[hpsdr] Hermes 144mhz

[Ton PA0TBR]

Hello Helmut,

Thank you for your reaction. What you describe is the correct way and as
you say, difficult to do.
I have the ANAN-100B (Angelia and the path to the ADC is:
Attenuator - Filter - Transformer - PreAmp - ADC
All parts, except the Filter, have sufficient bandwidth to cover 144MHz.

I don't like to remove parts, cut tracks or loose HF, so instead of
replacing the filter RLP-50+ or cutting the track, I thought of injecting
the output of the new 70MHz or 144MHz bandpass filter on the input of the
transformer TC4-1T / output of RLP-50+.
I assume that the filter response of the filters will be negative affected,
this could be overcome by adding a buffer amp to the new filter(s) and an
electronic switch. The switch prevents negative effects on the existing HF
bands.

The transmit path is:
DAC - Transformer - Filter - Amplifier

Instead of replacing the filter LPF-850+ I thought of taking the signal
from the output of the transformer TC4-1T / input of the LPF-850+ filter
and injecting the signal into the new 70MHz or 144MHz bandpass filters. I
think that buffer amps are needed in front of the new bandpass filters. New
VHF amplifiers would follow the new VHF filters.

These mods mean that no components need to be removed or tracks be cut and
that the HF performance should still be the same. What do you think?

73,
Ton PA0TBR


On Wed, Sep 10, 2014 at 9:44 AM, Helmut Oeller <dc6ny at gmx.de> wrote:

> It's necessary to substitute the two LPFs (RLP-50+ and the LPF between
> preamp and ADC) on the RX path by BPFs for 144MHz. On the TX side a BPF
> directly behind DAC is needed. IMO it's too cumbersome to provide these
> modifications on Hermes. It was much more comfortable to use Mercury and
> Penelope for this job. BTW the 122.800
> MHz sampling oscillator produces such low jitter that SNR is also very well
> in undersampling application on 144 MHz.
>
> 73, Helmut, DC6NY
>
> -----Ursprüngliche Nachricht-----
> Von: Hpsdr [mailto:hpsdr-bounces at lists.openhpsdr.org] Im Auftrag von Ton
> PA0TBR
> Gesendet: Mittwoch, 10. September 2014 01:18
> An: hpsdr at lists.openhpsdr.org
> Betreff: Re: [hpsdr] Hermes 144mhz
>
> ***** High Performance Software Defined Radio Discussion List *****
>
>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.openhpsdr.org/pipermail/hpsdr-openhpsdr.org/attachments/20140911/a6053533/attachment-0003.htm>