70.5 - 71.5 MHz

The place to discuss reduced bandwidth fast scan amateur television on 70cms and below
G4GUO
Posts: 469
Joined: Tue Feb 16, 2010 12:51 pm
Location: Worthing

70.5 - 71.5 MHz

Postby G4GUO » Thu Apr 02, 2015 3:54 pm

http://rsgb.org/main/blog/news/gb2rs/he ... mentation/

I have a 5 ele yagi for this band. Might be time to put it on the mast again.

- Charles G4GUO

g0mjw
Posts: 330
Joined: Sat Sep 20, 2014 9:15 am

Re: 70.5 - 71.5 MHz

Postby g0mjw » Thu Nov 09, 2017 11:41 am

I'm just working on this. Just an exercise leveraging the $5 for 10 PCBs offer from PCBway.

Mixer Board 2.jpg
Mixer Board 2.jpg (339.19 KiB) Viewed 576 times


The minitiouner will not, as far as I know tune down to 71MHz. Plan is to up-convert to a higher frequency that the minitiouner can cope with better. It uses an ADE11+ mixer and a PGA103+ to provide some amplification if needed. I have added lots of pads to the board to allow flexible use with different filter designs e.g. low pass, high pass, band pass, band stop, all pass, no pass which would allow it to be used as a down-converter, a filtered preamp etc. Good RF design principles have largely been ignored so it's not going to work at very high frequencies.

The LO +7dBm comes from whatever, e.g. the ADF4351 as used in the Portsdown, or an SI571.

Is anyone else interested in this sort of thing or is it just me?

Mike

g8gtz
Posts: 764
Joined: Wed Apr 07, 2010 6:26 pm

Re: 70.5 - 71.5 MHz

Postby g8gtz » Thu Nov 09, 2017 12:19 pm

Hi Mike,

Yes - I'm interested and it will make fine CQ-TV article :-)

Could it be used to make a 50MHz version as well?

We can more boards for the shop if there is much interest.

Noel

F1NST-Bernard
Posts: 25
Joined: Mon Mar 27, 2017 9:45 pm

Re: 70.5 - 71.5 MHz

Postby F1NST-Bernard » Thu Nov 09, 2017 4:14 pm

Yes very interesting particularly if down to 50Mhz. 70Mhz not allowed in France.. ;-)Thank your idea.
Bernard

g0uhy
Posts: 43
Joined: Fri Aug 05, 2011 3:09 pm

Re: 70.5 - 71.5 MHz

Postby g0uhy » Fri Nov 10, 2017 11:09 am

Hi Mike,

also interested in the project. Probably 6m to start with and then probably 4m if I can get through the NOV process.

73

Malcolm G0UHY

F6DZP
Posts: 146
Joined: Fri May 27, 2011 9:59 am
Location: Poitiers - France
Contact:

Re: 70.5 - 71.5 MHz

Postby F6DZP » Sun Nov 12, 2017 9:26 pm

Yes I am also interested if it can work also for the 50MHz band.

Jean-Pierre F6DZP

g0mjw
Posts: 330
Joined: Sat Sep 20, 2014 9:15 am

Re: 70.5 - 71.5 MHz

Postby g0mjw » Thu Nov 23, 2017 8:16 am

The test boards have arrived from PCBway earlier than expected. Not bad for $16 shipped. The vias are so well implemented I had to use a torch to check there really were holes there. The silk screen looks good. The jury will be out on the design until I get all the parts together. I have already made some improvements to the board design. Even thought about putting the LO on-board using one of those 400MHz LVDS chips, but it's probably best and more flexible left as it is.

Mixer PCB.jpg
Mixer PCB.jpg (506.63 KiB) Viewed 360 times


Capture.PNG
Capture.PNG (808.26 KiB) Viewed 329 times

G4CPE
Posts: 11
Joined: Mon Oct 31, 2016 3:59 pm

Re: 70.5 - 71.5 MHz

Postby G4CPE » Thu Nov 23, 2017 5:58 pm

Can anyone offer some advice with the SRP application for 70.5 - 71.5.
I completed the application form 12 months ago but have never had a reply from OFCOM so I thought I would have another attempt.
Has anyone managed to get a NOV for this band.? All my ATV gear uses 70MHz has the first IF and this could easily be moved up the band and amplified.
Arthur G4CPE

g8gtz
Posts: 764
Joined: Wed Apr 07, 2010 6:26 pm

Re: 70.5 - 71.5 MHz

Postby g8gtz » Fri Nov 24, 2017 1:34 pm

Hi Arthur,

The consensus seems to be if you have not had a response from your original application you will need to reapply to Ofcom for a special permit. Once you have this, the 70MHz NoV is a simple on line application like 146MHz.

http://rsgb.org/main/blog/news/gb2rs/he ... mentation/

BTW - has anyone done the Field strength questimates required on the form?

73 Noel

G4GUO
Posts: 469
Joined: Tue Feb 16, 2010 12:51 pm
Location: Worthing

Re: 70.5 - 71.5 MHz

Postby G4GUO » Fri Nov 24, 2017 5:48 pm



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