[hpsdr] [Hpsdr] Call for Comments - ALEX

[Graham Haddock]

CT1IZU wrote:
> Graham
> I don't belive a 5 ele LPF is adequate for the tx. It needs to be a 7ele (
> first element capacitive). For 100W a T50 is pushing it on 80/160, T68 would
> be much better. Attached is an similar auto LPF  I designed some years ago.
>
> >From a kitting point of view I would go for  red -2 powdered iron for for
> both 80/160 rather than have the odd -1. In view of the IP3 issues if size
> was not a constraint I would also use T68 on the 80/160 HPF.
>
> For the rx filters above 30MHz something like the Toko MC120 is good . They
> are easy to adjust and have a good Q. On the TX side on 6 up to around 10W
> the Toko S18 with an alloy core is ok.
>
> Shel CT1IZU
>   
Shel:
Thanks for the comments and the photo of your LPF board.  That is a nice 
clean looking design.

Yes, I have some concerns about the T-50 cores at 100 watts, also.  
There is a commercial
example (Elecraft K2) using this size at 100 watts, so we will test them 
at that level.

I have another request to increase the second harmonic suppression of 
the TX 160 and 80 Meter LPF,
so we may change them to Cauer/elliptic.

As far the TOKO coils with ferrite core, the data we have seen suggests 
poor IP3 performance,
so we are likely to stay with the T-50 toroids or go with air wound coils.

--- Graham / KE9H

==



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