[TowerTalk] 2m intermod filter placement

[Joe Subich, W4TV]

It depends on whether the preamp is generating the intermod or the
IC-9100 is generating the intermod.  If the intermod is due to mixing
in the IC-9100's internal preamp, put the notch filter between the
LNA and IC-9100 so it does not impact the system noise figure.

73,

    ... Joe, W4TV


On 5/11/2014 2:14 PM, Drax Felton wrote:
> The notch will only be in the receive path since the setup has a mast
> mounted rx/tx relay too that protects the LNA.
>
> -----Original Message-----
> From: John Lemay [mailto:john at carltonhouse.eclipse.co.uk]
> Sent: Sunday, May 11, 2014 2:12 PM
> To: 'Drax Felton'
> Subject: RE: [TowerTalk] 2m intermod filter placement
>
> Drax
>
> The right answer will depend on your individual circumstances. However, it's
> far easier to try it after the preamp, ie next to the rig. If it works,
> that's just fine. If it doesn't work then you need to try it before the
> preamp. Doing that will undoubtedly place some loss before the preamp and
> affect your overall noise figure, which is a good reason for this to be the
> second choice.
>
> Is the notch filter designed to withstand your EME transmit power ?
>
> John G4ZTR
>
>
> -----Original Message-----
> From: TowerTalk [mailto:towertalk-bounces at contesting.com] On Behalf Of Drax
> Felton
> Sent: 11 May 2014 19:00
> To: towertalk at contesting.com
> Subject: [TowerTalk] 2m intermod filter placement
>
> I recently put up a phased set of four 2m meter antenna for EME to find out
> that the front end of my IC-9100 is being blasted by pager intermod.
>
> I got a notch filter for the frequencies involved from PAR Electronics.
> Question is now:   Where inline is the best place to put the filter?
>
>
>
> Before or after the mast mounted pre-amp?  Or down at the radio end?
>
>
>
>
>
> KB3X
>
>
>
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