[hpsdr] Filter Switching for Out of Band Band Use

Wed May 14 17:56:56 PDT 2014

Hi Jim, 

RR thanks for the clarifications.   Seems to me that there are a couple approaches you could take to realize the switching you desire: 

1)  One approach is to modify the firmware (maybe in a special firmware edition for your use) so that there are 11 bits sent to the filter board instead of 6 bits for HPF and 7 bits for LPF as is currently done, such that each band has its own bit for controlling the respective filter in your unit, or alternatively and much more simply,

2) Turn one of the Open Collector outputs on (in PowerSDR) when an Rx frequency is used that is outside of any ham band.  The Open Collector Output could then be used by your filter unit to cause the all filters to be bypassed when the Open Collector Output is active.   

The disadvantage of either approach is that you would need personalized firmware (and perhaps software too) in the first case or personalized software in the second case instead of using the public releases of HPSDR firmware and software, of course.  As far as practical implementation goes I would lean toward the second, personally.  

73, Joe K5SO

On May 14, 2014, at 1:24 PM, Jim Gailer wrote:

> 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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> 
> 
> 

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