[hpsdr] Fwd: Re: Hermes 2 design

[K4KV]

-------- Forwarded Message --------
Subject: 	Re: [hpsdr] Hermes 2 design
Date: 	Wed, 9 Aug 2017 18:35:25 -0400
From: 	K4KV <k4kv at k4kv.com>
To: 	Marc OLANIE <marc.olanie at decision.fr>



Marc,

Yes, I just thought about it before I came to check my email.  I was in
error talking about the one spare line,

just adding another serial latch chip onto the other rx latches to make
it 24-bit makes the most sense.

8 outputs is plenty!

I can share the whole design and make it public.  I have it in EaglePCB
ver. 5x.  Or, make it public on OSH park

and let folks make their own.

My tx filter design is Chebyshev 0.2db ripple, utilizing two inductors
and 3 caps.  I used a calculator on line

somewhere in the UK.

The rx filter is also Chebyshev 0.2db using smt components, 3 inductors
and 4 caps (per band).  Relays are NEC

model EC2-12NU.

All SMA connectors except the two antenna relays.  20db gain 6M preamp.
Two banks of additional attenuators

like the original Alex.  However, I have never needed them, so the
attenuators may be a candidate for elimination.

I have an additional attentuator from the PS input connector to the PS
relay which can be populated or bypassed...

Let me know.

73

Glen K4KV




On 8/9/2017 16:09, Marc OLANIE wrote:
> Hi Glenn & All
>
> Could you pse give use more infos about your Alex version ? (just to avoid reinventing the wheel 😉  )
>
> What kind of topology did you choose for LPF and HPF? What max power level are you targeting ? What order level did you choose ? did you published any measurement of your different filter configurations ? what EDA software did you use ?
>
> Imho, driving a second set of filters could easily be done with a small firmware mod. But the last time I asked for info about the possibility to fire a specific order from the SPI, I got no answer. It seems this question is out of scope for the moment.
> Such a mod would probably also need a second "J16" param window  in the client software  - New gen PowerSDR, CuSDR, SparkSDR or any other compatible code.
>
>  From a pure hardware point of view, you already could switch the same pair of TX and RX filter by just adding another pair of latches (https://github.com/F6ITU/Mentor/blob/master/Mentor%20Schematic.pdf ... batteries not included, bug certainly are ). That's the "dumb way of doing things".
>
> The only but important drawback of this design is that the second filter will be totally synchronized with the first one. Being able to configure RX1 on a specific bw (1 to 7 MHz for example) and RX2 on another part of the spectrum (20 to 30 or 30 to 50) is impossible.
> It  would be possible if the SPI protocol could be enhanced (with almost the same schematic but with a signaling able to address a "filter one" and a "filter two")
>
> The secondary lpf won't have to handle high level of power as it is only used in an RX variable bpf configuration. But that doesn't mean surface mounting coils (at least T50 or T68 toroids... IMD ruleZ.
>
>  From an architectural/physical/mechanical point of view, designing such a dual filter on only one board would be counterproductive. The PCB would be too large, bad IMD and unwanted coupling would probably occur. And the prototyping phase would be more complex.
>
> Using a modular approach could help a lot, giving the ability to use one or two lpf, one or two hpf (same and smaller pcb) or a full or half populated control/latching board. Or simply one lpf alone (for people living far away from big cities and using rigs with only one receiver, as the Hermes board is not the only one using the SPI/J16 protocol). In this configuration, Coax input/output switching should also be located on a specific board
>
> All this to say "indeed, it's a really interesting project" 😊
>
> My 2 cts
> 73'
> Marc f6itu
>
>
>
> -----Message d'origine-----
> De : Hpsdr [mailto:hpsdr-bounces at lists.openhpsdr.org] De la part de K4KV
> Envoyé : mercredi 9 août 2017 19:59
> À : hpsdr <hpsdr at lists.openhpsdr.org>
> Objet : [hpsdr] Hermes 2 design
>
> ***** High Performance Software Defined Radio Discussion List *****
>
> Hello,
>
> I have designed my own version of Alex that has both the tx and rx filters on one Hermes-sized board.  I have
>
> been using this for more than 1 year.  To save room on my board, I eliminated the 3rd antenna port, and put
>
> a Pure Signal input sma connector and associated relay.
>
> In anticipation of the Hermes 2, I would like to add a second set of rx filters for another ADC(or 2nd channel).
>
> I see there is one line left unused on the serial latch U4 (U3/U4 rx pair).
>
> Is it 'your' plan to use this line for a second set of rx filters???
>
> I believe I could fit an extra smt filter bank with tiny relays. Most of the leds could be eliminated as well, but we
>
> need a power and xmit led.
>
> What is the thinking regarding this for the powers that be?
>
> 73
>
> Glen K4KV
>
>
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