddled with to increase harmonic suppression. The board should be fitted in an aluminum box to reduce radiation. The next time we have PC boards made we will create more space for the inductors. We will also increase the pad size on the components that have larger diameter leads. If anyone else has comments on the kit, please send PM Last edited by mikelect; 5th Oct 2005 at 6:18 pm. Reason: E-mail address

5th Oct 2005, 6:22 pm	#4
Sean Williams Dekatron Join Date: Feb 2005 Location: St.Ippolyts, Hitchin, Hertfordshire QRA IO91UW Posts: 3,529	Re: ETF Modulator Hi Steve, Point taken on the harmonic emmissions, but it is a problem when you have various HAM recievers in the same room, and of course we all ought to do our bit to supress harmonic emmissions..... I certainly had no gripes regarding the modulator board, just a couple of suggestions - considering the low cost of the parts this is really very good - it may be worth looking at a double sided board with a ground plane on the upper face - this will allow a screen to be attached to keep the audio and video oscillators seperate, and reduce mixing products from the oscillators. I am very pleased however with the unit thus far, when I have finished the build I will post some more observations. I wonder has a review been done for anyone of this design - if not I would be happy to do so! Cheers Sean __________________ Engineers make things work and have spare bits when finished

5th Oct 2005, 7:50 pm	#5
ppppenguin Retired Dormant Member Join Date: Dec 2003 Location: North London, UK. Posts: 6,168	Re: ETF Modulator Sean Well worth you writing a review. Either for this forum, the BVWS Bulletin or both. I know you are very well equipped for the RF side of things but if you need any extra input on the video side I'm always willing to help.