[hpsdr] Filter Switching for Out of Band Band Use

[Jim Gailer]

Hi Joe, thanks for your reply.

I suspect that its me who is missing something!

For the Alex switching mode, if I lie to HPSDR that I have an Alex fitted,
and set the Manual option in the Alex...HPF/LPF box, I have options relating
to the use of high pass / low pass combinations and I can set filter
combinations for 160, 80, 60+40, 30+20, 17+15, 12+10 and 6+bypass. My PA3AKE
filters are one per band, so 30+20 for example will not work, I need to
select either 30 or 20 (these are band pass filters).

For the open collector outputs, these are able to control my receive filter
just fine, when the radio is operating in-band. Outside a ham band however,
the open collector outputs appear to select the appropriate combination of
Alex filters so as I tune between two bands, there is a point where the
filter combination changes automatically. With the PA3AKE filters, however,
my filter response is some 80dB down not long after I leave a band. I have
provided a pass-through board in the filter which is, for example, switched
in for 60 metres (until I get round to designing a 60m band pass filter!).
What I need to do is to switch this pass-through into circuit when I am not
tuned to a frequency in any band (e.g., 9MHz). I suppose that what I need is
for the Hermes Control setup tab to contain an additional row for 'not in
band' (for receive only!) or perhaps a check box to make the first four open
collectors off when out of band (or with GEN or WWV selected).

I think that the critical point is that the PA3AKE filters are single-band
band pass filters whereas Alex uses switched combinations of LPF and HPF.
Why am I using this filter? Well I had built the filters (and PA3AKE crystal
filters) before I was converted to HPSDR. They have a very good performance
in terms of intermod and are great when operating multiple stations near
together. The downside for me of course is that I have to use low pass
transmit filters too.

Regards

Jim G3RTD

-----Original Message-----
From: Joe Martin K5SO [mailto:k5so at valornet.com] 
Sent: 14 May 2014 19:25
To: Jim Gailer
Cc: hpsdr at openhpsdr.org
Subject: Re: [hpsdr] Filter Switching for Out of Band Band Use

Hi Jim, 

Unless I'm missing something in your explanation, it seems to me that
selecting "manual" Alex switching mode in PowerSDR, then using the "by-pass"
options and/or setting whatever switch points you desire in terms of
filter/frequency range specified for that filter you desire for any of the
desired frequency ranges you like in the Setup > Alex > HPF/LPF menu should
allow you to do what you wish, yes?   There is a huge amount of flexibility
in terms of configuration options available within that manual Alex menu.   

As far as using one of the open collector outputs to do whatever you wish,
that capability is certainly supported in the Hermes firmware.  I'm not sure
at the moment whether or not the current version of PowerSDR implements a
menu-selectable option for control of the Open Collector Outputs generally
but the firmware would certainly repsond to such controls if commands from
the software were sent to the hardware in accordance with the current USB
comm protocol document (v1.54, I believe is the latest protocol description
document).  The comm protocol document can be downloaded from
http://svn.tapr.org/repos_sdr_hpsdr/trunk/Documentation.  

If there is no generally available menu within the public version of
PowerSDR presently to allow user control of the Open Collector Outputs, it
would not be difficult to modify a version of PowerSDR to do precisely what
you wish with regard to Open Collector Output control.  If there isn't an
already-accessible method within the public PowerSDR program for you to do
that I'd be happy to try to modify a speical version for you that will do
it.   Or perhaps Doug W5WC has some comments/suggestions about some features
within his current public PowerSDR version, that are unknown to me at the
moment, that will fill the bill as far as giving you control of some of
those Open Collector Outputs.  

73, Joe K5SO


 
On May 14, 2014, at 7:10 AM, Jim Gailer wrote:

> ***** High Performance Software Defined Radio Discussion List *****
> 
> Hi
> 
> I am using a PA3AKE receive filter set with Hermes 
> <http://martein.home.xs4all.nl/pa3ake/hmode/bpf_intro.html>. My filter 
> unit has band pass filters for the 160, 80, 40, 30, 20, 17, 15, 12, 10 
> and 6 metre bands, currently with a pass-through on 60 metres. I have 
> built a new decoder for the filters that decodes the band select lines 
> on J12 (the I2C interface seems not to cater for all separate band 
> selects). These filters are not much wider than the amateur bands and 
> have >80dB out of band rejection, so for use out of band, I need to 
> select the pass-through position.
> As far as I can tell, when tuning departs from the amateur band or 
> when GEN or WWV is selected, the filter select lines set an appropriate
(Alex based?
> filter.
> Does anyone know of a work-around for this? (For me, asserting one of 
> the spare open collector lines would be ideal!) I would prefer not to 
> access the CAT interface for this, but it may be the only solution.
> 
> Regards Jim G3RTD
> 
> 
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