Re: Scatterpoint Activity column


Paul Randall G3NJV
 

Hi, I intend to mix down to 2m and bought a  TOKO 5HW-73050A-735 filter off eBay for 3 quid to give the mixer a better chance.

What mixers are you guys planning to use? 


Paul


Sent from my Samsung Galaxy smartphone.



-------- Original message --------
From: "John E. Beech" <john@...>
Date: 18/05/2020 22:26 (GMT+00:00)
To: UKMicrowaves@groups.io
Subject: Re: [UKMicrowaves] Scatterpoint Activity column

Tnx fer that Andy. In that case I might try a very simple Schottky diode mixer for starters. I've got a series of 3dB, 6 dB & 10 dB BNC attenuators I can clag in to see how much I need & then build a dedicated attenuator.

de John G8SEQ

>  -------Original Message-------
>  From: Andy G4JNT <andy.g4jnt@...>
>  To: UK Microwaves groups.io <UKMicrowaves@groups.io>
>  Subject: Re: [UKMicrowaves] Scatterpoint Activity column
>  Sent: May 18 '20 18:46

>  The output of any LNB is so high you'll need attenuation rather than
>  gain
>  The broadband noise output over the complete IF band from 600MHz to
>  2GHz or so is so high, it can run into compression in some mixers.
>  DBMs shpuld be OK, but the I/Q downconverter I used to get to 28MHz
>  required at least 10dB attenuation of the 739MHz input to stay
>  comfortably in the linear region.

>  Don't forget image filtering if you use a simple mixer - otherwise you
>  throw away 3dB S/N on every signal you hear

>  Andy
www.g4jnt.com

>  On Mon, 18 May 2020 at 17:57, John E. Beech <john@...> wrote:

>  > Hi John,
>  > I don't know if this is of any interest, but while I have been
>  > trying to revive my SSB electronics L 23 S TVTR, my brain went into
>  > overdrive. Having recently bought a NanoVNA, I now have an easily
>  > programmable LO with which to make a simpler SDR for QO-100. My LNB
>  > puts out 739 MHz. By injecting 739 MHz into a suitable mixer ( ie a
>  > copy of the Rx mixer in the L 23 S, I down convert the 739 MHz to
>  > baseband to use with some existing software I have.
>  > But there are more questions than answers. Will I need any
>  > amplification/filtering at 739 MHz before the mixer or will it have
>  > sufficient gain? Should I put an audio buffer amplifier between the
>  > mixer and the sound card input. Has anyone already done this or am I
>  > barking up the wrong tree?
>  >
>  > de John G8SEQ
>  >
>  >> -------Original Message-------
>  >> From: John Worsnop <johnworsnop@...>
>  >> To: UKMicrowaves@groups.io <UKMicrowaves@groups.io>
>  >> Subject: [UKMicrowaves] Scatterpoint Activity column
>  >> Sent: May 18 '20 17:45
>  >>
>  >> GE All,
>  >> I've had no contributions for the Scatterpoint activity news this
>  >> month so far, so it'll be "The G4BAO report" unless I get
>  > something
>  >> before lunchtime Wednesday.
>  >>
>  >> Doing anything interesting? made any out of the ordinary QSOs?
>  >> switched the rig on instead of checking the web for activity? had
>  > a
>  >> QSO that didn't involve exchanging "59007 IO92WI" ?
>  >>
>  >> ;-)
>  >>
>  >> Send it to me at the above address before Wednesday Lunchtime and
>  > the
>  >> UKuG will put your name in lights............
>  >>
>  >> 73
>  >> John
>  >>
>  >>





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