Re: Duo with pc headset ssb #eladduo


Paul Andrews
 

Are you using this 144 Mhz filter / amp design with your Duo?

The Duo as a 28 MHz IF radio is excellent.  I use it on 432 and 1296 MHz.

No I better understand the limitations at 144 MHz undersampling.

If the Duo is run at 144 MHz with a transverter, is the filtering still required?

73 - Paul - W2HRO

On Sat, Oct 17, 2020, 18:34 Neil Smith G4DBN <neil@...> wrote:
Hi Paul I use a G4DDK Anglian transverter to get the DUO on to 144, but
it is quite simple to get around the mathematical and technological
issues with the DUO at 144 MHz.  Running 144 MHz on a 122.88 MHz sampled
A/D converter means you lose a lot of sensitivity simply because of the
way sampling works. The noise figure of the DUO at 144 MHz is extremely
poor as a result.  Also there is aliasing, so you get noise from the
image frequency as well, and Band 2 FM broadcast breakthrough from
around 100 MHz.

Andy G4JNT has designed a filter and amplifier board to improve the DUO
performance on 144. Have a look at
http://www.g4jnt.com/FDM-DUO_at_VHF.pdf
<http://www.g4jnt.com/FDM-DUO_at_VHF.pdf> where all is explained...

Neil G4DBN

On 17/10/2020 23:19, Paul Andrews wrote:
> Neil,
>
> Do you use a 144 MHz IF with your 10 GHz system.   I tried using my
> FDM-DUO configured for 144 MHz with a Khune transverter.  I was not
> successful looking for the beacon.
>
> 73 - Paul - W2HRO






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